http://www.mdpi.com/journal/jfb Latest open access articles published in J. Funct. Biomater. at http://www.mdpi.com/journal/jfb http://www.mdpi.com/2079-4983/4/2/74 While fibroin isolated from the cocoons of domesticated silkworm Bombyx mori supports growth of human corneal limbal epithelial (HLE) cells, the mechanism of cell attachment remains unclear. In the present study we sought to enhance the attachment of HLE cells to membranes of Bombyx mori silk fibroin (BMSF) through surface functionalization with an arginine-glycine-aspartic acid (RGD)-containing peptide. Moreover, we have examined the response of HLE cells to BMSF when blended with the fibroin produced by a wild silkworm, Antheraea pernyi, which is known to contain RGD sequences within its primary structure. A procedure to isolate A. pernyi silk fibroin (APSF) from the cocoons was established, and blends of the two fibroins were prepared at five different BMSF/APSF ratios. In another experiment, BMSF surface was modified by binding chemically the GRGDSPC peptide using a water-soluble carbodiimide. Primary HLE were grown in the absence of serum on membranes made of BMSF, APSF, and their blends, as well as on RGD-modified BMSF. There was no statistically significant enhancing effect on the cell attachment due to the RGD presence. This suggests that the adhesion through RGD ligands may have a complex mechanism, and the investigated strategies are of limited value unless the factors contributing to this mechanism become better known. Journal of Functional Biomaterials 2013-05-17 4 2 Article 10.3390/jfb4020074 74 88 2079-4983 2013-05-17 doi: 10.3390/jfb4020074 Laura Bray Shuko Suzuki Damien Harkin Traian Chirila http://www.mdpi.com/2079-4983/4/2/59 Sequestration of harmful proteases as human neutrophil elastase (HNE) from the chronic wound environment is an important goal of wound dressing design and function. Monosaccharides attached to cellulose conjugates as ester-appended aldohexoses and ketohexoses were prepared on cotton gauze as monosccharide-citrate-cellulose-esters for HNE sequestration. The monosaccharide-cellulose analogs demonstrated selective binding when the derivatized cotton dressings were measured for sequestration of HNE. Each monosaccharide-cellulose conjugate was prepared as a cellulose citrate-linked monosaccharide ester on the cotton wound dressing, and assayed under wound exudate-mimicked conditions for elastase sequestration activity. A series of three aldohexose and four ketohexose ester cellulose conjugates were prepared on cotton gauze through citric acid-cellulose cross linking esterification. The monosaccharide portion of the conjugate was characterized by hydrolysis of the citrate-monosaccharide ester bond, and subsequent analysis of the free monosaccharide with high performance anion exchange chromatography. The ketohexose and aldohexose conjugate levels on cotton were quantified on cotton using chromatography and found to be present in milligram/gram amounts. The citrate-cellulose ester bonds were characterized with FTIR. Ketohexose-citrate-cellulose conjugates sequestered more elastase activity than aldohexose-citrate-cellulose conjugates. The monosaccharide cellulose conjugate families each gave distinctive profiles in elastase-lowering effects. Possible mechanisms of elastase binding to the monosaccharide-cellulose conjugates are discussed. Journal of Functional Biomaterials 2013-05-17 4 2 Article 10.3390/jfb4020059 59 73 2079-4983 2013-05-17 doi: 10.3390/jfb4020059 Judson Edwards Sonya Caston-Pierre http://www.mdpi.com/2079-4983/4/1/38 Human corneal endothelial cells have a limited ability to replicate in vivo and in vitro. Allograft transplantation becomes necessary when an accident or trauma results in excessive cell loss. The reconstruction of the cornea endothelium using autologous cell sources is a promising alternative option for therapeutic or in vitro drug testing applications. The native corneal endothelium rests on the Descemet’s membrane, which has nanotopographies of fibers and pores. The use of synthetic topographies mimics the native environment, and it is hypothesized that this can direct the behavior and growth of human microvascular endothelial cells (HMVECs) to resemble the corneal endothelium. In this study, HMVECs are cultivated on substrates with micron and nano-scaled pillar and well topographies. Closely packed HMVEC monolayers with polygonal cells and well-developed tight junctions were formed on the topographical substrates. Sodium/potassium (Na+/K+) adenine triphosphatase (ATPase) expression was enhanced on the microwells substrate, which also promotes microvilli formation, while more hexagonal-like cells are found on the micropillars samples. The data obtained suggests that the use of optimized surface patterning, in particular, the microtopographies, can induce HMVECs to adopt a more corneal endothelium-like morphology with similar barrier and pump functions. The mechanism involved in cell contact guidance by the specific topographical features will be of interest for future studies. Journal of Functional Biomaterials 2013-03-21 4 1 Article 10.3390/jfb4010038 38 58 2079-4983 2013-03-21 doi: 10.3390/jfb4010038 Jie Chua Li Liew Evelyn Yim http://www.mdpi.com/2079-4983/4/1/27 For the purpose of developing a novel ablation therapy for oral cancer, the heat generation and transfer properties of a Ti-coated carbon steel rod with 20-mm length and 1.8-mm outer diameter were investigated by means of a high-frequency induction technique at 300 kHz. The heat generation measurement performed using water (15 mL) revealed that the difference of the inclination angles (θ = 0°, 45° and 90°) relative to the magnetic flux direction only slightly affects the heating behavior, exhibiting the overlapped temperature curves during an induction time of 1200 s. These results suggest that the effect of the shape magnetic anisotropy is almost eliminated, being convenient for the precise control of the ablation temperature in clinical use. In the experiments utilizing a tissue-mimicking phantom, the heat transfer concentrically occurred in the lateral direction for both the planar surface and a 10-mm deep cross-section. However, the former exhibited a considerably lower increase in temperature (ΔT), probably due to the effect of heat dissipation to the ambient air. No significant heat transfer was found to occur to the lower side of the inserted Ti-coated carbon steel rod, which is situated in the longitudinal direction. Journal of Functional Biomaterials 2013-02-18 4 1 Communication 10.3390/jfb4010027 27 37 2079-4983 2013-02-18 doi: 10.3390/jfb4010027 Takashi Naohara Hiromichi Aono Tsunehiro Maehara Hideyuki Hirazawa Shinya Matsutomo Yuji Watanabe http://www.mdpi.com/2079-4983/4/1/14 The capsule drug ring (CDR) is a reservoir and delivery agent, which is designed to be placed within the capsular bag during cataract surgery. Prototypes were manufactured by hot melt extrusion of Bionate II®, a polycarbonate urethane. The devices have been optimized using Avastin® as the drug of interest. In vitro biocompatibility was assessed with human lens epithelial cell (B-3), mouse macrophage (J774A.1) and mouse fibroblast (L-929) cell lines. Cell migration and proliferation were assessed after in vitro culture. Pro-inflammatory cytokines (i.e., MIP-1β, MIP-1α, MCP-1, IL-1β, TNF and TGF-β1) were quantified using cytometric bead array (CBA). Preliminary in vivo biocompatibility and pharmacokinetics testing has been performed in rabbits. Journal of Functional Biomaterials 2013-01-18 4 1 Article 10.3390/jfb4010014 14 26 2079-4983 2013-01-18 doi: 10.3390/jfb4010014 Nathan Gooch Randon Burr Dolly Holt Bruce Gale Balamurali Ambati http://www.mdpi.com/2079-4983/4/1/6 To investigate the temporary tamponade effects of an ophthalmic viscosurgical device (OVD) for experimental retinal tears, we performed vitrectomy in four rabbit eyes and created a posterior vitreous detachment and artificial retinal tear to produce retinal detachment. The retina was flattened with liquid perfluorocarbon (PFC), the area peripheral to the tear was photocoagulated, an OVD was applied to the retinal tear surface below the PFC and the PFC was removed by aspiration. In the control group, PFC was removed without application of OVD. At one, three and seven days postoperatively, funduscopy and optical coherence tomography (OCT) were performed to examine the sealing process of the retinal tear. In OVD-treated eyes, the OVD remained on the retinal surface, and the retinal tear was patched for ≥ 3 days postoperatively. By seven days postoperatively, the OVD on the retinal surface had disappeared, and the retina was reattached. In control eyes, the edge of the retinal tear was rolled, and retinal detachment persisted. In OVD-treated eyes, the border of the retinal tear was indistinct, and the defect area was significantly decreased. These results show that application of an OVD effectively seals retinal tears and eliminates retinal detachments. Journal of Functional Biomaterials 2013-01-18 4 1 Communication 10.3390/jfb4010006 6 13 2079-4983 2013-01-18 doi: 10.3390/jfb4010006 Akira Hirata Soichiro Yamamoto Satoshi Okinami http://www.mdpi.com/2079-4983/4/1/1 1. Discusses the properties of enamel and dentin and their role in adhesive dental restoration;2. Chapters also examine the wear properties of dental ceramics, glasses and bioactive glass ceramics for tooth repair and replacement;3. Dental composites and antibacterial restorative materials are also considered;4. Provides a concise overview of non-metallic biomaterials for dental clinicians, materials scientists and academic researchers alike.As the demand for healthy, attractive teeth increases, the methods and materials employed in restorative dentistry have become progressively more advanced. Non-metallic biomaterials for tooth repair and replacement focuses on the use of biomaterials for a range of applications in tooth repair and, in particular, dental restoration. Journal of Functional Biomaterials 2013-01-14 4 1 New Book Received 10.3390/jfb4010001 1 5 2079-4983 2013-01-14 doi: 10.3390/jfb4010001 Shu-Kun Lin http://www.mdpi.com/2079-4983/3/4/879 Extracellular matrix plays an important role in stem cell niche which maintains the undifferentiated stem cell phenotype. Human corneal epithelial stem cells are presumed to reside mainly at the limbal basal epithelium. Efforts have been made to characterize different components of the extracellular matrix that are preferentially expressed at the limbus. Mounting evidence from experimental data suggest that these components are part of the stem cell niche and play a role in the homeostasis of limbal stem cells. The extracellular matrix provides a mechanical and structural support as well as regulates cellular functions such as adhesion, migration, proliferation, self-renewal and differentiation. Optimization of the extracellular matrix components might be able to recreate an ex vivo stem cell niche to expand limbal stem cells. Journal of Functional Biomaterials 2012-12-10 3 4 Review 10.3390/jfb3040879 879 894 2079-4983 2012-12-10 doi: 10.3390/jfb3040879 Hua Mei Sheyla Gonzalez Sophie Deng http://www.mdpi.com/2079-4983/3/4/864 Some bacteria can synthesize cellulose when they are cultivated under adequate conditions. These bacteria produce a mat of cellulose on the top of the culture medium, which is formed by a three-dimensional coherent network of pure cellulose nanofibers. Bacterial cellulose (BC) has been widely used in different fields, such as the paper industry, electronics and tissue engineering due to its remarkable mechanical properties, conformability and porosity. Nanocomposites based on BC have received much attention, because of the possibility of combining the good properties of BC with other materials for specific applications. BC nanocomposites can be processed either in a static or an agitated medium. The fabrication of BC nanocomposites in static media can be carried out while keeping the original mat structure obtained after the synthesis to form the final nanocomposite or by altering the culture media with other components. The present article reviews the issue of biocompatibility of BC and BC nanocomposites. Biomedical aspects, such as surface modification for improving cell adhesion, in vitro and in vivo studies are given along with details concerning the physics of network formation and the changes that occur in the cellulose networks due to the presence of a second phase. The relevance of biocompatibility studies for the development of BC-based materials in bone, skin and cardiovascular tissue engineering is also discussed. Journal of Functional Biomaterials 2012-12-05 3 4 Review 10.3390/jfb3040864 864 878 2079-4983 2012-12-05 doi: 10.3390/jfb3040864 Fernando Torres Solene Commeaux Omar Troncoso http://www.mdpi.com/2079-4983/3/4/839 Tissue engineering strategies employing biomaterials have made great progress in the last few decades. However, the tissues of the brain and spinal cord pose unique challenges due to a separate immune system and their nature as soft tissue. Because of this, neural tissue engineering for the brain and spinal cord may require re-establishing biocompatibility and functionality of biomaterials that have previously been successful for tissue engineering in the body. The goal of this review is to briefly describe the distinctive properties of the central nervous system, specifically the neuroimmune response, and to describe the factors which contribute to building polymer hydrogels compatible with this tissue. These factors include polymer chemistry, polymerization and degradation, and the physical and mechanical properties of the hydrogel. By understanding the necessities in making hydrogels biocompatible with tissue of the brain and spinal cord, tissue engineers can then functionalize these materials for repairing and replacing tissue in the central nervous system. Journal of Functional Biomaterials 2012-11-15 3 4 Review 10.3390/jfb3040839 839 863 2079-4983 2012-11-15 doi: 10.3390/jfb3040839 Emily R. Aurand Jennifer Wagner Craig Lanning Kimberly B. Bjugstad http://www.mdpi.com/2079-4983/3/4/799 Damage to articular cartilage can eventually lead to osteoarthritis (OA), a debilitating, degenerative joint disease that affects millions of people around the world. The limited natural healing ability of cartilage and the limitations of currently available therapies make treatment of cartilage defects a challenging clinical issue. Hopes have been raised for the repair of articular cartilage with the help of supportive structures, called scaffolds, created through tissue engineering (TE). Over the past two decades, different designs and fabrication techniques have been investigated for developing TE scaffolds suitable for the construction of transplantable artificial cartilage tissue substitutes. Advances in fabrication technologies now enable the strategic design of scaffolds with complex, biomimetic structures and properties. In particular, scaffolds with hybrid and/or biomimetic zonal designs have recently been developed for cartilage tissue engineering applications. This paper reviews critical aspects of the design of engineered scaffolds for articular cartilage repair as well as the available advanced fabrication techniques. In addition, recent studies on the design of hybrid and zonal scaffolds for use in cartilage tissue repair are highlighted. Journal of Functional Biomaterials 2012-11-14 3 4 Review 10.3390/jfb3040799 799 838 2079-4983 2012-11-14 doi: 10.3390/jfb3040799 Zohreh Izadifar Xiongbiao Chen William Kulyk http://www.mdpi.com/2079-4983/3/4/776 Synthetic tissue scaffolds have a high potential impact for patients experiencing osteogenesis imperfecta. Using electrospinning, tissue scaffolds composed of hydroxyapatite/polycaprolactone (HAp/PCL) composite nanofibers were fabricated with two different HAp concentrations—1% and 10% of the solid scaffold weight. After physico-chemical scaffold characterization, rat bone marrow stromal cells were cultured on the composite scaffolds in maintenance medium and then in osteogenic medium. Quantitative PCR, colorimetric assays, immunofluorescent labeling, and electron microscopy measured osteogenic cell responses to the HAp/PCL scaffolds. In maintenance conditions, both Hap/PCL scaffolds and control scaffolds supported cell colonization through seven days with minor differences. In osteogenic conditions, the 10% HAp scaffolds exhibited significantly increased ALP assay levels at week 3, consistent with previous reports. However, qPCR analysis demonstrated an overall decrease in bone matrix-associated genes on Hap/PCL scaffolds. Osteopontin and osteocalcin immunofluorescent microscopy revealed a trend that both mineralized scaffolds had greater amounts of both proteins, though qPCR results indicated the opposite trend for osteopontin. Additionally, type I collagen expression decreased on HAp scaffolds. These results indicate that cells are sensitive to minor changes in mineral content within nanofibers, even at just 1% w/w, and elucidating the sensing mechanism may lead to optimized osteogenic scaffold designs. Journal of Functional Biomaterials 2012-11-14 3 4 Article 10.3390/jfb3040776 776 798 2079-4983 2012-11-14 doi: 10.3390/jfb3040776 Timothy Ruckh Derek Carroll Justin Weaver Ketul Popat http://www.mdpi.com/2079-4983/3/4/760 Keratoconus is a disease where the cornea becomes cone-like due to structural thinning and ultimately leads to compromised corneal integrity and loss of vision. Currently, the therapeutic options are corrective lenses for early stages and surgery for advanced cases with no in vitro model available. In this study, we used human corneal fibroblasts (HCFs) and compared them to human Keratoconus fibroblasts (HKCs) cultured in a 3-dimensional (3D) model, in order to compare the expression and secretion of specific extracellular matrix (ECM) components. For four weeks, the cells were stimulated with a stable Vitamin C (VitC) derivative ± TGF-β1 or TGF-β3 (T1 and T3, respectively). After four weeks, HKCs stimulated with T1 and T3 were significantly thicker compared with Control (VitC only); however, HCF constructs were significantly thicker than HKCs under all conditions. Both cell types secreted copious amounts of type I and V collagens in their assembled, aligned collagen fibrils, which increased in the degree of alignment upon T3 stimulation. In contrast, only HKCs expressed high levels of corneal scarring markers, such as type III collagen, which was dramatically reduced with T3. HKCs expressed α-smooth muscle actin (SMA) under all conditions in contrast to HCFs, where T3 minimized SMA expression. Fast Fourier transform (FFT) data indicated that HKCs were more aligned when compared to HCFs, independent of treatments; however, HKC’s ECM showed the least degree of rotation. HKCs also secreted the most aligned type I collagen under T3 treatment, when compared to any condition and cell type. Overall, our model for Keratoconus disease studies is the first 3D in vitro tissue engineered model that can mimic the Keratoconus disease in vivo and may be a breakthrough in efforts to understand the progression of this disease. Journal of Functional Biomaterials 2012-11-13 3 4 Article 10.3390/jfb3040760 760 775 2079-4983 2012-11-13 doi: 10.3390/jfb3040760 Dimitrios Karamichos Ramin Zareian Xiaoqing Guo Audrey Hutcheon Jeffrey Ruberti James Zieske http://www.mdpi.com/2079-4983/3/4/745 Voclosporin is a highly potent, new cyclosporine-A derivative that is currently in Phase 3 clinical trials in the USA as a potential treatment for inflammatory diseases of the eye. Voclosporin represents a number of very sparingly soluble drugs that are difficult to administer. We therefore selected it as a model drug that is dispersed within amphiphilic polymer matrices, and investigated the changing morphology of the matrices using neutron and x-ray scattering during voclosporin release and polymer resorption. The hydrophobic segments of the amphiphilic polymer chain are comprised of desaminotyrosyl-tyrosine ethyl ester (DTE) and desaminotyrosyl-tyrosine (DT), and the hydrophilic component is poly(ethylene glycol) (PEG). Water uptake in these matrices resulted in the phase separation of hydrophobic and hydrophilic domains that are a few hundred Angstroms apart. These water-driven morphological changes influenced the release profile of voclosporin and facilitated a burst-free release from the polymer. No such morphological reorganization was observed in poly(lactide-co-glycolide) (PLGA), which exhibits an extended lag period, followed by a burst-like release of voclosporin when the polymer was degraded. An understanding of the effect of polymer composition on the hydration behavior is central to understanding and controlling the phase behavior and resorption characteristics of the matrix for achieving long-term controlled release of hydrophobic drugs such as voclosporin. Journal of Functional Biomaterials 2012-10-30 3 4 Article 10.3390/jfb3040745 745 759 2079-4983 2012-10-30 doi: 10.3390/jfb3040745 I. John Khan N. Sanjeeva Murthy Joachim Kohn http://www.mdpi.com/2079-4983/3/4/726 Human corneal endothelial cells (HCECs) do not replicate after wounding. Therefore, corneal endothelial deficiency can result in irreversible corneal edema. Descemet stripping automated endothelial keratoplasty (DSAEK) allows selective replacement of the diseased corneal endothelium. However, DSAEK requires a donor cornea and the worldwide shortage of corneas limits its application. This review presents current knowledge on the tissue engineering of corneal endothelium using cultured HCECs. We also provide our recent work on tissue engineering for DSAEK grafts using cultured HCECs. We reconstructed DSAEK grafts by seeding cultured DiI-labelled HCECs on collagen sheets. Then HCEC sheets were transplanted onto the posterior stroma after descemetorhexis in the DSAEK group. Severe stromal edema was detected in the control group, but not in the DSAEK group throughout the observation period. Fluorescein microscopy one month after surgery showed numerous DiI-labelled cells on the posterior corneal surface in the DSAEK group. Frozen sections showed a monolayer of DiI-labelled cells on Descemet’s membrane. These findings indicate that cultured adult HCECs, transplanted with DSAEK surgery, maintain corneal transparency after transplantation and suggest the feasibility of performing DSAEK with HCECs to treat endothelial dysfunction. Journal of Functional Biomaterials 2012-10-17 3 4 Review 10.3390/jfb3040726 726 744 2079-4983 2012-10-17 doi: 10.3390/jfb3040726 Tatsuya Mimura Seiichi Yokoo Satoru Yamagami http://www.mdpi.com/2079-4983/3/4/706 In this study three chemical agents Amino-propyl-triethoxy-silane (APS), sorbitol ended PLA oligomer (SPLA) and Hexamethylene diisocyanate (HDI) were identified to be used as coupling agents to react with the phosphate glass fibre (PGF) reinforcement and the polylactic acid (PLA) polymer matrix of the composite. Composites were prepared with short chopped strand fibres (l = 20 mm, ϕ = 20 µm) in a random arrangement within PLA matrix. Improved, initial composite flexural strength (~20 MPa) was observed for APS treated fibres, which was suggested to be due to enhanced bonding between the fibres and polymer matrix. Both APS and HDI treated fibres were suggested to be covalently linked with the PLA matrix. The hydrophobicity induced by these coupling agents (HDI, APS) helped to resist hydrolysis of the interface and thus retained their mechanical properties for an extended period of time as compared to non-treated control. Approximately 70% of initial strength and 65% of initial modulus was retained by HDI treated fibre composites in contrast to the control, where only ~50% of strength and modulus was retained after 28 days of immersion in PBS at 37 °C. All coupling agent treated and control composites demonstrated good cytocompatibility which was comparable to the tissue culture polystyrene (TCP) control, supporting the use of these materials as coupling agent’s within medical implant devices. Journal of Functional Biomaterials 2012-10-16 3 4 Article 10.3390/jfb3040706 706 725 2079-4983 2012-10-16 doi: 10.3390/jfb3040706 Muhammad Sami Hasan Ifty Ahmed Andrew Parsons Gavin Walker Colin Scotchford http://www.mdpi.com/2079-4983/3/3/688 The osseointegration rate of implants is related to their composition and surface roughness. Implant roughness favors both bone anchoring and biomechanical stability. Osteoconductive calcium phosphate (Ca-P) coatings promote bone healing and apposition, leading to the rapid biological fixation of implants. It has been clearly shown in many publications that Ca-P coating accelerates bone formation around the implant. This review discusses two main routes for the manufacturing of polymer-based osteoconductive scaffolds for tissue engineering, namely the incorporation of bioceramic particles in the scaffold and the coating of a scaffold with a thin layer of apatite through a biomimetic process. Journal of Functional Biomaterials 2012-09-20 3 3 Review 10.3390/jfb3030688 688 705 2079-4983 2012-09-20 doi: 10.3390/jfb3030688 Maria G. Raucci Vincenzo Guarino Luigi Ambrosio http://www.mdpi.com/2079-4983/3/3/642 Corneal structure is highly organized and unified in architecture with structural and functional integration which mediates transparency and vision. Disease and injury are the second most common cause of blindness affecting over 10 million people worldwide. Ninety percent of blindness is permanent due to scarring and vascularization. Scarring caused via fibrotic cellular responses, heals the tissue, but fails to restore transparency. Controlling keratocyte activation and differentiation are key for the inhibition and prevention of fibrosis. Ophthalmic surgery techniques are continually developing to preserve and restore vision but corneal regression and scarring are often detrimental side effects and long term continuous follow up studies are lacking or discouraging. Appropriate corneal models may lead to a reduced need for corneal transplantation as presently there are insufficient numbers or suitable tissue to meet demand. Synthetic optical materials are under development for keratoprothesis although clinical use is limited due to implantation complications and high rejection rates. Tissue engineered corneas offer an alternative which more closely mimic the morphological, physiological and biomechanical properties of native corneas. However, replication of the native collagen fiber organization and retaining the phenotype of stromal cells which prevent scar-like tissue formation remains a challenge. Careful manipulation of culture environments are under investigation to determine a suitable environment that simulates native ECM organization and stimulates keratocyte migration and generation. Journal of Functional Biomaterials 2012-09-18 3 3 Review 10.3390/jfb3030642 642 687 2079-4983 2012-09-18 doi: 10.3390/jfb3030642 Samantha L. Wilson Alicia J. El Haj Ying Yang http://www.mdpi.com/2079-4983/3/3/615 Chitosan is one of the most used polysaccharides in the design of drug delivery strategies for administration of either biomacromolecules or low molecular weight drugs. For these purposes, it is frequently used as matrix forming material in both nano and micron-sized particles. In addition to its interesting physicochemical and biopharmaceutical properties, which include high mucoadhesion and a great capacity to produce drug delivery systems, ensuring the biocompatibility of the drug delivery vehicles is a highly relevant issue. Nevertheless, this subject is not addressed as frequently as desired and even though the application of chitosan carriers has been widely explored, the demonstration of systems biocompatibility is still in its infancy. In this review, addressing the biocompatibility of chitosan carriers with application in drug delivery is discussed and the methods used in vitro and in vivo, exploring the effect of different variables, are described. We further provide a discussion on the pros and cons of used methodologies, as well as on the difficulties arising from the absence of standardization of procedures. Journal of Functional Biomaterials 2012-09-17 3 3 Review 10.3390/jfb3030615 615 641 2079-4983 2012-09-17 doi: 10.3390/jfb3030615 Susana Rodrigues Marita Dionísio Carmen Remuñán López Ana Grenha http://www.mdpi.com/2079-4983/3/3/601 Biopolymers are easily denatured by heating, a change in pH or chemical substances when they are immobilized on a substrate. To prevent denaturation of biopolymers, we developed a method to trap a polynucleotide on a substrate by hydrogen bonding using silica particles with surfaces modified by aminoalkyl chains ([A-AM silane]/SiO2). [A-AM silane]/SiO2 was synthesized by silane coupling reaction of N-2-(aminoethyl)-3-aminopropyltrimethoxysilane (A-AM silane) with SiO2 particles with a diameter of 5 μm at 100 °C for 20 min. The surface chemical structure of [A-AM silane]/SiO2 was characterized by Fourier transform infrared spectroscopy and molecular orbital calculations. The surface of the silica particles was modified with A-AM silane and primary amine groups were formed. [A-AM silane]/SiO2 was trapped with single-stranded nucleic acids [(Poly-X; X = A (adenine), G (guanine) and C (cytosine)] in PBS solution at 37 °C for 1 h. The single-stranded nucleic acids were trapped on the surface of the [A-AM silane]/SiO2 by hydrogen bonding to form conjugated materials. The resulting complexes were further conjugated by derivatives of acridine orange (AO) as fluorescent labels under the same conditions to form [AO:Poly-X:A-AM silane]/SiO2 complexes. Changes in the fluorescence intensity of these complexes originating from interactions between the single-stranded nucleic acid and aromatic compounds were also evaluated. The change in intensity displayed the order [AO: Poly-G: A-AM silane]/SiO2 > [AO:Poly-A:A-AM silane]/SiO2 >> [AO:Poly-C:A-AM silane]/SiO2. This suggests that the single-stranded nucleic acids conjugated with aminoalkyl chains on the surfaces of SiO2 particles and the change in fluorescence intensity reflected the molecular interaction between AO and the nucleic-acid base in a polynucleotide. Journal of Functional Biomaterials 2012-09-05 3 3 Article 10.3390/jfb3030601 601 614 2079-4983 2012-09-05 doi: 10.3390/jfb3030601 T. Isoda R. Maeda http://www.mdpi.com/2079-4983/3/3/588 Unique functional materials provide a platform as scaffolds for cell/tissue regeneration. Investigation of cell-materials’ chemical and biological interactions will enable the application of more functional materials in the area of bioengineering, which provides a pathway to the novel treatment for patients who suffer from tissue/organ damage and face the limitation of donation sources. Many studies have been made into tissue/organ regeneration. Development of new substrate materials as platforms for cell/tissue regeneration is a key research area. Studies discussed in this paper focus on the investigation of novel ultrananocrystalline diamond (UNCD) films as substrate/scaffold materials for developmental biology. Specially designed quartz dishes have been coated with different types of UNCD films and cells were subsequently seeded on those films. Results showed the cells’ growth on UNCD-coated culture dishes are similar to cell culture dishes with little retardation, indicating that UNCD films have no or little inhibition on cell proliferation and are potentially appealing as substrate/scaffold materials. The mechanisms of cell adhesion on UNCD surfaces are proposed based on the experimental results. The comparisons of cell cultures on diamond-powder-seeded culture dishes and on UNCD-coated dishes with matrix-assisted laser desorption/ionization—time-of-flight mass spectroscopy (MALDI-TOF MS) and X-ray photoelectron spectroscopy (XPS) analyses provided valuable data to support the mechanisms proposed to explain the adhesion and proliferation of cells on the surface of the UNCD platform. Journal of Functional Biomaterials 2012-08-16 3 3 Article 10.3390/jfb3030588 588 600 2079-4983 2012-08-16 doi: 10.3390/jfb3030588 Bing Shi Qiaoling Jin Liaohai Chen Amina S. Woods Albert J. Schultz Orlando Auciello http://www.mdpi.com/2079-4983/3/3/569 All vascular implants, including stents, heart valves and graft materials exhibit suboptimal biocompatibility that significantly reduces their clinical efficacy. A range of biomolecules in the subendothelial space have been shown to play critical roles in local regulation of thrombosis, endothelial growth and smooth muscle cell proliferation, making these attractive candidates for modulation of vascular device biointegration. However, classically used biomaterial coatings, such as fibronectin and laminin, modulate only one of these components; enhancing endothelial cell attachment, but also activating platelets and triggering thrombosis. This review examines a subset of extracellular matrix molecules that have demonstrated multi-faceted vascular compatibility and accordingly are promising candidates to improve the biointegration of vascular biomaterials. Journal of Functional Biomaterials 2012-08-14 3 3 Review 10.3390/jfb3030569 569 587 2079-4983 2012-08-14 doi: 10.3390/jfb3030569 Steven G. Wise Anna Waterhouse Praveesuda Michael Martin K.C. Ng http://www.mdpi.com/2079-4983/3/3/556 Osteoarticular pathologies very often require an implementation therapy to favor regeneration processes of bone, cartilage and/or tendons. Clinical approaches performed on osteoarticular complications in dogs constitute an ideal model for human clinical translational applications. The adipose-derived mesenchymal stem cells (ASCs) have already been used to accelerate and facilitate the regenerative process. ASCs can be maintained in vitro and they can be differentiated to osteocytes or chondrocytes offering a good tool for cell replacement therapies in human and veterinary medicine. Although ACSs can be easily obtained from adipose tissue, the amplification process is usually performed by a time consuming process of successive passages. In this work, we use canine ASCs obtained by using a Bioreactor device under GMP cell culture conditions that produces a minimum of 30 million cells within 2 weeks. This method provides a rapid and aseptic method for production of sufficient stem cells with potential further use in clinical applications. We show that plasma rich in growth factors (PRGF) treatment positively contributes to viability and proliferation of canine ASCs into caprolactone 2-(methacryloyloxy) ethyl ester (CLMA) scaffolds. This biomaterial does not need additional modifications for cASCs attachment and proliferation. Here we propose a framework based on a combination of approaches that may contribute to increase the therapeutical capability of stem cells by the use of PRGF and compatible biomaterials for bone and connective tissue regeneration. Journal of Functional Biomaterials 2012-08-09 3 3 Article 10.3390/jfb3030556 556 568 2079-4983 2012-08-09 doi: 10.3390/jfb3030556 Francisco Javier Rodríguez-Jiménez Teresa Valdes-Sánchez José M. Carrillo Mónica Rubio Manuel Monleon-Prades Dunia Mercedes García-Cruz Montserrat García Ramón Cugat Victoria Moreno-Manzano http://www.mdpi.com/2079-4983/3/3/544 Osmotic loading of articular cartilage has been used to study cell-tissue interactions and mechanisms in chondrocyte volume regulation in situ. Since cell volume changes are likely to affect cell’s mechanotransduction, it is important to understand how environmental factors, such as composition of the immersion medium and temperature affect cell volume changes in situ in osmotically challenged articular cartilage. In this study, chondrocytes were imaged in situ with a confocal laser scanning microscope (CLSM) through cartilage surface before and 3 min and 120 min after a hypo-osmotic challenge. Samples were measured either in phosphate buffered saline (PBS, without glucose and Ca2+) or in Dulbecco’s modified Eagle’s medium (DMEM, with glucose and Ca2+), and at 21 °C or at 37 °C. In all groups, cell volumes increased shortly after the hypotonic challenge and then recovered back to the original volumes. At both observation time points, cell volume changes as a result of the osmotic challenge were similar in PBS and DMEM in both temperatures. Our results indicate that the initial chondrocyte swelling and volume recovery as a result of the hypo-osmotic challenge of cartilage are not dependent on commonly used immersion media or temperature. Journal of Functional Biomaterials 2012-08-09 3 3 Article 10.3390/jfb3030544 544 555 2079-4983 2012-08-09 doi: 10.3390/jfb3030544 Mari Huttu Siru Turunen Viktoria Sokolinski Virpi Tiitu Mikko Lammi Rami K. Korhonen http://www.mdpi.com/2079-4983/3/3/528 This review describes different strategies of surface elaboration for a better control of biomolecule adsorption. After a brief description of the fundamental interactions between surfaces and biomolecules, various routes of surface elaboration are presented dealing with the attachment of functional groups mostly thanks to plasma techniques, with the grafting to and from methods, and with the adsorption of surfactants. The grafting of stimuli-responsive polymers is also pointed out. Then, the discussion is focused on the protein adsorption phenomena showing how their interactions with solid surfaces are complex. The adsorption mechanism is proved to be dependent on the solid surface physicochemical properties as well as on the surface and conformation properties of the proteins. Different behaviors are also reported for complex multiple protein solutions. Journal of Functional Biomaterials 2012-08-07 3 3 Review 10.3390/jfb3030528 528 543 2079-4983 2012-08-07 doi: 10.3390/jfb3030528 Fabienne Poncin-Epaillard Tjasa Vrlinic Dominique Debarnot Miran Mozetic Arnaud Coudreuse Gilbert Legeay Benaïssa El Moualij Willy Zorzi http://www.mdpi.com/2079-4983/3/3/514 The encapsulation of biomolecules in solid materials that retain the native properties of the molecule is a desired feature for the development of biosensors and biocatalysts. In the current study, protein entrapment in silica-based materials is explored using the sol-gel technique. This work surveys the effects of silica confinement on the structure of several model polypeptides, including apomyoglobin, copper-zinc superoxide dismutase, polyglutamine, polylysine, and type I antifreeze protein. Changes in the secondary structure of each protein following encapsulation are monitored by circular dichroism spectroscopy. In many cases, silica confinement reduces the fraction of properly-folded protein relative to solution, but addition of a secondary solute or modification of the silica surface leads to an increase in structure. Refinement of the glass surface by addition of a monosubstituted alkoxysilane during sol-gel processing is shown to be a valuable tool for testing the effects of surface chemistry on protein structure. Because silica entrapment prevents protein aggregation by isolating individual protein molecules in the pores of the glass material, one may monitor aggregation-prone polypeptides under solvent conditions that are prohibited in solution, as demonstrated with polyglutamine and a disease-related variant of superoxide dismutase. Journal of Functional Biomaterials 2012-08-02 3 3 Article 10.3390/jfb3030514 514 527 2079-4983 2012-08-02 doi: 10.3390/jfb3030514 Phillip J. Calabretta Mitchell C. Chancellor Carlos Torres Gary R. Abel Clayton Niehaus Nathan J. Birtwhistle Nada M. Khouderchah Genet H. Zemede Daryl K. Eggers http://www.mdpi.com/2079-4983/3/3/497 Hydrogels, electrospun fiber mats (EFMs), and their composites have been extensively studied for tissue engineering because of their physical and chemical similarity to native biological systems. However, while chemically similar, hydrogels and electrospun fiber mats display very different topographical features. Here, we examine the influence of surface topography and composition of hydrogels, EFMs, and hydrogel-EFM composites on cell behavior. Materials studied were composed of synthetic poly(ethylene glycol) (PEG) and poly(ethylene glycol)-poly(ε-caprolactone) (PEGPCL) hydrogels and electrospun poly(caprolactone) (PCL) and core/shell PCL/PEGPCL constituent materials. The number of adherent cells and cell circularity were most strongly influenced by the fibrous nature of materials (e.g., topography), whereas cell spreading was more strongly influenced by material composition (e.g., chemistry). These results suggest that cell attachment and proliferation to hydrogel-EFM composites can be tuned by varying these properties to provide important insights for the future design of such composite materials. Journal of Functional Biomaterials 2012-07-27 3 3 Article 10.3390/jfb3030497 497 513 2079-4983 2012-07-27 doi: 10.3390/jfb3030497 Ning Han Jed K. Johnson Patrick A. Bradley Kunal S. Parikh John J. Lannutti Jessica O. Winter http://www.mdpi.com/2079-4983/3/3/480 Heart valve disease (HVD) is a globally increasing problem and accounts for thousands of deaths yearly. Currently end-stage HVD can only be treated by total valve replacement, however with major drawbacks. To overcome the limitations of conventional substitutes, a new clinical approach based on cell colonization of artificially manufactured heart valves has been developed. Even though this attempt seems promising, a confluent and stable cell layer has not yet been achieved due to the high stresses present in this area of the human heart. This study describes a bioreactor with a new approach to cell conditioning of tissue engineered heart valves. The bioreactor provides a low pulsatile flow that grants the correct opening and closing of the valve without high shear stresses. The flow rate can be regulated allowing a steady and sensitive conditioning process. Furthermore, the correct functioning of the valve can be monitored by endoscope surveillance in real-time. The tubeless and modular design allows an accurate, simple and faultless assembly of the reactor in a laminar flow chamber. It can be concluded that the bioreactor provides a strong tool for dynamic pre-conditioning and monitoring of colonized heart valve prostheses physiologically exposed to shear stress. Journal of Functional Biomaterials 2012-07-19 3 3 Article 10.3390/jfb3030480 480 496 2079-4983 2012-07-19 doi: 10.3390/jfb3030480 Fabian König Trixi Hollweck Stefan Pfeifer Bruno Reichart Erich Wintermantel Christian Hagl Bassil Akra http://www.mdpi.com/2079-4983/3/3/464 The deformation behavior of a pH-sensitive hydrogel micro-fluidic valve system is investigated using inhomogeneous gel deformation theory, in which the fluid-structure interaction (FSI) of the gel solid and fluid flow in the pipe is considered. We use a finite element method with a well adopted hydrogel constitutive equation, which is coded in commercial software, ABAQUS, to simulate the hydrogel valve swelling deformation, while FLUENT is adopted to model the fluid flow in the pipe of the hydrogel valve system. The study demonstrates that FSI significantly affects the gel swelling deformed shapes, fluid flow pressure and velocity patterns. FSI has to be considered in the study on fluid flow regulated by hydrogel microfluidic valve. The study provides a more accurate and adoptable model for future design of new pH-sensitive hydrogel valves, and also gives a useful guideline for further studies on hydrogel fluidic applications. Journal of Functional Biomaterials 2012-07-10 3 3 Article 10.3390/jfb3030464 464 479 2079-4983 2012-07-10 doi: 10.3390/jfb3030464 Yan Zhang Zishun Liu Somsak Swaddiwudhipong Haiyan Miao Zhiwei Ding Zhengzhi Yang http://www.mdpi.com/2079-4983/3/2/432 Strategies for bone tissue engineering and regeneration rely on bioactive scaffolds to mimic the natural extracellular matrix and act as templates onto which cells attach, multiply, migrate and function. Of particular interest are nanocomposites and organic-inorganic (O/I) hybrid biomaterials based on selective combinations of biodegradable polymers and bioactive inorganic materials. In this paper, we review the current state of bioactive and biodegradable nanocomposite and O/I hybrid biomaterials and their applications in bone regeneration. We focus specifically on nanocomposites based on nano-sized hydroxyapatite (HA) and bioactive glass (BG) fillers in combination with biodegradable polyesters and their hybrid counterparts. Topics include 3D scaffold design, materials that are widely used in bone regeneration, and recent trends in next generation biomaterials. We conclude with a perspective on the future application of nanocomposites and O/I hybrid biomaterials for regeneration of bone. Journal of Functional Biomaterials 2012-06-20 3 2 Review 10.3390/jfb3020432 432 463 2079-4983 2012-06-20 doi: 10.3390/jfb3020432 Bedilu A. Allo Daniel O. Costa S. Jeffrey Dixon Kibret Mequanint Amin S. Rizkalla http://www.mdpi.com/2079-4983/3/2/418 In this study we present a scheme for quantitative determination of biofilm viability offering significant improvement over existing methods with metabolic assays. Existing metabolic assays for quantifying viable bacteria in biofilms usually utilize calibration curves derived from planktonic bacteria, which can introduce large errors due to significant differences in the metabolic and/or growth rates of biofilm bacteria in the assay media compared to their planktonic counterparts. In the presented method we derive the specific growth rate of Streptococcus mutans bacteria biofilm from a series of metabolic assays using the pH indicator phenol red, and show that this information could be used to more accurately quantify the relative number of viable bacteria in a biofilm. We found that the specific growth rate of S. mutans in biofilm mode of growth was 0.70 h−1, compared to 1.09 h−1 in planktonic growth. This method should be applicable to other bacteria types, as well as other metabolic assays, and, for example, to quantify the effect of antibacterial treatments or the performance of bactericidal implant surfaces. Journal of Functional Biomaterials 2012-06-01 3 2 Article 10.3390/jfb3020418 418 431 2079-4983 2012-06-01 doi: 10.3390/jfb3020418 Ken Welch Yanling Cai Maria Strømme http://www.mdpi.com/2079-4983/3/2/398 With a range of desirable mechanical and optical properties, single wall carbon nanotubes (SWCNTs) are a promising material for nanobiotechnologies. SWCNTs also have potential as biomaterials for modulation of cellular structures. Previously, we showed that highly purified, dispersed SWCNTs grossly alter F-actin inside cells. F-actin plays critical roles in the maintenance of cell structure, force transduction, transport and cytokinesis. Thus, quantification of SWCNT-actin interactions ranging from molecular, sub-cellular and cellular levels with both structure and function is critical for developing SWCNT-based biotechnologies. Further, this interaction can be exploited, using SWCNTs as a unique actin-altering material. Here, we utilized molecular dynamics simulations to explore the interactions of SWCNTs with actin filaments. Fluorescence lifetime imaging microscopy confirmed that SWCNTs were located within ~5 nm of F-actin in cells but did not interact with G-actin. SWCNTs did not alter myosin II sub-cellular localization, and SWCNT treatment in cells led to significantly shorter actin filaments. Functionally, cells with internalized SWCNTs had greatly reduced cell traction force. Combined, these results demonstrate direct, specific SWCNT alteration of F-actin structures which can be exploited for SWCNT-based biotechnologies and utilized as a new method to probe fundamental actin-related cellular processes and biophysics. Journal of Functional Biomaterials 2012-05-23 3 2 Article 10.3390/jfb3020398 398 417 2079-4983 2012-05-23 doi: 10.3390/jfb3020398 Brian D. Holt Hengameh Shams Travis A. Horst Saurav Basu Andrew D. Rape Yu-Li Wang Gustavo K. Rohde Mohammad R. K. Mofrad Mohammad F. Islam Kris Noel Dahl http://www.mdpi.com/2079-4983/3/2/382 Implants formed of metals, bioceramics, or polymers may provide an alternative to autografts for treating large bone defects. However, limitations to each material motivate the examination of composites to capitalize on the beneficial aspects of individual components and to address the need for conferring bioactive behavior to the polymer matrix. We hypothesized that the inclusion of different bioceramics in a ceramic-polymer composite would alter the physical properties of the implant and the cellular osteogenic response. To test this, composite scaffolds formed from poly(lactide-co-glycolide) (PLG) and either hydroxyapatite (HA), β-tricalcium phosphate (TCP), or bioactive glass (Bioglass 45S®, BG) were fabricated, and the physical properties of each scaffold were examined. We quantified cell proliferation by DNA content, osteogenic response of human osteoblasts (NHOsts) to composite scaffolds by alkaline phosphatase (ALP) activity, and changes in gene expression by qPCR. Compared to BG-PLG scaffolds, HA-PLG and TCP-PLG composite scaffolds possessed greater compressive moduli. NHOsts on BG-PLG substrates exhibited higher ALP activity than those on control, HA-, or TCP-PLG scaffolds after 21 days, and cells on composites exhibited a 3-fold increase in ALP activity between 7 and 21 days versus a minimal increase on control scaffolds. Compared to cells on PLG controls, RUNX2 expression in NHOsts on composite scaffolds was lower at both 7 and 21 days, while expression of genes encoding for bone matrix proteins (COL1A1 and SPARC) was higher on BG-PLG scaffolds at both time points. These data demonstrate the importance of selecting a ceramic when fabricating composites applied for bone healing. Journal of Functional Biomaterials 2012-05-23 3 2 Article 10.3390/jfb3020382 382 397 2079-4983 2012-05-23 doi: 10.3390/jfb3020382 Diana G. Morales-Hernandez Damian C. Genetos David M. Working Kaitlin C. Murphy J. Kent Leach http://www.mdpi.com/2079-4983/3/2/372 Protein adsorption is known to direct biological response to biomaterials and is important in determining cellular response in tissue scaffolds. In this study we investigated the effect of the duration of protein adsorption to 3D polymer scaffolds on cell attachment and proliferation. 3D macro-porous polymer scaffolds were pre-aged in serum-containing culture medium for 5 min, 1 d or 7 d prior to seeding osteoblasts. The total amount of protein adsorbed was found to increase with pre-ageing time. Cell attachment and proliferation were measured 1 d and 14 d, respectively, after cell seeding. Osteoblast proliferation, but not attachment, increased with scaffold pre-ageing time and amount of adsorbed serum protein. These results demonstrate that the amount of time that scaffolds are exposed to serum-containing medium can affect cell proliferation and suggest that these effects are mediated by differences in the amount of protein adsorption. Journal of Functional Biomaterials 2012-05-22 3 2 Communication 10.3390/jfb3020372 372 381 2079-4983 2012-05-22 doi: 10.3390/jfb3020372 Kaushik Chatterjee Stevephen Hung Girish Kumar Carl G. Simon http://www.mdpi.com/2079-4983/3/2/361 The synthesis of a novel functional biomaterial for wound healing treatment was carried out by adopting a free-radical grafting procedure in aqueous media. With this aim, ciprofloxacin (CFX) was covalently incorporated into collagen (T1C) chains employing an ascorbic acid/hydrogen peroxide redox pair as biocompatible initiator system. The covalent insertion of CFX in the polymeric chains was confirmed by FT-IR and UV analyses, while an antibacterial assay demonstrated the activity of the synthesized conjugate against Staphylococcus aureus and Escherichia coli, microorganisms that commonly infect wounds. A catechin blended conjugate was also tested in order to evaluate the ability to influence fibroblast cell growth. The observed antibacterial activity and stimulation of fibroblast growth support the applicability of CFX-T1C conjugate in wound treatment encouraging the healing process. Journal of Functional Biomaterials 2012-05-15 3 2 Article 10.3390/jfb3020361 361 371 2079-4983 2012-05-15 doi: 10.3390/jfb3020361 Francesco Puoci Cristiana Piangiolino Francesco Givigliano Ortensia Ilaria Parisi Roberta Cassano Sonia Trombino Manuela Curcio Francesca Iemma Giuseppe Cirillo Umile Gianfranco Spizzirri Donatella Restuccia Rita Muzzalupo Nevio Picci http://www.mdpi.com/2079-4983/3/2/349 In this study, a porous oxide layer was formed on the surface of 316L stainless steel (SS) by combining Ti magnetron sputtering and plasma electrolytic oxidation (PEO) with the aim to produce a polymer-free drug carrier for drug eluting stent (DES) applications. The oxidation was performed galvanostatically in Na3PO4 electrolyte. The surface porosity, average pore size and roughness varied with PEO treatment duration, and under optimum conditions, the surface showed a porosity of 7.43%, an average pore size of 0.44 µm and a roughness (Ra) of 0.34 µm. The EDS analyses revealed that the porous layer consisted of Ti, O and P. The cross-sectional morphology evidenced a double-layer structure, with a porous titania surface and an un-oxidized dense Ti film towards the interface with 316L SS. After the PEO treatment, wettability and surface free energy increased significantly. The results of the present study confirm the feasibility of forming a porous TiO2 layer on stainless steel by combining sputtering technology and PEO. Further, the resultant porous oxide layer has the potential to be used as a drug carrier for DES, thus avoiding the complications associated with the polymer based carriers. Journal of Functional Biomaterials 2012-05-11 3 2 Article 10.3390/jfb3020349 349 360 2079-4983 2012-05-11 doi: 10.3390/jfb3020349 Zhiguang Huan Lidy E. Fratila-Apachitei Iulian Apachitei Jurek Duszczyk http://www.mdpi.com/2079-4983/3/2/327 This work investigated the ability of electropolished Ti surface to induce Hydroxyapatite (HA) nucleation and growth in vitro via a biomimetic method in Simulated Body Fluid (SBF). The HA induction ability of Ti surface upon electropolishing was compared to that of Ti substrates modified with common chemical methods including alkali, acidic and hydrogen peroxide treatments. Our results revealed the excellent ability of electropolished Ti surfaces in inducing the formation of bone-like HA at the Ti/SBF interface. The chemical composition, crystallinity and thickness of the HA coating obtained on the electropolished Ti surface was found to be comparable to that achieved on the surface of alkali treated Ti substrate, one of the most effective and popular chemical treatments. The surface characteristics of electropolished Ti contributing to HA growth were discussed thoroughly. Journal of Functional Biomaterials 2012-04-25 3 2 Article 10.3390/jfb3020327 327 348 2079-4983 2012-04-25 doi: 10.3390/jfb3020327 Elnaz Ajami Kondo-Francois Aguey-Zinsou http://www.mdpi.com/2079-4983/3/2/313 VEGF (vascular endothelial growth factor) promotes vascularization and remodeling of bone substitutes. The aim of this study was to examine the effect of distinct resorbable ceramic carriers on bone forming capacities of VEGF transfected bone marrow stromal cells (BMSC). A critical size defect of the radius in rabbits was filled either by a low surface scaffold called beta-TCP (tricalciumphsphate) or the high surface scaffold CDHA (calcium deficient hydroxy-apatite) loaded with autologous BMSC, which were either transfected with a control plasmid or a plasmid coding for phVEGF165. They were compared to unloaded scaffolds. Thus, six treatment groups (n = 6 in each group) were followed by X-ray over 16 weeks. After probe retrieval, the volume of new bone was measured by micro-CT scans and vascularization was assessed in histology. While only minor bone formation was found in both carriers when implanted alone, BMSC led to increased osteogenesis in both carriers. VEGF promoted vascularization of the scaffolds significantly in contrast to BMSC alone. Bone formation was increased in the beta-TCP group, whereas it was inhibited in the CDHA group that showed faster scaffold degradation. The results indicate that the interaction of VEGF transfected BMSC with resorbable ceramic carrier influences the ability to promote bone healing. Journal of Functional Biomaterials 2012-04-19 3 2 Article 10.3390/jfb3020313 313 326 2079-4983 2012-04-19 doi: 10.3390/jfb3020313 Florian Geiger Mirjam Beverungen Helga Lorenz Julia Wieland Michael Fehr Philip Kasten http://www.mdpi.com/2079-4983/3/2/298 The main objective of this paper was to illustrate the enhancement of the sensitivity of ELISA titration for neurodegenerative proteins by reducing nonspecific adsorptions that could lead to false positives. This goal was obtained thanks to the association of plasma and wet chemistries applied to the inner surface of the titration well. The polypropylene surface was plasma-activated and then, dip-coated with different amphiphilic molecules. These molecules have more or less long hydrocarbon chains and may be charged. The modified surfaces were characterized in terms of hydrophilic—phobic character, surface chemical groups and topography. Finally, the coated wells were tested during the ELISA titration of the specific antibody capture of the α-synuclein protein. The highest sensitivity is obtained with polar (Θ = 35°), negatively charged and smooth inner surface. Journal of Functional Biomaterials 2012-04-18 3 2 Article 10.3390/jfb3020298 298 312 2079-4983 2012-04-18 doi: 10.3390/jfb3020298 Caroline Mille Dominique Debarnot Willy Zorzi Benaïssa El Moualij Arnaud Coudreuse Gilbert Legeay Isabelle Quadrio Armand Perret-Liaudet Fabienne Poncin-Epaillard http://www.mdpi.com/2079-4983/3/2/283 Biocompatibility improvements for blood contacting materials are of increasing interest for implanted devices and interventional tools. The current study focuses on inorganic (titanium, titanium nitride, titanium oxide) as well as diamond-like carbon (DLC) coating materials on polymer surfaces (thermoplastic polyurethane), deposited by magnetron sputtering und pulsed laser deposition at room temperature. DLC was used pure (a-C:H) as well as doped with silicon, titanium, and nitrogen + titanium (a-C:H:Si, a-C:H:Ti, a-C:H:N:Ti). In-vitro testing of the hemocompatibility requires mandatory dynamic test conditions to simulate in-vivo conditions, e.g., realized by a cone-and-plate analyzer. In such tests, titanium- and nitrogen-doped DLC and titanium nitride were found to be optimally anti-thrombotic and better than state-of-the-art polyurethane polymers. This is mainly due to the low tendency to platelet microparticle formation, a high content of remaining platelets in the whole blood after testing and low concentration of platelet activation and aggregation markers. Comparing this result to shear-flow induced cell motility tests with e.g., Dictostelium discoideum cell model organism reveals similar tendencies for the investigated materials. Journal of Functional Biomaterials 2012-04-17 3 2 Article 10.3390/jfb3020283 283 297 2079-4983 2012-04-17 doi: 10.3390/jfb3020283 Juergen M. Lackner Wolfgang Waldhauser Paul Hartmann Franz Bruckert Marianne Weidenhaupt Roman Major Marek Sanak Martin Wiesinger Daniel Heim http://www.mdpi.com/2079-4983/3/2/269 In this work, molecularly imprinted nanospheres for controlled/sustained release of quercetin were synthesized employing methacrylic acid and ethylene glycoldymethacrylate as functional monomer and crosslinking agent, respectively. One pot precipitation polymerization was chosen as polymerization technique to obtain nanosized materials with spherical shape. Morphological and hydrophilic properties by scanning electron microscopy and water content measurements were determined, and recognition and selectivity properties of the imprinted materials were tested using the template quercetin and its structural analogue, the flavonoid catechin. Finally, the applicability of the obtained materials as drug delivery devices was evaluated by performing in vitro release studies in plasma simulating fluids and cytotoxicity testson HeLa cells. Journal of Functional Biomaterials 2012-03-29 3 2 Article 10.3390/jfb3020269 269 282 2079-4983 2012-03-29 doi: 10.3390/jfb3020269 Manuela Curcio Giuseppe Cirillo Ortensia Ilaria Parisi Francesca Iemma Nevio Picci Francesco Puoci http://www.mdpi.com/2079-4983/3/2/257 Synthesis of a homologous series of photo-polymerizable α,w-polytetrahydrofuranether-diacrylate (PTHF-DA) resins is described with characterization by NMR, GPC, DSC, soaking and rheometrical measurements. The curing speeds of the resins are determined under UV light exposure. Young’s modulus and tensile strength of fully cured resins show flexible to soft material attributes dependent on the molar mass of the used linear PTHF-diacrylates. Structuring the materials by stereo lithography (SL) and multiphoton polymerization (MPP) leads to tubes and bifurcated tube systems with a diameter smaller than 2 mm aimed at small to smallest supplying systems with capillary dimensions. WST-1 biocompatibility tests ofm polymer extracts show nontoxic characteristics of the adapted polymers after a washing process. Some polymers show shape memory effect (SME). Journal of Functional Biomaterials 2012-03-29 3 2 Article 10.3390/jfb3020257 257 268 2079-4983 2012-03-29 doi: 10.3390/jfb3020257 Wolfdietrich Meyer Sascha Engelhardt Esther Novosel Burkhard Elling Michael Wegener Hartmut Krüger http://www.mdpi.com/2079-4983/3/2/239 Responsive polymers attached to the inside of nano/micro-pores have attracted great interest owing to the prospect of designing flow-control devices and signal responsive delivery systems. An intriguing possibility involves functionalizing nanoporous materials with smart polymers to modulate biomolecular transport in response to pH, temperature, ionic concentration, light or electric field. These efforts open up avenues to develop smart medical devices that respond to specific physiological conditions. In this work, an overview of nanoporous materials functionalized with responsive polymers is given. Various examples of pH, temperature and solvent responsive polymers are discussed. A theoretical treatment that accounts for polymer conformational change in response to a stimulus and the associated flow-control effect is presented. Journal of Functional Biomaterials 2012-03-26 3 2 Review 10.3390/jfb3020239 239 256 2079-4983 2012-03-26 doi: 10.3390/jfb3020239 Shashishekar P. Adiga Donald W. Brenner http://www.mdpi.com/2079-4983/3/2/225 Extracellular matrix components such as hyaluronan (HA) and chondroitin sulfate (CS) were combined with a synthetic matrix of p(HEMA-co-METAC) (poly(2-hydroxyethylmethacrylate-co-2-methacryloxyethyltrimethylammonium)) at 1% and 2% w/w concentration following a previously developed procedure. The resulting semi-interpenetrating hydrogels were able to extensively swell in water incrementing their dry weight up to 13 fold depending on the glycosamminoglycan content and nature. When swollen in physiological solution, materials water uptake significantly decreased, and the differences in swelling capability became negligible. In physiological conditions, HA was released from the materials up to 38%w/w while CS was found almost fully retained. Materials were not cytotoxic and a biological evaluation, performed using 3T3 fibroblasts and an original time lapse videomicroscopy station, revealed their appropriateness for cell adhesion and proliferation. Slight differences observed in the morphology of adherent cells suggested a better performance of CS containing hydrogels. Journal of Functional Biomaterials 2012-03-23 3 2 Article 10.3390/jfb3020225 225 238 2079-4983 2012-03-23 doi: 10.3390/jfb3020225 Annalisa La Gatta Chiara Schiraldi Antonella D’Agostino Agata Papa Mario De Rosa http://www.mdpi.com/2079-4983/3/1/209 Mechanotransduction refers to the mechanisms by which cells sense and respond to local loads and forces. The process of mechanotransduction plays an important role both in maintaining tissue viability and in remodeling to repair damage; moreover, it may be involved in the initiation and progression of diseases such as osteoarthritis and osteoporosis. An understanding of the mechanisms by which cells respond to surrounding tissue matrices or artificial biomaterials is crucial in regenerative medicine and in influencing cellular differentiation. Recent studies have shown that some cells may be most sensitive to low-amplitude, high-frequency (i.e., 1–100 Hz) mechanical stimulation. Advances in finite-element modeling have made it possible to simulate high-frequency mechanical loading of cells. We have developed a viscoelastic finite-element model of an osteoblastic cell (including cytoskeletal actin stress fibers), attached to an elastomeric membrane undergoing cyclic isotropic radial strain with a peak value of 1,000 µstrain. The results indicate that cells experience significant stress and strain amplification when undergoing high-frequency strain, with peak values of cytoplasmic strain five times higher at 45 Hz than at 1 Hz, and peak Von Mises stress in the nucleus increased by a factor of two. Focal stress and strain amplification in cells undergoing high-frequency mechanical stimulation may play an important role in mechanotransduction. Journal of Functional Biomaterials 2012-03-22 3 1 Article 10.3390/jfb3010209 209 224 2079-4983 2012-03-22 doi: 10.3390/jfb3010209 Jaques S. Milner Matthew W. Grol Kim L. Beaucage S. Jeffrey Dixon David W. Holdsworth http://www.mdpi.com/2079-4983/3/1/199 In the injured spinal cord, chondroitin sulfate proteoglycans (CSPGs) are the principal responsible of axon growth inhibition and they contribute to regenerative failure, promoting glial scar formation. Chondroitinase ABC (chABC) is known for being able to digest proteoglycans, thus degrading glial scar and favoring axonal regrowth. However, its classic administration is invasive, infection-prone and clinically problematic. An agarose-carbomer (AC1) hydrogel, already used in SCI repair strategies, was here investigated as a delivery system capable of an effective chABC administration: the material ability to include chABC within its pores and the possibility to be injected into the target tissue were firstly proved. Subsequently, release kinetic and the maintenance of enzymatic activity were positively assessed: AC1 hydrogel was thus confirmed to be a feasible tool for chABC delivery and a promising device for spinal cord injury topic repair strategies. Journal of Functional Biomaterials 2012-03-19 3 1 Article 10.3390/jfb3010199 199 208 2079-4983 2012-03-19 doi: 10.3390/jfb3010199 Filippo Rossi Pietro Veglianese Marco Santoro Simonetta Papa Cristina Rogora Valentina Dell’Oro Gianluigi Forloni Maurizio Masi Giuseppe Perale http://www.mdpi.com/2079-4983/3/1/183 Following laser vision correction, corneal keratocytes must repopulate areas of cell loss by migrating through the intact corneal stroma, and this can impact corneal shape and transparency. In this study, we evaluate 3D culture models for simulating this process in vitro. Buttons (8 mm diameter) were first punched out of keratocyte populated compressed collagen matrices, exposed to a 3 mm diameter freeze injury, and cultured in serum-free media (basal media) or media supplemented with 10% FBS, TGFb1 or PDGF BB. Following freeze injury, a region of cell death was observed in the center of the constructs. Although cells readily migrated on top of the matrices to cover the wound area, a limited amount of cell migration was observed within the constructs. We next developed a novel “sandwich” model, which better mimics the native lamellar architecture of the cornea. Using this model, significant migration was observed under all conditions studied. In both models, cells in TGFb and 10% FBS developed stress fibers; whereas cells in PDGF were more dendritic. PDGF stimulated the most inter-lamellar migration in the sandwich construct. Overall, these models provide insights into the complex interplay between growth factors, cell mechanical phenotypes and the structural properties of the ECM. Journal of Functional Biomaterials 2012-03-19 3 1 Article 10.3390/jfb3010183 183 198 2079-4983 2012-03-19 doi: 10.3390/jfb3010183 Walter Matthew Petroll Neema Lakshman Lisha Ma http://www.mdpi.com/2079-4983/3/1/173 Current methods for screening cell-material interactions typically utilize a two-dimensional (2D) culture format where cells are cultured on flat surfaces. However, there is a need for combinatorial and high-throughput screening methods to systematically screen cell-biomaterial interactions in three-dimensional (3D) tissue scaffolds for tissue engineering. Previously, we developed a two-syringe pump approach for making 3D scaffold gradients for use in combinatorial screening of salt-leached scaffolds. Herein, we demonstrate that the two-syringe pump approach can also be used to create scaffold gradients using a gas-foaming approach. Macroporous foams prepared by a gas-foaming technique are commonly used for fabrication of tissue engineering scaffolds due to their high interconnectivity and good mechanical properties. Gas-foamed scaffold gradient libraries were fabricated from two biodegradable tyrosine-derived polycarbonates: poly(desaminotyrosyl-tyrosine ethyl ester carbonate) (pDTEc) and poly(desaminotyrosyl-tyrosine octyl ester carbonate) (pDTOc). The composition of the libraries was assessed with Fourier transform infrared spectroscopy (FTIR) and showed that pDTEc/pDTOc gas-foamed scaffold gradients could be repeatably fabricated. Scanning electron microscopy showed that scaffold morphology was similar between the pDTEc-rich ends and the pDTOc-rich ends of the gradient. These results introduce a method for fabricating gas-foamed polymer scaffold gradients that can be used for combinatorial screening of cell-material interactions in 3D. Journal of Functional Biomaterials 2012-03-07 3 1 Communication 10.3390/jfb3010173 173 182 2079-4983 2012-03-07 doi: 10.3390/jfb3010173 Kaushik Chatterjee Alison M. Kraigsley Durgadas Bolikal Joachim Kohn Carl G. Simon http://www.mdpi.com/2079-4983/3/1/163 To develop a novel ablation therapy for human solid cancer, the heating properties of a ferromagnetic carbon steel rod and a prototype Ti-coated needle using this carbon steel rod, were investigated in several high-frequency outputs at 300 kHz. In the former, the heating property was drastically different among the three inclination angles (θ = 0°, 45° and 90°) relative to the magnetic flux direction as a result of the shape magnetic anisotropy. However, the effect of the inclination angles was completely eliminated in the latter. It is considered that the complete non-oriented heating property relative to the magnetic flux direction allows the precise control of the ablation temperature during minimally invasive thermotherapy without a lead-wire connected to a fiber-optic thermometer. This newly designed Ti-coated device will be suitable for clinical use combined with its superior biocompatibility for ablation treatments using high-frequency induction heating. Journal of Functional Biomaterials 2012-03-06 3 1 Communication 10.3390/jfb3010163 163 172 2079-4983 2012-03-06 doi: 10.3390/jfb3010163 Takashi Naohara Hiromichi Aono Tsunehiro Maehara Hideyuki Hirazawa Shinya Matsutomo Yuji Watanabe http://www.mdpi.com/2079-4983/3/1/143 Our study seeks to explore anabolic effects of a periodontal regenerative agent enamel matrix derivative (EMD). Its modulation by nicotine and the anti-oxidant glutathione (GSH) are investigated in human periosteal fibroblasts (HPF) and MG63 osteoblasts. Androgen biomarkers of oxidative stress and healing, resulting from radiolabeled androgen substrates are assayed. This in vitro model simulates a redox environment relevant to the periodontal lesion. It aims to confirm the hypothesis that EMD is an effective regenerative agent in a typically redox environment of the periodontal lesion. Monolayer cultures of MG63 osteoblasts and HPF established in culture medium are incubated with androgen substrates, and optimal concentrations of EMD, nicotine and GSH, alone and in combination. EMD significantly enhances yields of 5α-dihydrotestosterone (DHT) an effective bioactive metabolite, alone and in combination with GSH, to overcome oxidative effects of nicotine across cultures. The ‘in vitro’ findings of this study could be extrapolated to “in vivo” applications of EMD as an adjunctive regenerative therapeutic agent in an environment of chronic inflammation and oxidative stress. Increased yields of DHT implicated in matrix synthesis and direct antioxidant capacity, confirm the potential applications for enamel matrix derivative in periodontal regenerative procedures. Journal of Functional Biomaterials 2012-02-29 3 1 Article 10.3390/jfb3010143 143 162 2079-4983 2012-02-29 doi: 10.3390/jfb3010143 Tareq Al-Qattan Mena Soory http://www.mdpi.com/2079-4983/3/1/131 A molecularly imprinted polymer (MIP) was synthesized by non-covalent imprinting polymerization using irinotecan as template. Methacrylic acid and 4-vinylpyridine were selected as functional monomers. An optimized procedure coupled to LC-PDA analysis was developed for the selective solid-phase extraction of irinotecan from various organic media. A specific capacity of 0.65 µmol•g−1 for the MIP was determined. The high specificity of this MIP was demonstrated by studying the retention behaviour of two related compounds, camptothecin and SN-38. This support was applied for the extraction of irinotecan from human serum samples. Journal of Functional Biomaterials 2012-02-20 3 1 Article 10.3390/jfb3010131 131 142 2079-4983 2012-02-20 doi: 10.3390/jfb3010131 Béatrice Roy Sung Vo Duy Jean-Yves Puy Charlotte Martin Jérome Guitton Charles Dumontet Christian Périgaud Isabelle Lefebvre-Tournier http://www.mdpi.com/2079-4983/3/1/114 Composite chitosan-nano-hydroxyapatite microspheres and scaffolds prepared using a co-precipitation method have shown potential for use in bone regeneration. The goal of this research was to improve the functional properties of the composite scaffolds by modifying the fabrication parameters. The effects of degree of deacetylation (DDA), drying method, hydroxyapatite content and an acid wash on scaffold properties were investigated. Freeze-dried 61% DDA scaffolds degraded faster (3.5 ± 0.5% mass loss) than air-dried 61% DDA scaffolds and 80% DDA scaffolds, but had a lower compressive modulus of 0.12 ± 0.01 MPa. Air-dried 80% DDA scaffolds displayed the highest compressive modulus (3.79 ± 0.51 MPa) and these scaffolds were chosen as the best candidate for use in bone regeneration. Increasing the amount of hydroxyapatite in the air-dried 80% DDA scaffolds did not further increase the compressive modulus of the scaffolds. An acid wash procedure at pH 6.1 was found to increase the degradation of air-dried 80% DDA scaffolds from 1.3 ± 0.1% to 4.4 ± 0.4%. All of the formulations tested supported the proliferation of SAOS-2 cells. Journal of Functional Biomaterials 2012-02-13 3 1 Article 10.3390/jfb3010114 114 130 2079-4983 2012-02-13 doi: 10.3390/jfb3010114 Benjamin T. Reves Jessica A. Jennings Joel D. Bumgardner Warren O. Haggard http://www.mdpi.com/2079-4983/3/1/100 Background: Prospective comparative studies to predict the risk of hemodynamic deterioration in patients referred for transplantation were performed on the basis of standard invasive and non-invasive data and new wave intensity (WI) parameters. Methods and results: Study Group 1 consisted of 151 consecutive outpatients (age 48.7 ± 12 years; 110 men) with end-stage dilative cardiomyopathy. Group 2, consisting of 11 consecutive patients (age 50 ± 11 years; 6 men) with sinus rhythm and “true” decompensation, was used to create “critical values” of WI. There were no demographic or somatic (weight and height) differences between the groups. The follow-up period of ambulatory patients was 31 ± 8 months. Non-invasive WI was studied in the common carotid artery. Complete invasive and non-invasive data were also recorded on the day of investigation. During follow-up 44 pts were lost; there were 15 cardiac deaths (10%), life-saving ventricular assist device implantation in 10 (6.6%) and transplantation in 19 (12.7%). For statistical purposes this group was named the “events” Group B (n = 44). A predisposing factor for events (death, “true” decompensation and “urgent” transplantation in ambulatory patients) was low first peak (“cut-off value” assessed in Group 2 < 4100 mmHg*s³) (OR 45.6, CI 14.5–143.3, p < 0.001). Less powerful predictors of the risk of deterioration were pulmonary capillary pressure (PCP), diastolic pulmonary artery pressure (PAP) and E/A mitral wave relation (p = 0.05). Conclusions: The new ventricular-arterial coupling parameter 1st peak of WI can potentially be used to distinguish patients at high risk for true deterioration and death. This parameter can be used to predict the need for assist device implantation. Journal of Functional Biomaterials 2012-02-01 3 1 Article 10.3390/jfb3010100 100 113 2079-4983 2012-02-01 doi: 10.3390/jfb3010100 Henryk Siniawski Hans Lehmkuhl Michael Dandel Axel Unbehaun Dagmar Kemper Yuguo Weng Roland Hetzer http://www.mdpi.com/2079-4983/3/1/79 Bone-seeking (osteotropic) drug delivery systems (ODDS) represent an interesting solution for targeting different types of drugs to the bones. In particular, anticancer and antibacterial agents could take advantage of such therapeutic strategy. We have recently developed an innovative approach to this aim: a new osteotropic biomaterial was prepared, based on the conjugation of a poly(lactide-co-glycolide) (PLGA) with the bisphosphonate drug alendronate (PLGA-ALE); its hemo- and cytocompatibility were verified. Starting with this copolymer, an osteotropic nanoparticle system (NP) was produced for the targeted delivery of antineoplastic drugs to osteolytic bone metastases; in particular, doxorubicin was tested as a model drug. The in vitro and in vivo results of the new ODDS are validated in this article. All the experimental data confirmed that the drug retained its activity after loading in the PLGA-ALE NP; they can be thus considered a new promising strategy for active targeting of drugs to bone tissues in different pathological situations. Journal of Functional Biomaterials 2012-01-19 3 1 Review 10.3390/jfb3010079 79 99 2079-4983 2012-01-19 doi: 10.3390/jfb3010079 Rosario Pignatello Maria Grazia Sarpietro Francesco Castelli http://www.mdpi.com/2079-4983/3/1/61 A recombinant 130 kDa dihemoglobin which is made up of a single-chain tetra-α globin and four β globins has been expressed as a soluble protein in E. coli. The sequence of the single chain tetra-α is: αI-Gly-αII-(SerGlyGly)5Ser-αIII-Gly-αIV. This dihemoglobin has been purified and characterized in vitro by size exclusion chromatography, electrospray mass spectroscopy, equilibrium oxygen binding, and analytical ultracentrifugation. The observed values of P50 and nmax for the dihemoglobin are slightly lower than those observed for the recombinant hemoglobin rHb1.1 (a “monohemoglobin” comprised of two β globins and an αI-Gly-αII diα-globin chain). Titration of the deoxy form of dihemoglobin with CO shows that all eight heme centers bind ligand. In vivo, dihemoglobin showed increased circulating halflife and a reduced pressor response in conscious rats when compared to rHb1.1. These observations suggest that dihemoglobin is an oxygen carrying molecule with desirable in vivo properties and provides a platform for an isooncotic hemoglobin solution derived solely from a recombinant source. A 260 kDa tetrahemoglobin has also been produced by chemical crosslinking of a dihemoglobin that contains a Lys16Cys mutation in the C-terminal α-globin subunit. Tetrahemoglobin also shows reduced vasoactivity in conscious rats that is comparable to that observed for dihemoglobin. Journal of Functional Biomaterials 2012-01-13 3 1 Article 10.3390/jfb3010061 61 78 2079-4983 2012-01-13 doi: 10.3390/jfb3010061 David A. Marquardt Michael P. Doyle Jeffrey S. Davidson Janet K. Epp Jacqueline F. Aitken Douglas D. Lemon Spencer J. Anthony-Cahill http://www.mdpi.com/2079-4983/3/1/49 Previous generations of hemoglobin (Hb)-based oxygen carriers (HBOCs) have been plagued by key biophysical limitations that result in severe side-effects once transfused in vivo, including protein instability, high heme oxidation rates, and nitric oxide (NO) scavenging. All of these problems emerge after mammalian Hbs are removed from red blood cells (RBCs) and used for HBOC synthesis/formulation. Therefore, extracellular Hbs (erythrocruorins) from organisms which lack RBCs might serve as better HBOCs. This review focuses on the erythrocruorin of Lumbricus terrestris (LtEc), which has been shown to be extremely stable, resistant to oxidation, and may interact with NO differently than mammalian Hbs. All of these beneficial properties show that LtEc is a promising new HBOC which warrants further investigation. Journal of Functional Biomaterials 2012-01-06 3 1 Review 10.3390/jfb3010049 49 60 2079-4983 2012-01-06 doi: 10.3390/jfb3010049 Jacob Elmer Andre F. Palmer http://www.mdpi.com/2079-4983/3/1/37 Chitosan is currently proposed to be one of the most promising polymers in wound dressing development. Our research focuses on its potential as a vehicle for nano-delivery systems destined for burn therapy. One of the most important features of wound dressing is its bioadhesion to the wounded site. We compared the bioadhesive properties of chitosan with those of Carbopol, a synthetic origin polymer. Chitosan-based hydrogels of different molecular weights were first analyzed by texture analysis for gel cohesiveness, adhesiveness and hardness. In vitro release studies showed no difference in release of model antimicrobial drug from the different hydrogel formulations. Bioadhesion tests were performed on pig ear skin and the detachment force, necessary to remove the die from the skin, and the amount of remaining formulation on the skin were determined. Although no significant difference regarding detachment force could be seen between Carbopol-based and chitosan-based formulations, almost double the amount of chitosan formulation remained on the skin as compared to Carbopol formulations. The findings confirmed the great potential of chitosan-based delivery systems in advanced wound therapy. Moreover, results suggest that formulation retention on the ex vivo skin samples could provide deeper insight on formulation bioadhesiveness than the determination of detachment force. Journal of Functional Biomaterials 2012-01-06 3 1 Article 10.3390/jfb3010037 37 48 2079-4983 2012-01-06 doi: 10.3390/jfb3010037 Julia Hurler Nataša Škalko-Basnet http://www.mdpi.com/2079-4983/3/1/23 Biomechanical signals play an important role in normal disc metabolism and pathology. For instance, nucleus pulposus (NP) cells will regulate metabolic activities and maintain a balance between the anabolic and catabolic cascades. The former involves factors such as transforming growth factor-β (TGFβ) and mechanical stimuli, both of which are known to regulate matrix production through autocrine and paracrine mechanisms. The present study examined the combined effect of TGFβ and mechanical loading on anabolic activities in NP cells cultured in agarose constructs. Stimulation with TGFβ and dynamic compression reduced nitrite release and increased matrix synthesis and gene expression of aggrecan and collagen type II. The findings from this work has the potential for developing regenerative treatment strategies which could either slow down or stop the degenerative process and/or promote healing mechanisms in the intervertebral disc. Journal of Functional Biomaterials 2012-01-05 3 1 Article 10.3390/jfb3010023 23 36 2079-4983 2012-01-05 doi: 10.3390/jfb3010023 Reshma K. Tilwani Dan L. Bader Tina T. Chowdhury http://www.mdpi.com/2079-4983/3/1/1 Molecular imprinting is a technique for making a selective binding site for a specific chemical. The technique involves building a polymeric scaffold of molecular complements containing the target molecule. Subsequent removal of the target leaves a cavity with a structural “memory” of the target. Molecularly imprinted polymers (MIPs) can be employed as selective adsorbents of specific molecules or molecular functional groups. In addition, sensors for specific molecules can be made using optical transduction through lumiphores residing in the imprinted site. We have found that the use of metal ions as chromophores can improve selectivity due to selective complex formation. The combination of molecular imprinting and spectroscopic selectivity can result in sensors that are highly sensitive and nearly immune to interferences. A weakness of conventional MIPs with regard to processing is the insolubility of crosslinked polymers. Traditional MIPs are prepared either as monoliths and ground into powders or are prepared in situ on a support. This limits the applicability of MIPs by imposing tedious or difficult processes for their inclusion in devices. The size of the particles hinders diffusion and slows response. These weaknesses could be avoided if a means were found to prepare individual macromolecules with crosslinked binding sites with soluble linear polymeric arms. This process has been made possible by controlled free radical polymerization techniques that can form pseudo-living polymers. Modern techniques of controlled free radical polymerization allow the preparation of block copolymers with potentially crosslinkable substituents in specific locations. The inclusion of crosslinkable mers proximate to the binding complex in the core of a star polymer allows the formation of molecularly imprinted macromolecules that are soluble and processable. Due to the much shorter distance for diffusion, the polymers exhibit rapid responses. This paper reviews the methods that have been employed for the trace determination of organophosphates in real world samples using MIPs. Journal of Functional Biomaterials 2011-12-23 3 1 Review 10.3390/jfb3010001 1 22 2079-4983 2011-12-23 doi: 10.3390/jfb3010001 Abhilasha Verma George M. Murray http://www.mdpi.com/2079-4983/2/4/414 OxyVita Hb is a new generation hemoglobin based oxygen carrier (HBOC) produced through modification of a zero-linked polymerization mechanism using activators which incorporate cross-linked bovine tetramer hemoglobin into “super-polymeric” macromolecules (Average molecular weight = 17 MDa) for the purpose of oxygen delivery when whole blood or packed red cells are not available. This molecular design approach was generated in order to address several fundamental biochemical and physiological weaknesses of previous generations of HBOCs. Observation during pre-clinical and clinical studies provided evidence that these early generation acellular HBOCs were directly associated with loss of retention within the circulatory system, extravasation across endothelial tissue membranes due to their small molecular size leading to arterial and venous vasoconstriction with coupled increases in mean arterial pressure (MAP). The inherent increase in molecular size and structural stability of the OxyVita Hb is a direct response to addressing these serious weaknesses that have occurred during the evolution of HBOC development within the past two decades. The nature of the zero-linked synthetic route eliminates any chemical linkers remaining in the product, eliminating side reaction concerns, such as reversibility and decomposition due to weak chemical bonds, dependency on temperature and pressure, and residual toxicity. Journal of Functional Biomaterials 2011-12-16 2 4 Review 10.3390/jfb2040414 414 424 2079-4983 2011-12-16 doi: 10.3390/jfb2040414 John P. Harrington Hanna Wollocko http://www.mdpi.com/2079-4983/2/4/391 Wound healing is a complex series of biochemical and cellular events. Optimally, functional material design addresses the overlapping acute and inflammatory stages of wound healing based on molecular, cellular, and bio-compatibility issues. In this paper the issues addressed are uncontrolled hemostasis and inflammation which can interfere with the orderly flow of wound healing. In this regard, we review the serine proteases thrombin and elastase relative to dressing functionality that improves wound healing and examine the effects of charge in cotton/cellulosic dressing design on thrombin production and elastase sequestration (uptake by the wound dressing). Thrombin is central to the initiation and propagation of coagulation, and elastase is released from neutrophils that can function detrimentally in a stalled inflammatory phase characteristic of chronic wounds. Electrokinetic fiber surface properties of the biomaterials of this study were determined to correlate material charge and polarity with function relative to thrombin production and elastase sequestration. Human neutrophil elastase sequestration was assessed with an assay representative of chronic wound concentration with cotton gauze cross-linked with three types of polycarboxylic acids and one phosphorylation finish; thrombin production, which was assessed in a plasma-based assay via a fluorogenic peptide substrate, was determined for cotton, cotton-grafted chitosan, chitosan, rayon/polyester, and two kaolin-treated materials including a commercial hemorrhage control dressing (QuickClot Combat Gauze). A correlation in thrombin production to zeta potential was found. Two polycarboxylic acid cross linked and a phosphorylated cotton dressing gave high elastase sequestration. Journal of Functional Biomaterials 2011-12-15 2 4 Article 10.3390/jfb2040391 391 413 2079-4983 2011-12-15 doi: 10.3390/jfb2040391 Judson Vincent Edwards Nicolette Prevost http://www.mdpi.com/2079-4983/2/4/373 The conformation of the imprinted pockets in stimulus-responsive networks can be notably altered when the stimulus causes a volume phase transition. Such a tunable affinity for the template molecule finds interesting applications in the biomedical and drug delivery fields. Nevertheless, the effect that the binding of the template causes on the stimuli-responsiveness of the network has barely been evaluated. In this work, the effect of two ionic drugs used as templates, namely propranolol hydrochloride and ibuprofen sodium, on the responsiveness of N-isopropylacrylamide-based hydrogels copolymerized with acrylic acid (AAc) and N-(3-aminopropyl) methacrylamide (APMA) and on their ability to rebind and to control the release of the template was evaluated. The degree of swelling and, in some cases, energetics (HS-DSC) of the transitions were monitored as a function of temperature, pH, and concentration of drug. Marked decrease in the transition temperature of the hydrogels, accompanied by notable changes in the transition width, was observed in physiological NaCl solutions and after the binding of the drug molecules, which reveals relevant changes in the domain structure of the hydrogels as the charged groups are shielded. The ability of the hydrogels to rebind propranolol or ibuprofen was quantified at both 4 and 37 °C and at two different drug concentrations, in the range of those that cause major changes in the network structure. Noticeable differences between hydrogels bearing AAc or APMA and between imprinted and non-imprinted networks were also observed during the release tests in NaCl solutions of various concentrations. Overall, the results obtained evidence the remarkable effect of the template molecules on the responsiveness of intelligent imprinted hydrogels. Journal of Functional Biomaterials 2011-12-15 2 4 Article 10.3390/jfb2040373 373 390 2079-4983 2011-12-15 doi: 10.3390/jfb2040373 Miguel A. Lago Valerij Ya. Grinberg Tatiana V. Burova Angel Concheiro Carmen Alvarez-Lorenzo http://www.mdpi.com/2079-4983/2/4/355 Quantum dots (QDs) are nanometer-sized semiconductor particles with tunable fluorescent optical property that can be adjusted by their chemical composition, size, or shape. In the past 10 years, they have been demonstrated as a powerful fluorescence tool for biological and biomedical applications, such as diagnostics, biosensing and biolabeling. QDs with high fluorescence quantum yield and optical stability are usually synthesized in organic solvents. In aqueous solution, however, their metallic toxicity, non-dissolubility and photo-luminescence instability prevent the direct utility of QDs in biological media. Polymers are widely used to cover and coat QDs for fabricating biocompatible QDs. Such hybrid materials can provide solubility and robust colloidal and optical stability in water. At the same time, polymers can carry ionic or reactive functional groups for incorporation into the end-use application of QDs, such as receptor targeting and cell attachment. This review provides an overview of the recent development of methods for generating biocompatible polymer/QDs hybrid materials with desirable properties. Polymers with different architectures, such as homo- and co-polymer, hyperbranched polymer, and polymeric nanogel, have been used to anchor and protect QDs. The resulted biocompatible polymer/QDs hybrid materials show successful applications in the fields of bioimaging and biosensing. While considerable progress has been made in the design of biocompatible polymer/QDs materials, the research challenges and future developments in this area should affect the technologies of biomaterials and biosensors and result in even better biocompatible polymer/QDs hybrid materials. Journal of Functional Biomaterials 2011-12-02 2 4 Review 10.3390/jfb2040355 355 372 2079-4983 2011-12-02 doi: 10.3390/jfb2040355 Lei Shen http://www.mdpi.com/2079-4983/2/4/338 Chronic wounds typically have excessive levels of matrix metalloproteinases (MMPs) and proinflammatory cytokines that impair healing. Reducing these detrimental proteins may be key to healing chronic wounds. Proprietary protease blends were formulated specifically to degrade excessive amounts of proinflammatory factors that could prevent wound healing. Applications of protease-containing wound dressings to acute and chronic wounds have been observed clinically to resolve inflammation and appear to aid healing. The purpose of this study was to test in vitro a deliberate blend of proteases for the ability to deactivate or activate known proteins associated with inflammation or healing. Purified human target proteins were incubated with test and control solutions and samples removed at various time points. Blinded samples were tested using a novel infrared protein multiplex sandwich-ELISA-type array technique. Many proinflammatory proteins such as MMPs, cytokines and chemokines were susceptible to degradation. Many proteins such as growth factors, cytokines and TIMP1 were resistant to degradation. Not all proinflammatory proteins were deactivated. Family protein structure did not appear to affect susceptibility to degradation or deactivation. These results suggest that specific protease containing wound dressings appear to reduce multiple detrimental components which may disrupt their deleterious effects on the wound bed and microenvironment. By improving the wound microenvironment through the use of definitive proteases, these novel wound dressings may help transition wounds into the subsequent phase of healing. Journal of Functional Biomaterials 2011-12-02 2 4 Article 10.3390/jfb2040338 338 354 2079-4983 2011-12-02 doi: 10.3390/jfb2040338 Laura K.S. Parnell http://www.mdpi.com/2079-4983/2/4/308 Porous materials are highly preferred for bone tissue engineering due to space for blood vessel ingrowth, but this may introduce extra experimental variations because of the difficulty in precise control of porosity. In order to decide whether it is absolutely necessary to use porous materials in in vitro comparative osteogenesis study of materials with different chemistries, we carried out osteoinductivity study using C3H/10T1/2 cells, pluripotent mesenchymal stem cells (MSCs), on seven material types: hydroxyapatite (HA), α-tricalcium phosphate (α-TCP) and b-tricalcium phosphate (β-TCP) in both porous and dense forms and tissue culture plastic. For all materials under test, dense materials give higher alkaline phosphatase gene (Alp) expression compared with porous materials. In addition, the cell density effects on the 10T1/2 cells were assessed through alkaline phosphatase protein (ALP) enzymatic assay. The ALP expression was higher for higher initial cell plating density and this explains the greater osteoinductivity of dense materials compared with porous materials for in vitro study as porous materials would have higher surface area. On the other hand, the same trend of Alp mRNA level (HA > β-TCP > α-TCP) was observed for both porous and dense materials, validating the use of dense flat materials for comparative study of materials with different chemistries for more reliable comparison when well-defined porous materials are not available. The avoidance of porosity variation would probably facilitate more reproducible results. This study does not suggest porosity is not required for experiments related to bone regeneration application, but emphasizes that there is often a tradeoff between higher clinical relevance, and less variation in a less complex set up, which facilitates a statistically significant conclusion. Technically, we also show that the base of normalization for ALP activity may influence the conclusion and there may be ALP activity from serum, necessitating the inclusion of “no cell” control in ALP activity assay with materials. These explain the opposite conclusions drawn by different groups on the effect of porosity. Journal of Functional Biomaterials 2011-11-08 2 4 Communication 10.3390/jfb2040308 308 337 2079-4983 2011-11-08 doi: 10.3390/jfb2040308 Juliana T. Y. Lee King L. Chow Kefeng Wang Wai-Hung Tsang http://www.mdpi.com/2079-4983/2/3/271 Our studies of amorphous calcium phosphate (ACP)-based dental materials are focused on the design of bioactive, non-degradable, biocompatible, polymeric composites derived from acrylic monomer systems and ACP by photochemical or chemically activated polymerization. Their intended uses include remineralizing bases/liners, orthodontic adhesives and/or endodontic sealers. The bioactivity of these materials originates from the propensity of ACP, once exposed to oral fluids, to release Ca and PO4 ions (building blocks of tooth and bone mineral) in a sustained manner while spontaneously converting to thermodynamically stable apatite. As a result of ACP’s bioactivity, local Ca- and PO4-enriched environments are created with supersaturation conditions favorable for the regeneration of tooth mineral lost to decay or wear. Besides its applicative purpose, our research also seeks to expand the fundamental knowledge base of structure-composition-property relationships existing in these complex systems and identify the mechanisms that govern filler/polymer and composite/tooth interfacial phenomena. In addition to an extensive physicochemical evaluation, we also assess the leachability of the unreacted monomers and in vitro cellular responses to these types of dental materials. The systematic physicochemical and cellular assessments presented in this study typically provide model materials suitable for further animal and/or clinical testing. In addition to their potential dental clinical value, these studies suggest the future development of calcium phosphate-based biomaterials based on composite materials derived from biodegradable polymers and ACP, and designed primarily for general bone tissue regeneration. Journal of Functional Biomaterials 2011-09-14 2 3 Article 10.3390/jfb2030271 271 307 2079-4983 2011-09-14 doi: 10.3390/jfb2030271 Drago Skrtic Joseph M. Antonucci http://www.mdpi.com/2079-4983/2/3/249 Sensory neural hearing loss and vestibular dysfunction have become the most common forms of sensory defects, affecting millions of people worldwide. Developing effective therapies to restore hearing loss is challenging, owing to the limited regenerative capacity of the inner ear hair cells. With recent advances in understanding the developmental biology of mammalian and non-mammalian hair cells a variety of strategies have emerged to restore lost hair cells are being developed. Two predominant strategies have developed to restore hair cells: transfer of genes responsible for hair cell genesis and replacement of missing cells via transfer of stem cells. In this review article, we evaluate the use of several genes involved in hair cell regeneration, the advantages and disadvantages of the different viral vectors employed in inner ear gene delivery and the insights gained from the use of embryonic, adult and induced pluripotent stem cells in generating inner ear hair cells. Understanding the role of genes, vectors and stem cells in therapeutic strategies led us to explore potential solutions to overcome the limitations associated with their use in hair cell regeneration. Journal of Functional Biomaterials 2011-09-13 2 3 Article 10.3390/jfb2030249 249 270 2079-4983 2011-09-13 doi: 10.3390/jfb2030249 Keerthana Devarajan Hinrich Staecker Michael S. Detamore http://www.mdpi.com/2079-4983/2/3/230 In this paper we explore the ability of thermal analysis to check elastin and collagen integrity in different biomaterial applications. Differential Scanning Calorimetry (DSC) has been used to analyze the first and second order transitions of the biological macromolecules in the hydrated and dehydrated state. First, we report the characterization of control cardiovascular tissues such as pericardium, aortic wall and valvular leaflet. Their thermal properties are compared to pure elastin and pure collagen. Second, we present results obtained on two collagen rich tissues: pericardia with different chemical treatments and collagen with physical treatments. Finally, more complex cardiovascular tissues composed of elastin and collagen are analyzed and the effect of detergent treatment on the physical structure of collagen and elastin is brought to the fore. Journal of Functional Biomaterials 2011-09-13 2 3 Article 10.3390/jfb2030230 230 248 2079-4983 2011-09-13 doi: 10.3390/jfb2030230 Valérie Samouillan Florian Delaunay Jany Dandurand Nofel Merbahi Jean-Pierre Gardou Mohammed Yousfi Alessandro Gandaglia Michel Spina Colette Lacabanne http://www.mdpi.com/2079-4983/2/3/213 Corneal integrity is critical for vision. Corneal wounds frequently heal with scarring that impairs vision. Recently, human umbilical cord mesenchymal stem cells (cord stem cells) have been investigated for tissue engineering and therapy due to their availability and differentiation potential. In this study, we used cord stem cells in a 3-dimensional (3D) stroma-like model to observe extracellular matrix organization, with human corneal fibroblasts acting as a control. For 4 weeks, the cells were stimulated with a stable Vitamin C (VitC) derivative ±TGF-b1. After 4 weeks, the mean thickness of the constructs was ~30 mm; however, cord stem cell constructs had 50% less cells per unit volume, indicating the formation of a dense matrix. We found minimal change in decorin and lumican mRNA, and a significant increase in perlecan mRNA in the presence of TGF-b1. Keratocan on the other hand decreased with TGF-b1 in both cell lineages. With both cell types, the constructs possessed aligned collagen fibrils and associated glycosaminoglycans. Fibril diameters did not change with TGF-b1 stimulation or cell lineage; however, highly sulfated glycosaminoglycans associated with the collagen fibrils significantly increased with TGF-b1. Overall, we have shown that cord stem cells can secrete their own extracellular matrix and promote the deposition and sulfation of various proteoglycans. Furthermore, these cells are at least comparable to commonly used corneal fibroblasts and present an alternative for the 3D in vitro tissue engineered model. Journal of Functional Biomaterials 2011-09-01 2 3 Article 10.3390/jfb2030213 213 229 2079-4983 2011-09-01 doi: 10.3390/jfb2030213 Dimitrios Karamichos Celeste B. Rich Audrey E.K. Hutcheon Ruiyi Ren Biagio Saitta Vickery Trinkaus-Randall James D. Zieske http://www.mdpi.com/2079-4983/2/3/195 This computational study investigates the sensing and actuating behavior of a pH-sensitive hydrogel-based microfluidic flow controller. This hydrogel-based flow controller has inherent advantage in its unique stimuli-sensitive properties, removing the need for an external power supply. The predicted swelling behavior the hydrogel is validated with steady-state and transient experiments. We then demonstrate how the model is implemented to study the sensing and actuating behavior of hydrogels for different microfluidic flow channel/hydrogel configurations: e.g., for flow in a T-junction with single and multiple hydrogels. In short, the results suggest that the response of the hydrogel-based flow controller is slow. Therefore, two strategies to improve the response rate of the hydrogels are proposed and demonstrated. Finally, we highlight that the model can be extended to include other stimuli-responsive hydrogels such as thermo-, electric-, and glucose-sensitive hydrogels. Journal of Functional Biomaterials 2011-08-25 2 3 Article 10.3390/jfb2030195 195 212 2079-4983 2011-08-25 doi: 10.3390/jfb2030195 Jundika C. Kurnia Erik Birgersson Arun S. Mujumdar http://www.mdpi.com/2079-4983/2/3/173 Temperature-triggered copolymers are proposed for a number of bio-applications but there is no ideal material platform, especially for injectable drug delivery. Options are needed for degradable biomaterials that not only respond to temperature but also easily accommodate linkage of active molecules. A first step toward realizing this goal is the design and synthesis of the novel materials reported herein. A multifunctional macromer, methacrylated hyperbranched polyglycerol (HPG-MA) with an average of one acrylate unit per copolymer, was synthesized and copolymerized with N-isopropylacrylamide (NIPAAm), hydroxyethyl methacrylate-polylactide (HEMAPLA) and acrylic acid (AAc). The potential to fully exploit the copolymers by modification of the multiple HPG hydroxyl groups will not be discussed here. Instead, this report focuses on the thermoresponsive, biocompatible, and degradation properties of the material. Poly(NIPAAm-co-HEMAPLA-co-AAc-co-HPG-MA) displayed increasing lower critical solution temperatures (LCST) as the HPG content increased over a range of macromer ratios. For the copolymer with the maximum HPG incorporation (17%), the LCST was ~30 °C. In addition, this sample showed no toxicity when human uterine fibroid cells were co-cultured with the copolymer for up to 72 h. This copolymer lost approximately 92% of its mass after 17 hours at 37 °C. Thus, the reported biomaterials offer attractive properties for the design of drug delivery systems where orthogonally triggered mechanisms of therapeutic release in relatively short time periods would be attractive. Journal of Functional Biomaterials 2011-08-23 2 3 Article 10.3390/jfb2030173 173 194 2079-4983 2011-08-23 doi: 10.3390/jfb2030173 Darlene K. Taylor Friederike L. Jayes Alan J. House Melony A. Ochieng http://www.mdpi.com/2079-4983/2/3/155 For back disorders, cell therapy is one approach for a real regeneration of a degenerated nucleus pulposus. Human mesenchymal stem cells (hMSC) could be differentiated into nucleus pulposus (NP)-like cells and used for cell therapy. Therefore it is necessary to find a suitable biocompatible matrix, which supports differentiation. It could be shown that a differentiation of hMSC in a microbial transglutaminase cross-linked gelatin matrix is possible, but resulted in a more chondrocyte-like cell type. The addition of porcine NP extract to the gelatin matrix caused a differentiation closer to the desired NP cell phenotype. This concludes that a hydrogel containing NP extract without any other supplements could be suitable for differentiation of hMSCs into NP cells. The NP extract itself can be cross-linked by transglutaminase to build a hydrogel free of NP atypical substrates. As shown by side-specific biotinylation, the NP extract contains molecules with free glutamine and lysine residues available for the transglutaminase. Journal of Functional Biomaterials 2011-08-08 2 3 Article 10.3390/jfb2030155 155 172 2079-4983 2011-08-08 doi: 10.3390/jfb2030155 Denise Salzig Alexandra Schmiermund Elke Gebauer Hans-Lothar Fuchsbauer Peter Czermak http://www.mdpi.com/2079-4983/2/3/119 Current tissue engineering techniques have various drawbacks: they often incorporate uncontrolled and imprecise scaffold geometries, whereas the current conventional cell seeding techniques result mostly in random cell placement rather than uniform cell distribution. For the successful reconstruction of deficient tissue, new material engineering approaches have to be considered to overcome current limitations. An emerging method to produce complex biological products including cells or extracellular matrices in a controlled manner is a process called bioprinting or biofabrication, which effectively uses principles of rapid prototyping combined with cell-loaded biomaterials, typically hydrogels. 3D tissue printing is an approach to manufacture functional tissue layer-by-layer that could be transplanted in vivo after production. This method is especially advantageous for stem cells since a controlled environment can be created to influence cell growth and differentiation. Using printed tissue for biotechnological and pharmacological needs like in vitro drug-testing may lead to a revolution in the pharmaceutical industry since animal models could be partially replaced by biofabricated tissues mimicking human physiology and pathology. This would not only be a major advancement concerning rising ethical issues but would also have a measureable impact on economical aspects in this industry of today, where animal studies are very labor-intensive and therefore costly. In this review, current controlled material and cell positioning techniques are introduced highlighting approaches towards 3D tissue printing. Journal of Functional Biomaterials 2011-08-04 2 3 Review 10.3390/jfb2030119 119 154 2079-4983 2011-08-04 doi: 10.3390/jfb2030119 Silke Wüst Ralph Müller Sandra Hofmann http://www.mdpi.com/2079-4983/2/3/107 After myocardial infarction, the implantation of stem cell seeded scaffolds on the ischemic zone represents a promising strategy for restoration of heart function. However, mechanical integrity and functionality of tissue engineered constructs need to be determined prior to implantation. Therefore, in this study a novel pulsatile bioreactor mimicking the myocardial contraction was developed to analyze the behavior of mesenchymal stem cells derived from umbilical cord tissue (UCMSC) colonized on titanium-coated polytetrafluorethylene scaffolds to friction stress. The design of the bioreactor enables a simple handling and defined mechanical forces on three seeded scaffolds at physiological conditions. The compact system made of acrylic glass, Teflon®, silicone, and stainless steel allows the comparison of different media, cells and scaffolds. The bioreactor can be gas sterilized and actuated in a standard incubator. Macroscopic observations and pressure-measurements showed a uniformly sinusoidal pulsation, indicating that the bioreactor performed well. Preliminary experiments to determine the adherence rate and morphology of UCMSC after mechanical loadings showed an almost confluent cellular coating without damage on the cell surface. In summary, the bioreactor is an adequate tool for the mechanical stress of seeded scaffolds and offers dynamic stimuli for pre-conditioning of cardiac tissue engineered constructs in vitro. Journal of Functional Biomaterials 2011-07-20 2 3 Article 10.3390/jfb2030107 107 118 2079-4983 2011-07-20 doi: 10.3390/jfb2030107 Trixi Hollweck Bassil Akra Simon Häussler Peter Überfuhr Christoph Schmitz Stefan Pfeifer Markus Eblenkamp Erich Wintermantel Günther Eissner http://www.mdpi.com/2079-4983/2/3/88 As our population ages, there is a greater need for a suitable supply of engineered tissues to address a range of debilitating ailments. Stem cell based therapies are envisioned to meet this emerging need. Despite significant progress in controlling stem cell differentiation, it is still difficult to engineer human tissue constructs for transplantation. Recent advances in micro- and nanofabrication techniques have enabled the design of more biomimetic biomaterials that may be used to direct the fate of stem cells. These biomaterials could have a significant impact on the next generation of stem cell based therapies. Here, we highlight the recent progress made by micro- and nanoengineering techniques in the biomaterials field in the context of directing stem cell differentiation. Particular attention is given to the effect of surface topography, chemistry, mechanics and micro- and nanopatterns on the differentiation of embryonic, mesenchymal and neural stem cells. Journal of Functional Biomaterials 2011-06-24 2 3 Review 10.3390/jfb2030088 88 106 2079-4983 2011-06-24 doi: 10.3390/jfb2030088 Alireza Dolatshahi-Pirouz Mehdi Nikkhah Kristian Kolind Mehmet R. Dokmeci Ali Khademhosseini http://www.mdpi.com/2079-4983/2/2/67 It is a general concern that the success of regenerative medicine-based applications is based on the ability to recapitulate the molecular events that allow stem cells to repair the damaged tissue/organ. To this end biomaterials are designed to display properties that, in a precise and physiological-like fashion, could drive stem cell fate both in vitro and in vivo. The rationale is that stem cells are highly sensitive to forces and that they may convert mechanical stimuli into a chemical response. In this review, we describe novelties on stem cells and biomaterials interactions with more focus on the implication of the mechanical stimulation named mechanotransduction. Journal of Functional Biomaterials 2011-06-21 2 2 Review 10.3390/jfb2020067 67 87 2079-4983 2011-06-21 doi: 10.3390/jfb2020067 Francesco D’Angelo Roberto Tiribuzi Ilaria Armentano Josè Maria Kenny Sabata Martino Aldo Orlacchio http://www.mdpi.com/2079-4983/2/2/39 A novel bioactive sponge was created with a composite of type I collagen sponges or porous poly(e-caprolactone) (PCL) scaffolds, platelet-rich plasma (PRP), BMP2-loaded nanoporous silicon enclosure (NSE) microparticles, mineralizing peptide amphiphiles (PA), and mesenchymal stem cells (MSC). Primary MSC from cortical bone (CB)  tissue proved to form more and larger colony units, as well as produce more mineral matrix under osteogenic differentiation, than MSC from bone marrow (BM). Coating pre-treatments were optimized for maximum cell adhesion and mineralization, while a PRP-based gel carrier was created to efficiently deliver and retain MSC and  microparticles within a porous scaffold while simultaneously promoting cell recruitment, proliferation, and angiogenesis. Components and composite sponges were evaluated for osteogenic differentiation in vitro. Osteogenic sponges were loaded with MSC, PRP, PA, and NSE and implanted subcutaneously in rats to evaluate the formation of bone tissue and angiogenesis in vivo. It was found that the combination of a collagen sponge with CB MSC, PRP, PA, and the BMP2-releasing NSE formed the most bone and was most vascularized by four weeks compared to analogous composites featuring BM MSC or PCL or lacking PRP, PA, and NSE. This study indicates that CB MSC should be considered as an alternative to marrow as a source of stem cells, while the PRP-PA cell and microparticle delivery system may be utilized for diverse tissue engineering applications. Journal of Functional Biomaterials 2011-06-21 2 2 Article 10.3390/jfb2020039 39 66 2079-4983 2011-06-21 doi: 10.3390/jfb2020039 Matthew B. Murphy Daniel Blashki Rachel M. Buchanan Dongmei Fan Enrica De Rosa Ramille N. Shah Samuel I. Stupp Bradley K. Weiner Paul J. Simmons Mauro Ferrari Ennio Tasciotti http://www.mdpi.com/2079-4983/2/2/31 The incorporation of strontium chloride to brushite cement was successful to introduce strontium ions within the lattice of brushite crystals. The effect of strontium ions on brushite cement properties was concentration dependent; such that, the addition of 5% and 10% (w/w) SrCl2 significantly increased the cement FST and the addition of 10% SrCl2 decreased the cement tensile strength. Further, cement weight loss was shown to be increased by cement modification with SrCl2. The combination of ionic substitution and the degradability of brushite cements would constitute a system for the local delivery of strontium ions in the treatment of osteoporosis. Journal of Functional Biomaterials 2011-05-31 2 2 Article 10.3390/jfb2020031 31 38 2079-4983 2011-05-31 doi: 10.3390/jfb2020031 Mohammad H. Alkhraisat Carmen Rueda Enrique López Cabarcos http://www.mdpi.com/2079-4983/2/1/18 The condensation polymer derived from reaction between titanocene dichloride and 2-nitro-1,4-phenylenediamine was doped by mixing the polymer with different amounts of iodine. This bulk doping of the titanocene polyamine resulted in an increase in bulk conductivity from 10 to over 1,000 fold. Conductivity increased to a doping level of about 10 to 15% iodine. Conductivity decreased as the sample discs were heated returning to pre-doped levels after the samples were heated for eight minutes. It is believed that this decrease in conductivity is due to the surface evaporation of iodine as the samples were heated. MALDI MS and IR results are consistent with the formation of C-I compounds for doped materials. Journal of Functional Biomaterials 2011-03-17 2 1 Article 10.3390/jfb2010018 18 30 2079-4983 2011-03-17 doi: 10.3390/jfb2010018 Charles E. Carraher Amitabh J. Battin Michael R. Roner http://www.mdpi.com/2079-4983/2/1/1 A novel polymeric material with antioxidant properties and suitable for ophthalmic application was synthesized by free radical grafting reaction between 2-hydroxyethyl methacrylate and quercetin. The presence of quercetin in the polymeric chain was confirmed by FT-IR and UV-Vis analyses, while an estimation of the amount of quercetin bound per gram of polymer was obtained by the Folin-Ciocalteu assay. The conjugate shows high biocompatibility (HET-CAM assay) and antioxidant and anti-inflammatory properties which were extensively investigated by specific in vitro tests. Journal of Functional Biomaterials 2011-01-27 2 1 Article 10.3390/jfb2010001 1 17 2079-4983 2011-01-27 doi: 10.3390/jfb2010001 Manuela Curcio Giuseppe Cirillo Ortensia Ilaria Parisi Francesca Iemma Umile Gianfranco Spizzirri Ilaria Altimari Nevio Picci Francesco Puoci http://www.mdpi.com/2079-4983/1/1/22 In the late 1960s, much interest was raised in regard to biomedical applications of various ceramic materials. A little bit later, such materials were named bioceramics. This review is limited to bioceramics prepared from calcium orthophosphates only, which belong to the categories of bioactive and bioresorbable compounds. There have been a number of important advances in this field during the past 30–40 years. Namely, by structural and compositional control, it became possible to choose whether calcium orthophosphate bioceramics were biologically stable once incorporated within the skeletal structure or whether they were resorbed over time. At the turn of the millennium, a new concept of calcium orthophosphate bioceramics—which is able to promote regeneration of bones—was developed. Presently, calcium orthophosphate bioceramics are available in the form of particulates, blocks, cements, coatings, customized designs for specific applications and as injectable composites in a polymer carrier. Current biomedical applications include artificial replacements for hips, knees, teeth, tendons and ligaments, as well as repair for periodontal disease, maxillofacial reconstruction, augmentation and stabilization of the jawbone, spinal fusion and bone fillers after tumor surgery. Exploratory studies demonstrate potential applications of calcium orthophosphate bioceramics as scaffolds, drug delivery systems, as well as carriers of growth factors, bioactive peptides and/or various types of cells for tissue engineering purposes. Journal of Functional Biomaterials 2010-11-30 1 1 Review 10.3390/jfb1010022 22 107 2079-4983 2010-11-30 doi: 10.3390/jfb1010022 Sergey V. Dorozhkin http://www.mdpi.com/2079-4983/1/1/14 Induced tissue regeneration around percutaneous medical implants could be a useful method to prevent the failure of the medical device, especially when the epidermal seal around the implant is disrupted and the implant must be maintained over a long period of time. In this manuscript, a novel concept and technique is introduced in which autologous keratinocytes were delivered to the interfacial area of a skin-implant using the hollow interior of a fixator pin as a conduit. Full thickness human skin explants discarded from surgeries were cultured at the air-liquid interface and were punctured to fit at the bottom of hollow cylindrical stainless steel fixator pins. Autologous keratinocytes, previously extracted from the same piece of skin and cultured separately, were delivered to the specimens thorough the interior of the hollow pins. The delivered cells survived the process and resembled undifferentiated epithelium, with variations in size and shape. Viability was demonstrated by the lack of morphologic evidence of necrosis or apoptosis. Although the cells did not form organized epithelial structures, differentiation toward a keratinocyte phenotype was evident immunohistochemically. These results suggest that an adaptation of this technique could be useful for the treatment of complications arising from the contact between skin and percutaneous devices in vivo. Journal of Functional Biomaterials 2010-11-25 1 1 Communication 10.3390/jfb1010014 14 21 2079-4983 2010-11-25 doi: 10.3390/jfb1010014 Antonio Peramo http://www.mdpi.com/2079-4983/1/1/3 Phosphorylated chitooligosaccharides (P-COS) were prepared using a H3PO4, P2O5, Et3PO4 and hexanol solvent system. The P-COS were characterized by Fourier Transform Infrared Spectroscopy (FT-IR), Thermo gravimetric-Differential Thermal Analyzer (TG-DTA), 13C NMR, 31P NMR, X-ray diffraction analysis, solubility studies, biocompatibility and Alkaline Phosphatase Activity (ALP). The results reveal that phosphorylation occurred at the C3 and C6 position of OH groups and the C2 position of NH2 group. FT-IR confirmed no decomposition in pyranose ring in P-COS even with heating and treatment in acidic conditions. The amorphous nature of P-COS was confirmed by X-ray diffraction analysis. Further, the biocompatibility and alkaline phosphatase activity of P-COS were checked against the osteosarcoma MG63 cell line at different concentrations and no cytotoxicity was observed. After 12 h and 24 h of incubation, the ALP activity of P-COS was higher compared with the control group. These results suggest that P-COS is a biocompatible material and in future P-COS could open up a number of promising pharmaceutical and clinical applications to mankind. Journal of Functional Biomaterials 2010-10-22 1 1 Article 10.3390/jfb1010003 3 13 2079-4983 2010-10-22 doi: 10.3390/jfb1010003 Jayachandran Venkatesan Ratih Pangestuti Zhong-Ji Qian BoMi Ryu Se-Kwon Kim http://www.mdpi.com/2079-4983/1/1/1 The biomaterials field is one of the largest and fastest growing research areas both in the scientific community and in the industrial one. Biomaterials are the result of collaborations between different disciplines: chemistry, medicine, pharmacology, engineering and biology. The objective of this collaboration is to lead to the implementation of new devices to restore form and human body functions. The research on biomaterials reflects the constant need to replace or supplement human tissues and organs that have been physiologically compromised due to disease or traumatic events. [...] Journal of Functional Biomaterials 2010-06-23 1 1 Editorial 10.3390/jfb1010001 1 2 2079-4983 2010-06-23 doi: 10.3390/jfb1010001 Puoci