Search Results (16)

Median sternotomy and steel wires for sternal closure are the standard approach for cardiac surgery. An incomplete repair associated with chest wall motion, especially in the presence of predisposing factors, can lead to life-threatening deep sternal wound infection, also known as mediastinitis, in 2–5% of cases. Despite current antibiotic and surgical treatments, mediastinitis is associated with a 10–40% mortality rate and a significant increase in morbidity and hospital stay. High mortality and difficult treatment appear to be due to bacterial biofilm, a self-produced extracellular polymeric product that incorporates host tissue and is responsible for the failure of immune defenses and standard antimicrobial therapies. Nanostructures are an effective strategy to enhance the healing process, as they establish a favorable environment for the neosynthesis of the extracellular matrix, supporting tissue development. Synthetic polymers have been proven to exhibit suitable biodegradable and mechanical properties, and their biofunctionalization to enhance cell attachment and interaction with the extracellular matrix is being widely investigated. The use of antibiotic treatments suspended in poly-D,L-lactide and polyethylene oxide and electrospun into nanofibers, or in sponges, has been shown to inhibit bacterial biofilm production. Additionally, growth factors can be incorporated into 3D bioresorbable scaffolds with the aim of constituting a structural and biological framework to organize and expedite the healing process. Therefore, these combined approaches may change the treatment of mediastinitis in the near future. Full article

In this nanotechnology era, nanostructures play a crucial role in the investigation of novel functional nanomaterials. Complex nanostructures and their corresponding fabrication techniques provide powerful tools for the development of high-performance functional materials. In this study, advanced micro-nanomanufacturing technologies and composite micro-nanostructures were applied to the development of a new type of pharmaceutical formulation, aiming to achieve rapid hemostasis, pain relief, and antimicrobial properties. Briefly, an approach combining a electrohydrodynamic atomization (EHDA) technique and reversed-phase solvent was employed to fabricate a novel beaded nanofiber structure (BNS), consisting of micrometer-sized particles distributed on a nanoscale fiber matrix. Firstly, Zein-loaded Yunnan Baiyao (YB) particles were prepared using the solution electrospraying process. Subsequently, these particles were suspended in a co-solvent solution containing ciprofloxacin (CIP) and hydrophilic polymer polyvinylpyrrolidone (PVP) and electrospun into hybrid structural microfibers using a handheld electrospinning device, forming the EHDA product E3. The fiber-beaded composite morphology of E3 was confirmed through scanning electron microscopy (SEM) images. Fourier-transform infrared (FTIR) spectroscopy and X-ray diffraction (XRD) analysis revealed the amorphous state of CIP in the BNS membrane due to the good compatibility between CIP and PVP. The rapid dissolution experiment revealed that E3 exhibits fast disintegration properties and promotes the dissolution of CIP. Moreover, in vitro drug release study demonstrated the complete release of CIP within 1 min. Antibacterial assays showed a significant reduction in the number of adhered bacteria on the BNS, indicating excellent antibacterial performance. Compared with the traditional YB powders consisting of Chinese herbs, the BNS showed a series of advantages for potential wound dressing. These advantages include an improved antibacterial effect, a sustained release of active ingredients from YB, and a convenient wound covering application, which were resulted from the integration of Chinese herbs and Western medicine. This study provides valuable insights for the development of novel multiscale functional micro-/nano-composite materials and pioneers the developments of new types of medicines from the combination of herbal medicines and Western medicines. Full article

In this nano era, nanomaterials and nanostructures are popular in developing novel functional materials. However, the combinations of materials at micro and macro scales can open new routes for developing novel trans-scale products with improved or even new functional performances. In this work, a brand-new hybrid, containing both nanofibers and microparticles, was fabricated using a sequential electrohydrodynamic atomization (EHDA) process. Firstly, the microparticles loaded with drug (berberine hydrochloride, BH) molecules in the cellulose acetate (CA) were fabricated using a solution electrospraying process. Later, these microparticles were suspended into a co-dissolved solution that contained BH and a hydrophilic polymer (polypyrrolidone, PVP) and were co-electrospun into the nanofiber/microparticle hybrids. The EHDA processes were recorded, and the resultant trans-scale products showed a typical hybrid topography, with microparticles distributed all over the nanofibers, which was demonstrated by SEM assessments. FTIR and XRD demonstrated that the components within the hybrids were presented in an amorphous state and had fine compatibility with each other. In vitro dissolution tests verified that the hybrids were able to provide the designed dual-step drug release profiles, a combination of the fast release step of BH from the hydrophilic PVP nanofibers through an erosion mechanism and the sustained release step of BH from the insoluble CA microparticles via a typical Fickian diffusion mechanism. The present protocols pave a new way for developing trans-scale functional materials. Full article

Electrospun nanofiber constructs represent a promising alternative for mimicking the natural extracellular matrix in vitro and have significant potential for cardiac patch applications. While the effect of fiber orientation on the morphological structure of cardiomyocytes has been investigated, fibers only provide contact guidance without accounting for substrate stiffness due to their deposition on rigid substrates (e.g., glass or polystyrene). This paper introduces an in situ fabrication method for suspended and well aligned nanofibrous scaffolds via roller electrospinning, providing an anisotropic microenvironment with reduced stiffness for cardiac tissue engineering. A fiber surface modification strategy, utilizing oxygen plasma treatment combined with sodium dodecyl sulfate solution, was proposed to maintain the hydrophilicity of polycaprolactone (PCL) fibers, promoting cellular adhesion. Human-induced pluripotent stem cell (hiPSC)-derived cardiomyocytes (CMs), cultured on aligned fibers, exhibited an elongated morphology with extension along the fiber axis. In comparison to Petri dishes and suspended random fiber scaffolds, hiPSC-CMs on suspended aligned fiber scaffolds demonstrated enhanced sarcomere organization, spontaneous synchronous contraction, and gene expression indicative of maturation. This work demonstrates the suspended and aligned nano-fibrous scaffold provides a more realistic biomimetic environment for hiPSC-CMs, which promoted further research on the inducing effect of fiber scaffolds on hiPSC-CMs microstructure and gene-level expression. Full article

This article reviews the heat transfer enhancement of nanofluids with non-spherical nanoparticles. We divided the non-spherical nanoparticles suspended in nanofluids into three categories based on the dimension of geometric particle structure. Based on the measured data in experimental studies, we then evaluated the shape effect of non-spherical nanoparticles on thermal conductivity and convective heat transfer enhancement of nanofluids. Recent studies explored the numerical predictions and related heat transfer mechanisms. Due to large aspect ratios, thermal conductivity is abnormally enhanced only for nanofluids with carbon nanotubes/nanofibers/nanowires. The approximate enhancement effect exerted by three types of non-spherical nanoparticles on thermal conductivity was 4.5:2.5:1. Thermal conductivity enhancement per concentration was larger for nanorods/ellipsoids with small aspect ratios. The convective heat transfer coefficient was increased by suspending non-spherical nanoparticles in the base fluid. Consequently, no significant thermohydraulic performance was discovered for convective heat transfer of non-spherical nanoparticle nanofluid flow, specifically for turbulent flows, due to increased pumping power. However, the temperature and particle concentration effect on convective heat transfer remains unclear. In addition, no perfect model for predicting the thermal conductivity and convective heat transfer of non-spherical nanoparticle nanofluids has been reported. Full article

Water is needed for food processing facilities to carry out a number of tasks, including moving goods, washing, processing, and cleaning operations. This causes them to produce wastewater effluent, and they are typically undesirable since it contains a high volume of suspended solids, bacteria, dyestuffs, salts, oils, fats, chemical oxygen demand and biological oxygen demand. Therefore, treatment of food industry wastewater effluent is critical in improving process conditions, socio-economic benefits and our environmental. This short review summarizes the role of available membrane technologies that have been employed for food wastewater treatment and analyse their performance. Particularly, electrospun nanofiber membrane technology is revealed as an emerging membrane science and technology area producing materials of increasing performance and effectiveness in treating wastewater. This review reveals the challenges and perspectives that will assist in treating the food industry wastewater by developing novel membrane technologies. Full article

Nanocelluloses are promising bio-nano-materials for use as water treatment materials in environmental protection and remediation. Over the past decades, they have been integrated via novel nanoengineering approaches for water treatment processes. This review aims at giving an overview of nanocellulose requirements concerning emerging nanotechnologies of waster treatments and purification, i.e., adsorption, absorption, flocculation, photocatalytic degradation, disinfection, antifouling, ultrafiltration, nanofiltration, and reverse osmosis. Firstly, the nanocellulose synthesis methods (mechanical, physical, chemical, and biological), unique properties (sizes, geometries, and surface chemistry) were presented and their use for capturing and removal of wastewater pollutants was explained. Secondly, different chemical modification approaches surface functionalization (with functional groups, polymers, and nanoparticles) for enhancing the surface chemistry of the nanocellulose for enabling the effective removal of specific pollutants (suspended particles, microorganisms, hazardous metals ions, organic dyes, drugs, pesticides fertilizers, and oils) were highlighted. Thirdly, new fabrication approaches (solution casting, thermal treatment, electrospinning, 3D printing) that integrated nanocelluloses (spherical nanoparticles, nanowhiskers, nanofibers) to produce water treatment materials (individual composite nanoparticles, hydrogels, aerogels, sponges, membranes, and nanopapers) were covered. Finally, the major challenges and future perspectives concerning the applications of nanocellulose based materials in water treatment and purification were highlighted. Full article

This study aimed to produce electrospun nanofibers from a polyvinyl butyral polymer (PVB) solution enriched with red and grey selenium nanoparticles. Scanning electron microscopic analysis was used to observe the samples, evaluate the fiber diameters, and reveal eventual artifacts in the nanofibrous structure. Average fiber diameter is determined by manually measuring the diameters of randomly selected fibers on scanning electron microscopic (SEM) images. The obtained nanofibers are amorphous with a diameter of approximately 500 nm, a specific surface area of approx. 8 m² g⁻¹, and 5093 km cm⁻³ length. If the red and grey selenium nanoparticles were produced in powder form and suspended to the ethanolic solution of PVB then they were located inside and outside the fiber. When selenium nanoparticles were synthesized in the PVB solution, then they were located only inside the fiber. These nanofiber sheets enriched with selenium nanoparticles could be a good candidate for high-efficiency filter materials and medical applications. Full article

Polymer solutions with different concentrations of SU-8 2002/poly(ethylene) glycol/tetrabutyl ammonium tetrafluoroborate (SU-8/PEO/TBATFB) were electrospun in a low-voltage near-field electrospinning platform (LVNFES) at different velocities. Their diameters were related to the concentration contents as well as to their Deborah (De) numbers, which describes the elasticity of the polymer solution under determined operating conditions. We found a direct correlation between the concentration of PEO/TBATFB, the De and the diameter of the fibers. Fibers with diameters as thin as 465 nm can be achieved for De ≈ 1. Full article

The thermal conductivity (k) of poly(acrylic acid) (PAA) nanofibers, which were electrospun at various electrospinning voltages, was measured using suspended microdevices. While the thermal conductivities of the as-spun PAA nanofibers varied depending on the electrospinning voltages, the most pronounced 3.1-fold increase in thermal conductivity in comparison to that of bulk PAA was observed at the electrospinning voltage of 14 kV. On the other hand, a reduction in the thermal conductivity of the nanofibers was observed when the as-spun nanofibers were either thermally annealed at the glass transition temperature of PAA or thermally crosslinked. It is notable that the thermal conductivity of crosslinked PAA nanofibers was comparable to that of crosslinked bulk PAA. Polarized Raman spectroscopy and Fourier transform infrared spectroscopy verified that the k enhancement via electrospinning and the k reduction by the thermal treatments could be attributed to the conformational changes between gauche and trans states, which may be further related to the orientation of molecular chains. In contrast, hydrogen bonds did not contribute significantly to the k enhancement. Additionally, the suppression of k observed for the crosslinked PAA nanofibers might result from the shortening of single molecular chains via crosslinking. Full article

The demand for multifunctional requirements in aerospace, military, automobile, sports, and energy applications has encouraged the investigation of new composite materials. This study focuses on the development of multiwall carbon nanotube (MWCNT) filled polypropylene composites and carbon nanofiber composite mats. The developed systems were then used to prepare interlayered composites that exhibited improved electrical conductivity and electromagnetic interference (EMI) shielding efficiency. MWCNT-carbon nanofiber composite mats were developed by centrifugally spinning mixtures of MWCNT suspended in aqueous poly(vinyl alcohol) solutions. The developed nanofibers were then dehydrated under sulfuric acid vapors and then heat treated. Interlayered samples were fabricated using a nanoreinforced polypropylene composite as a matrix and then filled with carbon fiber composite mats. The in-plane and through-plane electrical conductivity of an eight-layered flexible carbon composite (0.65 mm thick) were shown to be 6.1 and 3.0 × 10⁻² S·cm⁻¹, respectively. The EMI shielding effectiveness at 900 MHz increased from 17 dB for the one-layered composite to 52 dB for the eight-layered composite. It was found that the reflection of the electromagnetic waves was the dominating mechanism for EMI shielding in the developed materials. This study opens up new opportunities for the fabrication of novel lightweight materials that are to be used in communication systems. Full article

We previously described the novel synthesis of a copper high-aspect ratio structure (CuHARS) biohybrid material using cystine. While extremely stable in water, CuHARS is completely (but slowly) degradable in cellular media. Here, integration of the CuHARS into cellulose matrices was carried out to provide added control for CuHARS degradation. Synthesized CuHARS was concentrated by centrifugation and then dried. The weighed mass was re-suspended in water. CuHARS was stable in water for months without degradation. In contrast, 25 μg/mL of the CuHARS in complete cell culture media was completely degraded (slowly) in 18 days under physiological conditions. Stable integration of CuHARS into cellulose matrices was achieved through assembly by mixing cellulose micro- and nano-fibers and CuHARS in an aqueous (pulp mixture) phase, followed by drying. Additional materials were integrated to make the hybrids magnetically susceptible. The cellulose-CuHARS composite films could be transferred, weighed, and cut into usable pieces; they maintained their form after rehydration in water for at least 7 days and were compatible with cell culture studies using brain tumor (glioma) cells. These studies demonstrate utility of a CuHARS-cellulose biohybrid for applied applications including: (1) a platform for biomedical tracking and (2) integration into a 2D/3D matrix using natural products (cellulose). Full article

Nanofibrous scaffolds provide high surface area for cell attachment, and resemble the structure of the collagen fibers which naturally occur in the basement membrane and extracellular matrix. A label free and non-destructive method of assessing the interaction of cell tissue and scaffolds aids in the ability to discern the effective quality and magnitude of any scaffold modifications. Impedance cell spectroscopy is a biosensing method that employs a functional approach to assessing the cell monolayer. The electrical impedance barrier function of a cell monolayer represents the level of restriction to diffusion of charged species between all adjacent cells across an entire contiguous cellular monolayer. The impedance signals from many individual paracellular pathways contribute to the bulk measurement of the whole monolayer barrier function. However, the scaffold substrate must be entirely porous in order to be used with electrochemical cell impedance spectroscopy (ECIS) and cells must be closely situated to the electrodes. For purposes of evaluating cell-scaffold constructs for tissue engineering, non-invasive evaluation of cell properties while seeded on scaffolds is critical. A Transwell-type assay makes a measurement across a semi-permeable membrane, using electrodes placed on opposing sides of the membrane immersed in fluid. It was found that by suspending a nanofiber scaffold across a Transwell aperture, it is possible to integrate a fully functional nanofiber tissue scaffold with the ECIS Transwell apparatus. Salivary epithelial cells were grown on the nanofiber scaffolds and tight junction formation was evaluated using ECIS measurements in parallel with immunostaining and confocal imaging. The trans-epithelial resistance increased coordinate with cell coverage, culminating with a cell monolayer, at which point the tight junction proteins assemble and strengthen, reaching the peak signal. These studies demonstrate that ECIS can be used to evaluate tight junction formation in cells grown on nanofiber scaffolds and on effects of scaffold conditions on cells, thus providing useful biological feedback to inform superior scaffold designs. Full article

Tendon is commonly injured, heals slowly and poorly, and often suffers re-injury after healing. This is due to failure of tenocytes to effectively remodel tendon after injury to recapitulate normal architecture, resulting in poor mechanical properties. One strategy for improving the outcome is to use nanofiber scaffolds and mesenchymal stem cells (MSCs) to regenerate tendon. Various scaffold parameters are known to influence tenogenesis. We designed suspended and aligned nanofiber scaffolds with the hypothesis that this would promote tenogenesis when seeded with MSCs. Our aligned nanofibers were manufactured using the previously reported non-electrospinning Spinneret-based Tunable Engineered Parameters (STEP) technique. We compared parallel versus perpendicular nanofiber scaffolds with traditional flat monolayers and used cellular morphology, tendon marker gene expression, and collagen and glycosaminoglycan deposition as determinants for tendon differentiation. We report that compared with traditional control monolayers, MSCs grown on nanofibers were morphologically elongated with higher gene expression of tendon marker scleraxis and collagen type I, along with increased production of extracellular matrix components collagen (p = 0.0293) and glycosaminoglycan (p = 0.0038). Further study of MSCs in different topographical environments is needed to elucidate the complex molecular mechanisms involved in stem cell differentiation. Full article

A comparative study is given for the sensitivity of several typical Si nanophotonic waveguides, including SOI (silicon-on-insulator) nanowires, nanoslot waveguides, suspended Si nanowires, and nanofibers. The cases for gas sensing (n_cl ~ 1.0) and liquid sensing (n_cl ~ 1.33) are considered. When using SOI nanowires (with a SiO₂ buffer layer), the sensitivity for liquid sensing (S ~ 0.55) is higher than that for gas sensing (S ~ 0.35) due to lower asymmetry in the vertical direction. By using SOI nanoslot waveguides, suspended Si nanowires, and Si nanofibers, one could achieve a higher sensitivity compared to sensing with a free-space beam (S = 1.0). The sensitivity for gas sensing is higher than that for liquid sensing due to the higher index-contrast. The waveguide sensitivity of an optimized suspended Si nanowire for gas sensing is as high as 1.5, which is much higher than that of a SOI nanoslot waveguide. Furthermore, the optimal design has very large tolerance to the core width variation due to the fabrication error (∆w ~ ±50 nm). In contrast, a Si nanofiber could also give a very high sensitivity (e.g., ~1.43) while the fabrication tolerance is very small (i.e., ∆w < ±5 nm). The comparative study shows that suspended Si nanowire is a good choice to achieve ultra-high waveguide sensitivity. Full article