Search Results (32)

Osteosarcoma is medically defined as a bone-forming tumor with associated bone-degrading activity. There is a lack of knowledge about the network that generates the overproduction of bone. We studied the early stage of osteosarcoma development with mice enduring a periosteum injection of osteosarcoma cells at the proximal third of the tibia. On day 7 (D7), tumor cells activate the over-synthesis of bone-like material inside the medulla. This overproduction of bone is quickly (D13) followed by degradation. Samples were characterized by microfocus small-angle X-ray scattering (SAXS), wide-angle X-ray scattering (WAXS), optical and electron microscopies, and micro-indentation. This intramedullary apatite–collagen composite synthesis highlights an unknown network of bone synthesis stimulation by extramedullary osteosarcoma cells. This synthesis activation mechanism, coupled with the well-known bone induced osteosarcoma growth activation, produces a rare synergy that may enlighten the final osteosarcoma morphology. With this aim, a 3D cellular automaton was developed that only included two rules. Simulations can accurately reproduce the bi-continuous sponge macroscopic structure that was analyzed from mice tumor micro-tomography. This unknown tumor activation pathway of bone synthesis, combined with the known bone activation of tumor growth, generates a positive feedback synergy explaining the unusual sponge-like morphology of this bone cancer. From a biomaterials point of view, how nature controls self-assembly processes remains an open question. Here, we show how the synergy between two biological growth processes is responsible for the complex morphology of a bone tumor. This highlights how hierarchical morphologies, accurately defined from the nanometer to the centimeter scale, can be controlled by positive feedback between the self-assembly of a scaffold and the deposition of solid material. Full article

The Zheduo–Gongga Mountain, an enormous tower located at the boundary of the eastern Tibetan Plateau, is an ideal place to study the contribution of the climate and/or tectonics to the mountain building. Here, we report new zircon U–Pb ages, biotite ⁴⁰Ar–³⁹Ar, and apatite fission track (AFT) ages of granites along the Zhonggu transect in the northern part of the Zheduo–Gongga massif to investigate the detailed exhumation history and mechanism. The results show zircon U-Pb ages of 14.3 ± 0.3 and 11.3 ± 0.2 Ma, Biotite ⁴⁰Ar–³⁹Ar ages of 4.39 ± 0.07 and 3.62 ± 0.05 Ma, and AFT ages of ~2.6–0.9 Ma. Combining previous structural and geochronological studies, we argue that the growth and exhumation of the Zheduo–Gongga Mountain experienced the following stages. Late Oligocene–early Miocene crust shortening and magmatism marked the initiation of the crustal thickening and surface uplift during ~32–11 Ma, forming a migmatite–granitic belt along the Xianhuihe fault, in response to the northward advancing of the Indian plate into the Eurasian plates. Subsequently, the massif experienced episodic phases of exhumation with variable rates. The exhumation occurred at a rate of ~1–1.5 km/Ma with a cooling rate of 70 ± 20 °C/m.y. during ~11–5 Ma coinciding with the coeval intensification of the Asian monsoon and clockwise rotation of the Chuandian block, south of the Xianshuihe fault. During ~5–2 Ma, a phase of accelerated exhumation (~2–5 km/Ma) started, followed by a possible phase of decelerated exhumation (~1–1.5 km/Ma, corresponding to a cooling rate of 120 ± 20 °C/m.y.) since ~2 Ma, when alpine glaciations initiated due to global cooling. This study highlights the importance of tectonic deformation during ~11–5 Ma in controlling the early growth and exhumation of high mountains in the eastern Tibetan Plateau. The climate may account for the later exhumation of the Zheduo–Gongga mountain since ~5 Ma. Full article

The occurrence of fractures has emerged as one of the most prevalent injuries in the human body. In bone reconstruction surgery, after the implantation of porous hydroxyapatite materials, there is an initial infiltration of body fluids into the porous implant, followed by biomineralization-mediated apatite crystal formation and the subsequent ingrowth of bone cells. Despite extensive research efforts in this field, previous investigations have primarily focused on the formation of apatite crystals on exposed surfaces, with limited literature available regarding the formation of apatite crystals within the internal microstructures of bone implants. Herein, we demonstrate the occurrence of dynamic biomineralization within a three-dimensional porous hydroxyapatite/wollastonite (HA/WS) skeleton, leading to the abundant formation of nano-sized apatite crystals across diverse internal environments. Our findings reveal that these apatite nanocrystals demonstrate distinct rates of nucleation, packing densities, and crystal forms in comparison to those formed on the surface. Therefore, the objective of this study was to elucidate the temporal evolution of biomineralization processes by investigating the microstructures of nanocrystals on the internal surfaces of HA/WS three-dimensional porous materials at distinct stages of biomineralization and subsequently explore the biological activity exhibited by HA/WS when combined with cell investigation into apatite crystal biomineralization mechanisms at the nanoscale, aiming to comprehend natural bone formation processes and develop efficacious biomimetic implants for tissue engineering applications. The simultaneous examination of bone cell attachment and its interaction with ongoing internal nanocrystal formation will provide valuable insights for designing optimal scaffolds conducive to bone cell growth, which is imperative in tissue engineering endeavors. Full article

An apatite-wollastonite glass ceramic (AWGC) has been recognized as one of the popular bioactive materials due to its good osteoconductivity and high mechanical properties in the field of tissue engineering. Various processes have been developed to fabricate AWGCs. Among them, the sol-gel process is one of the most popular processes. However, sol-gel has the drawbacks of discontinuous processing and long processing time, making it unsuitable for mass production. This study demonstrates a successful synthesis of AWGCs using a spray pyrolysis method to overcome these drawbacks, and the prepared pellets were sintered at temperatures of 700, 800, 900, 1000, and 1100 °C for four hours. In addition, X-ray diffraction, scanning electron microscopy, and X-ray energy-dispersive spectroscopy were used to obtain the phase composition, morphology, and chemical information of AWGCs. For bioactive measurements, among these AWGC samples, the 1100 °C sintered sample reveals the highest bioactivity. The MTT result indicates that all AWGCs are not non-toxic to the MC3T3-E1 cells and increase the growth rate of MC3T3-E1 cells. Full article

Hydrogels have been widely applied to the fabrication of tissue engineering scaffolds via three-dimensional (3D) bioprinting because of their extracellular matrix-like properties, capacity for living cell encapsulation, and shapeable customization depending on the defect shape. However, the current hydrogel scaffolds show limited regeneration activity, especially in the application of periodontal tissue regeneration. In this study, we attempted to develop a novel multi-component hydrogel that possesses good biological activity, can wrap living cells for 3D bioprinting and can regenerate periodontal soft and hard tissue. The multi-component hydrogel consisted of gelatin methacryloyl (GelMA), sodium alginate (SA) and bioactive glass microsphere (BGM), which was first processed into hydrogel scaffolds by cell-free 3D printing to evaluate its printability and in vitro biological performances. The cell-free 3D-printed scaffolds showed uniform porous structures and good swelling capability. The BGM-loaded scaffold exhibited good biocompatibility, enhanced osteogenic differentiation, apatite formation abilities and desired mechanical strength. The composite hydrogel was further applied as a bio-ink to load with mouse bone marrow mesenchymal stem cells (mBMSCs) and growth factors (BMP2 and PDGF) for the fabrication of a scaffold for periodontal tissue regeneration. The cell wrapped in the hydrogel still maintained good cellular vitality after 3D bioprinting and showed enhanced osteogenic differentiation and soft tissue repair capabilities in BMP2- and PDGF-loaded scaffolds. It was noted that after transplantation of the cell- and growth factor-laden scaffolds in Beagle dog periodontal defects, significant regeneration of gingival tissue, periodontal ligament, and alveolar bone was detected. Importantly, a reconstructed periodontal structure was established in the treatment group eight weeks post-transplantation of the scaffolds containing the cell and growth factors. In conclusion, we developed a bioactive composite bio-ink for the fabrication of scaffolds applicable for the reconstruction and regeneration of periodontal tissue defects. Full article

Novel biomaterials with promising bone regeneration potential, derived from rich, renewable, and cheap sources, are reported. Thus, thin films were synthesized from marine-derived (i.e., from fish bones and seashells) hydroxyapatite (MdHA) by pulsed laser deposition (PLD) technique. Besides the physical–chemical and mechanical investigations, the deposited thin films were also evaluated in vitro using dedicated cytocompatibility and antimicrobial assays. The morphological examination of MdHA films revealed the fabrication of rough surfaces, which were shown to favor good cell adhesion, and furthermore could foster the in-situ anchorage of implants. The strong hydrophilic behavior of the thin films was evidenced by contact angle (CA) measurements, with values in the range of 15–18°. The inferred bonding strength adherence values were superior (i.e., ~49 MPa) to the threshold established by ISO regulation for high-load implant coatings. After immersion in biological fluids, the growth of an apatite-based layer was noted, which indicated the good mineralization capacity of the MdHA films. All PLD films exhibited low cytotoxicity on osteoblast, fibroblast, and epithelial cells. Moreover, a persistent protective effect against bacterial and fungal colonization (i.e., 1- to 3-log reduction of E. coli, E. faecalis, and C. albicans growth) was demonstrated after 48 h of incubation, with respect to the Ti control. The good cytocompatibility and effective antimicrobial activity, along with the reduced fabrication costs from sustainable sources (available in large quantities), should, therefore, recommend the MdHA materials proposed herein as innovative and viable solutions for the development of novel coatings for metallic dental implants. Full article

This study reports the development of magnesium alloy/hydroxyapatite-based biodegradable metal matrix composites (BMMCs) through rapid microwave sintering. Magnesium alloy (AZ31) and hydroxyapatite powder were used in four compositions 0, 10, 15 and 20% by weight. Developed BMMCs were characterized to evaluate physical, microstructural, mechanical and biodegradation characteristics. XRD results show Mg and HA as major phases and MgO as a minor phase. SEM results correlate with the XRD findings by identifying the presence of Mg, HA and MgO. The addition of HA powder particles reduced density and increased the microhardness of BMMCs. The compressive strength and Young’s modulus increased with increasing HA up to 15 wt.%. AZ31-15HA exhibited the highest corrosion resistance and lowest relative weight loss in the immersion test for 24 h and weight gain after 72 and 168 h due to the deposition of Mg(OH)₂ and Ca(OH)₂ layers at the sample surface. XRD analysis of the AZ31-15HA sintered sample after an immersion test was carried out and these results revealed the presence of new phases Mg(OH)₂ and Ca(OH)₂ that could be the reason for enhancing the corrosion resistance. SEM elemental mapping result also confirmed the formation of Mg(OH)₂ and Ca(OH)₂ at the sample surface, which acted as protective layers and prevented the sample from further corrosion. It showed that the elements were uniformly distributed over the sample surface. In addition, these microwave-sintered BMMCs showed similar properties to the human cortical bone and help bone growth by depositing apatite layers at the surface of the sample. Furthermore, this apatite layer can enhance osteoblast formation due to the porous structure type, which was observed in the BMMCs. Therefore, it is indicative that developed BMMCs can be an artificial biodegradable composite for orthopedic applications. Full article

Synthesized hydroxyapatite (sHA)—calcium phosphate (CaP) based biomaterials play a vital role and have been widely used in the process of bone regeneration for bone defect repair, due to their similarities to the inorganic components of human bones. However, for bone tissue engineering purpose, the composite components, physical and biological properties, efficacy and safety of sHA still need further improvements. In this work, we synthesized inhomogeneous hydroxyapatite based on biomimetic trace elements (Mg, Fe, Zn, Mn, Cu, Ni, Mo, Sr, Co, BO₃³⁻, and CO₃²⁻) co-doped into HA (THA) (Ca_10−δM_δ(PO₄)_5.5(CO₃)_0.5(OH)₂, M = trace elements) via co-precipitation from an ionic solution. The physical properties, their bioactivities using in vitro osteoblast cells, and in vivo cytotoxicity using zebrafish were studied. By introducing biomimetic trace elements, the as-prepared THA samples showed nanorod (needle-like) structures, having a positively charged surface (6.49 meV), and showing paramagnetic behavior. The bioactivity studies demonstrated that the THA substrate can induce apatite particles to cover its surface and be in contact with surrounding simulated body fluid (SBF). In vitro biological assays revealed that the osteoblast-like UMR-106 cells were well-attached with growth and proliferation on the substrate’s surface. Upon differentiation, enhanced ALP (alkaline phosphatase) activity was observed for bone cells on the surface of the THA compared with that on the control substrates (sHA). The in vivo performance in embryonic zebrafish studies showed that the synthesized THA particles are nontoxic based on the measurements of essential parameters such as survivability, hatching rate, and the morphology of the embryo. The mechanism of the ions release profile using digital conductivity measurement revealed that sustained controlled release was successfully achieved. These preliminary results indicated that the synthesized THA could be a promising material for potential practical applications in bone tissue engineering. Full article

In the present study, we have analyzed the mechanical characteristics and bioactivity of titanium coating with hydroxyapatite/bovine collagen. Hydroxyapatite (HAp) was synthesized from a Pinctada maxima shell and has a stoichiometry (Ca/P) of 1.72 and a crystallinity of 92%, suitable for coating materials according to ISO and Food and Drug Administration (FDA) standards. Titanium (Ti) substrate coatings were fabricated at HAp concentrations of 1% (Ti/HAp-1) and 3% (Ti/HAp-3) and a bovine collagen concentration of 1% (Ti/HAp/Coll) by the electrophoresis deposition (EPD) method. The compressive strength of Ti/HAp-1 and Ti/HAp-3 was 87.28 and 86.19 MPa, respectively, and it increased significantly regarding the control/uncoated Ti (46.71 MPa). Furthermore, the Ti/HAp-coll (69.33 MPa) has lower compressive strength due to collagen substitution (1%). The bioactivity of Ti substrates after the immersion into simulated body fluids (SBF) for 3–10 days showed a high apatite growth (Ca²⁺ and ${\mathrm{PO}}_4^{3-}$), according to XRD, FTIR, and SEM-EDS results, significantly on the Ti/HAp-coll. Full article

The number of bone fractures and cracks requiring surgical interventions increases every year; hence, there is a huge need to develop new potential bone scaffolds for bone regeneration. The goal of this study was to gain knowledge about the basic properties of novel curdlan/whey protein isolate/hydroxyapatite biomaterials in the context of their use in bone tissue engineering. The purpose of this research was also to determine whether the concentration of whey protein isolate in scaffolds has an influence on their properties. Thus, two biomaterials differing in the concentration of whey protein isolate (i.e., 25 wt.% and 35 wt.%; hereafter called Cur_WPI25_HAp and Cur_WPI35_HAp, respectively) were fabricated and subjected to evaluation of porosity, mechanical properties, swelling ability, protein release capacity, enzymatic biodegradability, bioactivity, and cytocompatibility towards osteoblasts in vitro. It was found that both biomaterials fulfilled a number of requirements for bone scaffolds, as they demonstrated limited swelling and the ability to undergo controllable enzymatic biodegradation, to form apatite layers on their surfaces and to support the viability, growth, proliferation, and differentiation of osteoblasts. On the other hand, the biomaterials were characterized by low open porosity, which may hinder the penetration of cells though their structure. Moreover, they had low mechanical properties compared to natural bone, which limits their use to filling of bone defects in non-load bearing implantation areas, e.g., in the craniofacial area, but then they will be additionally supported by application of mechanically strong materials such as titanium plates. Thus, this preliminary in vitro research indicates that biomaterials composed of curdlan, whey protein isolate, and hydroxyapatite seem promising for bone tissue engineering applications, but their porosity and mechanical properties should be improved. This will be the subject of our further work. Full article

Biomaterials that effectively act in biological systems, as in treatment and healing of damaged or lost tissues, must be able to mimic the properties of the body’s natural tissues in its various aspects (chemical, physical, mechanical and surface). These characteristics influence cell adhesion and proliferation and are crucial for the success of the treatment for which a biomaterial will be required. In this context, the electrospinning process has gained prominence in obtaining fibers of micro- and nanometric sizes from polymeric solutions aiming to produce scaffolds for tissue engineering. In this manuscript, poly(vinylidene fluoride) (PVDF) was used as a polymeric matrix for the manufacture of piezoelectric scaffolds, exploring the formation of the $\beta$-PVDF piezoelectric phase. Micro- and nanometric hydroxyapatite (HA) particles were incorporated as a dispersed phase in this matrix, aiming to produce multifunctional composite membranes also with bioactive properties. The results show that it is possible to produce membranes containing micro- and nanofibers of the composite by the electrospinning process. The HA particles show good dispersion in the polymer matrix and predominance of $\beta$-PVDF phase. Also, the composite showed apatite growth on its surface after 21 days of immersion in simulated body fluid (SBF). Tests performed on human fibroblasts culture revealed that the electrospun membranes have low cytotoxicity attesting that the composite shows great potential to be used in biomedical applications as bone substitutions and wound healing. Full article

The anisotropic microstructure of bone, composed of collagen fibers and biological apatite crystallites, is an important determinant of its mechanical properties. Recent studies have revealed that the preferential orientation of collagen/apatite composites is closely related to the direction and magnitude of in vivo principal stress. However, the mechanism of alteration in the collagen/apatite microstructure to adapt to the mechanical environment remains unclear. In this study, we established a novel ex vivo bone culture system using embryonic mouse femurs, which enabled artificial control of the mechanical environment. The mineralized femur length significantly increased following cultivation; uniaxial mechanical loading promoted chondrocyte hypertrophy in the growth plates of embryonic mouse femurs. Compressive mechanical loading using the ex vivo bone culture system induced a higher anisotropic microstructure than that observed in the unloaded femur. Osteocytes in the anisotropic bone microstructure were elongated and aligned along the long axis of the femur, which corresponded to the principal loading direction. The ex vivo uniaxial mechanical loading successfully induced the formation of an oriented collagen/apatite microstructure via osteocyte mechano-sensation in a manner quite similar to the in vivo environment. Full article

Background: Bisphosphonates are widely employed drugs for the treatment of pathologies with high bone resorption, such as osteoporosis, and display a great affinity for calcium ions and apatitic substrates. Here, we aimed to investigate the potentiality of zoledronate functionalized hydroxyapatite nanocrystals (HAZOL) to promote bone regeneration by stimulating adhesion, viability, metabolic activity and osteogenic commitment of human bone marrow derived mesenchymal stromal cells (hMSCs). Methods: we adopted an advanced three-dimensional (3D) in vitro fracture healing model to study porous scaffolds: hMSCs were seeded onto the scaffolds that, after three days, were cut in halves and unseeded scaffolds were placed between the two halves. Scaffold characterization by X-ray diffraction, transmission and scanning electron microscopy analyses and cell morphology, viability, osteogenic differentiation and extracellular matrix deposition were evaluated after 3, 7 and 10 days of culture. Results: Electron microscopy showed a porous and interconnected structure and a uniform cell layer spread onto scaffolds. Scaffolds were able to support cell growth and cells progressively colonized the whole inserts in absence of cytotoxic effects. Osteogenic commitment and gene expression of hMSCs were enhanced with higher expressions of ALPL, COL1A1, BGLAP, RUNX2 and Osterix genes. Conclusion: Although some limitations affect the present study (e.g., the lack of longer experimental times, of mechanical stimulus or pathological microenvironment), the obtained results with the adopted experimental setup suggested that zoledronate functionalized scaffolds (GHAZOL) might sustain not only cell proliferation, but positively influence osteogenic differentiation and activity if employed in bone fracture healing. Full article

Biocompatible β-Ca₃(PO₄)₂ and mechanically stable t-ZrO₂ composites are currently being combined to overcome the demerits of the individual components. A series of five composites were synthesized using an aqueous precipitation technique. Their structural and mechanical stability was examined through X-ray diffraction, Rietveld refinement, FTIR, Raman spectroscopy, high-resolution scanning electron microscopy, and nanoindentation. The characterization results confirmed the formation of β-Ca₃(PO₄)₂–t-ZrO₂ composites at 1100 °C. Heat treatment above 900 °C resulted in the degradation of the composites because of cationic interdiffusion between Ca²⁺ ions and O⁻² vacancy in Zr⁴⁺ ions. Sequential thermal treatments correspond to four different fractional phases: calcium-deficient apatite, β-Ca₃(PO₄)₂, t-ZrO₂, and m-ZrO₂. The morphological features confirm in situ synthesis, which reveals abnormal grain growth with voids caused by the upsurge in ZrO₂ content. The mechanical stability data indicate significant variation in Young’s modulus and hardness throughout the composite. Full article

A novel fluorapatite/glucan composite (“FAP/glucan”) was developed for the treatment of bone defects. Due to the presence of polysaccharide polymer (β-1,3-glucan), the composite is highly flexible and thus very convenient for surgery. Its physicochemical and microstructural properties were evaluated using scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), mercury intrusion, mechanical testing and compared with the reference material, which was a hydroxyapatite/glucan composite (“HAP/glucan”) with hydroxyapatite granules (HAP) instead of FAP. It was found that FAP/glucan has a higher density and lower porosity than the reference material. The correlation between the Young’s modulus and the compressive strength between the materials is different in a dry and wet state. Bioactivity assessment showed a lower ability to form apatite and lower uptake of apatite-forming ions from the simulated body fluid by FAP/glucan material in comparison to the reference material. Moreover, FAP/glucan was determined to be of optimal fluoride release capacity for osteoblasts growth requirements. The results of cell culture experiments showed that fluoride-containing biomaterial was non-toxic, enhanced the synthesis of osteocalcin and stimulated the adhesion of osteogenic cells. Full article