Promising Bone Repair Material Research Articles

Poly (propylene fumarate)/β-calcium phosphate composites for enhanced bone repair

A composite based on poly (propylene fumarate) (PPF) was investigated as a potential bone repair material for clinical use and it showed low heat release, suitable mechanical property and good biocompatibility. The in situ curing process would finish in less than 10 min. Compared with PMMA, PPF/TCP showed great decrease in heat release as the maximum temperature during curing process was 54.7 °C ± 1.69 °C. The compressive strength was between 109 ± 2 and 133 ± 6 MPa and the compressive modulus was 146 ± 11 to 161 ± 27 MPa, which were believed to be compatible and further supportive to surrounding bone. Besides, the surface morphology and hydrophilicity could be tailored by adjusting the content of β-calcium phosphate (β-TCP). Relatively stable pH value during degradation in PBS solution implied that it would not bring about acidification when implanted in vivo. In addition, PPF/TCP would boost mineralization and the apatite-like deposits on surface may advance the integrity of bone and materials. Moreover, the PPF/TCP obviously degraded and new bone formed especially when loaded with recombinant human bone morphogenetic protein-2 (rhBMP-2) in vivo. In summary, PPF/TCP composites showed suitable physical and chemical properties as well as good bioactivity and may therefore be a promising material for bone repair.

NMgO-incorporated PLLA bone scaffolds: Enhanced crystallinity and neutralized acidic products

Poly‑l‑lactic acid (PLLA) is a promising bone repair material because of its good biocompatibility and natural degradability. Nevertheless, the poor mechanical properties and local inflammatory response limits its further application in bone repair. In this research, nano magnesium oxide (nMgO) was incorporated into PLLA scaffold manufactured by selective laser sintering technique. Results shown that nMgO with good affinity to PLLA could act as nucleating agent during crystallization process and effectively enhance the crystallinity of PLLA, which was proved by the isothermal behavior and non-isothermal behavior analysis. The evolution of crystallization was also achieved by polarized optical microscopy. Mechanical tests confirmed that the tensile strength, young modulus and Vickers hardness of PLLA/3nMgO was enhanced by 38%, 24% and 11%, respectively, as compared with PLLA. On the other hand, the incorporated nMgO neutralized the acid degradation by-products of PLLA, forming a weak alkaline environment which might contribute to avoiding sever local inflammation after implantation. Moreover, in vitro cell culture revealed an improved biocompatibility of PLLA/nMgO scaffolds. All these positive results suggested that PLLA/3nMgO scaffold was a potential material for bone repair application.

3D printed PCL/SrHA scaffold for enhanced bone regeneration

Strontium-containing hydroxyapatite (SrHA) is a promising material for bone repair and bone replacement due to the similar inorganic components with natural bone. In this study, the poly(ɛ-caprolactone) (PCL)/SrHA composite scaffold was fabricated by 3D printing method. Scanning electron microscopy (SEM) images of the fabricated scaffolds showed that SrHA was uniformly embedded in the interior of scaffold struts, and in vitro release profiles revealed that Sr and Ca ions released from the PCL/SrHA scaffold in a sustained manner. To confirm the performance of the fabricated composite scaffolds for bone regeneration, the cell proliferation and osteogenic differentiation of rat bone marrow-derived mesenchymal stem cells (BMSCs) grown on the scaffolds were evaluated. The experimental results indicated that incorporation of SrHA in the 3D printed PCL scaffold significantly facilitated the cell proliferation, and the PCL/SrHA scaffolds induced higher levels of BMSCs differentiation compared to the PCL and PCL/HA scaffolds, as demonstrated by ALP activity and osteo-related gene expression. Furthermore, in vivo cranial defect experiments further revealed that the incorporation of SrHA into 3D printed PCL scaffold was capable of promoting bone regeneration. Taken together, these results indicate that the PCL/SrHA composite scaffold can be readily fabricated by 3D printing technology and is highly promising as implantable material for bone tissue engineering application.

Bioactive poly(etheretherketone) composite containing calcium polyphosphate and multi-walled carbon nanotubes for bone repair: Mechanical property and in vitro biocompatibility

Poly(etheretherketone) exhibits good biocompatibility, excellent mechanical properties, and bone-like stiffness. However, the natural bio-inertness of pure poly(etheretherketone) hinders its applications in biomedical field, especially when direct bone-implant osteo-integration is desired. For developing an alternative biomaterial for load-bearing orthopedic application, combination of bioactive fillers with poly(etheretherketone) matrix is a feasible approach. In this study, a bioactive multi-walled carbon nanotubes/calcium polyphosphate/poly(etheretherketone) composite was prepared through a compounding and injection-molding process for the first time. Bioactive calcium polyphosphate was added to polymer matrix to enhance the bioactivity of the composite, and incorporation of multi-walled carbon nanotubes to composite was aimed to improve both the mechanical property and biocompatibility. Furthermore, the microstructures, surface hydrophilicity, and mechanical property of multi-walled carbon nanotubes/calcium polyphosphate/poly(etheretherketone) composite, as well as the cellular responses of MC3T3-E1 osteoblast cells to this material were investigated. The mechanical testing revealed that mechanical performance of the resulting ternary composite was significantly enhanced by adding the multi-walled carbon nanotubes and the mechanical values obtained were close to or higher than those of human cortical bone. More importantly, cell culture tests showed that initial cell adhesion, cell viability, and osteogenic differentiation of MC3T3-E1 cells were significantly promoted on the multi-walled carbon nanotubes/calcium polyphosphate/poly(etheretherketone) composite. Accordingly, the multi-walled carbon nanotubes/calcium polyphosphate/poly(etheretherketone) composite may be used as a promising bone repair material in dental and orthopedic applications.

Comparative investigation of hydroxyapatite/collagen composites prepared by CaCl2 addition at different time points in collagen self-assembly process

Mineralization of collagen is a common combination process mainly involving collagen self-assembly and hydroxyapatite formation. Previous measurement of turbidity showed that collagen self-assembly follows the nucleation–growth model. In the present study, 1.0 M CaCl2 was mixed with 0.6 mg/mL collagen solution in PBS (10 mM phosphate, 80 mM NaCl, pH 7.2, and T = 35 °C) at the beginning of the lag period, at the beginning of the growth period, at t1/2 (the time to reach half of the total turbidity change), and during the plateau period. Four different hydroxyapatite/collagen (HAp/COL) composites were prepared [COL (1), COL (2), COL (3), and COL (4)]. The optical densities increased with CaCl2 addition, and a wave trough appeared in the mineralization kinetic curves because of amorphous/crystalline conversion. HAp formation was confirmed by Fourier transform infrared spectroscopy and X-ray diffraction measurements. Energy-dispersive spectroscopy results showed that the calcium/phosphorus ratio of COL (2) is close to that of human bone. Images obtained by scanning electron microscopy revealed that nanosized plate-like HAp of COL (2) formed and became uniformly embedded in collagen, whereas HAp formed large clusters in COL (1), COL (3), and COL (4). Quantitation analyses of collagen and HAp incorporated into composites showed that mineralization at different time points promote collagen fibril generation and have little impact on the HAp content. These results suggest that the composite fabricated by addition of CaCl2 at the beginning of the growth period is a promising material for bone repair and implantation.

Preparation, mechanical properties and in vitro cytocompatibility of multi-walled carbon nanotubes/poly(etheretherketone) nanocomposites

Desired bone repair material must have excellent biocompatibility and high bioactivity. Moreover, mechanical properties of biomaterial should be equivalent to those of human bones. For developing an alternative biocomposite for load-bearing orthopedic application, combination of bioactive fillers with polymer matrix is a feasible approach. In this study, a series of multi-walled carbon nanotubes (MWCNTs)/poly(etheretherketone) (PEEK) bioactive nanocomposites were prepared by a novel coprecipitation-compounding and injection-molding process. Scanning electron microscope (SEM) images revealed that MWCNTs were adsorbed on the surface of PEEK particles during the coprecipitation-compounding process and dispersed homogeneously in the nanocomposite because the conjugated PEEK polymers stabilized MWCNTs by forming strong π–π stack interactions. The mechanical testing revealed that mechanical performance of PEEK was significantly improved by adding MWCNTs (2–8 wt%) and the experimental values obtained were close to or higher than that of human cortical bone. In addition, incorporation of MWCNTs into PEEK matrix also enhanced the roughness and hydrophilicity of the nanocomposite surface. In vitro cytocompatibility tests demonstrated that the MWCNTs/PEEK nanocomposite was in favor of cell adhesion and proliferation of MC3T3-E1 osteoblast cells, exhibiting excellent cytocompatibility and biocompatibility. Thus, this MWCNTs/PEEK nanocomposite may be used as a promising bone repair material in orthopedic implants application.

A lithium-containing nanoporous coating on entangled titanium scaffold can enhance osseointegration through Wnt/β-catenin pathway

An entangled titanium wire porous (ETP) scaffold shows similar mechanical properties of cancellous bone and is a promising bone repair material. However, the ETP scaffold's inert biocompatibility and poor osteogenic ability limit its clinical application. In this study, a Li-containing nanoporous coating was added on ETP by micro-arc oxidation (MAO). The SEM results indicated that a hierarchical and compact coating was formed on the Li-MAO-ETP scaffold. In vitro cell tests showed improved osteoblast morphology, adhesion, and viability in the Li-MAO-ETP group. Moreover, the Li-MAO-ETP scaffold exhibited improved osteogenic differentiation properties by activating the Wnt/β-catenin signal pathway based on the western blotting and RT-PCR results. The push-out test, sequential fluochrome labeling, and toluidine staining demonstrated that the Li-MAO-ETP scaffold contained improved osteogenic ability in vivo. The in vitro and in vivo experiments showed that the Li incorporated entangled porous titanium could be a suitable biomaterial for bone defect repair.

Acceleration of bone formation during fracture healing by poly(pro-hyp-gly)10 and basic fibroblast growth factor containing polycystic kidney disease and collagen-binding domains from Clostridium histolyticum collagenase.

Growth factor delivered in combination with animal-derived collagen materials has been used to accelerate bone fracture healing in human patients. However, the introduction of bovine proteins into humans carries the risk of zoonotic and immunologic complications. Here, we developed a collagen-like polypeptide-based bone formation system consisting of poly(Pro-Hyp-Gly)10 , which mimics the triple helical conformation of collagen, and basic fibroblast growth factor (bFGF) fused to the polycystic kidney disease (PKD) domain and collagen-binding domain (CBD) of Clostridium histolyticum collagenase. Circular dichroism spectral analysis showed that when pepsin-soluble bovine type I collagen was treated at 50°C, a positive signal corresponding to the collagen triple helix at 220 nm was not detected. In contrast, poly(Pro-Hyp-Gly)10 retained the 220-nm positive peak, even when treated at 80°C. The combination of the collagen binding-bFGF fusion protein (bFGF-PKD-CBD) with poly(Pro-Hyp-Gly)10 induced greater bone formation compared to bFGF alone in mice bone fracture models. Taken together, these properties suggest that the bFGF-PKD-CBD/poly(Pro-Hyp-Gly)10 composite is a promising material for bone repair in the clinical setting. © 2016 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 104A: 1372-1378, 2016.

The synergistic effects of Chinese herb and injectable calcium silicate/β-tricalcium phosphate composite on an osteogenic accelerator in vitro.

This study investigates the physicochemical and biological effects of traditional Chinese medicines on the β-tricalcium phosphate (β-TCP)/calcium silicate (CS) composites of bone cells using human dental pulp cell. CS is an osteoconductive and bioactive material. For this research we have combined β-TCP and CS and check its effectiveness, a series of β-TCP/CS composites with different ratios of Xu Duan (XD) were prepared to make new bioactive and biodegradable biocomposites for bone repair. XD has been used in Traditional Chinese Medicine for hundreds of years as an antiosteoporosis, tonic and antiaging agent for the therapy of low back pain, traumatic hematoma, threatened abortion and bone fractures. Formation of bone-like apatite, the diametral tensile strength, and weight loss of composites were considered before and after immersion in simulated body fluid (SBF). In addition, we also examined the effects of XD released from β-TCP/CS composites and in vitro human dental pulp cell (hDPCs) and studied its behavior. The results show the XD-contained paste did not give any demixing when the weight ratio of XD increased to 5-10 % due to the filter-pressing effect during extrusion through the syringe. After immersion in SBF, the microstructure image showed a dense bone-like apatite layer covered on the β-TCP/CS/XD composites. In vitro cell experiments shows that the XD-rich composites promote human dental pulp cells (hDPCs) proliferation and differentiation. However, when the XD quantity in the composite is more than 5 %, the amount of cells and osteogenesis protein of hDPCs were stimulated by XD released from β-TCP/CS composites. The combination of XD in degradation of β-TCP and osteogenesis of CS gives strong reason to believe that these calcium-based composite cements may prove to be promising bone repair materials.

Enhancement of periosteal bone formation by basic fibroblast-derived growth factor containing polycystic kidney disease and collagen-binding domains from Clostridium histolyticum collagenase.

Recombinant basic fibroblast growth factor (bFGF) is a potent mitogen for mesenchymal cells that accelerates bone union and repair when applied locally at defect sites. However, because bFGF diffuses rapidly from bone defect sites, repeated dosing is required for sustained therapeutic effect. We previously fused the collagen-binding domain (CBD) and polycystic kidney disease (PKD) domain of Clostridium histolyticum class II collagenase (ColH) to bFGF and demonstrated that the fusion protein markedly enhances bone formation when loaded onto collagen materials used for grafting. However, systemic injection of a fusion protein consisting of parathyroid hormone (PTH) and a CBD was shown to accelerate bone formation in an osteoporosis model more rapidly than treatment with a PTH-PKD-CBD fusion protein. Here, we compared the biological properties of two collagen-binding forms of bFGF, bFGF-CBD and bFGF-PKD-CBD. Both fusion proteins promoted the in vitro proliferation of periosteal mesenchymal cells, indicating that they had biological activity similar to that of native bFGF. In vivo periosteal bone formation assays in rat femurs showed that both bFGF-CBD and bFGF-PKD-CBD induced periosteal bone formation at higher rates than collagen sheet alone and bFGF. However, bFGF-PKD-CBD markedly enhanced bone formation and had higher collagen-binding ability than bFGF-CBD in in vitro protein release assays. Taken together, these results suggest that the PKD domain increases the retention of bFGF at graft sites by enhancing collagen-binding affinity. Therefore, bFGF-PKD-CBD-collagen composite appears to be a promising material for bone repair in the clinical setting. Copyright © 2015 John Wiley & Sons, Ltd.

Physicochemical properties and biocompatibility of silica doped β-tricalcium phosphate for bone cement

Background/purposeβ-Tricalcium phosphate (β-TCP) is an osteoconductive material. Earlier reports revealed that silica plays an important role in bone mineralization, and its incorporation would enhance the biocompatibility of implants. Materials and methodsIn this study, silica doping at various concentrations (0 wt.%, 10 wt.%, 20 wt.%, and 30 wt.%) was performed. Si-â-TCP was obtained upon calcining the as-prepared powders at 1400°C. To check its effectiveness, different Si-â-TCP samples were prepared to make new bioactive and biodegradable biocomposites for bone repair. Formation of bonelike apatite, the diametral tensile strength, ions released, and weight loss of composites were considered before and after immersion in simulated body fluid. We also examined the behavior of human dental pulp cells (hDPCs) cultured on these materials. ResultsThe results showed that the apatite deposition ability of the β-TCP was enhanced as the Si content was increased. For composites with >20% Si content, the apatite layer covered the samples. At the end of the immersion point, weight losses of 52%, 45%, 33%, and 26% were observed for the β-TCP containing 0%, 10%, 20%, and 30% Si, respectively. In vitro cell experiments showed that the Si-rich cement promotes hDPC proliferation and differentiation. However, when the Si content in the cement is >20%, the amount of cells and osteogenesis protein of hDPCs were stimulated by Si released from Si-β-TCP. ConclusionThe degradation of β-TCP and osteogenesis of Si give us a strong reason to believe that these Si-based cements may prove to be promising bone repair materials.

Avaliação pré-clínica de um material substituto ósseo xenógeno a base de hidroxiapatita/colágeno

Objective: The aim of this study was to evaluate the physical, chemical and biological properties of a bovine xenograft for bone repair. Methods: Physicochemical analysis was performed using X-ray diffraction, Fourier transform infrared spectroscopy and scanning eletron microscopy. In vitro biocompatibility was evaluated through cytotoxicity and cell adhesion assays using a fibroblast cell line culture and murine pre-osteoblasts, respectively. Furthermore, an in vivo assay using a subcutaneous grafting on a rat model (5 and 10 weeks, synthetic hydroxyapatite as a control material) and yet a long term experiment in criticalsize calvarial defects (6 and 9 months, blood clot and autogenous bone as negative and positive controls, respectively). Results: The test material presented a three-dimensional architecture consisting of dense granules and micropores (various sizes), composed of crystalline hydroxyapatite/collagen fibers. The xenograft was cytocompatible and after 7 days pre-osteoblast spreading on material granules was observed. Histopathological analysis of the implanted material into rat subcutaneous showed the intact xenograft after 10 weeks surrounded by loose connective tissue with a mild inflammatory infiltrate and giant multinuclear cells around the particles (5 and 10 weeks) similar to the synthetic hydroxyapatite. Concerning the critical-size calvarial defects it was observed 1.7 times more new bone formation in the xenograft than the blood clot group (P<0.001), a similar result was verified on autograft. There was no significant variation in the volume density of the xenograft (37.9%±4.3). Conclusion: It was concluded that the xenogenic material is biomimetic, biocompatible, osteoconductive and non-resorbable, therefore being a promising material for bone repair.

Preparation, characterization, in vitro bioactivity, and cellular responses to a polyetheretherketone bioactive composite containing nanocalcium silicate for bone repair.

In this study, a nanocalcium silicate (n-CS)/polyetheretherketone (PEEK) bioactive composite was prepared using a process of compounding and injection-molding. The mechanical properties, hydrophilicity, and in vitro bioactivity of the composite, as well as the cellular responses of MC3T3-E1 cells (attachment, proliferation, spreading, and differentiation) to the composite, were investigated. The results showed that the mechanical properties and hydrophilicity of the composites were significantly improved by the addition of n-CS to PEEK. In addition, an apatite-layer formed on the composite surface after immersion in simulated body fluid (SBF) for 7 days. In cell culture tests, the results revealed that the n-CS/PEEK composite significantly promoted cell attachment, proliferation, and spreading compared with PEEK or ultrahigh molecular weight polyethylene (UHMWPE). Moreover, cells grown on the composite exhibited higher alkaline phosphatase (ALP) activity, more calcium nodule-formation, and higher expression levels of osteogenic differentiation-related genes than cells grown on PEEK or UHMWPE. These results indicated that the incorporation of n-CS to PEEK could greatly improve the bioactivity and biocompatibility of the composite. Thus, the n-CS/PEEK composite may be a promising bone repair material for use in orthopedic clinics.

Osteogenesis and angiogenesis properties of dental pulp cell on novel injectable tricalcium phosphate cement by silica doped

β-Tricalcium phosphate (β-TCP) is an osteoconductive material in clinical. In this study, we have doped silica (Si) into β-TCP and enhanced its bioactive and osteostimulative properties. To check its effectiveness, a series of Si-doped with different ratios were prepared to make new bioactive and biodegradable biocomposites for bone repair. Formation of the diametral tensile strength, ions released and weight loss of cements was considered after immersion. In addition, we also examined the behavior of human dental pulp cells (hDPCs) cultured on Si-doped β-TCP cements. The results showed that setting time and injectability of the Si-doped β-TCP cements were decreased as the Si content was increased. At the end of the immersion point, weight losses of 30.1%, 36.9%, 48.1%, and 55.3% were observed for the cement doping 0%, 10%, 20%, and 30% Si into β-TCP cements, respectively. In vitro cell experiments show that the Si-rich cements promote human dental pulp cell (hDPC) proliferation and differentiation. However, when the Si-doped in the cement is more than 20%, the amount of cells and osteogenesis protein of hDPCs was stimulated by Si released from Si-doped β-TCP cements. The degradation of β-TCP and osteogenesis of Si gives a strong reason to believe that these Si-doped β-TCP cements may prove to be promising bone repair materials.

Preparation and antibacterial property of silver-containing mesoporous 58S bioactive glass

The modified mesoporous 58S bioglass (SM58S) was prepared through surface modification of the mesoporous 58S bioglass (M58S) with γ-aminopropyl triethoxysilane (KH550). The results of Fourier transform infrared spectroscopy (FTIR) and thermogravimetric analysis (TGA) showed that the amino groups were grafted to the surface of M58S after modification with KH550. The silver-containing SM58S (Ag-SM58S) and M58S (Ag-M58S) were prepared by the dipping method. The Ag+ loading capacity, release rate and antibacterial properties of Ag-SM58S and Ag-M58S were investigated. It is indicated that surface modification of M58S with KH550 can improve the Ag+ loading capacity. The result of antibacterial property showed that Ag-SM58S exhibited significant anti-bacterial effects against Escherichia coli and Staphylococcus aureus. The sustained release of Ag+ from Ag-SM58S for 768h ensured excellent antibacterial property of Ag-SM58S. In vitro osteoblast proliferation and differentiation tests showed that Ag-SM58S was a good matrix for the growth of osteoblasts. Consequently, the results of the study suggested that Ag-SM58S might be a promising bone repair material.

Regulation of physicochemical properties, osteogenesis activity, and fibroblast growth factor-2 release ability of β-tricalcium phosphate for bone cement by calcium silicate

β-Tricalcium phosphate (β-TCP) is an osteoconductive material. For this research we have combined it with a low degradation calcium silicate (CS) to enhance its bioactive and osteostimulative properties. To check its effectiveness, a series of β-TCP/CS composites with different ratios were prepared to make new bioactive and biodegradable biocomposites for bone repair. Formation of bone-like apatite, the diametral tensile strength, and weight loss of composites were considered before and after immersion in simulated body fluid (SBF). In addition, we also examined the effects of fibroblast growth factor-2 (FGF-2) released from β-TCP/CS composites and in vitro human dental pulp cell (hDPC) and studied its behavior. The results showed that the apatite deposition ability of the β-TCP/CS composites was enhanced as the CS content was increased. For composites with more than 50% CS contents, the samples were completely covered by a dense bone-like apatite layer. At the end of the immersion point, weight losses of 19%, 24%, 33%, 42%, and 51% were observed for the composites containing 0%, 30%, 50%, 70% and 100% β-TCP cements, respectively. In vitro cell experiments show that the CS-rich composites promote human dental pulp cell (hDPC) proliferation and differentiation. However, when the CS quantity in the composite is less than 70%, the amount of cells and osteogenesis protein of hDPCs was stimulated by FGF-2 released from β-TCP/CS composites. The combination of FGF-2 in degradation of β-TCP and osteogenesis of CS gives a strong reason to believe that these calcium-based composite cements may prove to be promising bone repair materials.

Acceleration of periosteal bone formation by human basic fibroblast growth factor containing a collagen‐binding domain from Clostridium histolyticum collagenase

Basic fibroblast growth factor 2 (bFGF) is a potent mitogen for mesenchymal cells, and the local application of recombinant bFGF accelerates bone union and defect repair. However, repeated dosing is required for sustained therapeutic effect as the efficacy of bFGF decreases rapidly following its diffusion from bone defect sites. Here, we attempted to develop a collagen-based bone formation system using a fusion protein (collagen binding-bFGF, CB-bFGF) consisting of bFGF and the collagen-binding domain (CBD) of Clostridium histolyticum collagenase. The addition of the CBD to bFGF did not modify its native biological activity, as shown by the capacity of the fusion protein to promote the in vitro proliferation of periosteal mesenchymal cells. The affinity of the fusion protein towards collagen and demineralized bone matrix (DBM) was also confirmed by collagen-binding assays. Moreover, in vivo periosteal bone formation assays showed that the combination of CB-bFGF with a collagen sheet induced periosteal bone formation at protein concentrations lower than those required for bFGF alone. In addition, grafts of DBM loaded with CB-bFGF accelerated new bone formation in rat femurs compared to the same concentration of bFGF administered alone. Taken together, these properties suggest that the CB-bFGF/collagen composite is a promising material for bone repair in the clinical setting. © 2013 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 102A: 1737–1743, 2014.

Silicate-doped hydroxyapatite and its promotive effect on bone mineralization

Bone defect is one of the most common diseases in clinic. Existing therapeutic approaches have encountered many problems, such as lack of autogenous allogeneic bone and immunological rejection to allogeneic implant. Synthetic hydroxyapatite (HA) provided solutions for bone repair, since the HA is the main inorganic component of animals’ bone. However, HA has good biocompatibility, but does not possess osteogenic capability, which is of significance for modern bone repair materials. Si is an essential trace element in bone tissue, and it has been demonstrated to be able to promote bone formation. Therefore, silicate-doped hydroxyapatite (Si-HA) may serve as a promising material for bone repair, and promote bone regeneration in the repair. The current review discusses development of Si-HA, focusing on its preparation and characterization, in vitro and in vivo evaluations of the material, positive effect of Si-HA on promoting bone formation in clinical applications, and molecular mechanism investigation of such promotive effect.

Attachment and Proliferation of Human-Adipose-Tissue-Derived Stem Cells on Bioactive Glass/PVA Hybrid Scaffolds

Bioactive glass/polymer hybrids are promising materials for biomedical applications because they combine the bioactivity of bioceramics with the flexibility of polymers. These advantages may be used in porous scaffolds for tissue-engineering applications. In previous works, hybrid foams bioactive glass/polyvinyl alcohol (PVA) were prepared by the sol-gel process. The hybrid foam 50% PVA/50% bioactive glass was chosen in the composition range studied as the scaffold with better compromise in terms of pore structure and mechanical behavior. The aim of the present study was to evaluate the adhesion, viability, and growth behavior of human-adipose-tissue-derived stem cells on bioactive glass/PVA foams in vitro and their potential as scaffold for application in bone-tissue engineering. The pore structure of the hybrid samples used in the study was analyzed by microcomputed tomography, showing a modal pore diameter of 284 μm and modal interconnect diameter of 138 μm. We found that cells are capable of adhesion, proliferation, growth, and ECM production on the scaffolds tested. The results show that the hybrid bioactive glass/PVA is a promising material for bone repair, providing a good environment for the adhesion and proliferation of human-adipose-tissue-derived stem cells in vitro.

Calcium Phosphate Cement Modified with Sodium Citrate for Bone Repair

An injectable calcium phosphate cement (CPC) modified with sodium citrate was developed in the present study. The effects of sodium citrate concentration on the injectability, mechanical strength, and the self-setting properties of CPC were systematically investigated. The addition of sodium citrate significantly improved injectability and compressive strength of CPC. The specimens have an injectability of 93% and compressive strength of 36.43 ± 2.64 MPa at 15 wt% sodium citrate concentration, compared to injectability of 75% and compressive strength of 23.15 ± 2.12 MPa of the specimens without sodium citrate. XRD spectra indicated that addition of sodium citrate did not change the hydration reaction of CPC and the reaction product was mainly poorly crystallized hydroxyapatite. In conclusion, CPC developed in this work exhibited excellent injectability and high strength, which should be a promising material for bone repair.