Materials For Bone Tissue Engineering Research Articles

The effect of biomimetic coating and cuttlebone microparticle reinforcement on the osteoconductive properties of cellulose-based scaffolds

Polymer-based scaffolds have already gained popularity in many biomedical applications due to convenient routes for fabrication and favourable structural, physicochemical and functional characteristics. However, polymeric scaffolds lack osteoconductivity and some synthetic polymers carry the risk of inflammatory response caused by degradation by-products. Those facts limit their practical use in bone tissue engineering. In this study, three-dimensional (3D) porous scaffolds from naturally derived polymer, namely regenerated cellulose, were prepared using a non-hydrolytic sol-gel and lyophilization techniques. To induce osteoconductive properties of the polymeric scaffolds, cuttlebone microparticles were immobilized and the surface coating was achieved via in vitro mineralization using 10-fold concentrated simulated body fluid (10x SBF). Biogenic activity of cuttlebone is explained by its chemical composition, which includes polysaccharide β-chitin and macro-, micro- and trace elements favourable for mineralization. Parallel the scaffolds were examined during long-term (24 weeks) in vitro mineralization in 1x SBF for the purpose to investigate apatite-forming ability of the scaffolds. A nice cauliflower-like structures and needle-like dents of the spherical aggregates, which are characteristic to hydroxyapatite precursors, were observed on the surface of cellulose/cuttlebone scaffolds by SEM. 10x SBF coating enhanced cell attachment to the scaffolds because SBF elements are known to increase bioactivity by inducing re-deposition of carbonate apatite crystallites on scaffold surface. Additionally, calcium and phosphate depositions were clearly observed on the developed scaffolds using von Kossa and Alizarin Red S staining. Proliferative and osteoconductive effects on the osteoblast-like MG-63 cells demonstrate the cellulose/cuttlebone scaffolds soaked in 10x SBF as a favourable material for bone tissue engineering.

Arginine based poly (ester amide)/ hyaluronic acid hybrid hydrogels for bone tissue Engineering

Bone transplantations are still facing many serious challenges, hydrogel as a new kind of artificial bone substitutes has developed into a promising bone scaffold material. However, it is still a challenge to combine bioactive agents and hydrogel matrix to promote osteoinductivity. Herein, we developed a novel bioactive hydrogel based on arginine-based unsaturated poly (ester amide) (Arg-UPEA) and methacrylated hyaluronic acid (HA-MA) via photo-crosslinking. As the results indicated, we found that the introduction of Arg-UPEA into HA-MA hydrogels could finely modulate their compressive modulus, swelling level and porous structure. Besides, among groups of different feed ratio, groups of 10 % and 15 % of Arg-UPEA content effectively enhanced osteogenic differentiation in osteoblasts when compared with HA-MA hydrogel. Furthermore, better bone regeneration and expression of osteogenesis-related factors in vivo also verified the Arg-UPEA/HA-MA hybrid hydrogels as a promising scaffold material for bone tissue engineering.

Electroactive composite scaffold with locally expressed osteoinductive factor for synergistic bone repair upon electrical stimulation

Tissue engineering is a promising strategy for the repair of large-scale bone defects, in which scaffolds and growth factors are two critical issues influencing the efficacy of bone regeneration. Unfortunately, the broad application of growth factors is limited by their poor stability in the scaffolds. In the present study, the strictly controlled expression of human bone morphogenetic protein-4 (hBMP-4) in the presence of doxycycline is achieved by adding an hBMP-4 gene fragment into a non-viral artificial restructuring plasmid vector (pSTAR) to form the pSTAR-hBMP-4 plasmid (phBMP-4). Furthermore, the controlled release of phBMP-4 is obtained with an electroactive tissue engineering scaffold, generated by combining a triblock copolymer of poly(l-lactic acid)-block-aniline pentamer-block-poly(l-lactic acid) (PLA-AP) with poly(lactic-co-glycolic acid)/hydroxyapatite (PLGA/HA). This PLGA/HA/PLA-AP/phBMP-4 composite scaffold, with controlled gene release and Dox-regulated gene expression upon electrical stimulation, operating synergistically, exhibits an improved cell proliferation ability, enhanced osteogenesis differentiation in vitro, and effective bone healing in vivo in a rabbit radial defect model. Taking these results together, the proposed smart PLGA/HA/PLA-AP/phBMP-4 scaffold lays a solid theoretical and experimental basis for future applications of such multi-functional materials in bone tissue engineering to help patients in need.

Stretchable poly(glycerol‐sebacate)/β‐tricalcium phosphate composites with shape recovery feature by extrusion

ABSTRACTThere has been a great interest in research towards elastomers and their composites with an attempt to obtain the desired biological and mechanical response to scaffold materials in bone tissue engineering. Composites made of ceramic‐thermoplastic mixtures have been shown success to deliver the inorganic component while fail to provide replacement of an elastic protein, that is, collagen, of the target bone tissue. Thus, in order to match up with the inherent elasticity of the native tissue, it is proposed an alternative to well‐known thermoplastic‐containing matrices by using a poly(glycerol‐sebacate) (PGS)–beta‐tricalcium phosphate elastomeric composite to offer flexibility and mechanical integrity. This study reports for the first time a successful extrusion of PGS containing biodegradable composites with shape‐memory feature. The resulting structures are physically and chemically characterized. In vitro cell culture performance of the obtained materials is investigated by using an MC3T3‐E1 mouse preosteoblast cell line. The materials obtained in this study can be shaped into the desired size and various forms via temperature stimuli. Resulting materials have been proposed for craniofacial tissue engineering as a bone filler in which surgeons need to shape biomaterials during the surgical procedure due to the complex geometry of the bones. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019, 137, 48689.

Advanced Open-Celled Structures from Low-Temperature Sintering of a Crystallization-Resistant Bioactive Glass.

Most materials for bone tissue engineering are in form of highly porous open-celled components (porosity >70%) developed by means of an adequate coupling of formulations and manufacturing technologies. This paper is dedicated to porous components from BGMS10 bioactive glass, originally designed to undergo viscous flow sintering without crystallization, which is generally known to degrade the bioactivity of 45S5 bioglass. The adopted manufacturing technologies were specifically conceived to avoid any contamination and give excellent control on the microstructures by simple operations. More precisely, ‘green’ components were obtained by digital light processing and direct foaming of glass powders suspended in a photosensitive organic binder or in an aqueous solution, activated with an organic base, respectively. Owing to characteristic quite large sintering window of BGMS10 glass, sintering at 750 °C caused the consolidation of the structures generated at room temperature, without any evidence of viscous collapse.

Phosphate glass fibers facilitate proliferation and osteogenesis through Runx2 transcription in murine osteoblastic cells.

Cell-material interactions and compatibility are important aspects of bioactive materials for bone tissue engineering. Phosphate glass fiber (PGF) is an attractive inorganic filler with fibrous structure and tunable composition, which has been widely investigated as a bioactive filler for bone repair applications. However, the interaction of osteoblasts with PGFs has not been widely investigated to elucidate the osteogenic mechanism of PGFs. In this study, different concentrations of short PGFs with interlaced oriented topography were cocultured with MC3T3-E1 cells for different periods, and the synergistic effects of fiber topography and ionic product of PGFs on osteoblast responses including cell adhesion, spreading, proliferation, and osteogenic differentiation were investigated. It was found that osteoblasts were more prone to adhere on PGFs through Vinculin protein, leading to enhanced cell proliferation with polygonal cell shape and spreading cellular actin filaments. In addition, osteoblasts incubated on PGF meshes showed enhanced alkaline phosphatase activity, extracellular matrix mineralization, and increased expression of osteogenesis-related marker genes, which could be attributed to the Wnt/β-catenin/Runx2 signaling pathway. This study elucidated the possible mechanism of PGF on triggering specific osteoblast behavior, which would be highly beneficial for designing PGF-based bone graft substitutes with excellent osteogenic functions.

A method to visually observe the degradation-diffusion-reconstruction behavior of hydroxyapatite in the bone repair process

Nanostructured hydroxyapatite (HAp) has been applied widely as a scaffold material for bone tissue engineering for its good osteoinduction and biodegradability. However, the degradation process and the distribution of degraded HAp within the bone-defect cavity is still not clear. To visually study the behavior of HAp in bone repair process, a membrane of HAp/terbium (Tb)-HAp nanowires (NWs) was prepared with a concentric circle structure (CCS), of which the inner circle and the outer ring were constructed with Tb-HAp and HAp NWs, respectively. HAp/Tb-HAp CCS membrane possessed good osteogenic capacity and efficient fluorescence in the center for visualization. The in vitro experimental results proved that the Tb-HAp and HAp NWs membranes both presented high cytocompatibility and adequate efficiency to induce osteogenic differentiation of bone marrow stem cells (BMSCs). HAp/Tb-HAp CCS membranes were then implanted into a rat calvarial bone-defect model to study the behavior of HAp in bone repair process in vivo by tracking the fluorescence distribution. The results showed that the fluorescence of Tb-HAp diffused gradually from the inner circle to the outer ring, which suggested that the HAp was first degraded, and then the degraded product was diffused and finally reconstructed. Further, the histological results proved that the doping of Tb did not impair the promotive effect of HAp on bone repair process. Therefore, this study provided a visual method to observe the degradation-diffusion-reconstruction behavior of HAp nanomaterials in bone repair process. Statement of significanceThe study of dynamic degradation process of implanted hydroxyapatite (HAp) materials in bone-defect cavity is of great significance to bone tissue engineering applications. Here, we designed a HAp/Tb-HAp nanowires (NWs) membrane with concentric circle structure (CCS) to visibly observe the behavior of HAp during bone repair process. HAp/Tb-HAp CCS membrane possessed both osteoinduction ability and fluorescence property. Calvarial bone-defect repair experiments in vivo showed that the fluorescence of Tb-HAp diffused gradually from inner circle to outer ring, which suggested that HAp was first degraded, then diffused and finally reconstructed. Therefore, this invention provides not only a visible method to observe the degradation-diffusion-reconstruction behavior of HAp-based biomaterials, but also a basic understanding of the dynamic change of HAp-based biomaterials.

Effects of 3D Printing Poly(lactic-co-glycolic acid)-Hydroxyapatite Scaffolds on Femoral Defect Restoration and Serum Factors

Many researches aim at materials promoting osteogenesis, but few of these articles focus on serum. Here, we made Poly(lactic-co-glycolic acid)-Hydroxyapatite (PLGA/HA) scaffolds using 3D printing technology, and evaluated the effect of scaffolds promoting osteogenesis by serum detection and other tests. Sixty Sprague Dawley (SD) rats were selected to grind out a 4 mm long fullthickness bone defect of the bilateral femurs and were randomly divided into a PLGA/HA group which implanted with PLGA/HA scaffolds and a control group with no scaffolds implanted. Bone specimens and serum were collected on the 3rd day and 1st, 2nd, 3rd, 4th, and 5th week after operation and then detected respectively. Three-point bending test indicated that the bone strength of the control group was significantly lower than the PLGA/HA group in the later stage of the experiment. In terms of serum indexes, the calcium (Ca) and alkaline phosphatase (ALP) expressions were much higher in the PLGA/HA group, while the tartrate-resistant acid phosphatase (TRAP) level in the PLGA/HA group was lower in the early stage of the experiment. The level of bone morphogenetic protein 2 (BMP2) in the PLGA/HA group was significantly higher than that of the control group on the 1st, 2nd, and 4th weeks. These results revealed that 3D printing PLGA/HA scaffolds can effectively promote bone tissue formation and inhibit bone absorption. The scaffold has a good potential application prospect at clinic as a kind of bone tissue engineering material.

Nanofibrous poly(vinyl alcohol)/chitosan contained carbonated hydroxyapatite nanoparticles scaffold for bone tissue engineering.

A scaffold that mimics the physicochemical structure of bone at the nanoscale level is an attractive alternative to conventional bone grafts, but its development remains a main challenge in bone tissue engineering today. This work describes the fabrication of a nanofibrous poly(vinyl alcohol)/chitosan/carbonated hydroxyapatite (PVA/CS/CHAp) scaffold. CHAp nanoparticles were synthesized using a co-precipitation method, and nanofibrous PVA/CS/CHAp scaffolds were fabricated by electrospinning using CHAp concentrations of 0, 5, 10, 15, and 20 wt%. The physicochemical properties of the scaffolds were evaluated by SEM, XRD, FTIR, and EDS, and the mechanical properties were determined by tensile strength tests. Swelling behavior, protein adsorption onto the scaffold surfaces, surface biomineralization, and cells viability were also evaluated in vitro. The addition of CHAp to the composite decreased the fiber diameter from ∼160 nm at 0 wt% to ∼139 nm at 15 wt% and great agglomerations were evident at 20 wt%. XRD, FTIR, and EDS showed effective incorporation of CHAp into the nanofibrous structure. This CHAp incorporation significantly increased the modulus of the scaffold at PVA/CS/CHAp 15 wt%, with an average 103.86 MPa, but tensile strength was not significantly altered. However, the elongation at break was decreased as the CHAp concentration increased. Swelling capacity of scaffold increases due to CHAp addition. Protein adsorption onto the scaffold increased 2.3fold at 20 wt% when compared to 0 wt%. The PVA/CS/CHAp 15 wt% showed a better bioactivity when compared to PVA/CS/CHAp 0 wt% after immersion of the scaffolds in a simulated body fluid solution for 7 days. Cell viability and cell morphology results reveal that PVA/CS/CHAp able to facilitate osteoblast cells to attach and proliferate. Introducing higher CHAp into the scaffold could increase the cell viability of the scaffold. PVA/CS/CHAp has potential to serve as an alternative scaffold material for bone tissue engineering.

Osteogenic Differentiation of Mesenchymal Stem Cells with Silica-Coated Gold Nanoparticles for Bone Tissue Engineering.

Multifunctional nanofibrous scaffolds for effective bone tissue engineering (BTE) application must incorporate factors to promote neovascularization and tissue regeneration. In this study, silica-coated gold nanoparticles Au(SiO2) were tested for their ability to promote differentiation of human mesenchymal stem cells (hMSCs) into osteoblasts. Biocompatible poly-ε-caprolactone (PCL), PCL/silk fibroin (SF) and PCL/SF/Au(SiO2) loaded nanofibrous scaffolds were first fabricated by an electrospinning method. Electrospun nanofibrous scaffolds were characterized for fiber architecture, porosity, pore size distribution, fiber wettability and the relevant mechanical properties using field emission scanning electron microscopy (FESEM), porosimetry, determination of water contact angle, measurements by a surface analyzer and tabletop tensile-tester measurements. FESEM images of the scaffolds revealed beadless, porous, uniform fibers with diameters in the range of 164 ± 18.65 nm to 215 ± 32.12 nm and porosity of around 88–92% and pore size distribution around 1.45–2.35 µm. Following hMSCs were cultured on the composite scaffolds. Cell-scaffold interaction, morphology and proliferation of were analyzed by FESEM analysis, MTS (3-(4,5-dimethyl thiazol-2-yl)-5-(3-carboxymethoxyphenyl)-2-(4-sulfophenyl)-2H-tetrazolium inner salt) and CMFDA (5-choromethyl fluorescein acetate) dye assays. Osteogenic differentiation of MSCs into osteogenic cells were determined by alkaline phosphatase (ALP) activity, mineralization by alizarin red S (ARS) staining and osteocalcin expression by immunofluorescence staining. The results revealed that the addition of SF and Au(SiO2) to PCL scaffolds enhanced the mechanical strength, interconnecting porous structure and surface roughness of the scaffolds. This, in turn, led to successful osteogenic differentiation of hMSCs with improved cell adhesion, proliferation, differentiation, mineralization and expression of pro-osteogenic cellular proteins. This provides huge support for Au(SiO2) as a suitable material in BTE.

Collagen and bone morphogenetic protein-2 functionalized hydroxyapatite scaffolds induce osteogenic differentiation in human adipose-derived stem cells.

Surface modification is one important way to fabricate successful biocompatible materials in bone tissue engineering. Hydroxyapatite (HAp) materials have received considerable attention as suitable bioceramics for manufacturing osseous implants because of their similarity to bone mineral in terms of chemical composition. In this study, the surface of porous HAp scaffold was modified by collagen treatment and bone morphogenetic protein-2 (BMP-2) conjugation. The surface modification did not affect the HAp scaffold's bulk properties. No significant difference in compressive strength was found among different scaffolds, with HAp, collagen modified HAp, and collagen-BMP-2-functionalized HAp having compressive strengths of 45.8 ± 3.12, 51.2 ± 4.09, and 50.7 ± 3.98 MPa, respectively. In vitro studies were performed to compare adhesion and osteogenic differentiation between human adipose-derived stem cells (hADSCs) with modified surfaces and those unmodified HAp surfaces. Collagen or BMP-2 alone was insufficient and that both collagen and BMP-2 are necessary to get the desired results. The findings suggest the possibility of using three-dimensional HAp scaffold treated with gold-standard collagen coating and highly researched BMP-2 growth factor as a platform to deliver hADSCs. Results of this study could be used to develop treatment strategy for regenerating completely transected models using more synergistic approaches.

In Vivo Bone Regeneration Induced by a Scaffold of Chitosan/Dicarboxylic Acid Seeded with Human Periodontal Ligament Cells.

Chitosan/dicarboxylic acid (CS/DA) scaffold has been developed as a bone tissue engineering material. This study evaluated a CS/DA scaffold with and without seeded primary human periodontal ligament cells (hPDLCs) in its capacity to regenerate bone in calvarial defects of mice. The osteogenic differentiation of hPDLCs was analyzed by bone nodule formation and gene expression. In vivo bone regeneration was analyzed in mice calvarial defects. Eighteen mice were divided into 3 groups: one group with empty defects, one group with defects with CS/DA scaffold, and a group with defects with CS/DA scaffold and with hPDLCs. After 6 and 12 weeks, new bone formation was assessed using microcomputed tomography (Micro-CT) and histology. CS/DA scaffold significantly promoted in vitro osteoblast-related gene expression (RUNX2, OSX, COL1, ALP, and OPN) by hPDLCs. Micro-CT revealed that CS/DA scaffolds significantly promoted in vivo bone regeneration both after 6 and 12 weeks (p < 0.05). Histological examination confirmed these findings. New bone formation was observed in defects with CS/DA scaffold; being similar with and without hPDLCs. CS/DA scaffolds can be used as a bone regenerative material with good osteoinductive/osteoconductive properties.

Study of Carbonated Calcium Phosphate Precipitation on Collagen

Calcium phosphate biocomposites are candidate materials for bone tissue engineering due to their conductivity and biocompatibility. Calcium phosphate could be grown on collagen by precipitation method in long reaction time. Microwave irradiation is rapid method to assist precipitation by reducing reaction time. In order to study carbonated calcium phosphate precipitation on collagen and investigate the influence of microwave irradiation time, the carbonated calcium phosphate has been grown on collagen by microwave assisted precipitation method. The collagen sheets were soaked in carbonated calcium phosphate suspension prepared by using Ca(NO3)2.4H2O, (NH4)2HPO4, and NaHCO3 as starting materials, then microwave irradiated at 270 Watt for 2 minutes, 8 minutes, and 16 minutes. X-ray powder diffraction (XRD) pattern shows the transformation of dicalcium phosphate dyhydrate to apatite crystal structure. Increase in irradiation time had increased crystallinity of carbonate apatite phase. FTIR spectrum had confirmed presence of collagen, phosphate, and carbonate functional group. Scanning electron micrograph showed the presence of collagen with pore, and the carbonated calcium phosphate could attach and be deposited onto collagen.

Fabrication, characterization and examination of in vitro of baghdadite nanoparticles for biomedical applications

The present study aimed to fabricate, characterize and examine the in vitro behavior of baghdadite bioceramic nanoparticles (Ca3ZrSi2O9) for biomedical applications. Fabrication of baghdadite nanoparticles was carried out via sol-gel method. Nanoparticles were characterized using x-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), energy-dispersive x-ray spectroscopy (EDS analysis), Fourier transform infrared spectroscopy (FTIR), distribution of particles size via laser beam scatter method (DLS) and transmission electron microscopy (TEM). In addition, the examination of in vitro behavior of these nanoparticles was carried out via MTT, Ca-Activity (alizarin red staining) and ALP assays. The results revealed that baghdadite phase was developed in CaO–SiO2–ZrO2 ternary system after being calcinated at 1150 °C. Moreover, baghdadite particles were quasi-spherical with sizes less than 100 nm. The examination of in vitro behavior of baghdadite nanoparticles in culture medium containing human mesenchymal bone marrow stem cells presented no cytotoxicity of baghdadite nanoparticles, which can help the growth and viability of cells and acceleration of bone tissue formation and repair. It can be concluded that baghdadite nano-bioceramic can be utilized as a great bioactive material in biomedical applications and bone tissue engineering.

Novel bioresorbable tricalcium phosphate/polyhydroxyoctanoate (TCP/PHO) composites as scaffolds for bone tissue engineering applications

Development of new composite materials for bone tissue engineering is a constantly growing field of medicine. Therefore there is a continuous need in creating novel materials that can not only regenerate the defected tissue but also nourish it while the healing process progresses. Here we present a novel type of composite material that fulfils these requirements. The study describes creation of a composite with macroporous bioceramic core that is infiltrated with a thin biopolymer layer. The ceramic component, namely tricalcium phosphate (TCP), due to its mechanistic and bioactive properties may promote new bone creation as shown through the in vitro studies. To the best of our knowledge the coating layer was created for the first time from a representative of bacterially derived medium chain length polyhydroxyalkanoate polymers (mcl-PHA), namely polyhydroxyoctanoate (PHO). This polymer layer not only profoundly changed the stress-strain characteristics of the bioceramic foam but also released (R)-3-hydroxyacids and their dimers/trimers to the investigated environment. In the manuscript we have in depth characterised these materials employing a set of basic procedures, through 3D structure reconstruction and finishing with prolonged in vitro experiments.

Studies on Surface Properties and Cell Adhesion Properties of BSA Modified DBM Scaffold

As a scaffold material for bone tissue engineering, demineralized bone matrix(DBM) has such a limited ability to load cells and growth factors that the surface of the DBM scaffold was modified with bovine serum albumin( BSA) with different concentrations to improve the protein structure and physicochemical properties of the scaffold surface so as to enhance the adhesion of the cells. And the appropriate BSA concentration was explored. Compared with DBM, the scaffold with BSA coating had a smaller pore size and a lower porosity, also, the degradation rate was accelerated and the hydrophilic property was improved. Cells adhesion was observed inside the DBM sca ffold before and after it had been modified, and the BSA modified scaffold had a good cell compatibility. When the concentration of BSA was 20 mg/mL, the adhesion ability of the cells to modified scaffold was significantly increased, and the cell proliferation was facilitated.

Preparation of brushite cements with improved properties by adding graphene oxide.

Background: Brushite (dicalcium phosphate dihydrate, DCPD) cement as a promising bioactive material for bone tissue engineering is widely used to treat defects. However, relatively poor mechanical properties of brushite cement limit its application in loadbearing conditions. The aim of this study is to investigate the effect of graphene oxide (GO) addition to the physical-mechanical-biological properties of brushite cement.Methods: The brushite types of cement were prepared by mixing β-tricalcium phosphate [β-TCP, Ca3 (PO4)2] and monocalcium phosphate monohydrate [MCPM, Ca(H2PO4)2. H2O]. GO was introduced at 0, 0.5, 2, and 5 wt.% with the liquid. MG63 cells were cultured on the GO/CPC surfaces to observe various cellular activities and hydroxyapatite (HA) mineralization.Results: Based on our results, GO/CPC composites exhibit improvement in compressive strength compared to pure CPC. New Ca-deficient apatite layer was deposited on the composite surface after immersing immersion in SBF for 7 and 14 days. Field emission scanning electron microscope (FESEM) images indicated that pure and GO incorporated brushite cement facilitates cell adhesion. CPC/GO was slightly toxic to cells such that high concentrations of GO decreased the cell viability. Besides, alkaline phosphatase (ALP) activity of cells was improved compared with the pure CPC.Conclusion: Our results highlight the role of graphene oxide that may have great potential in enabling the utility of graphene-based materials in various biomedical applications.

Research on in vitro and in vivo biocompatibility of the low-friction Ti+C/amorphous carbon gradient multilayer films for hard tissue engineering

Ti+C/amorphous carbon (a-C) gradient multilayer (GM) films are prepared on the Ti-alloy substrates via physical vapor deposition. Transmission electron microscopy revealed that the Ti atoms combine with the a-C film to form a TiC phase in the inner layer and the sputtering current significantly influences the amount of the TiC phase. Further, the mechanical properties of the Ti+C/a-C GM films were obtained using nanoindentation, and the results denoted the significant improvement in the mechanical properties of the a-C film after adding the Ti+C transition layers. The hardness and elastic modulus of the a-C GM films became approximately 31 and 265 GPa, respectively, which were obviously greater than those of the a-C films. The biotribological properties of the a-C GM films in fetal bovine serum (FBS) were verified. The coefficient of friction (COF) and wear rate of the obtained Ti+C/a-C GM film were 0.057 and (1.06–1.24) × 10−6 mm3/(N m), respectively, which were lower than those of pure a-C and the bare Ti alloy. The excellent mechanical properties of the Ti+C gradient transition layer and the lubricating effect of the FBS medium caused the low COF of the a-C GM films, indicating the potential biotribology applications of the a-C films. The cell apoptosis tests suggested that the a-C GM films promoted cell proliferation and viability. Meanwhile, the a-C-GM-coated implants and muscle tissue combined, and hyperergic and inflammatory reactions were not observed six weeks after implantation. These data indicate that the Ti+C/a-C GM film exhibits good biocompatibility and is an ideal mounting material for bone tissue engineering.

Engineered bio-nanocomposite magnesium scaffold for bone tissue regeneration

Porous magnesium based materials are gaining intensive potential as a substitute scaffold material in the field of biomedical engineering as their mechanical properties such as compressive strength and elastic modulus are quite similar to that of human bone. Considering the poor mechanical integrity of ceramic and polymeric materials, metallic implants such as magnesium based alloy foams can be used as a promising scaffold material for bone tissue engineering. Magnesium foams also have properties like excellent biocompatibility and biodegradability so that revision surgery can be completely eliminated after implantation in orthopaedic applications. Against this background, porous Mg alloy based bioactive nano-composite foams were developed. Nano-hydroxyapatite (n-HA) was used as bioactive reinforcement which was anticipated to enhance bone tissue regenerations. Magnesium based alloy compositions were developed by incorporating selective alloying elements, while the bioactive nano-composite foams were fabricated using powder metallurgy route. The powder metallurgy route involved sequential stages of mixing and compaction of all powders with carbamide powder as a space holding material, followed by sintering of the green compacts. The microstructures of these nano-ceramic reinforced metal matrix foams were studied by scanning electron microscopy (SEM) in combination with energy dispersive X-ray spectroscopy (EDS), X-ray diffraction (XRD) and X-ray micro computed tomography (X-ray micro CT). Further, mechanical properties of the nanocomposite foams were evaluated. SEM and EDS results confirmed a homogeneous distribution of pores, alloying elements and n-HA. Structure–property correlations were established through the microstructural characterizations. The study therefore demonstrated that selected Mg alloy based composite foam can be an excellent candidate material for bone tissue engineering.

Strontium-incorporated mineralized PLLA nanofibrous membranes for promoting bone defect repair

Mineralized scaffolds, which are fabricated by electrodeposition, mimic the chemistry of natural bone and have attracted a great amount of attention due to their rapid and simple production. In this study, mineralized electrospun polylactic acid (PLLA) nanofibrous membranes containing different amounts of strontium (Sr) were fabricated by an electrodeposition method for potential use in bone regeneration applications. In vitro assays, including cell proliferation and osteogenic differentiation of rat bone marrow-derived mesenchymal stem cells (BMSCs) grown on these membranes and in vivo cranial bone defect repair assays, were carried out. It was found that mineral crystals could be uniformly deposited onto the electrospun nanofibrous membranes, while the morphologies of the formed crystals were affected by the amount of Sr. By analysis of the X-ray diffraction (XRD) measurements, the formed crystalline phase was dramatically affected by the incorporation of Sr, which drove a conversion from the hydroxyapatite (HA) phase to the dicalcium phosphate dehydrate (DCPD) phase. The release of Sr2+ from the Sr/PLLA nanofibrous membranes was monitored over 20 d, and the release rates of Ca2+ and PO43− from the Sr-incorporated samples were higher compared with those of the mineralized sample without Sr. In vitro cell proliferation experiments demonstrated that mineralized Sr/PLLA nanofibrous membranes could facilitate BMSC proliferation. Furthermore, the mineralized Sr/PLLA nanofibrous membranes induced a higher degree of osteogenic differentiation in the BMSCs compared with those of pure PLLA and mineralized PLLA, as determined by the results of alkaline phosphatase (ALP) activity, alizarin red (AR) and osteocalcin (OCN) staining and the expression of osteogenesis-related genes. More importantly, in vivo cranial defect experiments revealed that mineralized Sr/PLLA nanofibrous membranes promoted bone regeneration. These findings indicated that mineralized Sr/PLLA nanofibrous membranes are a promising material for bone tissue engineering.