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Precipitation of an apatite layer on the surface of bioactive materials is considered an important step in the bone healing procedure. Wollastonite (CaSiO 3) bioglass has been recently employed as a bone replacement material and also, a carrier for targeted drug delivery. Regarding the impact of a material structure on its biological activity, to achieve the 100 % clinical success, realizing the material crystallinity and bone bonding potential can be important. Therefore, this study tried to prepare pure wollastonite (WS) nano-powders (<20 nm) via an easy and fast hydrothermal process. Different quantities (5, 10 and 15 wt%) of the amorphous and crystalline particles have been added to polycaprolactone (PCL) to obtain composite films via a simple solvent casting technique. The in-vitro bioactivity of the prepared particles as well as composite films was studied by placing the samples in the simulated body fluid (SBF) for 21 days. The physicochemical and microstructural properties of the products were then characterized by XRD, FTIR, FESEM, EDS and TEM. Moreover, the influence of the crystallinity on the bioactivity of the synthesized nanoparticles and also the obtained composite films was investigated for the first time. The results indicated that the amorphous bioglass and the surface of composite containing 15 wt% WS were completely covered by a thick bone-like apatite layer Therefore, these findings revealed that the prepared composite films composed of amorphous WS could be regarded as promising bioactive candidates for bone filling applications. [ABSTRACT FROM AUTHOR]

Medical polymers of biostable nature ( e.g. polymethylmetacrylate, PMMA) are widely used in various clinical applications. In this study, novel PMMA-based composite bone cement was prepared. Bioactive glass (BAG) particulate filler (30 wt%) was added to enhance potentially the integration of bone to the cement. The polymer matrix was functionalized with trimethoxysilyl to achieve an interfacial bond between the matrix and the fillers of BAG. The amount of trimethoxysilyl in the monomer system varied from 0 to 75 wt%. The effects of dry and wet (simulated body fluid, SBF at +37 °C for 5 weeks) conditions were investigated. In total, 20 groups of specimens were prepared. The specimens were subjected to a destructive mechanical test in compression. Scanning electron microscopy (SEM) and micro-computed tomography (micro-CT) were used to study the surface and the three-dimensional morphology of the specimens. The results of the study indicated that the addition of trimethoxysilyl groups led to the formation of a hybrid polymer matrix which, in lower amounts (<10 wt% of total weight), did not significantly affect the compression properties. However, when the specimens stored in dry and wet conditions were compared, the water sorption increased the compression strength (~5–10 MPa per test group). At the same time, the water sorption also caused an evident porous structure formation for the specimens containing BAG and siloxane formation in the hybrid polymer matrix. [ABSTRACT FROM AUTHOR]

Abstract: Silica nanoparticle reinforced poly (vinyl alcohol) cast sheets 40μm thick were tested for mechanical and biological properties. The films were characterized using X-ray diffraction, scanning electron microscopy, and infrared spectroscopy. The crystallinity decreased with increased silica content. Changes in the morphology and structure upon the addition of silica suggest the formation of cross-linking. The modulus increased from 300MPa for PVA to 7.2GPa for 120wt.% silica nanoparticle in the blend and the tensile strength increased from 3.5MPa to 35MPa. The modulus estimated using dynamic tests, tensile tests, and nanoindentation was comparable and was predicted well using the Halpin-Tsai's equation. The nanocomposites were an order of magnitude tougher than the pure polymer. Silica based nanocomposite was also found to be an excellent template for the deposition of calcium hydroxyapatite when immersed in simulated body fluid. The modulus and tensile strength of apatite coated silica nanoparticle (120wt.%)–PVA composite increased to 11GPa and 65MPa respectively, close to that of cortical bone. The results represent one of the largest increases in mechanical properties of nanocomposite mimicking the properties of human bone. The addition of silica can also aid in osseointegration. [Copyright &y& Elsevier]

Self-hardening calcium phosphate cement (CPC) sets to form hydroxyapatite with high osteoconductivity, but its brittleness and low strength limit its use to only non-stress bearing locations. Previous studies developed bioactive composites containing hydroxyapatite fillers in Bis-GMA-based composites for bone repair applications, and they possessed higher strength values. However, these strengths were still lower than the strength of cortical bone. The aim of this study was to develop strong and bioactive composites by combining CPC fillers with nano-silica-fused whiskers in a resin matrix, and to characterize the mechanical properties and cell response. Silica particles were fused to silicon carbide whiskers to roughen the whisker surfaces for enhanced retention in the matrix. Mass ratios of whisker:CPC of 1:2, 1:1 and 2:1 were incorporated into a Bis-GMA-based resin and hardened by two-part chemical curing. Composite with only CPC fillers without whiskers served as a control. The specimens were tested using three-point flexure and nano-indentation. Composites with whisker:CPC ratios of 2:1 and 1:1 had flexural strengths (mean±SD; n=9) of (164±14) MPa and (139±22) MPa, respectively, nearly 3 times higher than (54±5) MPa of the control containing only CPC fillers (p<0.05). The strength of the new whisker-CPC composites was 3 times higher than the strength achieved in previous studies for conventional bioactive composites containing hydroxyapatite particles in Bis-GMA-based resins. The mechanical properties of the CPC-whisker composites nearly matched those of cortical bone and trabecular bone. Osteoblast-like cell adhesion, proliferation and viability were equivalent on the non-whisker control containing only CPC fillers, on the whisker composite at whisker:CPC of 1:1, and on the tissue culture polystyrene control, suggesting that the new CPC-whisker composite was non-cytotoxic. [Copyright &y& Elsevier]

The aim of this study was to evaluate biologic behavior of a composite of bioactive glass (BAG) (S53P4) and copolymer of poly(&epsiv;-caprolactone-co-dl-lactide) in experimental bone defects in rabbits. Twenty New Zealand white rabbits were used for the study. Bone defects (4×6 mm) were prepared in the medial surfaces of the femoral condyles and the tibia. Cavities were filled with three different composites: composite with 60 wt% of small BAG granules (granule size <45 μm) and composites with 40 and 60 wt% of large BAG granules (granule size 90–315 μm). Copolymer without BAG was used as a reference material. Follow-up period was 8 and 16 weeks.In the femur at 8 weeks all the samples were partly surrounded by fibrous capsule. New bone formation was noticed in the areas where glass granules were in direct contact with the bone. At 16 weeks fibrous capsule was thinner in all samples. Bone ingrowth was found in the superficial layers of the composites with large glass granules. However, the percent of direct bone contact decreased between 8 and 16 weeks (p<0.05).In the tibia at 8 weeks all the samples showed fibrous encapsulation. At 16 weeks fibrous capsules were thinner or occasionally disappeared. Bone ingrowth was noticed in the samples with large glass granules. Further, new bone formation was found in the medullary cavity. No signs of polymer degradation were seen at any time point.It can be concluded that the composite of BAG (S53P4) and copolymer of poly(&epsiv;-caprolactone-co-dl-lactide) is biocompatible with the bone tissue within the 16 weeks implantation period. [Copyright &y& Elsevier]

In vitro bioactivity of composites of poly(&epsiv;-caprolactone-co-DL-lactide) P(CL/DL-LA) containing different amounts (40, 60 and 70 wt%) of bioactive glass, S53P4, was evaluated. Two ranges of granule size of bioactive glass (<45 μm and 90–315 μm) were blended with P(CL/DL-LA) copolymer in a batch mixer. The composites were characterised by dynamic mechanical thermal analysis. The molecular weight and the melting temperature of the copolymer matrix were adjusted to enable the application of the composite material by injection below 50°C. Formation of Ca-P deposition on the surface of the composites after dissolution in simulated body fluid at 37°C was recorded by scanning electron microscopy. Degradation of the composite material was measured by water absorption and changes in the average molecular weights as a function of the dissolution time. In vitro bioactivity was found to be dependent on the weight fraction and granule size range of the bioactive glass used. The presence of the bioactive filler also accelerated the degradation compared with the neat polymer sample. [Copyright &y& Elsevier]

Polyimide (PI) may become a promising biomaterial for dental and orthopedic application due to its high mechanical strength, good biocompatibility and bio-stability as well as modulus of elasticity similar to the bone of human body. In this study, bioactive tantalum pentoxide (Ta 2 O 5 , TO)/polyimide (PI) composites (TPC) were fabricated by blending modification through a process of cold-pressing and sintering. The results revealed that the compressive strength, thermal stability, surface roughness, hydrophilicity and surface energy of TPC were significantly enhanced with the increase of TO content. Moreover, apatite mineralization of TPC in simulated body fluid (SBF) was obviously improved, in which TPC with TO of 50 wt% content (TPC50) displayed the best bioactivity. Furthermore, the cellular responses (adhesion, proliferation and differentiation) of rat bone mesenchymal stem cells (rBMSCs) to TPC were obviously upregulated with the increase of TO content. The results demonstrated that the TO content in the composites remarkably affected not only physical-chemical properties but also the cells behaviors. It can be suggested that TPC50 with improved surface properties and bioactivity as well as good cytocompatibility would have great potential and prospect for dental and orthopedic applications. • Tantalum pentoxide (Ta 2 O 5 , TO)/polyimide composite (TPC) was fabricated. • TO not only enhanced thermal and mechanical properties but also bioactivity of TPC. • TO remarkably improved surface properties of TPC and significantly promoted the responses of rBMSCs to TPC. • TPC content had obvious effects on physical, chemical and biological properties of TPC. [ABSTRACT FROM AUTHOR]