In vitro/in vivo biocompatibility and mechanical properties of bioactive glass nanofiber and poly(epsilon-caprolactone) composite materials.

In this study, a poly(epsilon-caprolactone) (PCL)/bioactive glass (BG) nanocomposite was fabricated using BG nanofibers (BGNFs) and compared with an established composite fabricated using microscale BG particles. The BGNFs were generated using sol-gel precursors via the electrospinning process, chopped into short fibers and then incorporated into the PCL organic matrix by dissolving them in a tetrahydrofuran solvent. The biological and mechanical properties of the PCL/BGNF composites were evaluated and compared with those of PCL/BG powder (BGP). Because the PCL/BG composite containing 20 wt % BG showed the highest level of alkaline phosphatase (ALP) activity, all evaluations were performed at this concentration except for that of the ALP activity itself. In vitro cell tests using the MC3T3 cell line demonstrated the enhanced biocompatibility of the PCL/BGNF composite compared with the PCL/BGP composite. Furthermore, the PCL/BGNF composite showed a significantly higher level of bioactivity compared with the PCL/BGP composite. In addition, the results of the in vivo animal experiments using Sprague-Dawley albino rats revealed the good bone regeneration capability of the PCL/BGNF composite when implanted in a calvarial bone defect. In the result of the tensile test, the stiffness of the PCL/BG composite was further increased when the BGNFs were incorporated. These results indicate that the PCL/BGNF composite has greater bioactivity and mechanical stability when compared with the PCL/BG composite and great potential as a bone regenerative material.

Mechanical and in vitro biological performances of hydroxyapatite-carbon nanotube composite coatings deposited on Ti by aerosol deposition.

Hydroxyapatite (HA)-carbon nanotube (CNT) composite coatings on Ti plate, produced by aerosol deposition using HA-CNT powders, were developed for biomedical applications. For the deposition process HA-CNT powder mixtures with CNT contents of 1 and 3 wt.% were used. Dense coatings with a thickness of 5 microm were fabricated, irrespective of the content of CNTs. No pores or microcracks were observed in the coatings. The coatings had good adhesion to the substrate, exhibiting a high adhesion strength, ranging from 27.3 to 29.0 MPa. Microstructural observation using field-emission gun scanning electron microscopy and transmission electron microscopy showed that CNTs with a typical tubular structure were found in the HA-CNT composite coatings. Nanoindentation tests revealed that the mechanical properties, such as the hardness and elastic modulus, were significantly improved by the addition of the CNTs to the HA coating. In addition, the proliferation and alkaline phosphatase (ALP) activity of MC3T3-E1 pre-osteoblast cells grown on the HA-CNT composite coatings were higher than those on the bare Ti and pure HA coating. The ALP activity of the composite coatings considerably improved as the CNT content increased. These results suggest that CNTs would be an effective reinforcing agent to enhance both the mechanical and biological performances of HA coatings.

Membrane of hybrid chitosan-silica xerogel for guided bone regeneration.

Chitosan-silica xerogel hybrid membranes were fabricated using a sol-gel process and their potential applications in guided bone regeneration (GBR) were investigated in terms of their in vitro cellular activity and in vivo bone regeneration ability. TEM observation revealed that the silica xerogel was dispersed in the chitosan matrix on the nanoscale. The hybrid membrane showed superior mechanical properties to chitosan in the wet state and the rapid induction of calcium phosphate minerals in simulated body fluid, reflecting its excellent in vitro bone bioactivity. Osteoblastic cells were observed to adhere well and grow actively on the hybrid membrane to a level higher than that observed on the chitosan membrane. The alkaline phosphatase activity of the cells was also much higher on the hybrid than on the chitosan membrane. The in vivo study in a rat calvarial model demonstrated significantly enhanced bone regeneration using the hybrid membrane compared to that observed using the pure chitosan one. Histomorphometric analysis performed 3 weeks after implantation revealed a fully closed defect in the hybrid membrane, whereas there was only 57% defect closure in the chitosan membrane.

Chitosan/nanohydroxyapatite composite membranes via dynamic filtration for guided bone regeneration.

Chitosan/hydroxyapatite (HA) composite membranes were prepared by the coprecipitation method and a subsequent dynamic filtration and freeze-drying process. The influences of the HA content of the membranes on their phase and morphology, mechanical properties, and bioactivity were investigated. FTIR analysis revealed that chitosan and HA had good miscibility over a wide range of compositions. Needle-like HA nanocrystals with low crystallinity were uniformly embedded in the chitosan matrix. As the HA content was increased, the tensile strength of the membranes exhibited a steady decrease, while the elastic modulus increased by a factor of 2 when 20% HA was added. The results of the in vitro cell culture showed that the highest alkaline phosphatase level was achieved when 30% HA was contained in the composites.

Three-layered membranes of collagen/hydroxyapatite and chitosan for guided bone regeneration.

The purpose of this study was to design a novel hybrid membrane with optimized properties for guided bone regeneration (GBR). Both the top and bottom layers of the sandwich-structured membrane were composed of collagen containing 20 wt% hydroxyapatite (HA), while the middle layer was made of chitosan. The above three layers were formulated into an integral membrane from their respective slurries through a layer-by-layer filtration process. The phase and composition of the membrane were confirmed by FT-IR and XRD analyses. The observation of its morphology by SEM showed that the membrane had a porous structure and structural integrity. The chitosan layer ensured the high tensile strength and elastic modulus of the membrane, while the presence of the collagen/HA composite layers endowed it with good flexibility and bioactivity. These results suggest that the integrated membrane prepared in this study would have the potential for use as a GBR material.

Bioactive nanocomposite coatings of collagen/hydroxyapatite on titanium substrates.

Collagen/hydroxyapatite (HA) nanocomposite thin films containing 10, 20, and 30 wt.% HA were prepared on commercially pure titanium substrates by the spin coating of their homogeneous sols. All of the nanocomposite coatings having a thickness of approximately 7.5 microm exhibited a uniform and dense surface, without any obvious aggregation of the HA particles. A minimum contact angle of 36.5 degrees was obtained at 20 wt.% HA, suggesting that these coatings would exhibit the best hydrophilicity. The in vitro cellular assays revealed that the coating treatment of the Ti substrates favored the adhesion of osteoblast-like cells and significantly enhanced the cell proliferation rate. The cells on the nanocomposite coatings expressed much higher alkaline phosphatase (ALP) levels than those on the uncoated Ti substrates. Increasing the amount of HA resulted in a gradual improvement in the ALP activity. The nanocomposite coatings on Ti substrates also exhibited much better cell proliferation behaviors and osteogenic potentials than the conventional composite coatings with equivalent compositions, demonstrating the greater potential of the former as implant materials for hard tissue engineering.