Assessment of the biocompatibility of nanostructured polymeric fibers

It is proposed that to satisfy a growing percentage of the population that requires greater than thirty-year survivability of load-bearing bone replacement devices, a concept shift, from emphasis on replacement of tissues to regeneration of tissues, is required. Based on the bioactivity of hydroxyapatite (HA) and the excellent mechanical and biocompatible performance of polyethylene terephthalate (PET), a composite of PET filled with nanograde HA was designed and fabricated to mimic the structure of biological bone which exhibits a composite of nanograde apatite crystals and natural polymer. The PET/HA nanocomposite was fabricated by compounding, and spun into fiber form so that the mechanical properties of a given structure can be custom tailored by changing the final 3D orientation of the fibers. This study primarily focused on the in vitro biocompatibility evaluation of the novel PET/HA nanocomposite as potential biomaterials. In a second place, this work evaluated the HA nanoparticles effects on the polymeric fibers surface chemistry by XPS analysis, and compared the effects induced by ethylene oxide (EtO) and low temperature plasma (LTP) sterilization on the composites chemical composition by XPS and in vitro cytotoxicity.; More precisely, to assess the in vitro biocompatibility of the various PET/HA nanocomposite fibers we investigated the in vitro proliferation, morphology, and viability of L929 fibroblast cell line, as well as the inflammation potential of RAW 264.7 macrophages cultured on the fibers scaffolds and extracts. This was done through the MTT assay with the extracts of the composite fibers in order to evaluate the short-term effects of the degradation products. The cell morphology of L929 fibroblasts was analyzed after direct contact with the 3D fibers scaffolds for different time periods and the cell viability was also analyzed by the Alamar Blue assay. The release of the inflammatory cytokine, TNF-alpha from RAW 264.7 macrophages in the presence of fibers extracts and fibers was used as a measure of the inflammatory response. The PET/HA nanocomposite fibers (made by twin screw compounding and melt blowing) chemical composition with increasing amounts of HA nanoparticles was analyzed by XPS, so that the effects of the HA addition can be elucidated onto the PET/HA nanofibers surface chemistry. The surface modifications on the PET/HA nanocomposite fibers after UP and EtO sterilization, were assessed by XPS. The biocompatibility was reassessed as previously described with LTP- and EtO-treated fibers as a measure of the sterilization method on the PET/HA fibers biocompatibility.; The in vitro cytotoxicity was re-evaluated after the LTP and EtO treatments. Despite the resulting surface modifications, the cell viability of both LTP and EtO-treated fibers remained similar. Following macrophages incubation with the fibers, a trend of higher TNF-alpha release by the EtO-treated polymer, as compared to the LTP sterilized ones, was observed. This trend suggests a higher inflammatory potential for the EtO sterilized fibers.; In conclusion, the ability of the fiber matrices to support L929 attachment, spreading and growth in vitro, combined with the compatible degradation extracts and low inflammation potential of the fibers and extracts, suggests potential use of these composites as load-bearing bone biomaterials. In an attempt to elucidate the favorable biological response at higher HA concentrations it was seen that HA loading of fibers increases the overall O content of composites while HA remains undetected by XPS. Both sterilization treatments seem acceptable, but UP demonstrated an additional advantage by the beneficial hydroxyl functional groups additions onto the PET/HA nanocomposite fibers surface leading to better biologic response as seen by the inflammation potential decrease. (Abstract shortened by UMI.)...