| Summary: | 碩士 === 國立臺灣大學 === 材料科學與工程學研究所 === 88 === ABSTRACT
The biological compatibility of implant biomaterials is directly related to their surface properties. Inadequate surface processing and alloy manufacturing procedures have been attributed to the harmful effects observed after the implantation of metallic materials and, consequently, have limited the employment of these biomaterials as joint prostheses. However, recent advancement in metal processing techniques has made it possible to generate metallic biomaterials with improved surface properties that are more biocompatible. In light of the high failure rate of prosthesis using ultra-high molecular weight polyethylene (UHMWPE) in the contact interface, application of new metallic biomaterial in joint replacement surgery has been reevaluated by myriad orthopedic research centers.
The present work utilized nitrogen supplementation to cobalt-chromium-molybdenum (Co-Cr-Mo) alloys using high pressure induction melting (HPIM) to enhance metallic strength. Alloys so generated were examined for physical properties such as nitrogen content, metallic phases, and hardness. Furthermore, biocompatibility of these alloys was investigated by measuring proinflammatory responses of cultured murine macrophages in the context of different physical features, primarily nitrogen content and surface roughness. The muring macrophage cell line RAW264.7 was cultured in various Co-Cr-Mo alloys in the presence of a bacterial endotoxin, lipopolysaccharide (LPS), as proinflammatory stimulant and production of nitric oxide (NO), interleukin-1 (IL-1) and tumor necrosis factor- (TNF) by these cells was measured as indicators of inflammatory response. Within 24 hrs of culture period, nitrogen content appeared to have no effect on proinflammatory responses in these macrophages. On the other hand, surface roughness generated by diamond powder polish (smooth surface) or wheel grinding (rough surface) had significant impact on cellular responses. The rough surface was significantly more preferable than the smooth surface for macrophages to adhere. In addition, cell viability measurement indicated that these macrophages survived successfully on the rough surface while significant cell death occurred when cultured on the smooth surface. In contrast to inferior cell viability and adherence on the smooth surface, cells cultured in such condition produced significantly more amounts NO, IL-1, and TNF- in the presence of LPS stimulation. These data indicate that surface properties of implant alloys may play important role in the modulation of proinflammatory responses of macrophages. The data also support the proposition that increased roughness on the surface of prosthetic alloys where no joint contact was necessary may be beneficial for biocompatibility by reducing proinflammatory responses of adherent macrophages.
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