Biocompatibility and surface modification of metallic biomaterials in biochemical/ mechanical environment

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In this study, I revealed that dissolution and repassivaiton behavior strongly depended on substrate material even with/ without cells. On Ti6Al4V alloy, a slight increase of current was observed in elastic region due to the breakdown of passive films. Then soon after the plastic deformation started, the current rapidly increased, indicating that the area of newly created surfaces drastically increased as a result of formation of slip band. The similar current behavior was observed on pure Ti. On the other hand, for type 316L stainless steel, the current did not change in elastic region and started to increase at the onset of plastic deformation. After the end of elongation, the current rapidly decreased approaching to the level before straining as a result of repassivation. For the charge density during deformation, there was little difference with/ without cells. On the other hand, for the charge density after deformation, the larger charge density was recognized on the sample adsorbed proteins and the maximum charge density was observed on the sample with cells. This result suggests that proteins and cells inhibit the repassivation. When proteins or cells accumulate on the sample surface, a closed space is made between proteins or cells and metal surface. In this space, the diffusion of solute is blocked and H+ ions reach a high concentration. As a result, the pH becomes low and repassivation is inhibited. The current stagnation on Ti6Al4V alloy with cells is the remarkable example of the repassivation inhibition.