Further Biocompatibility Testing of Silica-Chitosan Complex Membrane in the Produciton of Tissue Plasminogen Activator by Epithelial and Fibroblast Cells

摘要

The effects of the physiochemical characteristics of a silica-chitosan complex membrane (SiCM) on the expression of tissue plasminogen activator (tPA) by contacting cells were investigated with the aim of improving the biocompatibility of the novel implant biomaterial. Expression of tPA is considered to be effective in wound healing by preventing thrombus formation, which causes inflammatory responses and rejection of implant materials, Inducting the epithelicla cells surrounding implant materials to secrete tPA, which served as an early signaling system to proliferate cells underlying connective tissues, would be further effective in accelerating wound healing. An epithelial 293 cell line derived from human embryonic kidney and a fibroblast IMR-90 cell line from human lung possessing the ability to secrete tPA were cultured on SiCMs, whose composition was stepwise controlled by adjusting the mixing ratio between silica and chitosan to give silica contents of 20, 33, 43, and 50wt%. Both strains showed strong adhesion on chitosan (0%-SiCM) and 50%-SiCM. The cell proliferation rates were also accelerated in a manner that was dependent on the increase in the adhesion strength of the cells cultured on the SiCMs. Furthermore, the tPA activity in the culture medium increased in accordance with the cell density, while the cellular specific activity of IMR-90 cells to secrete tPA was synergistically enhanced by strong adhesion and a high cell density on the surface of chitosan and 50%-SiCM. Analysis of the physicochemical effects of the SiCMs revealed that the cells were dominantly affected by the surface hydrophobicity rather than by the zeta potential, as well as by the mixing ratio between chitosan and silica. The wet contact angles of 50%-SiCM and chitosan, which were 68 deg and 65 deg, respectively, were found to be suitable for adhesion and growth of both the epithelial 293 cells and fibroblase IMR-90 cells. A hydrophobic surface at 65 deg-68 deg was also effective for the production of tPA by IMR-90 cells, whereas the tPA activity of 293 cells reached its highest level on the SiCM with a wet contact angle of 63 deg. These results suggest that a suitable adhesion strength is a significant factor in the expression of tPA by cells contacting an implant biolmaterial.