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Abstract
An organotypic culture assay has been used to assess the biocompatibility and cytotoxicity of an arterial prosthesis developed at the University of Texas-Arlington (the UTA graft) from a structurally modified polyurethane (PU) elastomer (Tecoflex®). The cell culture test was applied to the UTA graft after sterilization by ethylene oxide and by gamma radiation in two separate series. First, small specimens of the prosthesis were incubated for 7 days on a semisolid nutrient medium with their luminal surface in direct contact with endothelium explanted from the aorta of chick embryos. Second, the possibility of cytotoxic contaminants being leached from the polyurethane was assessed by immersing the biomaterial in the liquid culture medium for 5 days at 37°C prior to conducting the organo-typic culture assay on a standard control surface.
The structure of the UTA polyurethane prosthesis is porous, but the graft wall is impervious because it contains closed (i.e., noncommunicating) pores. In addition, four other vascular prostheses were included in the study for comparison. They were the Hydrophilic Mitrathane® PU graft with a similar impervious, closed pore structure, an experimental Hydrophobic Mitrathane® PU graft with a fibrous, open pore structure, and the commercial Impra® and Reinforced Goretex® expanded PTFE grafts.
Following 7 days of cell culture, the biocompatibility and cytotoxicity of the various biomaterials were measured in terms of the area of migrating cells, the density of cells surrounding the explants, and the level of cell adhesion. Comparison of the results against control cultures demonstrated that the UTA graft, along with the other four prostheses, does not release cytotoxic extractables. Microscopic observations of its cultured surface indicated that the UTA graft promotes a high density of cell growth over a limited area, similar to the Hydrophilic Mitrathane® graft. This level of biocompatibility is considered inferior to that of the two PTFE and the Hydrophobic Mitrathane® prostheses, which promote more extensive cell migration, greater cell adhesion, and cell growth in a continuous single layer.