DYNAMIC BLOOD-CELL CONTACT WITH BIOMATERIALS - VALIDATION OF A FLOW CHAMBER SYSTEM ACCORDING TO INTERNATIONAL STANDARDS

The increasing number of patients requiring prosthetic substitution of segments of the vascular system strongly supports the need to optimiz e a relevant, standardized testing panel for new materials designed fo r synthetic vascular prostheses. The ISO gives the standard requiremen ts for testing biomaterials provided for implantation. Our primary int erest was the establishment of a reliable in vitro panel as a useful a nd relevant screening system for vascular implant devices to evaluate blood/device interactions under flow conditions. The aim of the presen t study was to evaluate influences of different flow conditions on blo od cell-biomaterial interactions with special emphasis on the interact ions of human granulocytes (PMN) and polymeric surfaces. PMN were isol ated and vital cells were quantified by flow cytometrical analysis dir ectly before, as well as immediately after the experiments. The viscos ity of the final cellular suspension was analysed by using a computeri zed cone-plate rheometer. As reference materials we used FEP-teflon, P VC-DEHD, PU, PP and PE. Dacron and ePTFE synthetic vascular protheses were tested in a comparative way to those references. The adhesion pro cesses were observed over a period of 40 minutes under arterial (shear stress 0.74 Pa) and venous (shear stress 0.16 Pa) flow conditions in a parallel plate flow chamber system under highly standardized conditi ons and laminar flow. The cells were observed with the help of inverse light microscopy. Cell behaviour was recorded and analysed in both an alogue (video) and digital (imaging system) modes. Samples of the cell suspensions were obtained at regular time intervals and analysed by e nzyme linked immune sorbent assay (ELISA) to quantify LTB(4) release. Irrespective of the material, approximately 3 to 4 times more PMN adhe red to the biomaterial surfaces under venous flow conditions compared to the arterial. Shear intensity did not influence the running order o f biomaterials with respect to cell numbers. This response in descendi ng order at the end of the experiments was as follows: PU, PVC-DEHD, P P, PE and ePTFE. The biochemical analyses indicate that in the system used only a weak effect on LTB(4) release induced by the different mat erials could be determined. A significant effect caused by flow condit ions was not observed. Further experiments, both static as well as dyn amic, must be performed for multiple, relevant parameters of haemocomp atibility, for potential biomaterials as well as those currently in us e in vascular prostheses.