IN-VITRO EVALUATION OF PLATELET BIOMATERIAL INTERACTIONS IN AN EPIFLUORESCENT VIDEO MICROSCOPY COMBINED WITH A PARALLEL-PLATE FLOW CELL/

Suitable evaluation systems are critical for ranking various biomateri als in order to develop a method to design and synthesize nonthromboge nic biomaterials. We have recently developed an in vitro test system t o evaluate platelet/biomaterial interactions in whole blood. The syste m consists of a parallel plate flow cell and epifluorescent video micr oscopy (EVM). A glass coverslip coated with a polymer was incorporated into the flow cell, and blood was perfused using a syringe pump via a polymer-coated PVC tubing connected to the flow cell. Whole human blo od was anticoagulated with heparin (2 U/ml), and the platelets were la beled with the fluorescent dye mepacrine (5 mu M). This system permitt ed real-time and dynamic observations of platelet/biomaterial interact ions in whole blood under a defined flow condition. In order to evalua te the feasibility of this system, two different segmented polyether-p oryurethanes (SPEUs), PU-PTMG(650) and PU-PTMG(2000), were chosen as t est polymers. Surface characteristics verified with electron spectrosc opy for chemical analysis (ESCA) and contact angle measurements showed similar results in both SPEUs. Blood was perfused at a wall shear rat e of 200 s(-1) for 20 min. Excitation light was applied for 2 s at 1 m in intervals. The real-time image was then analyzed at each time point for the percentage of surface area of platelet coverage. Plasma beta- thromboglobulin (beta-TG) levels were also measured before and after e ach run. PU-PTMG(650) showed a significantly higher number of adhered platelets than PU-PTMG(2000) at each time point. beta-TG levels of PU- PTMG(650) were also higher than those of PU-PTMG(2000), which is compa rable to the results of EVM. Thus, this EVM system has been proven to be an excellent and highly sensitive in vitro analytical method for ev aluating platelet/biomaterial interactions.