In Vitro Evaluation of Six Different Segmented Polyurethanes and HEMA/St Block Copolymer Using Epifluorescent Video Microscopy

Abstract

We evaluated the blood compatibility of six different segmented polyurethanes (PU), including five polyether-PUs and one polyurethane-urea (PUU), with poly (tetramethylene etherglycol) (PTMG) as the soft segment, using epifluorescent video microscopy (EVM) combined with a parallel plate flow chamber. An amphiphilic block copolymer composed of 2-hydroxyethyl methacrylate (HEMA) and styrene (St) (HEMA/St), which has already been proven to be an excellent nonthrombogenic polymer, was used as a control. The EVM system measured the platelet adhesion on the surfaces of the PUs, using whole human blood containing Mepacrine-labeled platelets perfused at a wall shear rate of 200 s−1 at 1-min intervals for a period of 20 min. Platelet activation (β-thromboglobulin; β-TG) and complement activation (C3 activation products; C3a) were also measured. PUU showed significantly higher levels of platelet adhesion than the other PUs. However, PU-PTMG (MW, 1500) showed the lowest platelet adhesion among the six PUs, comparable to that of HEMA/St. The β-TG levels of each polymer also corresponded to the platelet adhesion results. Furthermore, complement activation was inversely correlated with the results for platelet adhesion and activation potentials, except for HEMA/St, which showed the lowest platelet and complement activation levels. From their chemical compositions, we divided these PUs into three categories; (A) PUU, (B) PUs with a PTMG of lower MW and (C) PUs with a PTMG of higher MW. From our experimental results, we confirmed that, of these PUs, (C) showed the lowest levels of platelet adhesion and a higher activation level than (B), with (A) showing the highest platelet adhesion and complement activation level of the three categories. From these findings, it can be seen that the blood compatibility of the PUs was greatly influenced by the MW of the PTMG as the soft segment. We also found that the blood compatibility of the PUs varied according to whether urea binding was present.