REDUCTION OF SURFACE-INDUCED PLATELET ACTIVATION ON PHOSPHOLIPID POLYMER

omega-Methacryloyloxyalkyl phosphorylcholine (MAPC) polymers which hav e been synthesized with attention to the surface structure of a biomem brane show excellent blood compatibility, i.e., resistance to protein adsorption and blood cell adhesion. To clarify the stability of platel ets in contact with the MAPC polymer surfaces, cytoplasmic free calciu m concentration ([Ca2+](i)) in the platelets was measured. A platelet suspension was passed through a column packed with various polymer bea ds after treatment with plasma, and the [Ca2+](i) in the platelets elu ted from the column was measured. The [Ca2+](i) in contact with the MA PC polymers, i.e., poly[2-methacryloyloxyethyl phosphorylcholine-co-n- butyl methacrylate (BMA)] (PMEB) and poly(6-methacryloyloxyhexyl phosp horylcholine-co-BMA) (PMHB), was less than that in contact with poly(B MA). However, poly(10-methacryloyloxydecyl phosphorylcholine-co-BMA) ( PMDB) was not effective in suppressing the increase in [Ca2+](i), and thus was at the same level as in the poly(BMA). This result indicated that platelets in contact with PMEB or PMHB were less activated compar ed with those in contact with PMDB and poly(BMA). Moreover, the state of the platelets adhered to these polymer surfaces, both morphological ly and immunologically, was examined. Scanning electron microscopic ob servation of the polymer surface after contact with a platelet suspens ion revealed that many platelets adhered and changed their shape on th e poly(BMA). The numbers of adherent platelets were reduced on all MAP C polymer surface. The relative amount of cc-granule membrane glycopro tein (GMP-140) which appears on the cell membrane by activation of pla telets on the PMEB surfaces was less than that on poly(BMA) and poly(2 -hydroxyethyl methacrylate). These results suggest that PMEB and PMHB suppressed not only platelet adhesion but also activation of the plate lets in contact with these surfaces. (C) 1997 John Wiley & Sons, Inc.