In Vitro and in Vivo Nonthorombogenicity of Microdomain Polymers

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We have already reported that block copolymers composed of 2-hydroxyethyl methacylate (HEMA) and styrene (St), having hydrophilic/hydrophobic microdomain structures, demonstrated excellent nonthorombogenicty. In this study, we discuss about relationship between surface structure and activation of platelets by using well-defined HEMA-St block copolymer. The surface structure of block copolymers were estimated by TEM observation, ESCA measurement and contact angle measurement. The lamella structure was clearly observed by TEM and domain spacings were from 100 to 600A. ESCA and contact angle measurement suggested that St segment was concentrated on air surface at dry state. After soaking polymers into water, however, wetability of polymer surface increase and contact angle of polymer surface show almost same value as that of PHEMA. Nonthombogenicity of block copolymers were measured by column method. As the domain spacing was altered, the platelet adhesion exhibited minimum value at 160A of micro domain spacing. Furthermore, to clarify effects of membrane movement on platelets adhesion on polymer surface, platelets were treated with low temperature and colchichine In the block copolymer coated glass bead column, the amount of eluted platelet show no deference between colchichine treated PRP and control PRP. This results indicate that platelets membrane movement was suppressed without drug when platelet contact with the micro domain structure and the active adhesion of platelet is not progressed. Further more, as in vivo application, new skin grafting technique with using artificial blood tubes as saphenous blood tubes was developed.