Heparin bioconjugate with a thermoresponsive cationic branched polymer: a novel aqueous antithrombogenic coating material.

With a view to reducing the thrombogenic potential of artificial blood-contact devices and natural tissues, we developed a novel aqueous antithrombogenic coating material, comprising a heparin bioconjugate that incorporated a thermoresponsive cationic polymer as a surfactant. The polymer was prepared by the sequential steps of initiator-transfer agent-terminator (iniferter)-based living radical photopolymerization of N-[3-(dimethylamino)propyl]acrylamide, followed by the polymerization of N-isopropylacrylamide from tetra(N,N-diethyldithiocarbamylmethyl)benzene as a multifunctional iniferter. The polymer obtained possessed four branched chains, each consisting of a cationic PDMAPAAm block (Mn:  ca. 3000 g·mol-1) forming an inner domain for heparin binding and a thermoresponsive PNIPAM block (Mn:  ca. 6000 g·mol-1) forming an outer domain for surface fixation; bioconjugation of the polymer with heparin occurred immediately upon simple mixing in an aqueous medium. Because the lower critical solution temperat...