Application of radiation-grafted hydrogels as blood-contacting biomaterials

This article reviews the interactions of radiation-grafted hydrogels with blood and its components, both in vitro and in vivo. It has been found that as the hydrogel water content increases for radiation-grafted hydrogels of moderate to high water contents (15-85%) they tend a) to adsorb fewer protein molecules, and to desorb them more readily in vitro, b) to form thrombus but to adhere the thrombi less readily in the in vivo canine ring tests, and c) to cause more rapid formation and greater volumes of platelet microemboli in the ex vivo A-V femoral baboon shunt. At low water contents (below 10%) the grafted HEMA/EMA copolymer "hydrogels" exhibit an unexpected minimum in platelet consumption, which may be related less to the absorbed water in the graft copolymer than to the polymer composition at the surface. These results suggest that special radiation graft copolymer compositions may be selected to fit specific biological needs.