Reactions of human platelets with microspheres of poly(hydroxymethyl methacrylate) and polyacrylamide

We have studied the contact interaction of platelets with hydrogels. In the form of microspheres, 0.6-1.0 mu, poly(glycol methacrylate) (polyHEMA) and poly(methyl methacrylate) beads cause platelets to aggregate at concentrations of about 10(8) beads/ml. Polyacrylamide and (20/80) poly(acrylamide-HEMA) copolymer were ineffective in aggregating platelets. The admixture of 20% methacrylate to polyHEMA rendered the beads inactive. Blood plasma components other than fibrinogen were found essential to the interaction of the beads with platelets. Near-infrared spectra of the hydrogels polyacrylamide and polyHEMA showed the water hydrogen bonds to be the same for both and different from those in pure water. The monomer HEMA is an inhibitor of platelet aggregation and the release reaction at levels of 0.1%. It is concluded that the two hydrogels have different blood compatibilities, which depend more on the network structures than the water structures in the respective gels.