Zwitterionic polymethacrylamides, poly(N-alpha-methacrylamide-L-lysine) [poIy(alpha-LysMA)] and poly(N-epsilon-methacrylamide-L-lysine) [poly(epsilon-LysMA)] were prepared to examine their bioactivity by an evaluation of fibrinolytic activity and a binding assay using resonant mirror biosensor (IAsys). Poly(alpha-LysMA) enhanced the fibrinolytic activity by plasminogen/tissue-type plasminogen activator while no enhancement was observed in the case of poly(epsilon-LysMA). A strong interaction between Pig to poly(alpha-LysMA) was also observed by IAsys when compared with poly(epsilon-LysMA).