Preparation of zwitterionic random and block poly(-α-acrylamide--lysine--2-methacryloyloxyethyl phosphorylcholine) copolymers and their effect on fibrinolytic activity

Random copolymers [P(L- r -M)] and block copolymers [P(L- b -M)] composed of N -α- l -lysineacrylamide (LysAA) and 2-(methacryloyloxyethyl phosphorylcholine) (MPC) were prepared by radical polymerization or reversible addition-fragmentation chain transfer (RAFT) polymerization. Poly(LysAA)-immobilized glass substrates (L- g -GL) and poly(LysAA- co -MPC) random copolymer immobilized glass substrates [LM( m : n )- g -GL] were prepared to create biomaterials with good antithrombotic properties. Such materials allow long-term selective binding of serum fibrinolytic factor (plasminogen: Plg; tissue-type plasminogen activator: t-PA), while exhibiting low adsorption of other serum proteins and suppressing their denaturation. The fibrinolytic activity of the LysAA-containing polymers in liquid and solid-phase conditions was evaluated using the chromogenic plasmin substrate H- d -Val-Leu-Lys- p -nitroaniline (S-2251) and Plg/t-PA in the presence of poly(LysAA), L- g -GL or P(L- r , b -M), and LM( m : n )- g -GL. The enzymatic reaction of Plg/t-PA was maximally enhanced under liquid-phase conditions with P(L- r -M) containing 75 mol% of LysAA in the copolymer but not with poly(LysAA). The solid-phase condition was greatly enhanced by LM(8:2)- g -GL containing a mol ratio of LysAA that approximated the liquid-phase condition. Enhancement was also observed for LM(2:8)- g -GL containing 20 mol% LysAA, which was not enhanced in the liquid-phase condition. We have developed N -α-lysine acrylamide (LysAA) with a lysine side chain that enhances the fibrinolytic system; random copolymerization of LysAA with MPC [20% molar ratio] enhanced the fibrinolytic activity of LysAA.