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

Abstract

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.