Bactericidal materials prepared via conjugation of responsive polymers to cysteine

Abstract

Hybrid bioconjugates based on poly(N-isopropylacrylamide)(PNIPAM)/poly(acrylic acid) (PAA) and cysteine (Cys) (PNIPAM-Cys/PAA-Cys) were synthesized via combination of reversible addition–fragmentation chain-transfer (RAFT) polymerization and 2,2,6,6-tetra methylpiperidin-1-yl)oxyl (TEMPO) initiated thiol-ene reaction. In order to use cysteine for the preparation of these hybrids materials, functionalization of cysteine with 1,4-bis(acryloyloxy)butane was carried out using TEMPO initiated thiol-ene reaction in an aqueous medium under ambient reaction conditions. The synthesized Cys-Ene was characterized by 1H and 13C NMR spectroscopy and Zeta potential measurement. Thiol-functionalized responsive polymers, for example, PNIPAM-SH and PAA-SH were synthesized by RAFT polymerization followed by an aminolysis reaction. The resulting thiol terminated polymers were functionalized with Cys-Ene again using TEMPO initiated thiol-ene reaction in an aqueous medium under ambient reaction conditions to yield responsive hybrid bioconjugates. The synthesized hybrid materials were characterized by 1H NMR spectroscopy, UV-visible spectroscopy, dynamic light scattering and Zeta potential analysis. In addition, the antibacterial activity of hybrid materials based on cysteine was evaluated and the minimum inhibitory concentrations (MICs) were found to be 70 and 100 μg/mL against E. coli and R. erythropolis respectively. The results suggest that the constructed hybrid bioconjugates because of its efficacy towards a broad range of bacteria could potentially be useful in several biomedical applications.