A quinine-based quaternized polymer: a potent scaffold with bactericidal properties without resistance

The drug resistance caused due to the overuse of antibiotics has grown into an emerging threat. It is urgent to develop novel strategies to combat bacterial resistance. In this work, a quinine-based quaternized polymer with amphiphilicity (QMTA) was prepared by free-radical copolymerization of quinine and (2-methacryloyloxyethyl) trimethyl ammonium chloride (MTA). Biological activity assays revealed that the polymer sterilized the drug-resistant Gram-negative E. coli and non-resistant Gram-positive bacteria B. subtilis, exhibiting a MIC value of 2 μg mL−1 and a bactericidal rate of more than 95%. Most importantly, both E. coli and B. subtilis treated with the polymer didn't develop resistance even after their 16th passages. Also, the polymer has low toxicity at a dose of up to 128 μg mL−1. The mechanism studies through SEM and 3D-SIM images, fluorescence staining and membrane potential determination reveal that the positively charged QMTA initially concentrates on the surface of bacteria by electrostatic adsorption, changes the membrane potential, binds to the bacteria by its quinine chain, and destroys the membrane structure of the bacteria. This study provides a potential approach through the existing drug to develop new bactericidal reagent/polymer materials without resistance.