Responsive Quaternized PDMAEMA Copolymers with Antimicrobial Action.

Theodore Manouras,Maria Vamvakaki,Maria Chatzinikolaidou,Varvara Platania,Anthie Georgopoulou

doi:10.3390/polym13183051

Abstract

In this work, the antimicrobial action of partially quaternized poly(2-(dimethylamino)ethyl methacrylate) (PQDMAEMA) copolymers using different alkyl halides is presented. The poly(2-(dimethylamino)ethyl methacrylate) (PDMAEMA) homopolymer was synthesized by group transfer polymerization, followed by the modification of its tertiary amine groups, using bromoethane, iodoethane, bromohexane and bromoethanol, to introduce permanent cationic, quaternary ammonium salt moieties, randomly distributed along the polymer chains. In all cases, the degree of quaternization was low, at ~10 mol%, as verified by proton nuclear magnetic resonance spectroscopy to preserve the thermo-responsive character of the PDMAEMA precursor polymer. The biocidal activity of the lightly quaternized PQDMAEMA copolymers against Escherichia coli and Staphylococcus aureus was evaluated by calculating the minimum inhibitory concentration (MIC) as well as the minimum bactericidal concentration (MBC) of the polymers and by comparing them to the respective values of the precursor non-quaternized PDMAEMA homopolymer. The antibacterial mechanism of action in the solution was studied by zeta potential measurements, scanning electron microscopy and protein leakage tests signifying the disruption of the outer membrane of the bacterial cells to release their periplasmic proteins.

Highlights

Microbial infections and diseases induced by pathogens, such as, bacteria, viruses and fungi, comprise a major threat to human health [1]
The degrees of quaternization of the poly(2(dimethylamino)ethyl methacrylate) (PDMAEMA) homopolymer were calculated by ratioing the integrals of the peaks which correspond to the methylene protons next to the nitrogen atom, before and after quaternization, at 2.6 ppm and 4.4 ppm, respectively
The molecular weights of the quaternized polymers were calculated from the molecular weight of the PDMAEMA homopolymer and the respective alkylating agent, using the degree of quaternization of each copolymer found by 1H NMR spectroscopy, and were found to be 26,500, 25,700, 26,000 and 26,800 for PQDMAEMA-EtI, PQDMAEMA-EtBr, PQDMAEMA-EtBrOH and PQDMAEMA-HexBr, respectively

Summary

Introduction

Microbial infections and diseases induced by pathogens, such as, bacteria, viruses and fungi, comprise a major threat to human health [1]. The antimicrobial action of these nanoparticles is based on four different mechanisms, operating simultaneously, and includes the adhesion of the nanoparticles onto the cell membrane, the penetration of the nanoparticles inside the bacteria to induce damage of the intracellular parts, the oxidative stress caused by the production of reactive oxygen species and the modulation of the signal transduction pathways of the bacteria [13] Another class of effective antimicrobial materials are those based on cationic compounds in the form of small molecules or polymers and these have been widely used as platforms to address bacterial contamination both in solution and on surfaces. Random copolymers bearing protonated 4-ammoniumbuthylstyrene units have been employed as broad spectrum antibiotics with enhanced killing efficiency against both gram-positive and gram-negative bacteria strains [17]

Methods

Results

Conclusion