Synthesis, Characterization and Broad-Spectrum Bactericidal Effects of Ammonium Methyl and Ammonium Ethyl Styrene-Based Nanoparticles.

Untreatable infections, growing healthcare costs, and increasing human mortality due to the rising resistance of bacteria to most of the available antibiotics are global phenomena that urgently require the discovery of new and effective antimicrobial agents. Cationic macromolecules, acting as membrane disruptors, are widely studied, and several compounds, including two styrene-based copolymers developed by us (P5 and P7), have proved to possess potent broad-spectrum antibacterial effects, regardless of the resistance profiles of the bacteria. Here, we first reported the synthesis and physicochemical characterization of new cationic nanoparticles (NPs) ( and ), obtained by polymerizing the monomers 4-ammoniummethylstyrene (4-AMSTY) and 4-ammoniumethylstyrene (4-AESTY) hydrochlorides, whose structures were designed using the cationic monomers of P5 and P7 as template compounds. The antibacterial activity of and was assessed against several Gram-positive and Gram-negative multi-drug resistant (MDR) pathogens, observing potent antibacterial effects for both (MICs = 0.1-0.8 µM) and (MICs = 0.35-2.8 µM) against most of the tested isolates. Additionally, time-killing studies carried out with and on different strains of the most clinically relevant MDR species demonstrated that they kill pathogens rapidly. Due to their interesting physicochemical characteristics, which could enable their mutual formulation as hydrogels, and could represent promising ingredients for the development of novel antibacterial dosage forms for topical applications, capable of overcoming severe infections sustained by bacteria resistant to the presently available antibiotics.