Enhancement of Cationic Antimicrobial Materials via Cholesterol Incorporation

Abstract

Cationic antimicrobial materials are an attractive option for treating drug-resistant bacteria. Their membrane lytic mechanism can provide broad spectrum antimicrobial activity while largely negating natural resistance development. Selectivity is achieved using non-specific electrostatic interactions since microbial membranes display significantly more peripheral negative charge than due eukaryotic bilayers. Following membrane association, structural changes occur causing bilayer destabilization and cell lysis. Herein, antimicrobial effects of enhanced membrane assimilation are examined. Cholesterol, a functionalizable small molecule that assimilates abundantly within cell membranes, is chosen to increase membrane penetration ability to improve antimicrobial activity. Furthermore, cholesterol has an ability to template interesting nanostructures due to its propensity for rotative face-on-face stacking. The installation of cationic polycarbonates with systematically varied chain lengths from three separate cholesteryl initiators is accomplished using organocatalytic ring-opening polymerization. Introduction of cholesteryl oligomers into aqueous media creates "coin" shaped self-assemblies possessing high exterior cationic charge density. Continued evaluation of these assemblies demonstrates broad spectrum activity against S. epidermidis, S. aureus, E. coli, P. aeraginosa, and C. albicans. Additional results show that, despite repeated sub-lethal dosing, E. coli does not evolve drug-resistance and maintains the wild-type minimum inhibitory concentration of 31.3 mg L-1. © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.