Structure–Activity Relationships and Practical Aspects of Cationic Gemini Surfactants as Antimicrobial Agents

Abstract

This mini-review summarizes current knowledge on cationic gemini surfactants as antimicrobial agents, with a focus on the structure–activity relationships that link their molecular architecture including headgroup type, alkyl chain length, spacer structure, and counter-ion identity to antimicrobial activity. Analyses of these relationships reveal consistent trends, such as the characteristic alkyl chain length cut-off and the influence of charge density and critical micellar concentration on biological activity. Compared with monomeric surfactants, gemini surfactants generally exhibit greater potency and broader antimicrobial spectra, although systematic investigations into resistance mechanisms remain limited. Documented mechanisms such as efflux pumps and biofilm tolerance highlight the importance of monitoring resistance development. Collectively, this review offers a mechanistic framework and practical insights for guiding the design, evaluation, and safe application of gemini surfactants in antimicrobial contexts.