Mechanistic insights of arginine-based surfactant interaction with bacteria and mammalian model lipid membranes.

Arginine-based surfactants exhibit antimicrobial activity attributed to their positive net charge and amphiphilic nature. These compounds typically disrupt cytoplasmic membranes, leading to cell leakage. We studied the mechanism of action of Nα-benzoyl-L-arginine dodecylamide (Bz-Arg-NHC12), an arginine-based surfactant synthesized in our laboratory through biocatalysis, using model lipid membranes. Bz-Arg-NHC12 shows selective membrane interactions, which correlate with its antimicrobial efficacy and haemolytic toxicity. In bacterial-like membranes, it penetrates deeply, increasing elasticity and destabilizing the membrane, leading to rapid vesicle permeabilization via sudden and graded lysis. Monolayer studies confirm strong electrostatic perturbations, consistent with dipole enhancement. For mammalian-like membranes, Bz-Arg-NHC12 incorporation appears as more superficial, preferentially partitioning into cholesterol-rich liquid-ordered domains in giant unilamellar vesicles. Surfactant enrichment stabilizes membranes and induces slow vesicle permeabilization, with lysis occurring primarily through graded mechanisms. Sub-lytic concentrations induce vesicle aggregation, while membrane solubilization aligns with higher thresholds. These findings highlight the potential surfactant's therapeutic window: deep bacterial membrane disruption drives antimicrobial action, while cholesterol-mediated superficial incorporation in mammalian membranes delays toxicity. Phase-selective liquid-ordered-domain localization may further enhance selectivity. These results provide a biophysical-based rationale for optimizing arginine surfactants as next-generation biocides.