Selective Antifungal Activity of Hyperbranched Polylysine Mediated by Charge-dependent Membrane Interactions

Abstract

Invasive fungal infections remain a significant global health threat, and the development of antifungal agents that selectively target fungi remains a critical challenge. This study investigates hyperbranched polylysine (HPL) with tunable molecular weight and charge density as a potential selective antifungal candidate. HPL1, with the lowest molecular weight, showed negligible antimicrobial activities, while HPL3, with the highest molecular weight, exhibited broad-spectrum antimicrobial effects against both bacteria and fungi. Notably, HPL2, the mediate molecular weight, demonstrated selective antifungal activities against clinically relevant Candida species, including C. albicans, C. krusei, C. parapsilosis, C. tropicalis, and C. glabrata. This selectivity is mainly ascribed to its optimal zeta potential and appropriate hydrodynamic size, enabling HPL2 to penetrate through the fungal cell wall while stuck in bacterial cell envelopes. Mechanistic studies revealed that HPL2 initially adheres to the fungal surfaces induced via electrostatic interactions, then passively penetrates the fungal cell wall, disrupts membrane integrity, induces intracellular damage, and ultimately leads to cell death. Furthermore, HPL2 exhibited excellent biocompatibility and in vivo therapy efficacy with minimal disruption to host gut microbiota. These results highlight HPL2 as a promising antifungal agent with potent efficacy and favorable safety, which can be easily synthesized at kilogram scale.