Conjugated oligoelectrolytes (COEs) are an emerging class of amphiphilic antimicrobial compounds with a modular molecular framework suitable for simple chemical derivatization. Here, a series of COE derivatives with a stilbene-conjugated segment and triphenylphosphonium (TPP) pendant groups was designed and synthesized to understand how lipophilic cationic groups impact antimicrobial activity. In vitro evaluations against ESKAPE pathogens showed broad-spectrum activity towards multi-drug resistant (MDR) bacteria and mycobacteria, with TPP groups enhancing antimicrobial activity towards clinically relevant Gram-negative strains compared to their ammonium analogues. We studied the interactions of DM6P, the most active TPP-COE compound, with various membrane assays. Treatment of bacterial cells with DM6P showed enhanced permeability of cell membranes without inducing the development of significant bacterial resistance. Moreover, DM6P eliminated 99.99 % of methicillin-resistant Staphyloccocus aureus (MRSA) in an in vivo wound model. These results represent a promising chemical strategy for increasing the activity spectrum of membrane-active COE antibiotics to tackle challenging drug-resistant targets.
Keywords: antimicrobial agents; conjugated oligoelectrolytes; mycobacteria; phosphonium; structure−activity relationships.
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