CO-driven cascade disruption of outer membrane barrier: A potent strategy to enhance treatment of gram-negative bacterial infections

The robust outer membrane (OM) barrier is a major contributor to antibiotic resistance in multidrug-resistant Gram-negative bacteria (MDR GNB). Disrupting this barrier presents a promising strategy to overcome this challenge. Herein, we propose a carbon monoxide (CO)-driven cascade inhibition strategy to disrupt the OM barrier, aiming to significantly boost the antimicrobial efficacy of existing treatments. As a proof of concept, we developed AIE&CO@G3, a nanogel that combines CO-releasing molecules (CORM-401) and aggregation-induced emission (AIE) photosensitizer (PSs). CO significantly potentiated the antimicrobial activity of AIE PSs-based antimicrobial photodynamic therapy (AIE-aPDT), with similar synergistic effects observed when combined with multiple first-line antibiotics. Mechanistically, CO-induced OM disruption facilitated the penetration of AIE PSs and antibiotics, thereby substantially boosting their efficacy both in vitro (against multiple MDR GNB) and in vivo (in models of MDR P. aeruginosa-infected bacterial keratitis and pneumonia). This was achieved by inhibiting adenosine triphosphate (ATP) synthesis and disrupting the biosynthesis and transport of glycerophospholipids (GPL) and lipopolysaccharides (LPS). This pioneering study highlights CO's potential in OM disruption and provides a novel strategy for combating MDR GNB infections.