Antimicrobial Activity of Nitric Oxide Delivery Nanoparticles for Lipopolysaccharides-Deficient Gram-Negative Bacteria

The rapid emergence of antimicrobial resistant Gram-negative bacteria compromises current antibiotic efficacy, including the last-resort antibiotic polymyxins, emphasizing the urgent need for novel therapeutic strategies. Nanoscale-based antimicrobials exhibit potential as an alternative treatment strategy. In this study, four furoxan-based nitric oxide (NO)-releasing nanoparticles (NPs) were prepared and their antimicrobial efficacy was tested against different Gram-negative bacteria, including: Acinetobacter baumannii, Pseudomonas aeruginosa, Klebsiella pneumoniae, and Escherichia coli via minimum inhibitory testing, where NPs exhibited selective activity against lipopolysaccharide (LPS)-deficient A. baumannii strains and LPS-truncated strains tested. Advanced microscopic techniques and mechanistic investigations using model membranes mimicking the LPS-deficient A. baumannii membrane and LPS-containing membrane, via neutron reflectometry and small-angle neutron scattering, indicated that the NPs specifically destabilize the LPS-deficient A. baumannii membrane, leading to the release of cellular content. This work provides mechanistic insight into the selective activity of the NPs against LPS-deficient A. baumannii and their lack of efficacy in strains with LPS, highlighting membrane-level determinants that may inform future antimicrobials development.