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: <i>Acinetobacter baumannii</i>, <i>Pseudomonas aeruginosa</i>, <i>Klebsiella pneumoniae</i>, and <i>Escherichia coli</i> via minimum inhibitory testing, where NPs exhibited selective activity against lipopolysaccharide (LPS)-deficient <i>A. baumannii</i> strains and LPS-truncated strains tested. Advanced microscopic techniques and mechanistic investigations using model membranes mimicking the LPS-deficient <i>A. baumannii</i> membrane and LPS-containing membrane, via neutron reflectometry and small-angle neutron scattering, indicated that the NPs specifically destabilize the LPS-deficient <i>A. baumannii</i> membrane, leading to the release of cellular content. This work provides mechanistic insight into the selective activity of the NPs against LPS-deficient <i>A. baumannii</i> and their lack of efficacy in strains with LPS, highlighting membrane-level determinants that may inform future antimicrobials development.