Insights into the Antibacterial Mode of Action of Cress Polysaccharide-Mediated NiO Nanoparticles

The global rise in resistance of pathogenic bacteria to the available therapeutics poses a serious challenge to the healthcare system. Recent studies unveiled the antimicrobial potential of nanoparticles. Here, we demonstrate that biocompatible green-synthesized nickel oxide nanoparticles (NiO NPs) eradicate resistant pathogenic bacteria through a concerted mechanism involving ROS-induced oxidative stress, membrane damage, and DNA fragmentation. Green synthesis of cress ( Lepidium sativum ) seed mucilage polysaccharides-based NiO (CSP-NiO) NPs was validated through extensive characterization using UV-Vis, FTIR, XRD, SEM, and EDX. The CSP-NiO NPs exhibited excellent biocompatibility with minimal hemolytic activity (< 5% at 200 µg/mL) and a dose-dependent antibacterial activity against both Gram-positive ( S. aureus and C. tetani ) and Gram-negative ( E. coli and K. pneumoniae ) pathogenic bacteria, with zone of inhibition increasing from 2.5 ± 0.38 to 10.25 ± 0.58 mm and MIC values ranging from 25 to 50 µg/mL. Growth kinetic analyses demonstrated a dose-dependent suppression of bacterial proliferation, while DCFH-DA fluorescence revealed a 1.6 to 2.0-fold increase in intracellular reactive oxygen species (ROS) levels compared to the controls. The protein leakage assay indicated significant membrane disruption up to 46.23 µg/mL, and agarose gel electrophoresis demonstrated extensive DNA fragmentation at higher concentrations. Our findings establish CSP-NiO nanoparticles as potent, biocompatible antibacterial agents and a promising sustainable platform against antibacterial resistance.