Green synthesis of Brassica rapa–mediated magnesium oxide nanoparticles MgO NPs with ROS-driven antibacterial and antibiofilm activities against multidrug-resistant gram-negative bacteria

The ability of multidrug-resistant Gram-negative bacteria to develop antibiotic-resistant biofilms enables their ongoing survival in various environments. In this study, MgO NPs were synthesized using an environmentally sustainable green method mediated by Brassica rapa . The antibacterial and antibiofilm activities of the synthesized MgO nanoparticles were evaluated against clinical isolates of A. baumannii , P. aeruginosa , K. pneumoniae , and E. coli . These nanoparticles were checked for their antibacterial and antibiofilm activities by broth microdilution assay and microtiter plate assay. The biogenic MgO NPs exhibited strong antibacterial activity with an MIC of 125–250 µg/ml and bactericidal effects at 500–1000 µg /ml. Planktonic growth inhibition exceeded 90% at 50 µg/ml after 48 h and reached 99% at 100 µg/ml after 72 h. Biofilm formation was suppressed by 60–90% at 50 µg/ml while pre-established biofilms were reduced by 97–99% following prolonged exposure. Mechanistic studies demonstrated substantial destruction of extracellular polymeric substances. Specifically, proteins decreased by 68%, carbohydrates by 55%, and extracellular DNA by 33%, while intracellular reactive oxygen species simultaneously increased by 2–3 times. The results demonstrate that Brassica rapa -derived MgO NPs function as effective, sustainable nanomaterial that prevents biofilm formation by multidrug-resistant Gram-negative pathogens.