Phytofabrication of copper oxide nanoparticles via Brassica napus L. var. napobrassica revealing mechanistic insights into ROS-induced antimicrobial and antibiofilm activity

The present study reports the phytofabrication of copper oxide nanoparticles (CuO NPs) using B. napus var. napobrassica extract, followed by comprehensive physicochemical characterization and evaluation of their antimicrobial and antibiofilm activities. The biosynthesized CuO NPs were characterized using UV–Vis, FT-IR, XRD, SEM, and DLS analyses. UV–Vis spectra confirmed nanoparticle formation with a narrow peak between 325 and 355 nm, while FT-IR results indicated the involvement of plant-derived functional groups in reduction and stabilization processes. XRD analysis verified the crystalline monoclinic phase of CuO, and SEM images revealed predominantly roughly spherical to aggregated morphologies with nanoscale dimensions. DLS results showed a hydrodynamic diameter of ~ 257 nm with moderate polydispersity. The antimicrobial activity of CuO NPs was assessed against Staphylococcus aureus , Escherichia coli , and Aspergillus niger . The nanoparticles exhibited strong antibacterial activity, with inhibition zones of 21 mm and 17 mm against S. aureus and E. coli , respectively, and notable antifungal activity (26 mm) against (A) niger . Minimum inhibitory concentration (MIC) values were determined as 50 µg/mL for S. aureus and 100 µg/mL for E. coli , with corresponding bactericidal effects (MBC/MIC = 2). Furthermore, CuO NPs demonstrated significant biofilm inhibition, reaching up to 89% and 84% inhibition for S. aureus and E. coli , respectively, at 200 µg/mL. Mechanistic investigations using the DCFH-DA assay revealed a concentration-dependent increase in intracellular reactive oxygen species (ROS) generation, with S. aureus exhibiting higher sensitivity than E. coli . The results indicate that ROS-mediated oxidative stress plays a crucial role in the antimicrobial and antibiofilm activity of CuO NPs. To the best of our knowledge, this study is the first to report the phytofabrication of CuO NPs using (B) napus var. napobrassica extract and to systematically correlate their physicochemical properties with antimicrobial, antibiofilm, and ROS-mediated mechanisms. Taken together, the results of the study demonstrates that CuO NPs synthesized via a green route using B. napus var. napobrassica extract possess potent antimicrobial properties and hold significant potential for biomedical and environmental applications.