Antioxidant, Antimicrobial, and Molecular Binding Affinity Applications of Green-Synthesized Nickel Oxide Nanoparticles.

The preparation of metal or metal oxide nanoparticles (NPs) using the green method is rapid, low-cost, and eco-friendly. In this study, nickel oxide NPs (NiO NPs) were synthesized using Foeniculum vulgare seed extract. The green-synthesized NiO NPs were characterized by X-ray diffraction, X-ray photoelectron spectroscopy, Fourier-transform infrared spectroscopy, scanning electron microscopy (SEM), and transmission electron microscopy (TEM) techniques. SEM and TEM images revealed spherical and sheet-like morphologies. The NiO NPs exhibited notable antioxidant, antimicrobial, and molecular interaction properties. Antioxidant activity was evaluated using DPPH⁺ and ABTS⁺ assays, showing IC₅₀ values of 12.68 ± 0.56 and 11.82 ± 0.84 µg/mL, respectively, compared to standard antioxidants ascorbic acid (8.94 ± 2.2 µg/mL) and gallic acid (1.2 ± 0.67 µg/mL). Antibacterial assays against Staphylococcus aureus, Bacillus sp., Pseudomonas aeruginosa, and Escherichia coli revealed concentration-dependent inhibition, with maximum zones of inhibition at 80 µg/mL, measuring 7.86 mm for E. coli and 7.21 mm for S. aureus. Antifungal activity showed dose-dependent inhibition of Aspergillus niger (6.00-7.96 mm) but minimal effect on Fusarium sp. (6.00-6.03 mm), compared to ketoconazole controls (9.36 and 9.21 mm, respectively). Molecular docking revealed strong binding affinities of NiO NPs with P. aeruginosa (-9.9 kcal/mol) and A. niger endoglucanase (-8.5 kcal/mol), comparable to streptomycin (-11.1 kcal/mol) and ketoconazole (-10.0 kcal/mol). These findings highlight the promising antioxidant and antimicrobial potential of NiO NPs for biomedical applications.