Bio-assisted synthesis, characterization, and antibacterial efficacy of titanium dioxide nanoparticles mediated by...

The search for high-efficiency antimicrobial nanomaterials has intensified due to the escalating threat of antibiotic resistance. In this study, titanium dioxide nanoparticles (TiO₂ NPs) were synthesized using aqueous leaf extract of Pterolobium hexapetalum. Physicochemical characterization confirmed the formation of a pure nanocrystalline anatase phase (XRD) with a primary crystallite size of 10-15 nm and an optical band gap of 3.18 eV. While UV-Visible spectroscopy showed characteristic absorption bands at 209.5 and 270.5 nm, DLS and Zeta potential (+ 9 mV) measurements indicated that the nanoparticles exist as aggregated colloidal clusters with a hydrodynamic diameter of 399.2 nm. FTIR and SEM verified the presence of plant-derived functional groups and a clustered, rough surface morphology. Biological evaluation via agar well diffusion, MIC, and MBC assays demonstrated that the TiO₂ NPs significantly outperformed the parent leaf extract. At a dose of 100 µg/well, the TiO₂ NPs produced inhibition zones of 22.67 mm for Staphylococcus aureus and 27.67 mm for Escherichia coli, surpassing the absolute zones produced by the ciprofloxacin (5 µg/well) control. The MIC values (31.25-62.5 µg/mL) and an MBC/MIC ratio of 2 indicate a potent, primarily bactericidal mode of action, achieving a two- to four-fold increase in potency over the crude extract. These findings establish P. hexapetalum-mediated TiO₂ NPs as a promising platform for antimicrobial applications in wound care and decontamination technologies.