Bio-assisted synthesis, characterization, and antibacterial efficacy of titanium dioxide nanoparticles mediated by Pterolobium hexapetalum leaf extract

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.