Evaluation of the antibacterial effects of titanium nanoparticles at multiple concentrations

This study systematically investigates the concentration-dependent antibacterial efficacy of titanium nanoparticles (Ti NPs). Ti NPs were synthesized at 10%, 15%, and 25% concentrations in aqueous suspensions. Structural characterization via X-ray diffraction confirmed the crystalline metallic titanium phase with a hexagonal close-packed structure. Morphological analysis using field-emission scanning electron microscopy revealed particles in the nano-range (20–300 nm), with particle size decreasing and agglomeration increasing at higher concentrations. Optical properties assessed by UV–vis spectroscopy showed strong absorption between 200 and 300 nm, and Tauc plot analysis indicated a reduction in the optical bandgap from 5.55 to 4.55 eV with increasing concentration, attributed to defect-induced states. Zeta potential measurements confirmed decreased colloidal stability at elevated concentrations. Antibacterial activity was evaluated against Klebsiella pneumoniae and Staphylococcus aureus using disk diffusion and minimum inhibitory concentration (MIC) assays. The results demonstrated significant, concentration-dependent antibacterial effects, with optimal inhibition zones of 16 and 15 mm for K. pneumoniae and S. aureus, respectively, and MIC values ranging from 125 to 500 µg/ml. This work highlights the tunable antimicrobial potential of Ti NPs and underscores the critical influence of concentration on their physicochemical and biological properties for biomedical applications.