Biosynthesis of Titanium Dioxide Nanoparticles from the Mangrove (Avicennia marina) and Investigation of its Antibacterial Activity

Background and purpose: Development of biocompatible and nontoxic methods for synthesis of nanoparticles is important in bio-nanotechnology. This study aimed at biosynthesis of titanium dioxide nanoparticles (TiO2 NPs) using leaf of the native mangrove (Avicennia marina) and investigating its antibacterial activity. Materials and methods: Effect of four different solutions composed of dry extract of mangrove leaf and different amounts of chemical titanium isopropoxide in biosynthesis of TiO2 NPs was evaluated. The biosynthesized TiO2 NPs were characterized using X-ray diffraction (XRD), scanning electron microscopy (SEM), UV–visible spectrophotometry (UV-Vis), and fourier transform infrared (FTIR) spectroscopy. The antibacterial activity was assessed using well diffusion method. Results: The solution color containing dry extract of mangrove leaf and titanium isopropoxide began to change 10 min after the reaction was started, showing the reduction of Ti ions by the extract and synthesizing TiO2 NPs. Combination of 1 g dry extract and 3.75 mL of titanium isopropoxide was considered the optimum concentration for TiO2 NPs biosynthesis. Conclusion: XRD analysis approved the formation of crystalline TiO2 NPs. SEM images identified TiO2 NPs with mean diameter of 25 nm and spherical shape. FTIR analysis distinguished Ti in NPs structure indicating the formation of TiO2 NPs. UV-Vis showed the reduction of bandgap energy in biosynthesized TiO2 NPs. Gram-negative bacteria showed more resistance against the bacterial pathogens. Gram-positive Micrococuss Sp. was recognized the most sensitive regarding the largest diameter of inhibitory zone and Gram-negative Vibrio harveyi was recognized the most resistant regarding no formation of inhibitory zone.