Green synthesis of titanium oxide nanoparticles using aqueous extracts of Limnospira fusiformis and their multifunctional applications in biomedical and biodiesel production

Abstract

Biosynthesis of Titanium oxide nanoparticles (TiO₂ NPs) is an emerging strategy that is being commonly employed in industrial and environmental wastewater treatments. This study adopted green chemistry technique to synthesize TiO₂ NPs, utilizing aqueous extract derived from cyanobacteria Limnospira fusiformis. A comprehensive characterization of the biogenic TiO₂ NPs was performed using spectroscopic and microscopic analysis. Antibiofilm potential of TiO₂ NPs was tested against human pathogens, specifically in Pseudomonas aeruginosa (Gram-negative) and Bacillus subtilis (Gram-positive) bacteria. Cytotoxicity of TiO₂ NPs was assessed against the cancer cell lines, human lung A549 and breast MDA-MB-231 employing MTT assay. The study also investigated the conversion of oil extracted from microalgae consortium (Chlorella vulgaris + Scenedesmus dimorphus), into biodiesel at varying catalyst concentration. In this study, the UV–visible spectrum of biogenic TiO₂ NPs exhibited a sharp absorption peak at 254 nm. FTIR analysis revealed peaks at 424, 1398, 1632, and 3479 cm⁻¹. XRD pattern shows five intense broad peaks indexed as (101), (004), (200), (105), and (205). SEM images displayed spherical-shaped structures in clustered form of TiO₂ NPs. The presence of titanium and oxygen was further confirmed by the EDS profile. Zeta potential and dynamic scattering analysis illustrated the TiO₂ NPs were highly stable at −49.4 mV with a mean size of 98.9 nm. Differential Thermal Analysis (DTA) and Thermogravimetric Analysis (TGA) confirmed the successful functionalization of TiO₂ NPs. Biogenic TiO₂ NPs exhibited a promising effect against Bacillus subtilis and the MDA-MB-231 cancer cell lines at 20 μg/mL and 10 μg/mL concentration, correspondingly. This research also revealed that these green-synthesized TiO₂ NPs performed as an effective catalyst for converting algal lipids into biodiesel. Maximum amount of FAME was produced at 6 mg/mL concentration. Moreover, these green-synthesized NPs show promising nano-biomaterials for various applications in biomedicine and could also significantly improve the large-scale production of biodiesel.