Evaluation of the cytotoxicity of titanium dioxide nanoparticles on Scenedesmus regularis

Objective Excessive use of nano-based materials has increased their disposal into the environment. Owing to their smaller size, these nanomaterials show their adverse effects on human health and the environment. The aim of this study was to explore the toxic impacts of titanium dioxide nanoparticles (TiO2 NPs) on the Scenedesmus regularis, green microalgae by evaluating several biological parameters. Methods Microalgal samples were collected from Baija Taal, Gwalior, Madhya Pradesh, India, and identified using morphological and molecular techniques. Titanium dioxide nanoparticles were chemically synthesized by coprecipitation method. Synthesized nanoparticles were characterized using electron microscopy, Fourier transform infrared spectroscopy (FTIR), and X-ray diffraction (XRD). Different concentrations of TiO2 nanoparticles were used to determine the impact on Scenedesmus regularis cells. Results TiO2 nanoparticles showed adverse effects on cell growth and chlorophyll-a content of Scenedesmus regularis at concentrations 5 and 10 mg/L. The concentration of phenolic compounds was increased, while the levels of carotenoids were noticeably decreased as compared to the control sample. In MTT (3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide) assay, 2 mg/L of NPs showed approximately 3.12% toxicity, and at 10 mg/L, NPs displayed nearly 31.32% toxicity. The FTIR analysis established that the treated sample showed an alteration in comparison to the control sample. EDX graph indicated the presence of TiO2 NPs in Scenedesmus regularis microalgae cells. Scanning electron microscopy (SEM) revealed damage to the cell membrane and the attachment of TiO2 nanoparticles on the algal cell wall, which could stimulate cell wall disruption. Conclusion Our results indicate the toxic effects of TiO2 nanoparticles on Scenedesmus regularis green microalgae and provide evidence for the cytotoxicity of TiO2 nanoparticles in eutrophic water ecosystems.