Environmental exposure and nanotoxicity of titanium dioxide nanoparticles in irrigation water with the flavonoid luteolin

Abstract

Different concentrations of titanium oxide nanoparticles (TiO₂NPs) have been frequently reported in treated wastewater used for the irrigation of crops. Luteolin is a susceptive anticancer flavonoid in many crops and rare medicinal plants that can be affected by exposure to TiO₂NPs. This study investigates the potential transformation of pure luteolin in exposure to TiO₂NP-containing water. In an in vitro system, three replicates of 5 mg L⁻¹ of pure luteolin were exposed to TiO₂NPs (0, 25, 50, 100 ppm). After 48 h exposure, the samples were extensively analyzed by Raman spectroscopy, ultraviolet-visible (UV-vis) spectroscopy, and dynamic light scattering (DLS). A positive correlation was found between TiO₂NPs concentrations and the structural alteration of luteolin content, where over 20% of luteolin structure was allegedly altered in the presence of 100 ppm TiO₂NPs. The increase of NPs diameter (∼70 nm) and dominant peaks in Raman spectra revealed that luteolin was adsorbed onto the TiO₂NPs surface. Further, the second-order derivative analysis confirmed the transformation of luteolin upon exposure to TiO₂NPs. This study provides fundamental insight into agricultural safety measures when exposed to air or water-borne TiO₂NPs.