Polystyrene nanoplastics diminish the toxic effects of Nano-TiO2 in marine algae Chlorella sp.

Widespread usage of nano-TiO2 in various commercial products and their consequent release into the seawater pose a severe threat to marine biota. Nanoplastics, a secondary pollutant in the marine environment, could influence adverse effects of nano-TiO2. The main goal of the present study was to investigate the influence of the differently functionalized polystyrene nanoplastics (COOH-PSNPs, NH2-PSNPs, and Plain-PSNPs) on the acute toxic effects of P25 nano-TiO2 in marine algae Chlorella sp. Three different concentrations of nano-TiO2, 0.25, 0.5, and 1 mg/L, mixed with 5 mg/L of the PSNPs were employed in this study. A substantial increase was noted in mean hydrodynamic sizes of nano-TiO2 when they were mixed with the PSNPs. This hetero-aggregation would reduce the bioavailability of the particles to the algae. The presence of the PSNPs in the mixture reduced the toxicity of nano-TiO2 significantly. A signficant decline in the oxidative stress parameters like total ROS, superoxide (Image 1), and hydroxyl radical generation was noted for the mixture of nano-TiO2 with the PSNPs in comparison with the pristine counterparts. The lipid peroxidation, and the antioxidant enzyme activities in the cells correlated well with the reactive species generation results. The treatments with the mixture resulted in notable enhancement in the esterase activity in the cells. The Independent Action model suggested antagonistic interactions between PSNPs and nano-TiO2. The results from this study clearly demonstrate that nano-TiO2 in presence of the PSNPs exerted significantly reduced cytotoxic effects in Chlorella sp, in comparison with the pristine particles.