The potential effects of in vitro digestion on the physicochemical and biological characteristics of polystyrene nanoplastics.

The presence of plastic waste in our environment has continued growing and become an important environmental concern. Because of its degradation into micro- and nanoplastics (MNPLs), MNPLs are becoming environmental pollutants of special environmental/health concern. Since ingestion is one of the main exposure routes to MNPLs, the potential effects of digestion on the physicochemical/biological characteristics of polystyrene nanoplastics (PSNPLs) were determined. The results indicated a high tendency of digested PSNPLs to agglomerate and a differential presence of proteins on their surface. Interestingly, digested PSNPLs showed greater cell uptake than undigested PSNPLs in all three tested cell lines (TK6, Raji-B, and THP-1). Despite these differences in cell uptake, no differences in toxicity were observed except for high and assumed unrealistic exposures. When oxidative stress and genotoxicity induction were determined, the low effects observed after exposure to undigested PDNPLs were not observed in the digested ones. This indicated that the greater ability of digested PSNPLs to internalize was not accompanied by a greater hazard. This type of analysis should be performed with other MNPLs of varying sizes and chemical compositions.