Fate and enzymatic response of co-exposed photoaged nanoplastic and PFAS: Insights from a human gastrointestinal simulation

This study investigated the bioaccessibility and enzymatic response of nanoplastics (NPs) and per- and poly-fluoroalkyl substances (PFAS) with different chain length and functional groups during co-exposure in simulated human gastrointestinal digestion. The important role of phototransformation of NPs in these processes was also assessed. Results showed that the bioaccessibility of photoaged NPs (ANPs) in the oral, gastric, and intestinal phases was 51.58-, 1.39-, and 5.50-fold of NPs, respectively. Co-exposure of ANPs and short-chain PFBA significantly increased the bioaccessibility of ANPs in the oral and the intestinal phases by 56.41 % and 41.98 %, respectively, and the bioaccessibility of PFBA was increased by 27.58 % and 163.57 %. However, in the gastric phase, co-exposure significantly reduced the bioavailability of PFAS, NPs, and ANPs by 10.77 %-93.61 %, 9.21 %-42.38 %, and 55.07 %-83.00 %, respectively. Pepsin activity was also significantly inhibited by 11.40 %-16.32 % in co-exposure treatments. Atomic force microscopy-infrared spectroscopy revealed that ANPs underwent surface chemical modifications in the gastric phase, with subsequent altering their interaction with pepsin. Molecular docking results showed that NPs primarily binds to pepsin through hydrophobic interaction near the tyrosine and alanine residues, and NPs+PFOA showed the highest binding stability with pepsin. The findings enhance the understanding of human health of co-exposed NPs and PFAS.