Green tea extracts rich in epicatechins inducing aggregation and inhibiting absorption of amine surface functionalized polystyrene microplastics in vitro mimick system

The current study aimed to investigate the effect of green tea extracts (GTEs) containing 35% epicatechins on the bioaccessibility of amine surface functionalized polystyrene microplastics (APSMPs), the cellular integrity of intestinal membrane, intestinal absorption, microstructural changes, and aggregation of APSMPs using in vitro digestion with a Caco-2 cell system. The bioaccessibility of APSMPs with GTEs in the ratio of 1:1, 1:2, and 1:5 was observed to be 12.31 ± 0.14, 3.18 ± 0.09, and 1.79 ± 0.16 %, respectively. The trans-epithelial electrical resistances (TEER) value was enhanced while the intestinal transport of APSMPs significantly was decreased by the co-treatment of GTEs. The average particle size of APSMPs treated with GTEs after in vitro digestion became larger in a GTEs dose-dependent manner. The zeta potential value of -12.15 mV exhibited by the APSMPs with GTEs at a 1:2 (v/v) ratio indicates a substantial interparticle agglomeration, implying that APSMPs strongly were bound to GTEs during digestion. Particularly, Epigallocatechin gallate (EGCG) from GTEs treated with APSMPs mostly decreased during digestion, indicating that EGCG was the main component bound to APSMPs. Results from the current study suggest that GTEs could make APSMPs insoluble by aggregation due to a charge difference between APSMPs and the bioactive components present in GTEs.