Mechanistic insights into polystyrene nanoplastic sequestration by a Procambarus clarkii-derived chitosan hydrogel in simulated gastric fluid: An in vitro study

Nanoplastics (NPs) are an emerging class of contaminants of increasing concern due to their small size, bioaccessibility, and potential adverse effects on human health. Strategies to limit their biological uptake remain poorly explored. This study investigates the potential of chitosan derived from Procambarus clarkii (PCC) produced from the food-grade biopolymer to sequester polystyrene nanoplastics (PS-NPs, 100 nm and 50 nm) under gastric conditions (pH 3). By employing complementary physicochemical techniques (SEM, TEM, DLS, ζ-potential, ATR-FTIR, and H NMR), the findings demonstrate that PCC exhibits protonation-driven self-assembly into a physically cross-linked hydrogel capable of immobilizing PS-NPs in a three-dimensional polysaccharide network. Colloidal tests revealed consistent aggregate formation controlled by electrostatic interactions between negatively charged PS-NPs and protonated PCC, while microscopy analyses demonstrated complete encapsulation of PS-NPs with no visible free particles. Spectroscopic evidence suggests a non-covalent sequestration mechanism involving hydrophobic contacts and hydrogen bonding, without requiring chemical alteration of either component. These findings demonstrate that, rather than acting as a straightforward sorbent, PCC performs as a pH-responsive sequestration matrix, utilizing gastric acidity to promote NP confinement. By proposing a biodegradable, food-grade hydrogel method that could decrease NP bioaccessibility in the gastric environment, the present study provides mechanistic insight into source-dependent polysaccharide self-assembly at biological interfaces. According to this study, the PCC is an intelligent, pH-responsive matrix rather than a straightforward passive filter. An acidic stomach environment (pH 3) acts as the “activator” resulting in PS-NP encapsulation and hydrogel formation. This in-situ gelation method of capturing NPs is a novel mechanical innovation.