Microplastic-mediated antibiotic migration and bioaccumulation in aquaculture: Implications for seafood safety.

Microplastics (MPs) in aquaculture may vector antibiotics (ATBs), posing food-safety risks. We quantified the adsorption of enrofloxacin (ENR) and sulfadiazine (SDZ) onto polyethylene (PE) and polypropylene (PP) MPs, examining the effects of pH, salinity, particle size, aging, and co-solutes. Adsorption followed pseudo-second-order kinetics and Langmuir isotherms, with maxima of 30.3 mg/g (PE-ENR) and 32.1 mg/g (PP-ENR). Spectroscopy and density functional theory showed adsorption is primarily driven by hydrophobic, electrostatic, and van der Waals forces. Aging increased adsorption by up to 14.6%, while smaller particle size negatively correlated with adsorption. SERS confirmed in situ ATB adsorption, and Raman detection revealed fewer MPs in shrimp tissue (14.3 ± 4.0 particles/g) than in water (138.0 ± 16.4 particles/L). Notably, ENR bioaccumulated more in MPs-exposed shrimp (16.4 μg/kg) compared to the ENR-only group (12.2 μg/kg). These results define a size-dependent MP-ATB-organism transport pathway with implications for seafood safety and analytical monitoring.