Unraveling the impact of polystyrene microplastics with varying particle sizes and concentrations on lipid in vitro digestion and ex vivo absorption.

The contamination of microplastics (MPs) in food has become a global concern due to their ingestion through the food chain and associated health risks. However, the impacts of MPs on lipid digestion and absorption remain poorly understood. This study investigates the effects of MPs on soybean oil in vitro digestion and ex vivo absorption, focusing on particle size (small ∼30 μm, medium ∼50 μm, and large ∼100 μm) and concentration (0.32, 0.64, and 1.28 mg/mL). During digestion, MPs interacted with digestive components, forming rough surface coronas and promoting aggregation, with mean size of small-sized MPs increasing by up to 57.9 %. The presence of MPs inhibited soybean oil digestion and pancreatic lipase activity in a concentration- and size-dependent manner. At 1.28 mg/mL, smaller MPs (∼30 μm) caused the most pronounced inhibition, reducing free fatty acid (FFA) release to 65.2 %, compared to 71.1 % for medium-sized MPs and 76.5 % for larger MPs. Pancreatic lipase activity similarly declined to 72.0 % with smaller MPs versus 83.0 % with larger MPs. In the ex vivo rat small intestine model, smaller MPs significantly impaired FFA absorption, with rates dropping from 43.4 % (no MPs) to 20.2 % with small MPs and 31.2 % with large MPs at the highest concentration. Fluorescent microscopy revealed that MPs, particularly smaller ones, adsorbed digestive enzymes and FFAs, forming physical barriers that hindered lipid migration toward intestinal villi. These findings provide mechanistic insight into how MPs disrupt lipid digestion and absorption, highlighting potential health risks of microplastic exposure.