Microplastics in simulated digestion: Surface modifications, enzyme interference, and chemical migration.

Area of Science:

• Environmental Science
• Toxicology
• Biochemistry

Background:

• Microplastic (MP) ingestion is a growing concern, but their behavior and health risks during human digestion are not well understood.
• Understanding MP transformation and interactions within the gastrointestinal tract is crucial for assessing human health impacts.

Purpose of the Study:

• To investigate the in vitro transformation of common food-grade microplastics (polystyrene, polyethylene, polypropylene, polyethylene terephthalate) under simulated human digestion.
• To analyze MP chemical modifications, interactions with dietary components (starch, protein, lipids), enzyme inhibition, and additive migration.

Main Methods:

• Simulated in vitro human digestion of microplastics (MPs) of two sizes (≈200 μm and ≈50 μm) with starch, protein, and lipids.
• Analysis of zeta potential, enzyme inhibition assays (α-amylase, α-glucosidase, lipase, pepsin), and liquid chromatography-mass spectrometry (LC-MS) for additive release.

Main Results:

• Microplastics adsorbed significant amounts of protein, evidenced by a substantial decrease in zeta potential, particularly for PET in protein-rich conditions.
• Smaller MPs (50 μm) demonstrated stronger inhibition of digestive enzymes like α-amylase, α-glucosidase, and lipase, while pepsin inhibition was minimal.
• Liquid chromatography-mass spectrometry detected increased release of di-n-butyl phthalate from MPs, especially during simulated gastric digestion.

Conclusions:

• In vitro digestion alters microplastic properties through component adsorption and impacts digestive enzyme functionality.
• Microplastics can release harmful additives like phthalates during digestion, posing potential health risks.
• Further in vivo studies are necessary to fully elucidate the human health implications of microplastic ingestion and digestion.