Copper adsorption on microplastics: Investigating toxicity in an in vitro digestive environment

This study aims to analyze how the presence of microplastics (MPs) affects the bioaccessibility and toxicity of adsorbed copper (Cu), an environmental contaminant, through an in vitro digestion process that mimics environmentally relevant exposure routes. The MPs used are naturally weathered, derived from a polypropylene (PP) rope found on a beach, and virgin PP MPs to assess the effect of weathering on adsorption capacity. The particles ranged between 63 μm and 125 μm, and Cu ions were used as a co-contaminant. Copper was detected on the surface of the weathered MPs, with lower Cu adsorption observed on virgin MPs. The toxicity of MPs was evaluated on bacterial species isolated from fish. Weathered MPs affected the growth of Bacillus thuringiensis and Pseudomonas aeruginosa; however, no inhibition was observed when MPs were associated with copper, and virgin MPs did not affect the growth of any bacterial species. Weathered MPs, alone and with associated Cu, underwent in vitro digestion simulating the digestion of rainbow trout (Oncorhynchus mykiss). The digestion consisted of a gastric phase with pepsin and an intestinal phase with bile extract and pancreatin, lasting 26 hours. Samples were collected at several time points to analyze Cu concentration. During digestion, no Cu was leached by the weathered MPs alone. When MPs with associated Cu were digested, a positive correlation was observed between desorbed copper concentration and time during the gastric phase, while lower Cu concentration was desorbed during the intestinal phase. Ongoing experiments include the addition of food during in vitro digestion to evaluate the bioaccessibility of Cu under environmentally relevant scenarios and the use of virgin MPs in the in vitro digestion. The toxicity of the liquid product of the digestion will be evaluated in a rainbow trout cell line. Also see: https://micro2024.sciencesconf.org/559427/document