DIGESTION OF POLYSTYRENE NANOPARTICLES IN A WHEY PROTEIN DRINK. A SIMULATED IN VITRO GASTROINTESTINAL DIGESTION USING A BATCH INFOGEST MODEL COMBINED WITH CELL ABSORPTION EXPERIMENTS

The small fragments of plastic material are becoming of great concern, as they can find their way into the environment and in the food we consume. The objective of this project was to evaluate the fate of nano and microplastic particles of well known size, during gastrointestinal transfer, after mixing them with a whey protein suspension. The cytotoxicity of polystyrene latex particles (60 nm and 1 ?m, monodisperse) and exposure experiments were performed using confluent Caco-2 cells with undigested samples. The cytotoxicity was determined by MTT assay with concentrations that ranged from 25 to 500 ?g/mL after 24 h, with no statistical differences observed in cell viability. The polystyrene latex exposure effect was assessed for 24, 48 and 72 h at a concentration of 500 ?g/mL, and media and cells were collected for further analysis. Moreover, polystyrene latex particles at a concentration of 68 mg/mL were mixed with 5% (w/v) whey protein solution and subjected to the INFOGEST digestion protocol. Oral, gastric (2 h) and duodenal (2 h) phases of digestion were performed at 37 °C. Microstructure analysis and particle size measurements of resulted digested samples were performed by confocal microscopy and laser light scattering, respectively. Digested samples were then diluted 1:16 to test their cytotoxicity for 4 h in confluent Caco-2 cells and results showed no cytotoxic effect. Intestinal permeability experiments were performed in 21 days differentiated co-cultures of Caco-2/HT29-MTX. Differentiated co-cultures were exposed to digested polystyrene latex particles for 4 hours, and samples of cells, apical and basolateral contents were collected for further analysis. Samples from the exposure, digestion and permeability experiments were analysed using mass spectrometry (MALDI, GCMS). This work for the first time shows the digestion of polystyrene latex particles (60 nm and 1 ?m) and their permeability in models of the intestinal barrier.