Key Physicochemical Properties Dictating Gastrointestinal Bioaccessibility of Microplastics-Associated Organic Xenobiotics: Insights from a Deep Learning Approach

Abstract

A potential risk from human uptake of microplastics is the release of plastics-associated xenobiotics, but the key physicochemical properties of microplastics controlling this process are elusive. Here, we show that the gastrointestinal bioaccessibility, assessed using an in vitro digestive model, of two model xenobiotics (pyrene, at 391–624 mg/kg, and 4-nonylphenol, at 3054–8117 mg/kg) bound to 18 microplastics (including pristine polystyrene, polyvinyl chloride, polyethylene terephthalate, polypropylene, thermoplastic polyurethane, and polyethylene, and two artificially aged samples of each polymer) covered wide ranges: 16.1–77.4% and 26.4–83.8%, respectively. Sorption/desorption experiments conducted in simulated gastric fluid indicated that structural rigidity of polymers was an important factor controlling bioaccessibility of the nonpolar, nonionic pyrene, likely by inducing physical entrapment of pyrene in porous domains, whereas polarity of microplastics controlled bioaccessibility of 4-nonylphenol, by regulating polar interactions. The changes of bioaccessibility induced by microplastics aging corroborated the important roles of polymeric structures and surface polarity in dictating sorption affinity and degree of desorption hysteresis, and consequently, gastrointestinal bioaccessibility. Variance-based global sensitivity analysis using a deep learning neural network approach further revealed that micropore volume was the most important microplastics property controlling bioaccessibility of pyrene, whereas the O/C ratio played a key role in dictating the bioaccessibility of 4-nonylphenol in the gastric tract.

In Vitro Digestion of Tire Particles in a Fish Model (Oncorhynchus mykiss): Solubilization Kinetics of Heavy Metals and Effects of Food Coingestion

“…Additionally, it is likely that the rougher aspect and higher porosity of the TRWP than those of the smoother CMTT (Image S1) also contributes to its larger specific surface area. The impact of the particle size on the solubilization kinetics of the pollutants from other types of microplastics has recently been observed and corroborates the results obtained in our study since an increase in the solubilization rate with smaller particles was reported. , As a consequence, Zn solubilization from TRWP was best fitted by a pseudo-zero-order model (Table ) before the equilibrium was reached after 30 min in SF GASTRIC and by a diffusion-controlled model before the equilibrium was reached after 6 h in SF INTESTINAL (Figure b). This result indicated that Zn was constantly solubilized without any solubility constraint and that a pseudo-equilibrium state was rapidly reached.…”

Bioaccessibility of organic compounds associated with tire particles using a fish in vitro digestive model: solubilization kinetics and effects of food co-ingestion

“…In our in vitro digestion experiments, only a small to moderate percentage of tire-associated compounds (between 0.4 % and 11.3 %) was found to be solubilized and bioaccessible in the simulated gastrointestinal fluids within a representative gut transit time for fish. These values are low compared to studies investigating the bioaccessibility of PAHs from microplastics where this parameter was assessed following loading of exogenous chemicals on the test material by an adsorption step 68 . Desorption of compounds adsorbed on the surface and micropores of a polymeric matrix is likely to be faster compared to tire-related compounds.…”

Organic Contaminants and Interactions with Micro- and Nano-Plastics in the Aqueous Environment: Review of Analytical Methods

“…For PE [118], and glassy polymeric domains of PS [32], a significant hysteresis for hydrophobic compounds has been reported. Therefore, desorption of hydrophobic compounds even within more complex matrices such as gut fluids is more unlikely than for polar compounds [120]. The desorption hysteresis is also a critical parameter of TOrC-polymer interaction concerning bioaccessibility and, therefore, the environmental impact [10].…”