The effects of polystyrene microplastics on human intestinal cells health and function

Abstract

Recent studies have shown that microplastics (MP) have been detected in drinking water and drinking water resources. Their presence has raised significant public health concerns since oral exposure to MP may be more common than expected, yet our understanding of the potential adversarial effects of ingested MP is far from complete. While in vivo experiments have shown clues of weight loss, reduced feeding behaviour, and change of gene expression associated with glucose/lipid metabolism, direct evidence of digested MPs affecting nutrient uptake at the cellular level remains scant. In addition, previous research mostly used pristine MPs and cancer cell models, neglecting the biotransformation of MPs in the digestive system and the dissimilar metabolism of normal cells. Therefore, this study aims to perform a comprehensive evaluation of the effects of polystyrene MPs on human and cancer intestine cells. It is hypothesized that MPs may negatively impact cellular health and functions such as nutrient uptake.

Polystyrene MPs of 0.1, 1 and 10 μm was used as the model MPs in our studies. To better appreciate the bio-accessibility of MPs, an in vitro digestive method was developed to simulate the physiological digestion process as the MPs passage through the gastrointestinal tract (GIT). Our study revealed several major findings. First, it was found that the digested MPs (D-MPs) underwent considerable biotransformation such as the formation of protein corona and larger hydrodynamic size as compared to the undigested pristine MPs. Correspondingly, using particokinetics analysis, D-MPs was found to sediment much faster (the deposited fraction of 0.1 μm and 1 μm D-MPs was 6.7 and 1.2-fold of P-MPs after 48 h, respectively). Amongst the different types and sizes of MPs screened, the 0.1 μm D-MPs displayed higher tendency to form agglomerates than 1 μm D-MPs. Furthermore, several in vitro comparative studies were also performed to examine the MPs' acute and sub-chronic biological effects using the NCM460 (normal) and Caco-2 (cancer) cells. Our findings revealed a complex interplay between the physiochemical properties of MPs and pathological states of the cells in determining the biological outcomes.