Tiered testing of micro- and nanoplastics using intestinal in vitro models to support hazard assessments

The uncertainty of potential risks associated with micro and nanoplastics (MNPs) are of growing public concern. However, the diversity of MNPs in the environment in terms of composition, size, shape, and other physicochemical properties, makes a systematic analysis of potential health effects challenging. New tools and approaches are necessary to investigate biological effects of MNPs. With this quick scoping review, we aim to analyse the suitability of in vitro models for assessing the interaction of MNPs with intestinal cells. Our analysis revealed that currently the majority of in vitro tests is based on the three cell lines Caco2, HT29, and HCT 116. They have particularly been used to assess endpoints related to basal cytotoxicity, the internalisation of MNPs and effects on the intestinal barrier, but they also allow to investigate additional effects such as inflammation, metabolic actions and the relevance of the intestinal mucus when various cell lines are co-cultured either under static or microfluidic conditions. However, methodological gaps remain regarding the assessment of potential accumulation of MNPs, leaching of additives/impurities and resulting long-term effects as well as cell-type specific toxicities. In addition, only few in vitro studies investigated effects of MNPs on the microbiome. Stem cell-based assays using for example the emerging organoid technology are promising to analyse MNP effects on tissue-like structures avoiding the particular characteristics of the currently used cancer derived cell lines. Nevertheless, additional test method development and standardisation programmes are necessary before such emerging cellular models can be employed in routine applications. The various cell lines and culture techniques can be combined in testing strategies to better elucidate potential biological interaction of MNPs with biological systems. We suggest implementing a tiered testing strategy in which monocultures, particularly of well-established Caco2 cells, can serve as a tool for high-throughput testing of MNPs. In a second step co-cultures can be used to potential of a systemic uptake of MNPs and organ-on-a-chip models will support more reliable insight into relevant doses triggering biological effects. Finally, organoids can help to discover new and more complex biological mechanism triggered by MNPs.

BREDECK Gerrit;  HALAMODA KENZAOUI Blanka;  BOGNI Alessia;  LIPŞA Dorelia;  BREMER Susanne; 

2021-11-30

PERGAMON-ELSEVIER SCIENCE LTD

JRC125869

0160-4120 (online),   

https://www.sciencedirect.com/science/article/pii/S0160412021005468#s0065,    https://publications.jrc.ec.europa.eu/repository/handle/JRC125869,   

10.1016/j.envint.2021.106921 (online),