A sticky situation – quantifying interactions between microplastic particles and cells

, Wieland Simon, Groß Wolfgang, Spreng Sarah, Lehmann Moritz, Gekle Stephan, Laforsch Christian, Kress Holger.

During the last decades, the production, use, and disposal of plastic products have experienced an unprecedented increase. As a consequence, by now microplastic particles (MPPs) can be found in a multitude of ecosystems all around the world. Increasingly, reports about negative effects of MPPs on organisms and ecosystems are published. A major concern is the translocation of MPPs into cells and, therefore, the interactions between MPPs and cells have gained attention in recent years. However so far, little is known about the mechanisms and factors affecting the attachment of MPPs to cells, which is a key determinant for their interactions. Here, we introduce a microfluidic device that enables high-throughput quantification of MPP-cell interactions. With a Poiseuille flow in a rectangular channel, we can exert defined forces on particles attached to cells, which are adhered to the bottom of the channel. The forces were quantified by Lattice-Boltzmann simulations. Following automated detection of the particles by a cross-correlation algorithm and classification by an artificial intelligence, the numbers of ruptured particles at different hydrodynamic forces were evaluated. We measured attachment strengths between various mammalian cell lines and pristine and functionalized polystyrene MPPs, and also MPPs that were previously incubated in freshwater and saltwater. We found that MPP attachment to cells was increased for functionalized MPPs and MPPs with an ecocorona, compared to pristine MPPs. Conclusively, our research has the potential to pinpoint the critical factors determining MPP-cell interactions. This not only might support risk assessment of potential toxicity of MPPs for organisms and ecosystems, but also facilitate the development of potentially safer, less sticky polymers, enabling a more sustainable use of plastic products.

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