Microplastic particles find their way into living cells if exposed to natural aquatic environments

The environment is polluted by microplastics worldwide. The tiny particles enter food chains, and thereby the digestive systems of animals and humans; moreover, they can be inhaled. Instead of being excreted, small microplastics can be incorporated into the body tissue.

A research team at the University of Bayreuth has now discovered that microplastic particles find their way into living cells more easily if they were exposed to natural aquatic environments, i.e. fresh water and seawater.

Biomolecules occurring in the water are deposited on the microplastic surfaces, which promote the internalization of the particles into cells. The researchers present their results in "Science Advances".

The interdisciplinary research team led by Prof. Dr. Christian Laforsch (Animal Ecology) and Prof. Dr. Holger Kress (Biological Physics) focused on microplastic particles with a diameter of around three micrometres for the new study. Particles of this size are often found in the environment.

To simulate their exposure in the environment, some microplastic particles were placed in fresh water from an artificial pond, while other microplastic particles were placed in salt water from a marine aquarium. Biomolecules were deposited on the surfaces of these particles within two weeks exposure time.

Spectroscopic examinations indicate that these biomolecules are carbohydrates, amino acids, nucleic acids, and proteins. We are talking about an 'eco-corona' that forms on the microplastic particles in a natural environment."

Anja Ramsperger M.Sc, Study First Author and PhD Student, Department of Animal Ecology I and in Biological Physics Group, University of Bayreuth

The research team has now examined the microplastic particles coated with biomolecules to see how they interact with living cells. For this purpose, cells from an established mouse cell line were used. In order to distinguish whether the particles are actually internalized or only adhere to the exterior of the cells, important components of the cell interior, the actin filaments, were stained.

On the resulting microscopic images, the internalized particles could be recognised as "dark holes". "The fluorescent labeling of the actin filaments enabled us to see exactly which particles were internalized by the cells. Based on spectroscopic methods, we verified that these particles were indeed microplastics - or more precisely: polystyrene particles - and not accidental impurities," says Prof. Dr. Holger Kress, Professor of Biological Physics at the University of Bayreuth.
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