The effects of microplastics are being explored by many studies around the world with special attention being paid to their environment and health impacts.
Electron micrographs of polystyrene particles of the same name from two different manufacturers. They show different surface morphologies that can lead to different cell interactions. (Image Credit: Julia Jasinski.)
The frequent use of spherical polystyrene microparticles in these studies has led to partly contradictory results. The reason for this has been discovered by an interdisciplinary research team at the University of Bayreuth.
Depending on their manufacturer, polystyrene particles that are commercially available and supposedly identical tend to differ considerably in terms of their properties and structure. This causes their interactions with living cells to have diverse outcomes for cell metabolism. The study has been published by the scientists in the Journal of Hazardous Materials.
The scientists used murine model cell lines as examples to obtain the new research results.
Our study impressively shows how problematic it is to make generalised statements about the health or ecological effects of microplastics. When particles of the same size and shape, and of the same polymer type, show such surprising chemical and physical differences in in-depth analyses, and when these differences affect interactions with living cells – then caution is advised against jumping to conclusions.
Prof. Dr. Christian Laforsch, Spokesperson, “SFB 1357 Microplastic” Collaborative Research Centre, University of Bayreuth
"Our findings contain clear indications that the polystyrene microparticles currently used in effect studies are poorly characterised. Because highly relevant differences remained undiscovered, contradictory results obtained under supposedly identical conditions have puzzled researchers,” adds Anja Ramsperger, one of the first authors of the study.
In future, we in Bayreuth will take a closer look at the microparticles used in our experiments. The replicability of experiments must be a top priority in microplastic research - especially when it comes to investigating health effects.
Anja Ramsperger, Study First Author, University of Bayreuth
Commercially available polystyrene particles supplied by different manufacturers have very obvious differences that are primarily associated with the monomers they contain. During the production of plastics, these basic building blocks of long-chain plastic molecules are connected together and this can have harmful effects on organisms and cells.
Other differences relate to the electrical charge distribution that occurs at the surface of the particles, commonly known as the zeta potential. The scientists used the laboratories at the University of Bayreuth and the Leibniz Institute of Polymer Research in Dresden to conduct the experiment within the framework of “SFB 1357 Microplastic.
According to the results, when compared with the use of other polystyrene microparticles, interactions happen more frequently when polystyrene microparticles with a greater zeta potential and a homogenous surface charge distribution are made to come in contact with living cells.
During frequent interactions, a lot of particles can enter the cells. Here, they damage the proliferation and metabolism of the cells, particularly when particle concentrations are high.
In the meantime, there are numerous toxicological studies seeking to get to the bottom of the effects of microplastics on living organisms. But only when we know the chemical composition and the surface properties of the particles used in detail can these studies be compared scientifically. Only on this basis will it be possible to decipher the properties that make certain types of microplastics potentially dangerous for the environment and humans.
Anja Ramsperger, Study First Author, University of Bayreuth
The new research is based on a close interdisciplinary partnership with the DFG Collaborative Research Centre 1357 "Microplastic" at the University of Bayreuth.
The participating scientists carry out research and teach in the fields of bioprocess technology, animal ecology, biophysics, biomaterials research and inorganic chemistry. Another research organization associated with the Collaborative Research Centre was the Leibniz Institute of Polymer Research in Dresden.
Journal Reference:
Ramsperger, A.F.R.M., et al. (2021) Supposedly identical microplastic particles substantially differ in their material properties influencing particle-cell interactions and cellular responses. Journal of Hazardous Materials. doi.org/10.1016/j.jhazmat.2021.127961.