"With this experiment we have shown that the theoretical model can even quantitatively predict the extent of the increase in cell membrane tension. This is an unexpected result given the model’s simplicity."Vladimir Baulin
"Study shows the mechanism by which microplastics, when in contact with cell membranes, stretch and much reduce their mechanical stability"With growing concerns about the ubiquity of microplastics in water, food and the air we breathe, and which are ingested by aquatic and human organisms alike, two researchers have shown that microplastics work to deform cell membranes, and can have an impact on their functioning at a molecular level.
There are thought to be over 70 million tonnes of microplastics in the world’s oceans, mainly from industrial manufacturing processes, with sizes ranging from 0.1 microns to 5 millimeters. They are manufactured mostly from polypropylene, polyethylene, polystyrene, polyamide and acrylics, while everyday products such as cosmetics, toothpaste and sunscreens also contain plastics that break down into smaller and smaller pieces. They are known to cross various barriers and enter blood and lymphatic systems, accumulating in organs such as kidney, liver and brain.
Although it is known that microplastics can oxidize or stress cells through biological processes, whether they could also stress a cell membrane through physical processes has been ignored to date. However, as reported in PNAS [Fleury, J.-B. and Baulin, V. A., Proc. Natl. Acad. Sci. U.S.A. (2021) DOI: 10.1073/pnas.2104610118], Vladimir Baulin from the University of Rovira i Virgili in Spain, in collaboration with Jean-Baptiste Fleury of the University of Saarland in Germany, showed the mechanism by which microplastics, when in contact with cell membranes, stretch and much reduce their mechanical stability.
To investigate this, a theoretical model was used that was later confirmed from experiments on the lipid bilayer, the barrier that protects the cell, using a special microfluidic device. This allowed identification of the mechanism that enables the mechanical stretching of membranes, before the results were then compared in red blood cells confined in a micropipette. The model predicted that each particle would consume part of the membrane area, which induces it to contract around the plastic particles, leading to a mechanical stretching.
A cell membrane has similar properties to that of a liquid, and any mechanical effect on a liquid should disappear over time. However, the membranes of artificial cells and red blood cells were found to stretch in the presence of microplastics, with the membrane of human red blood cells seeming to deform spontaneously, something that could explain the effect that these microplastics have on cell membranes.
The microfluid technique also showed that plastic particles were never static in cells, but continuously on the move due to diffusion, which could be why this mechanical effect is maintained and prevents the mechanical relaxation of the cell. Further research into the mechanical effects of nanoparticles is required, as well as the effects of biofilms and coatings, protein corona, and interaction with cell mechanics.