Microplastics Deform the Cell Membrane and Affect Its Function!

It is estimated that since the 1950s, more than 70 million tons of microplastics have been dumped into the ocean due to industrial production processes. These plastics are ingested by aquatic organisms and the human body through water, food, and the air we breathe. They are estimated to range in size from 0.1 microns to 5 mm and are mainly made of polypropylene, polyethylene, polystyrene, polyamide, and acrylic acid. Plastic particles of one micron in size are almost ubiquitous: in the ocean, in the air, in the snow of the Himalayas, and even in the human placenta. Toothpastes, sunscreens, common chemicals, or packaging also contain plastics. Although it has been shown that consumption of microplastics does not result in death or food poisoning, there is increasing evidence that microplastics have an effect on cells at the molecular scale, which is difficult to determine experimentally.

In this context, Vladimir Baulin, a physicist in the Department of Physics and Inorganic Chemistry at URV, in collaboration with Jean-Baptiste Fleury at the University of Saar, Germany, found in a recent study that microplastics can mechanically disrupt lipid membrane stability by attaching and tightening lipid membranes. The findings appear in the Proceedings of the National Academy of Sciences (PNAS).

To test how the mechanical effects of microplastics on these films occur, the researchers used a theoretical model that was later confirmed by experiments with a special microfluidic device on the lipid bilayer (a barrier to protect cells). Through this system, they found a mechanism to mechanically stretch the film. Once this mechanism was identified, the researchers examined the findings of red blood cells in microtubules. The results of this experiment show that microplastics stretch the cell membrane of human erythrocytes and greatly reduce their mechanical stability, which may affect their normal function and alter their ability to transport oxygen.

The theoretical approach developed by the URV physicist Vladimir Baulin accurately describes the action of microplastics on cell membranes. After testing, the model predicts that each particle consumes part of the film area, which leads to film shrinkage around the plastic particles. This action inevitably leads to mechanical stretching of the cell membrane. "Through this experiment, we have shown that the theoretical model can even quantitatively predict the increase in cell membrane tension. Considering the simplicity of the model, this is an unexpected result." To confirm the model predictions, microfluidic technology was used in a simpler model than human cell membranes (e.g., erythrocytes) and the tension of these cell membranes when in contact with microplastics was measured. The researchers found that plastic particles were not quiescent in the cells, but moved continuously by continuous diffusion. Considering these results, the researchers believe that this diffusion is responsible for this mechanical effect to be maintained and prevent mechanical relaxation of cells.

The researchers point out that through experimental testing of theoretical models, conclusions about the universal effectiveness of the mechanism can be drawn, and the conclusions can be transferred to a large number of human cells or organs.

"The possible toxicity of microplastics in human cells is currently being discussed," explains Jean-Batist Fleri, an experimental physicist at Saar University. "It has been inferred that microplastics are not immediately lethal after being ingested by organisms. However, it is increasingly recognized that microplastics can oxidize or stress cells through biological processes. They may also compress cell membranes through purely physical processes, however, the vast majority of studies completely ignore this possibility," he added.

In fact, from a physical point of view, there is no expected effect. Cell membranes are thought to have properties similar to those of liquids. It is well-known that any mechanical action on the fluid disappears over time. "Surprisingly, however, we observed that the membranes of artificial cells and erythrocytes were stretched in the presence of microplastics," he continued. According to the researchers, the cell membranes of human red blood cells clearly deform spontaneously, which explains the huge effects of these microplastics on the cell membranes.

This new research direction by Vladimir Baulin's team is focused on the microscopic mechanism of marine environmental pollution. For several months, URV has been promoting a new branch, the deep-sea value, aiming to establish an underwater laboratory network so that researchers from around the world can come to conduct underwater experiments to monitor and protect biodiversity.

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