Nanoparticles of polystyrene can penetrate the neural system of mice. The size of the particles, as well as the biomolecules surrounding them, seem to have a significant influence on the uptake. More research needs to be conducted to understand the potential medical consequences on humans.
Tiny particles of plastic can penetrate the brain.
A team of scientists proved that polystyrene particles breached the blood-brain barrier in mice just two hours after oral ingestion of one of the most widely-used plastics, including in food packaging.
The Medical University of Vienna, Austria, and the University of Debrecen in Hungary led this research on micro and nanoplastic particles (MNPs) published in the scientific journal Nanomaterials on April 19.
The blood-brain barrier (BBB) is an essential cellular barrier that prevents pathogens or toxins from reaching the brain. But while several scientific studies showed that the intestine’s protective wall could be breached by MNPs, the mechanism that enabled them to breach the blood-brain barrier was previously unknown to medical science.
Nanoplastics are defined as smaller than 0.001 millimeter, while at 0.001 to 5 millimeters (0,2 inch), some microplastics are still visible to the naked eye. Plastic particles can enter the food chain in various ways, including food packaging or even by drinking water from plastic bottles.
A study last year found that people eat five grams of micro and nanoplastics every week and people who drink 1.5 to 2 liters of water a day from plastic bottles take in 90,000 plastic particles per year.
The scientists performed short-term uptake studies in mice with orally administered micro and nanoparticles of polystyrene (9.55 µm or 0,0096 millimeter, 1.14 µm, 0.293 µm). The nanoparticles passed the intestine wall and reached the brain quickly, only two hours after gavage. But particles bigger than 0.293 µm (0,000293 mm) didn’t get to the brain, suggesting size may be a critical factor in their ability to penetrate the neural system.
Size of nanoplastics and biomolecular corona matter
Moreover, the study found that biomolecules accumulating on the surface of plastic particles, which form a biomolecular corona around them, can influence the crossing of the membrane. Before entering the body, the MNPs acquire a corona of organic matter and chemical and biological components with complex and variable composition.
“With the help of computer models, we discovered that a certain surface structure (biomolecular corona) was crucial in enabling plastic particles to pass into the brain,” Oldamur Hollóczki, from the University of Debrecen’s Department of Physical Chemistry, explained.
Cholesterol molecules on a corona enhanced the uptake of nanoplastics into the membrane, meaning particles passed through the blood-brain barrier more easily. On the other hand, proteins forming coronae inhibited particles from reaching the neural system.
“The type of corona can significantly impact their ability to enter the BBB and their overall toxicity,” according to the findings.
Short-term health effects of MNPs will have to be further considered, as contamination of brain tissue can lead to various neurological problems such as cognitive impairment and neurological disorders. “In the brain, plastic particles could increase the risk of inflammation, neurological disorders or even neurodegenerative diseases such as Alzheimer’s or Parkinson’s,” said Lukas Kenner, from the Department of Pathology at the Medical University of Vienna, pointing out that more research is needed in this area.
