As concerns grow over the impact of microplastics, which permeate all aspects of daily life, on human health, a study has found that the “surface chemical properties” of microplastics are a key factor determining brain inflammation and neuronal damage.

The research experimentally demonstrated that it is not simply the size or level of exposure, but the intrinsic properties of the microplastic surface that affect brain health.

A research team from the Department of Biomedical Science at the Catholic University of Korea College of Medicine, led by Professors Seung-Ah Yoo and Hyang-Sook Lim (co-corresponding authors), and including Dr. Min-Kyung Nam and graduate student Chae-Rin Kim (co–first authors), has for the first time in the world identified that brain immune responses and neuronal damage vary depending on the chemical structures formed on the surface of microplastics.

Microplastics change their surface properties over time as they come into contact with various substances in the environment. In this process, chemically structured groups with electrical properties, such as amine groups (-NH₂) or carboxyl groups (-COOH), become exposed on the surface.

The research team conducted experiments using polystyrene microplastics with different surface chemical structures to investigate how such surface differences affect the brain. The results showed that microplastics with exposed amine groups rapidly penetrated microglia, the immune cells in the brain, inducing a strong inflammatory response.

In this process, the levels of tumor necrosis factor-alpha (TNF-α) and interleukin-6 (IL-6), which are inflammatory signaling molecules, increased significantly, and the microglia shifted into a state that promotes inflammation.

The team also found that this reaction was caused by excessive production of reactive oxygen species in mitochondria, which are responsible for cellular energy. Microplastics with exposed amine groups promoted the generation of highly oxidative reactive oxygen species, disrupting the cellular energy system, and the activated immune cells were found to cause secondary damage to surrounding neurons.

The researchers further confirmed that treatment with Trolox, a vitamin E–like antioxidant, significantly reduced the inflammatory response and neuronal damage. This result suggests the potential to mitigate neurotoxicity caused by microplastics.

Professor Yoo stated, “This study is the first to show that the invisible ‘surface properties’ of microplastics can lead to brain immune responses and neural damage,” adding, “It will provide important evidence for understanding the relationship between environmental hazardous substances and neurological diseases and for reassessing the risk level of microplastics.” The study was published in the January issue of the international journal in the environmental and health field, “Ecotoxicology and Environmental Safety,” and the research team has filed two domestic patent applications related to the technology.

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