FLIM monitors mitochondrial responses to microplastics in KYSE-150 cells

As plastic pollution escalates, microplastics, particles less than 5 mm, have attracted significant attention due to their origins in everyday plastic waste, microbeads in personal care products, and bottled water packaging, posing threats to ecosystems and health. Polystyrene (PS), one type of widely used plastics, affect human health via absorption, ingestion, and dermal contact. In this study, we used microscopy methods to monitor the invasion progress of PS microplastics into KYSE-150 cells and to study the following influence of this invasion on the cellular status. Firstly, the mitochondrial probe Rhodamine 123 was used to label KYSE-150 cells, which indicated the mitochondrial status during the exposure of PS. Then the KYSE-150 cells were treated with fluorescent PS microspheres (approximately 100 nm in diameter) for one day. During this process, cells were observed by using both a confocal microscopy system and a Fluorescence Lifetime Imaging Microscopy (FLIM) system. Results showed that the microplastics appeared in the cell cytoplasm within one hour. The amount of microplastics within the cells kept increased till 24 hours. Images of incubated cells at each time point (1 h, 3 h, 6 h or 24 h) were collected by using the FLIM system and then analyzed with the software SPCImage. The data showed that the fluorescence lifetime values of R123 in the mitochondria of microplastic treated cells increased according to the incubation time. By contrast, the lifetime values in the control group (cells without PS) kept constant during the same period. These results showed that changes of lifetime values might be due to the accumulation of microplastics within the cells. Briefly, this study suggested that FLIM could be a rapid, non-destructive, and sensitive method suitable to monitor the invasion of microplastics into live cells, providing appropriate data to the toxicity assessment of microplastics.