Labo voor milieutoxicologie en aquatische ecologie (UGent)
As microplastics are posing a challenging problem for the environment, the need grows for relevant studies on the effects on humans and (aquatic) animals. In these studies, surfactants are used to help dissolving the plastics. Therefore, it is crucial that these don’t have any toxic effect on the cells. The goal of this study is to determine the effects of detergents used in microplastic reference-materials separately and in combination with polyethylene microplastics (< 5 µm) on human colorectal adenocarcinoma (Caco-2) cells. Four surfactants will be tested: Triton X-100, Tween 80, sodium cholic acid, and sodium hexametaphosphate in order to find out which might be the best to use in microplastic research. To understand the effects of surfactants on the (physiology of the) cells, four different assays were used to determine the mitochondrial activity, total protein count, cell viability, and reactive oxygen species (ROS)-production. At first, cells were seeded at 20,000 cells/well in a multiwell plate and grown for 24 hours. Hereafter six replicates of a concentration range of surfactant ranging from 0.008 ppm to a maximum 50,000 ppm are exposed to the cells. After a 48 hour exposure period, the four assays were performed on the multiwell plates. The results for Triton X-100 show that starting from a concentration of 1.6 ppm, cells are still affected by the surfactant. Tween 80 and sodium cholic acid on the other hand only shows effects starting from a concentration of 200 ppm. Despite having the same toxicity, Tween 80 can bring more plastics into a solution than sodium cholic acid making it better to use in microplastic research. Sodium hexametaphosphate has low toxicity showing effects at only a concentration from 5,000 ppm, however the use of this surfactant is discouraged since it cannot dissolve plastics. No differences in the effects are observed between exposure to solely surfactant and surfactant combined with microplastics (< 5 µm). This might be caused by the low concentrations of plastic present in the lower concentrations of surfactant. In conclusion, the best surfactant out of the ones tested in this research would be Tween 80 due to its lower toxicity and ability to dissolve more plastics. However the surfactant still shows some toxicity at certain concentrations. In the future, it might be interesting to investigate some other surfactants such as Pluronic acid which are already being used in cell culture maintenance.
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Karel De Schamphelaere