Reduced disparity in the physiological effects between perfluorooctanoic acid and its alternative GenX on freshwater microalgae during co-exposure with nanoplastics

The physiological and ecological risks of persistent organic pollutants mediated by nanoplastics (NPs) are substantially altered for aquatic organisms. However, the roles and underlying mechanisms of NPs in this process remain inadequately elucidated. Here, we investigated the physiological effects of polystyrene (PS)-NPs combined with perfluorooctanoic acid (PFOA) and its alternative hexafluoropropylene oxide dimer acid (HFPO-DA, commonly known as GenX) on freshwater microalgae. Results demonstrate that NPs exhibited relatively weaker effects than PFOA and GenX and primarily enhanced the microalgal adsorption and uptake of PFOA and GenX. The main target following the NP-mediated intracellular accumulation of PFOA and GenX was the photosynthetic electron transport in microalgae, which exacerbated the adverse effects of GenX on microalgae and induced a "hormesis effect" on Chlorella during PFOA exposure. At the proteomic level, PFOA primarily influenced the energy-dependent proteins involved in photosynthesis, whereas GenX did not significantly alter proteomic profiles in microalgae. Notably, NP-mediated "secondary transport" not only reduced the accumulation disparity between GenX and PFOA but also differentially amplified their adverse effects on the algal proteome. This was particularly evident in the more pronounced inhibition of translation-related enzymes by GenX, which ultimately diminished the difference in their overall physiological toxicity. Therefore, the biological impacts of emerging persistent pollutants, particularly with NPs acting as transport carriers, constitute a crucial research domain warranting further investigations.