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ElectrostaticAdsorption-Driven Reorganization ofPhycosphere Eco-Corona as a Toxicity Mechanism of Cationic Nanoplastics
Summary
Scientists found that tiny plastic particles (nanoplastics) can harm freshwater algae very differently depending on their electrical charge: positively charged particles caused major cell damage, oxidative stress, and killed up to nearly 90% of algae cells, while negatively charged particles were much less harmful. Since algae sit at the base of aquatic food chains, this matters because it suggests the type of plastic pollution—not just its presence—could shape how much damage spreads through ecosystems and, potentially, up the food chain to humans who rely on these waters for food and drinking supplies.
Nanoplastics (NPs) are emerging contaminants in freshwater ecosystems, readily forming heterogeneous aggregates with microalgae, yet their behavior in algal phycospheres remains poorly resolved. Here, we establish an aquatic phycosphere–plastic symbiotic system and a four-tiered analytical workflow, encompassing growth responses, cellular effects, phycosphere dynamics, and proteomic reprogramming to test how surface charge controls interactions between carboxylated and aminated polystyrene NPs (PS-COOH, PS-NH2, 50 nm) and Chlorella pyrenoidosa. Negatively charged PS-COOH exposure largely preserved physiological, ultrastructural, and redox homeostasis, indicating high tolerance of the symbiotic system. In contrast, positively charged PS-NH2 strongly inhibited biomass and chlorophyll, and triggered a cascade of intracellular stress, including sustained reactive oxygen species (ROS) production, lipid peroxidation, antioxidant imbalance, mitochondrial membrane depolarization, and up to 89.6% apoptosis. Three-dimensional excitation–emission fluorescence with parallel factor analysis and self-organizing map (PARAFAC-SOM) analysis revealed charge- and dose-dependent reorganization of tyrosine- and tryptophan-like protein components in tightly and loosely bound extracellular polymeric substances, indicating spatial eco-corona remodeling. Quantitative proteomics showed that PS-COOH mainly induced homeostasis regulation in photosystem and electron-transport proteins, whereas PS-NH2 broadly disrupted photosynthesis, carbon metabolism, and protein homeostasis. This multitier framework links NPs’ surface charge to coupled interfacial, cellular, and proteomic processes in microalgal phycospheres, providing a mechanistic basis to assess the biological footprint of NPs in freshwater ecosystems.