Characteristics of protein corona formation on the surface of micro- and nanoplastics and their effects on cellular uptake and transport.

Microplastics (MPs) and Nanoplastics (NPs), collectively known as micro- and nanoplastics (MNPs), are emerging contaminants. Their accumulation in organisms and the underlying mechanisms of transfer have attracted widespread attention. A protein corona (PC) can form on the surface of MNPs after they enter biological systems, which might affect cellular uptake, cytotoxicity and their ability to penetrate biological barriers. In turn, the formation of PC is affected by the physicochemical characteristics of MNPs. Our study explored the formation characteristics of PC on the surface of 2μm polystyrene microplastics (MPs) and 200 nm polystyrene nanoplastics (NPs) with positive and negative surface charges after incubation in 20% serum-containing medium. We further investigated how PC formation influences cellular uptake, barrier penetration, and the cytotoxicity of MNPs. Our results show that PC formation is affected by particle size and surface charge. Conversely, the PC affects the charge and hydrodynamic diameter (Hd) of MNPs and promotes aggregation of positively charged NPs (NPs+). These changes subsequently influence cellular uptake of MNPs. Additionally, positively charged MNPs exhibit higher cytotoxicity, which may induce non-significant barrier disruption and lead to passive leakage.