Molecular mechanism underlying the modulated toxicity of differently charged and sized nanoplastics by bovine serum albumin

The extensively presence of nanoplastics raises concerns about their harm to ecosystems and human health. They are easy to absorb serum albumin to form corona during the transport process. However, the regulation of serum albumin to the toxicity of nanoplastics with differing charges and sizes remains unknown. We examined the molecular mechanism of polystyrene nanoplastics (PS-NPs) to bovine serum albumin (BSA) and how corona modulates the mouse primary hepatocyte damage. In cells exposed to 100 mg/L of large PS-NH-NPs and PS-COOH-NPs, a significant reduction in cell viability of 27 % and 22 % was noted, respectively, under BSA-free conditions. In contrast, the reductions were limited to 17 % and 13 % in the presence of BSA. Additionally, BSA pretreatment also lowered the reactive oxygen species (ROS) levels compared to the use of two modified PS-NPs (200 nm) alone. However, the addition of BSA did not significantly alter the cell viability or the levels of ROS in small PS-NPs (80 nm). Molecular investigations demonstrated that PS-NPs mainly bound to the hydrophobic cavity of BSA through moderate hydrophobic forces with the binding affinity approximately 10 M. The formation of corona not only induced conformational changes in BSA but also modified its esterase activity. The molecular and cellular experiments both revealed the size and surface charge-specific toxicity pattern of nanoplastics. Big PS-NPs (200 nm) bound more tightly to the protein compared to small nanoplastics (80 nm), and PS-NH-NPs presented a greater risk to BSA than PS-COOH-NPs. This study elucidates how BSA corona formation modulates nanoplastic toxicity in a size- and charge-dependent manner.