The interactions of non-functionalized polystyrene nanoparticles with human albumin and erythrocyte proteins: implications and potential consequences

The aim of the study was to determine the concentration- and size-dependent effects of ~30 nm, ~45 nm and ~70 nm non-functionalized polystyrene nanoparticles (PS-NPs) on human serum albumin (HSA) and human erythrocyte proteins in vitro. . HSA or human erythrocytes were exposed to PS-NPs at concentrations ranging from 0.001 to 100 µg/mL for 24 h. Any resulting changes in HSA secondary structure were investigated using circular dichroism (CD), fluorescence spectrum analysis, and fluorescence lifetime measurements. Incubation with 50 µg/mL and 100 µg/mL PS-NPs resulted in an increase in the hydrodynamic diameter of PS-NPs and caused significant alterations in HSA secondary structure for all tested nanoparticle sizes. Additionally, treatment with the ~30 nm and ~45 nm PS-NPs resulted in a more intense HSA fluorescence signal and changes in mean fluorescence lifetimes, indicating interactions between PS-NPs and HSA. Incubation with PS-NPs (0.1-1 µg/mL) also led to significant changes in relative viscosity and increased protein carbonyl content in erythrocytes (10-100 µg/mL); however, no significant changes in acetylcholinesterase (AChE) activity or methemoglobin levels were observed. The study confirms that non-functionalized polystyrene nanoparticles influence the structure and functional properties of human plasma and erythrocyte proteins under in vitro conditions, and their effects are clearly dependent on the size and concentration of the nanoparticles. It is likely that PS-NPs can modify the structure of albumin, which may indirectly potentiate plastic-related damage to erythrocytes in vivo. The potential influence of albumin modified by plastic particles on the properties of human erythrocytes in vivo was discussed.