Size- and Surface Charge-Depending Effects of Polystyrene Nanoplastics on Cells of the Neurovascular Unit

The increasing production and accumulation of plastic waste, coupled with insufficient recycling practices, contribute to the growing presence of plastic in the environment. Nanoplastic particles are of particular concern, as they pose greater (health and environmental) risks and exhibit wider dispersion compared to macroplastics. The blood–brain barrier may be exposed to nanoplastics present in the blood, which could affect its functionality or even pass through and damage the central nervous system. This study examined the effects of polystyrene (PS) nanoparticles with different chemical surface modifications (pristine, carboxylated, aminated) and sizes (50 nm and 100 nm) on cells of the neurovascular unit (NVU): human brain endothelial cells, astrocytes, and pericytes. Results indicated that only high concentrations of nanoparticles (100 μg/mL and 300 μg/mL) applied for 48 h decreased cell viability and barrier integrity significantly. Specifically, 50 nm carboxylated PS particles reduced barrier integrity and altered tight junction gene expression substantially. Fluorescent labelling of the investigated particles enabled to confirm their uptake by all tested cell types of the NVU, but also highlighted that the labelling changes the particles’ properties. Furthermore, cell culture medium-dependent particle agglomeration and increase of size were inversely correlated with cellular internalisation, which has to be considered for future risk assessments.