Synchrotron nano-FTIR analysis of pollutant-loaded polystyrene microplastics and their impact on cell structure

Micro- and nanoplastics (MNPs) are ubiquitous pollutants that potentially harm human health. A better understanding of the precise health effects caused by MNPs is needed1. In this sense, MNPS increased adsorption capacity is an aggravating factor because they can act as vectors of pollutants that can be released inside the body2. We characterized the chemical surface of pollutant-loaded polystyrene (PS) spherical particles of 1 µm using the synchrotron nano-FTIR technique to identify possible changes in the PS IR spectra due to pollutant adsorption. The pollutant in this study was a cationic dye called brilliant green. The adsorption curve indicated that saturation was achieved at a pollutant concentration of 5 mg/L. Cell viability assays with Caco-2 cells showed a decrease in cell viability as pollutant concentration increases. In nano-FTIR analysis, pollutant concentrations of 1 and 6 mg/L were chosen, and it was possible to identify alterations in the PS IR spectra at two bands in 1485 and 1595 cm⁻¹, correspondent to C=C stretching in the aromatic ring. The first band shifted to 1490 cm⁻¹ in pollutant-loaded PS, and the second showed a decreased intensity upon pollutant adsorption. These changes can be associated with the adsorption process and correlated to cytotoxic effects.