Effects triggered by platinum nanoparticles on primary keratinocytes

The platinum (Pt)-group elements (PGEs) represent a new kind of environmental pollutant and a new hazard for human health. Since their introduction as vehicle-exhaust catalysts, their emissions into the environment have grown considerably compared with their low natural concentration in the earth crust. PGE emissions from vehicle catalysts can be also in the form of nanometer-sized particles (Pt nanoparticles [PtNPs]). These elements, both in their metallic form or as ions solubilized in biological media, are now recognized as potent allergens and sensitizers. Human skin is always exposed to toxic particles; therefore, in the present study we addressed the question of whether polyvinylpyrrolidone-coated PtNPs may have any negative effects on skin cells, including predominantly epidermal keratinocytes. In this study, PtNPs of two sizes were used: 5.8 nm and 57 nm, in concentrations of 6.25, 12.5, and 25 μg/mL. Both types of NPs were protected with polyvinylpyrrolidone. Primary keratinocytes were treated for 24 and 48 hours, then cytotoxicity, genotoxicity, morphology, metabolic activity, and changes in the activation of signaling pathways were investigated in PtNP-treated cells. We found that PtNPs trigger toxic effects on primary keratinocytes, decreasing cell metabolism, but these changes have no effects on cell viability or migration. Moreover, smaller NPs exhibited more deleterious effect on DNA stability than the big ones. Analyzing activation of caspases, we found changes in activity of caspase 9 and caspase 3/7 triggered mainly by smaller NPs. Changes were not so significant in the case of larger nanoparticles. Importantly, we found that PtNPs have antibacterial properties, as is the case with silver NPs (AgNPs). In comparison to our previous study regarding the effects of AgNPs on cell biology, we found that PtNPs do not exhibit such deleterious effects on primary keratinocytes as AgNPs and that they also can be used as potential antibacterial agents, especially in the treatment of Escherichia coli, representing a group of Gram-negative species.