Individual and combined cytotoxicity effects of positively charged polystyrene nanoplastics and ionic surfactants on budding yeast Saccharomyces cerevisiae

•Combined toxicity of nanoparticles (NPs) and anionic/cationic surfactants was studied.•Budding yeast cells and positively charged polystyrene NPs (pPS-NPs) were employed.•115-nm pPS-NPs were more cytotoxic than 204-nm pNPs in the absence of surfactants.•Toxicity of pPS-NPs was reduced by adding anionic surfactants (counteracting effect).•Toxicity of pPS-NPs was enhanced by adding cationic surfactants (synergistic effect).