The influence of surface functional coating in the Silver nanoparticle-induced reproductive and developmental toxicity

Since their antimicrobial properties, Silver nanoparticles (AgNPs) are among the most exploited nanomaterials in consumer products. Size and surface reactivity and coating are critical physicochemical properties responsible for NP toxicity. In this study the reproductive and developmental toxicity of citrate- (Cit-) and branched polyethyleneimine- (BPEI-) coated 10 nm AgNPs was investigated on Xenopus laevis fertilization and embryos by the Frog Embryo Teratogenesis Assay-Xenopus (FETAX). The effects were compared also with the exposure to Ag ions. Light, confocal and electron microscopy analyses have been performed on sperms and embryos to characterize the NP-cell interactions and uptake, as well as the histological and ultrastructural lesions. The results suggest that the positively-charged BPEI-AgNPs are more effective in inducing adverse reproductive and developmental outcomes, likely as a consequence of the enhanced interactions with sperm membrane and embryonic barriers (e.g. fertilization envelope and intestine) in respect of the negatively-charged Cit-AgNPs. Although Ag + resulted strongly embryolethal, the BPEI-AgNPs showed the highest teratogenic index, pointing out the role of NP size and functional coating in determining the teratogenicity. No lethal and slight malformation effects were induced by Cit-AgNPs. We conclude that possible reduced fertility and teratogenic risks may be associated to BPEI-AgNPs exposure, but the modality of NP-tissue interactions and the teratogenic mechanism need further scrutiny to be defined. This work was supported by Fondazione Cariplo (OverNanotox 2013-0987).