Project description:This study uses the RBEC4 cell model to examine if nanosilver of different sizes (10nm and 75nm) and cappings (citrate and polyvinylpyrrolidone(PVP)) affect its cellular permeability and genomic response. RBEC4 cells (95% confluent) were screeened for changes in gene expression after 18 hour exposure to 1.0 ppm of PVP or citrate coated nanosilver particles at 10 or 75 nanometer sizes. Analysis indicated that the cellular transcription profile alter by nanosilver 10nm+PVP was distinct from it 75nm counterpart and both sizes of citrate-coated particles.
Project description:Nanoparticles (<100 nm) are engineered to have unique physico-chemical properties compared to their larger counterparts. Nanosilver (nAg) is the most prevalent nanoparticle in consumer products due to its strong antimicrobial action. While nAg toxicity at high concentrations has been well described, the potential for sublethal effects at or below regulatory guidelines is relatively unknown. Amphibian metamorphosis is mediated by thyroid hormone (TH) and can be precociously induced by the addition of exogenous hormone. Low concentrations of nAg have been shown to disrupt TH-dependent responses in cultured premetamorphic Rana catesbeiana tadpole tail fin. The present study examined the effects of exposure to an environmentally relevant concentration (6 µg/L) of either nAg or ionic silver (iAg) on premetamorphic tadpoles in the absence and presence of exogenous TH. Disruption of thyroid hormone-mediated signalling in brain and liver transcriptomes was evaluated using the MAGEX cDNA microarray.
Project description:Nanoparticles (NPs) are engineered in the nanoscale (<100nm) to have unique physico-chemical properties from their bulk counterparts. Nanosilver (nAg) is the most prevalent nanoparticle in consumer products due to its strong antimicrobial action. While nAg toxicity at high concentrations has been well described, the sublethal effects at or below regulatory guidelines are relatively unknown. Amphibian metamorphosis is mediated by thyroid hormone (TH), and initial studies indicate that low concentrations of nAg disrupt TH-dependent responses in precociously induced premetamorphic bullfrog (Rana catesbeiana) tadpoles. The present study examined the effects of environmentally-relevant nAg concentrations (LoAg, 0.018 µg/L; MedAg, 0.18 µg/L; HiAg, 1.8 µg/L) on naturally metamorphosing Xenopus laevis tadpoles in two 28-day chronic exposures beginning with pre- and prometamorphic stages, respectively. nAg was found to significantly bioaccumulate in tadpoles after 28 days. While nAg didn’t alter metamorphic timing, it increased hindlimb length during early premetamorphosis and in post-metamorphic juvenile tadpoles. Using MAGEX microarray and QPCR transcript analyses, 7 markers of nAg exposure were discovered and validated, 5 of which showed nAg-induced disruption of their TH-response. The increased mRNA abundance of two peroxidase genes suggests that nAg could generate reactive oxygen species (ROS) even at low, environmental concentrations. Furthermore, differential responsiveness to nAg was observed between developmental stages. Therefore, low concentrations of nAg had endocrine disruptive effects at both the physiological and molecular level, indicating that regulatory guidelines for silver may need revision.
