Molecular level biological effects of silver and titania nanoparticles on zebrafish embryos

Nanotechnology raises issues concerning the toxic impact of nanoparticles (NPs) in organisms and the environment. Nanoparticles have been defined as materials with dimensions that are equal to or less than 100 nm. It is important to develop early warning tools of NP-induced biological effects to be able to monitor and manage for any possible impacts. In the current study, two types of NPs have been selected based on their wide use: silver-NPs (AgNPs) and titanium dioxide-NPs (TiO2NPs). Early zebrafish (Danio rerio) embryos exposed in vitro to 4-nm and 10-nm AgNPs, and to silver ions alone, and TiO2NPs have been used to measure the expression level of selected target genes. A global transcriptomic approach employing Suppression Subtractive Hybridization (SSH) was used in parallel to identify novel genes that may be involved in the fish embryo response as a result of exposure to NPs. TiO2NPs coated with different layers of anionic (PSS) and cationic (PAH) polyelectrolytes were also used to measure viability, morphology, and the expression level of selected target genes. The results indicate that pathways expressed in response to NP exposure differ among both AgNPs and TiO2NPs, either due to the size, concentration, exposure time, exposure conditions, surface chemistry and surface charge of coatings of the NPs. The responses indicate that D. rerio embryos respond to NPs with not only an oxidative stress response, but with transcripts associated with fertility and metabolic functions such as membrane transport and mitochondrial metabolism. This information may be used to inform early warning biomarker development for environmental monitoring applications in future