Developmental toxicity of glycine-coated silica nanoparticles in embryonic zebrafish.

Nanoparticle (NP) surface coatings are known to influence the toxicity of engineered nanomaterials. This work examines the effect of glycine functionalization on silica NPs and investigates changes in viability and developmental defects in the organs of zebrafish embryos upon exposure. Silica NPs and glycine-functionalized silica NPs are synthesized and characterized. Exposure of zebrafish embryos to glycine-silica NPs affects the mortality percentage in a similar manner to soluble glycine. Developmental defects are observed in embryos exposed to soluble glycine, glycine-silica NPs, or silica NPs in comparison with the unexposed embryos. The damage is localized in the brain, heart, and liver of zebrafish embryos. These observations suggest a complex mechanism of toxicity, with glycine maintaining its toxic activity even when covalently bound on silica surface. Our results illustrate that surface modification of non-lethal particles can create different toxicity outcomes in the organs of exposed zebrafish embryos.