Assessment of uptake and toxicity of fluorescent silica nanoparticles in zebrafish (Danio rerio) early life stages

In this study, we determined uptake and toxicity of fluorescent core-shell silica nanoparticles (FSNP) in early life stages of zebrafish. For this purpose fluorescent Ru@SiO2 nanoparticles with average size of ∼200 nm encapsulating [Ru(bpy)3]2+Cl2 dye (excitation wavelength λexci = 488 nm), and Cy5.5@SiO2 with average size of ∼60 nm (λexci = 700 nm) were synthesized. The FSNP were highly luminescent. Field emission SEM analysis showed monodispersed dual-shell Ru@SiO2 nanoparticles of ∼200 nm size. Zebrafish embryos were exposed less than 6 h post-fertilization (hpf) to the ∼60 and ∼200 nm FSNP at concentrations between 0.0025 and 200 mg/L in 24-well plates for up to 96 hpf. The concentrations were analysed using an Fourier transform infra-red (FTIR) technique. Uptake of FSNP by embryos was monitored using transmission and confocal fluorescence microscopy. Toxicity was assessed by mortality, hatching time and success, and by morphological alterations. The ∼60 and ∼200 nm-sized FSNP and/or aggregates were adsorbed on the chorion of eggs. Uptake and translocation in embryos was not observed, but nanoparticle uptake not detectable by confocal microscopy may have occurred. Hatching time and hatching success were not affected. No mortality or deformities occurred. These nanoparticles and/or aggregates mainly accumulate on the chorion of embryos and exhibit no overt embryotoxicity.