Toxicological Evaluation of SiO₂ Nanoparticles by Zebrafish Embryo Toxicity Test.

Sandra Vranic,Gaku Ichihara,Yasuhito Shimada,Masayuki Kimata,Sahoko Ichihara,Sonja Boland,Toshio Tanaka,Lang Tran,Wenting Wu

doi:10.3390/ijms20040882

Abstract

As the use of nanoparticles (NPs) is increasing, the potential toxicity and behavior of NPs in living systems need to be better understood. Our goal was to evaluate the developmental toxicity and bio-distribution of two different sizes of fluorescently-labeled SiO2 NPs, 25 and 115 nm, with neutral surface charge or with different surface functionalization, rendering them positively or negatively charged, in order to predict the effect of NPs in humans. We performed a zebrafish embryo toxicity test (ZFET) by exposing the embryos to SiO2 NPs starting from six hours post fertilization (hpf). Survival rate, hatching time, and gross morphological changes were assessed at 12, 24, 36, 48, 60, and 72 hpf. We evaluated the effect of NPs on angiogenesis by counting the number of sub-intestinal vessels between the second and seventh intersegmental vessels and gene expression analysis of vascular endothelial growth factor (VEGF) and VEGF receptors at 72 hpf. SiO2 NPs did not show any adverse effects on survival rate, hatching time, gross morphology, or physiological angiogenesis. We found that SiO2 NPs were trapped by the chorion up until to the hatching stage. After chemical removal of the chorion (dechorionation), positively surface-charged SiO2 NPs (25 nm) significantly reduced the survival rate of the fish compared to the control group. These results indicate that zebrafish chorion acts as a physical barrier against SiO2 NPs, and removing the chorions in ZFET might be necessary for evaluation of toxicity of NPs.

Highlights

Nanotechnologies are emerging technologies that have been gaining popularity in the last few decades and are still being developed
Using vascular-enhanced green fluorescent protein (EGFP) strains, Tg/nacre zebrafish, we previously investigated the effects of metal oxide NPs on angiogenesis [14]
We evaluated the effects of surface charge and size of SiO2 NPs on bio-distribution and vascularization in the embryos of vascular-EGFP zebrafish using fluorescent-labelled NPs

Summary

Introduction

Nanotechnologies are emerging technologies that have been gaining popularity in the last few decades and are still being developed. Human exposure to nanomaterials is a concern since there might be a negative impact on health, in occupational settings where NPs are produced and used, and in the general population and environment considering the life cycle of NPs from manufacturing to recycling and final disposal [3,4]. Due to their small size, which is in the size range of various cellular structures, NPs are capable of interacting with these structures, entering the cells, and/or translocating from the site of exposure toward the circulation and secondary organs [5,6]. It is of crucial importance to understand the key aspects of interactions of NPs with living systems and to properly compare benefits and potential hazard coming from use of nanomaterials

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