The combined toxicity of ultra-small SiO2 nanoparticles and bisphenol A (BPA) in the development of zebrafish

The complex combined effects of nanoparticles and environmental pollutants in the aqueous environment will inevitably affect aquatic ecosystem and human life. Bisphenol A (BPA) is listed as a typical kind of endocrine disruptors , there is little research about the joint toxicity of co-exposure of SiO 2 nanoparticles (NPs) and BPA. In this study, fluorescent ultra-small SiO 2 NPs (US-FMSNs) around 6.3  nm were synthesized and investigated for their combined effects with BPA on zebrafish during the early developmental stages within 4–168 h post fertilization (hpf). The results showed that US-FMSNs could accumulate in the chorion , abdomen and intestine in zebrafish. In addition, the different concentration (0.1, 1, 10 μg/mL) of BPA and US-FMSNs (200 μg/mL) demonstrated strong impact on multiple toxic endpoints at four periods (72, 96, 120, 168 hpf). We found US-FMSNs had no significant toxic effect on zebrafish, while BPA (10 μg/mL) showed a degree of developmental toxicity . Compared with single BPA (10 μg/mL) exposure, combined exposure enhanced the developmental toxicity of zebrafish, including increased mortality, decreased hatching rate and body length, and decreased activity of total superoxide dismutase (T-SOD) and increased malondialdehyde (MDA) levels. Our results indicated that US-FMSNs and BPA induced oxidative stress , and the effect of the co-exposure was less than that of single exposure (10 μg/mL). This study hereby provides a basis for the potential ecological and health risks of SiO 2  NPs and BPA exposure.