Comparative metal oxide nanoparticle toxicity using embryonic zebrafish

Abstract

Engineered metal oxide nanoparticles (MO NPs) are finding increasing utility in the medical field as anticancer agents. Before validation of in vivo anticancer efficacy can occur, a better understanding of whole-animal toxicity is required. We compared the toxicity of seven widely used semiconductor MO NPs made from zinc oxide (ZnO), titanium dioxide, cerium dioxide and tin dioxide prepared in pure water and in synthetic seawater using a five-day embryonic zebrafish assay. We hypothesized that the toxicity of these engineered MO NPs would depend on physicochemical properties. Significant agglomeration of MO NPs in aqueous solutions is common making it challenging to associate NP characteristics such as size and charge with toxicity. However, data from our agglomerated MO NPs suggests that the elemental composition and dissolution potential are major drivers of toxicity. Only ZnO caused significant adverse effects of all MO particles tested, and only when prepared in pure water (point estimate median lethal concentration = 3.5–9.1 mg/L). This toxicity was life stage dependent. The 24 h toxicity increased greatly (~22.7 fold) when zebrafish exposures started at the larval life stage compared to the 24 hour toxicity following embryonic exposure. Investigation into whether dissolution could account for ZnO toxicity revealed high levels of zinc ion (40–89% of total sample) were generated. Exposure to zinc ion equivalents revealed dissolved Zn2+ may be a major contributor to ZnO toxicity.

Developing a Novel Embryo–Larval Zebrafish Xenograft Assay to Prioritize Human Glioblastoma Therapeutics

“…7 and 8), which is the opposite of what we hypothesized would occur based on the in vitro data. However, the exposure concentrations used in the zebrafish xenograft assay were lower than the effective inhibitory concentrations in in vitro studies, 23,39,40 and we also identified that the ZnO NP agglomerated and underwent considerable dissolution (*47%-50%) when prepared in water (data previously published 28 ). Therefore, we cannot distinguish whether this increase in glioblastoma proliferation is due to a low-exposure NP effect, an ionic effect, or a combination of both.…”

“…ZnO NPs with a primary particle size of 8.37 nm were synthesized using forced hydrolysis as described previously in Wehmas et al 28 One gram of zinc acetate dehydrate and 99.5:0.5 mL diethylene glycol:nanopure water mix were heated to 160°C for 90 min followed by multiple ethanol rinses and separation using centrifugation for 20 min at 20,000 rpm after each rinse. Immediately before exposure, an aliquot of ZnO NP and ZnO bulk material control were suspended in 100% DMSO at a concentration of 10 mg/mL and water bath sonicated (Ultrasonik NDI; NEY, Inc., Bloomfield, CT) for 20 min at room temperature.…”

“…This resulted in a 3-day static nonrenewal, exposure to 1· (0.156-1.25 mg/L) ZnO NP or ZnO bulk control with 0.003% PTU and vehicle at 0.5% DMSO. 28 To minimize agglomeration with salts present in zebrafish embryo medium, the ZnO NP exposures were conducted in ultrapure water. 28,29 As previously reported in Wehmas et al, this ZnO NP has a mean hydrodynamic diameter on the order of microns when prepared in zebrafish embryo medium, whereas its mean hydrodynamic diameter is *400 nm and zeta potential (an indication of charge) is *20.2 mV when prepared in ultrapure water creating a more stable exposure suspension.…”

“…28 To minimize agglomeration with salts present in zebrafish embryo medium, the ZnO NP exposures were conducted in ultrapure water. 28,29 As previously reported in Wehmas et al, this ZnO NP has a mean hydrodynamic diameter on the order of microns when prepared in zebrafish embryo medium, whereas its mean hydrodynamic diameter is *400 nm and zeta potential (an indication of charge) is *20.2 mV when prepared in ultrapure water creating a more stable exposure suspension. 28 Following addition of compound, the 96-well plates were sealed with Parafilm, wrapped in aluminum foil to block incidental light and maintained in a 33°C -1°C incubator until 7 DPF.…”

Relation between biophysical properties of nanostructures and their toxicity on zebrafish

“…The majority of the NPs studied for their toxicity in zebrafish are inorganic (Wehmas et al 2015;Zhao et al 2013). Little is known about biodegradable NPs, except for chitosan NPs (Wang et al 2016;Yuan et al 2016).…”