Zhu, X., et al., "Developmental Toxicity in Zebrafish Embryos After Exposure to Manufactured Nanomaterials: Buckminsterfullerene Aggregates and Fullerol," Environmental Toxicology & Chemistry, Vol. 26, No. 5, pp. 976-979 (2007).
In this paper, several scientists test two nanomaterials — buckyballs nC60 and fullerols C60(OH)16–18 — on zebrafish embryos to determine whether these two particular nanomaterials are developmentally toxic under certain circumstances. The scientists purportedly eliminated material purity and solvent toxicity concerns that have plagued some prior tests, allowing them to fully focus on the nanomaterials themselves.
Measurement intervals after exposure to buckyball and fullerol nanoparticle concentrated solutions varied from 12 to 96 hours. Here are some of the findings:
- Fish embryos exposed to a fullerol solution (50 mg/L) experienced no mortality, slightly decreased hatching rates, and no alteration in heart beats or pericardial edema.
- Fish embryos exposed to a buckyball solution (1.5 mg/L) experienced a high rate of mortality, a significantly reduced hatching rate, a slowed heart beat, and increased pericardial edema.
- After 96 hours, embryos exposed to control solutions experienced less than 3% mortality, compared to 55% mortality for those exposed to the buckyball solution.
- Regarding hatching rates, after 60 hours, embryos exposed to control solutions had a 44% hatching rate, compared to 0% for those exposed to the buckyball solution.
- Surviving embryos exposed to the buckyball solution experienced heart beats slowed by 50% at 48 hours after exposure, and 77.8% experienced pericardial edema.
The scientists concluded: "Structurally, [fullerols are] a derivative of [buckballs] with 16 to 18 hydroxite radical groups connected by covalent bonds. This fullerol had no detectable developmental toxicity . . . similar to the results of other cytotoxicity experiments. Apparently, toxicity decreases as the number of chemical groups attached to [the buckyballs] (and their attachment symmetry) increases."
Also notable was a separate test in which the researchers exposed embryos to a solution of buckyballs and GSH (glutathione) which is a known antioxidant. With GSH added to the mix, survival rates were markedly increased (80% with GSH after 96 hours compared to 55% without GSH ), hatching rates were increased (100% survival with GSH after 96 hours compared to 15% without GSH ), slowing heartbeat rates were lessened (no slowed heart beat with GSH after 48 hours compared to 50% without GSH ), and less pericardial edema occurred (30% with GSH after 96 hours compared to 80% without GSH ). Thus, the scientists concluded that even though it “did not completely prevent embryo damage,” the “developmental toxicity of [buckyballs] was effectively attenuated by GSH.”