Thrust 4: Photo-Enhanced Toxicity of Graphene Oxide Nanosheets

Min-sik Kim, Sarah Yang, Joel Pedersen, Robert Hamers, Richard Peterson, Warren Heideman

Graphene oxide (GO) is a nanomaterial with many possible uses. Extending as a sheet only one atom thick, graphene oxide is a flat lacework of carbon atoms with oxygen’s sticking out on each side. Discovered over 150 years ago, GO now is looked to as a possible route to graphene manufacture, yielding new types of electrical conductors. GO is also being investigated for possible use in medicine and diagnostics. Amid this excitement, it is important to be aware of the possible toxicities of GO. GO is easily dispersed in water, and NSF-funded postdoctoral fellow Minsik-Kim has used zebrafish embryos to study the effects of GO on tissue development: sensitive markers of toxicity. Zebrafish embryos are quite small, readily produced in large numbers, and excellent sentinels of vertebrate toxicity.

Unlike its highly conductive cousin, graphene, GO does not easily conduct electricity. However, when exposed to ultraviolet light, the molecular structure of GO can change in a way that allows electrons to flow. Exposure of GO to ultraviolet light can also result in the production of chemicals known as reactive oxygen (ROS) such as hydrogen peroxide that can damage cells. Dr. Kim has shown that indeed, under simulated sunlight conditions, the GO nanoparticles produce ROS within the bodies of these 5-day-old zebrafish, along with the expected toxicities. Understanding what GO does in biological systems will make it possible to find safe ways to produce, use, and dispose of compounds such as GO.

Figure. (A) Photographs of aqueous dispersion of GO (500 µg/ml) before and after 24 h either under illumination or in the dark. (B) Color change in 24-well plates containing zebrafish embryos. GO solutions were found to change color with illumination.