Thrust 4: Confocal Raman Imaging of Graphene Oxide Uptake into the Developing Zebrafish Embryo (Danio rerio)

Min-Sik Kim, Min Yan, Joel A. Pedersen, Robert J. Hamers, Richard E. Peterson, Warren Heideman

Figure 1. (a) Live zebrafish larva following water-borne exposure to graphene oxide nanosheets. (b) Raman spectrum zebrafish gut showing prominent peaks indicating the presence of graphene oxide nanosheets.

Detecting uptake of graphene oxide and other nanomaterials into organisms is challenging due to the low concentration of nanoparticles present and background effects such as autofluorescence. In collaboration with ThermoFisher Scientific, we have been developing Raman Imaging Spectroscopy as a tool for in situ characterization of nanoparticle uptake into live zebrafish embryos. The historically low sensitivity of Raman is overcome using high-efficiency collection optics coupled with an electron-multiplying CCD array. This combination yields single-photon sensitivity in an array detector, allowing Raman imaging experiments to be performed at low laser powers.

Using this approach we succeeded in establishing that graphene oxide nanosheets were located primarily in the zebrafish digestive tract, not in the gills or on the skin. This distribution indicates that oral intake may be the major exposure route of graphene oxide nanosheets during water-borne exposure in zebrafish embryos. This study will help the assessment of the potential risks of exposure of aquatic organisms to graphene oxide nanosheets. Since Raman spectra of many nanoparticles are characterized by sharp lines, our work suggests that Raman Imaging may be a broadly applicable tool for spatially localizing nanoparticles within organisms in a non-destructive manner.