(27c) No Evidence of Cerium Oxide Nanoparticle Translocation In Maize Plants

The rapidly increasing production of engineered nanoparticles has raised questions regarding their environmental impact and their mobility to overcome biological important barriers. Nanoparticles were found to cross different mammalian barriers, which is summarized under the term translocation. The present work investigates the uptake and translocation of cerium dioxide nanoparticles in maize plants as one of the major agricultural crops.

In order to simulate the gas-phase exposure of maize plants to nanoparticles, flame spray pyrolysis (FSP) was utilized to directly synthesize a cerium oxide comprising aerosol. (Birbaum et al. 2010) The aerosol was produced in an enclosed cabinet (glove box, 2 m^3, see Figure 1) in which the maize plants were cultivated. After digestion of the maize leaves, the cerium concentrations were measured by a sector field inductively coupled mass spectrometer (ICP-SF-MS), allowing a detection limit of less than 1 ng of cerium per gram of leaf. (< 1 ppb mass/mass). The plant leaves were analysed for the cerium content directly after exposure and 12 weeks post exposure in order to measure the cerium translocation within the plant.

Element analysis results showed that cerium oxide nanoparticles were present on/in the maize leaves after the aerosol exposure. While it was not possible to discriminate between particles taken up by the plant cells and particles adsorbed to the surface of the leaves, the deposited nanoparticles could not be washed off with water (simulating rainfall). Examination of the concentrations in the leaves 3 months after the exposure experiments revealed that the cerium oxide nanoparticles did not translocate into newly formed leaves. No cerium oxide (detection limit of 0.4 ng cerium / g leaf) could be measured in the leaves grown during the three months post exposure period. 

The presentation will further show the influence of light (exposure under light and dark for open and closed stomata) and results on the suspension exposure of maize plants (via the soil). The results of the maize plant exposure will be discussed and compared with in vitro lung cell exposure experiments (Rothen-Ruthishauser et al. 2010, Raemy et al. 2011) performed under the same exposure conditions. 

Refs: 

Birbaum, K., Brogioli, R. Schellenberg, M., Martinoia, E., Stark, W.J., Günther, D. and Limbach, L.K. (2010) Environ. Sci. Technol. 44, 8718-8723.

Raemy, D.O., Limbach, L.K., Rothen-Rutishauser, B., Grass, R.N., Gehr, P., Birbaum, K., Brandenberger, C., Günther, D. and Stark, W.J. (2011) Eur. J. Pharm. Biopharm. doi: 10.1016/ j.ejpb.2010.11.017.

Rothen-Rutishauser, B., Grass, R.N., Blank, F., Limbach, L.K., Muehlfeld, C., Brandenberger, C., Raemy, D.O., Gehr, P. and Stark W.J. (2009) Environ. Sci. Technol. 43, 2634-2640.