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<p>To protect human health from nanoparticle exposure, it is crucial to understand the crop plant uptake of soil-associated carbon nanotubes (CNTs) and their accumulation in fresh products, which are governed by the physicochemical property and dispersion of CNTs. Our primary research objective is to analyze the impact of aromatic carbon-degrading microorganism on the transformation, aqueous stability and tomato plant uptake of CNTs. As a seed project, this proposed study will produce important preliminary data for understanding plant uptake of CNTs mediated by microbial activities. The long-term goal of this research is to evaluate the microbial-mediated accumulation of engineered nanoparticles in fresh produce, critical for protecting food safety under the influences of nanotechnology industry.</p>
<p>We will use single-walled carbon nanotubes (SWCNT), carboxylic single-walled carbon nanotubes (COO-SWCNT) and hydroxylic single-walled carbon nanotubes (OH-SWCNT). 14C-labeled CNTs will be synthesized by a chemical vapor deposition technique and treated with a 3:1 mixture of sulfuric to nitric acid, following the published method. CNTs will be incubated with various aromatic carbon-degrading microorganisms for 30 d, upon when various properties will be characterized for CNTs. Fourier-transformed infrared spectra (FTIR) and Raman spectra for CNTs will also be analyzed. Attachment of bacteria cells on the surface of CNTs also will be examined by observation through scanning electron microscope (SEM) and transmission electron microscope (TEM). 14C-labeled CNTs will be incubated with bacteria in a respirometer, to monitor the kinetics of 14CO2 produced by mineralization of the CNTs. Tomato plant uptake of CNTs will be studied in hydroponic culture with and without aromatic carbon-degrading microorganism. Aromatic carbon-degrading microorganisms will be inoculated into the tomato culture solution. In different culture periods, residual CNTs in solution will be characterized by elemental analysis and other spectroscopic techniques. SEM and TEM will be applied to analyze the residual CNT in solution phase. Plant tissues will also be observed for the potential uptake and accumulation of CNTs. In the culture with 14C-labeled CNTs, tissues of tomato root, leaf and stem will be analyzed for the accumulation of 14C-labeled CNTs. Amount of residual 14C-labeled CNTs in culture solutions will also be monitored.</p>