Quantitative evaluation of multi-wall carbon nanotube uptake by terrestrial plants

The extent and mechanisms by which multi-wall carbon nanotubes (MWCNTs) are accumulated by terrestrial plant species is currently unknown. In this study, we successfully measured the MWCNTs content in different plant (Arabidopsis thaliana, rice, maize and soybean) using 14C labeled MWCNTs. Quantitative relationships among the uptake amount of MWCNTs in different Arabidopsis tissues, the physiological (water loss, pigment content, and total protein content) and biochemical parameters (antioxidant enzyme activities) were further evaluated. Our results indicated that changes in biochemical parameters were much more sensitive than physiological parameters. The lowest CAT activities in the treatment with (1,3-dinitrobenzene + MWCNTs) were only 0.13- fold of that in the 1,3-dinitrobenzene alone treatment, suggesting MWCNTs could alleviate the toxicity to Arabidopsis. Due to the toxicity caused by small polar aromatic organic molecules (SPAOMs), the MWCNTs uptake in leaf in the treatment with (2,4-dichlorophenol + MWCNTs) was only 0.07-fold relative to the MWCNTs alone treatment. Hydrodynamic diameter of MWCNTs in solution did not significantly affect MWCNTs uptake. Uptake models for MWCNTs into root and leaf tissue were constructed via stepwise multiple linear regression analysis. This study will provide important information for the accurate determination of risk associated with MWCNT exposure.

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