Fourier transform infrared spectroscopy contribution to disentangle nanomaterial (DWCNT, TiO2) impacts on tomato plants

Carbon nanotubes (CNTs) and titanium dioxide nanoparticles (TiO2-NPs) are among the most used nanomaterials (NMs). However, their impacts especially on the terrestrial ecosystems and on plants are still controversial. Apart from obvious physico-chemical differences, a possible explanation of these contrasting results could be the wide range of methods used to evaluate the toxicity at different levels of plant physiology. Fourier transformed infrared (FTIR) spectroscopy is a sensitive and widely informative technique that probes the chemical composition of plants. In this study, we investigated the impacts of CNTs and TiO2-NPs (100 and 500 mg kg−1) on tomato plants after 5, 10, 15 and 20 days of exposure in soil. Using morphological parameters, no toxicity was found except after 15 days of exposure (−57% in height and −62% in foliar area for plants exposed to 100 mg kg−1 TiO2-NPs, but no impact after CNT exposure) while FTIR revealed effects of the two NMs starting after 5 days of exposure and being maximum after 15 days. After spectral data treatment optimization, FTIR results suggested modifications in leaf cell wall components of plants subjected to both NMs. Microarray polymer profiling confirmed changes in xyloglucan and homogalacturonan levels for plants exposed to TiO2-NPs. In summary, FTIR was an effective screening method to evaluate the impacts of NMs on tomato plants and to identify their implications on the plant cell walls.