Nanoparticle Uptake in Plants: Gold Nanomaterial Localized in Roots of Arabidopsis thaliana by X-ray Computed Nanotomography and Hyperspectral Imaging

Abstract

Terrestrial plants can internalize and translocate nanoparticles (NPs). However, direct evidence for the processes driving the NP uptake and distribution in plants is scarce at the cellular level. Here, NP-root interactions were investigated after 10 days of exposure of Arabidopsis thaliana to 10 mg·L of negatively or positively charged gold NPs (∼12 nm) in gels. Two complementary imaging tools were used: X-ray computed nanotomography (nano-CT) and enhanced dark-field microscopy combined with hyperspectral imaging (DF-HSI). The use of these emerging techniques improved our ability to detect and visualize NP in plant tissue: by spectral confirmation via DF-HSI, and in three dimensions via nano-CT. The resulting imaging provides direct evidence that detaching border-like cells (i.e., sheets of border cells detaching from the root) and associated mucilage can accumulate and trap NPs irrespective of particle charge. On the contrary, border cells on the root cap behaved in a charge-specific fashion: positively charged NPs induced a higher mucilage production and adsorbed to it, which prevented translocation into the root tissue. Negatively charged NPs did not adsorb to the mucilage and were able to translocate into the apoplast. These observations provide direct mechanistic insight into NP-plant interactions, and reveal the important function of border cells and mucilage in interactions of plants with charged NPs.

Increased Plant Growth with Hematite Nanoparticle Fertilizer Drop and Determining Nanoparticle Uptake in Plants Using Multimodal Approach

“…Electron microscopy is traditionally used to visualize NPs within the plants, but the sample preparation required for this method increases the probability of artifacts in the images. Therefore, we chose hyperspectral imaging (CytoViva), a minimally invasive and enhanced darkfield imaging technique requiring negligible sample preparation to investigate the uptake of hematite NPs in the legumes [29,40]. The enhanced darkfield illumination technology in this method minimized light loss and enabled scatter from the sample to be detected without source illumination interference.…”

“…The images and spectra from chickpea leaves and the raw hematite NP fertilizer are presented in the SI for further confirmation of our conclusion ( Figures S6 and S7). It should be noted that though hyperspectral imaging has been reported earlier in detecting NPs within animal tissues, the use of this technique for plant samples is relatively new [29].…”

“…Recently, darkfield hyperspectral imaging has emerged as a highly promising visualization tool to both detect and map the localization of NPs within complex microenvironments [28]. The charge-dependent uptake and mobility of Au NPs by the roots of Arabidopsis thaliana could be demonstrated using this technique [29]. When combined with an elemental analysis technique like X-ray tomography or mass spectroscopy, hyperspectral imaging provided further reliable insights into plant-NP interactions [29,30].…”

“…The charge-dependent uptake and mobility of Au NPs by the roots of Arabidopsis thaliana could be demonstrated using this technique [29]. When combined with an elemental analysis technique like X-ray tomography or mass spectroscopy, hyperspectral imaging provided further reliable insights into plant-NP interactions [29,30]. Another method requiring minimum sample preparation is FTIR, which has also proven useful in understanding the plant-NP interactions via chemical composition analysis in several reports.…”

X-ray spectroscopy uncovering the effects of Cu and Fe based nanoparticles on Phaseolus vulgaris L. germination and seedling development

“…61 and also to analyze archaeological seeds in the investigation of crop domestication. 62; 63 However, to the best of our knowledge, no other study examined 3D images of a nanoparticle-treated bean seed, although some researchers used this technique to verify the uptake and distribution of gold and yttrium nanoparticles in Arabidopsis thaliana 64 and cabbage plants. 65 The chemical form of Fe trapped in the hilum was evaluated by Fe K edge XANES.…”