Two-Photon Microscopy and Spectroscopy Studies to Determine the Mechanism of Copper Oxide Nanoparticle Uptake by Sweetpotato Roots during Postharvest Treatment

Abstract

The interaction of engineered nanoparticles with plant tissues is still not well understood. There is a lack of information about the effects of curing (postharvest treatment) and lignin content on copper uptake by sweetpotato roots exposed to copper-based nanopesticides. In this study, Beauregard-14 (lower lignin) and Covington (higher lignin) varieties were exposed to CuO nanoparticles (nCuO), bulk CuO (bCuO), and CuCl at 0, 25, 75, and 125 mg/L. Cured and uncured roots were submerged into copper suspensions/solutions for 30 min. Subsequently, root segments were sliced for imaging with a 2-photon microscope, while other root portions were severed into periderm, cortex, perimedulla, and medulla. They were individually digested and analyzed for Cu content by inductively coupled plasma-optical emission spectroscopy. Microscopy images showed higher fluorescence in periderm and cortex of roots exposed to nCuO, compared with bCuO. At 25 mg/L, only bCuO showed higher Cu concentration in the periderm and cortex of Beauregard-14 (2049 mg/kg and 76 mg/kg before curing; 6769 mg/kg and 354 mg/kg after curing, respectively) and in cortex of Covington (692 mg/kg before curing and 110 mg/kg after curing) compared with controls ( p ≤ 0.05). In medulla, the most internal tissue, only Beauregard-14 exposed to 125 mg bCuO/L showed significantly ( p ≤ 0.05) more Cu before curing (17 mg/kg) and after curing (28 mg/kg), compared with control. This research has shown that the 2-photon microscope can be used to determine CuO particles in nondyed plant tissues. The lack of Cu increase in perimedulla and medulla, even in roots exposed to high CuO concentrations (125 mg/L), suggests that nCuO may represent a good alternative to protect and increase the shelf life of sweetpotato roots, without exposing consumers to excess Cu.

Exploring the interaction between polystyrene nanoplastics and Allium cepa during germination: Internalization in root cells, induction of toxicity and oxidative stress

“…The red staining in the tegumental tissue (Figure 5d) may be allied to a partial physical/chemical dealing of nano PS with the root surface and could cause a general disturbance in root growth and functioning, as reported for Lemna minor (Kalčíková et al, 2017). In addition, our results demonstrated the presence of PS aggregates in different root compartments, suggesting that also nano PS, as other classes of nanoparticles (Geisler-Lee et al, 2013;Deng et al, 2017;Bonilla-Bird et al, 2018;Giorgetti et al, 2019;Bellani et al, 2020), are able to overcome different biological barriers and enter the cells of the roots. This fact is particularly clear when analysing our results of transmission electronic microscopy (see below).…”

CuO and ZnO Nanoparticle Application in Synthetic Soil Modulates Morphology, Nutritional Contents, and Metal Analysis of Brassica nigra

“…They reduce the length and biomass of the plants and alter different biochemical processes. Many other studies also described the effect of CuO on different plants. − It has been proven that toxicological and growth-stimulatory effects depend upon the characteristics of NPs used, the growth medium, and the plant type. However, NPs are found to be more toxic than ions and microparticles. , …”

Uptake and Translocation of Styrene Maleic Anhydride Nanoparticles in Murraya exotica Plants As Revealed by Noninvasive, Real-Time Optical Bioimaging

“…It is therefore intriguing to further explore the potential application of TPE-TR imaging in monitoring the interaction of PNPs with plants under physiological conditions. In this context, two-photon microscopy has been recently employed to investigate the uptake of copper oxide nanoparticles by sweetpotato roots during postharvest treatment . In contrast to TPE-TR imaging, this method relies on the selective detection of two-photon induced fluorescence from the lignin and the nanoparticles in biological tissues.…”