Phytotoxicity of zinc oxide nanoparticles and multi-walled carbon nanotubes, alone or in combination, on Arabidopsis thaliana and their mutual effects on oxidative homeostasis

Abstract

The extensive use of engineered nanoparticles (ENPs) has raised concerns about their potentially harmful effects on the ecosystem. Despite previous reports of a variety of individual ENPs, the mutual effects of ENPs when used in combination were not well understood. In this study, we first investigated the effects of different sizes and concentrations of ZnO nanoparticles (ZnO NPs) or multi-walled carbon nanotubes (MWCNTs) on the growth performance of Arabidopsis thaliana seedlings. Then, two concentrations of ZnO NP (40 and 50 mg/L) with a diameter of 90 nm and MWCNTs (100 and 500 mg/L) with an outer diameter of 40–60 nm were used to evaluate their respective or simultaneous phytotoxicity to Arabidopsis. The results showed that seedlings exposed to either ZnO NPs or MWCNTs exhibited significant phytotoxic symptoms. ZnO NPs caused stronger inhibitory effects than MWCNTs on several plant growth indices, including reduced root length, chlorophyll content, and increased ROS concentration. When applied together, the concurrent effects of ZnO NPs and MWCNTs on Arabidopsis seedlings appeared to be more negative, as evidenced not only by the further deterioration of several growth indices but also by their synergistic or additive regulation of the activities of several antioxidant enzymes such as superoxide dismutase (SOD), catalase (CAT) and glutathione reductase (GR). Moreover, qRT-PCR analysis revealed that in the presence of ZnO NPs and MWCNTs, the expression of genes important for maintaining cellular ROS homeostasis was differentially regulated in shoots and roots of Arabidopsis seedlings. Overall, our data may provide new insights into how plants respond to more than one type of nanomaterial and help us better understand the associated environmental risks.

Mercuric oxide nanoparticles deferred germination and devastated root anatomy of maize

“…Similar results were obtained in maize exposed to PbS-NPs (Ullah et al, 2020), alfalfa (Medicago sativa L.) treated with graphene oxide (Zhao et al, 2023) and Arabidopsis thaliana seedlings subjected to ZnO NPs and MWCNTs (Yang et al, 2023).…”

“…Once accumulated in soil, toxic agents such as heavy metal nanoparticles (HM-NPs) inhibit seeds germination and development of early seedlings in several plants (Asadi-Kavan et al, 2020;Seddighinia et al, 2020). In this regard, retardation of germination and growth of young seedlings due to nano-sized heavy metals, such as PbS-NPs (Ullah et al, 2020), CuO-NPs (Ibrahim et al, 2022), Y2O3-NPs (Zhao et al, 2021) and ZnO NPs (Yang et al, 2023), have been studied in maize, wheat, rice and Arabidopsis thaliana, respectively. These authors ascribed the delaying of seed germination and deterioration of seedling growth to: (a) deactivation of seed' amylase and protease via formation of S-Metal-S bridges instead of -SH group in the enzyme' proteins (b) blocking of aquaporins delay the rupture of seed coat and emergence of radical (c) restraining water imbibition and uptake due to metal-induced ionic toxicity (d) generation of free radicals and cellular oxidative damage, (e) decreasing internodal length and plant height and (f) distortion of root structures and disruption of water uptake.…”

A critical review on the toxicity regulation and ecological risks of zinc oxide nanoparticles to plants

“…135 The presence of naturally sourced cellulose nanocrystals (CNCs) also augmented the bioavailability and toxicity of NPs to the Eremosphaera viridis by diminishing the aggregation of ZnO NPs, where the toxicity mechanisms exhibited strong oxidative stress, disturbed elemental distribution patterns, disrupted enzyme activities, and catabolic lipid molecules. 44 Similarly, the synergistic effect of ZnO NPs and multiwalled carbon nanotubes (MWCNTs) altered genes that maintain cellular ROS homeostasis to regulate the activities of antioxidant enzymes such as SOD, CAT, and GR, 136 while the coexistence of ZnO NPs with nanoplastics increased abscisic acid (ABA) and H 2 O 2 concentrations in Hordeum vulgare L. and caused stronger damage to antioxidant and carbohydrate metabolism systems. 34 Polystyrene (PS) also aggravated structural damage to the cell wall of Chlorella vulgaris, facilitated the transfer of ZnO NPs through the food chain, and increased the ecological risk of NPs.…”

“…Similarly, the synergistic effect of ZnO NPs and multi-walled carbon nanotubes (MWCNTs) altered genes that maintain cellular ROS homeostasis to regulate the activities of antioxidant enzymes such as SOD, CAT, and GR, 136 while the coexistence of ZnO NPs with nanoplastics increased abscisic acid (ABA) and H 2 O 2 concentrations in Hordeum vulgare L. and caused stronger damage to antioxidant and carbohydrate metabolism systems. 34 Polystyrene (PS) also aggravated structural damage to the cell wall of Chlorella vulgaris , facilitated the transfer of ZnO NPs through the food chain, and increased the ecological risk of NPs.…”

Mg–Al LDH nanosheets as a nanotechnological tool in agriculture: an exploratory toxicity evaluation study

“…18 In the same plant model, zinc oxide nanoparticles (ZnO NPs) decreased the root length and negatively modulated the content of some nutrients. 19 However, there is still a long pathway to uncover other functional nanomaterials that may be toxic to plants, and that knowledge gap is even more significant for non-target organisms. 20 This article focuses on nanoclays, particularly of layered double hydroxide (LDH) nanosheets, which have been actively proposed as delivery systems for plant and plant pathogen treatments in the last few years.…”