CuO and ZnO Nanoparticles Modify Interkingdom Cell Signaling Processes Relevant to Crop Production

Copper-based nanomaterials: Opportunities for sustainable agriculture

The exponential growth of the global population has resulted in a significant surge in the demand for food worldwide. Additionally, the impact of climate change has exacerbated crop losses caused by pests and pathogens. The transportation and utilization of traditional agrochemicals in the soil are highly inefficient, resulting in significant environmental losses and causing severe pollution of both the soil and aquatic ecosystems. Nanotechnology is an emerging field with significant potential for market applications. Among metal-based nanomaterials, copper-based nanomaterials have demonstrated remarkable potential in agriculture, which are anticipated to offer a promising alternative approach for enhancing crop yields and managing diseases, among other benefits. This review firstly performed co-occurrence and clustering analyses of previous studies on copper-based nanomaterials used in agriculture. Then a comprehensive review of the applications of copper-based nanomaterials in agricultural production was summarized. These applications primarily involved in nano-fertilizers, nano-regulators, nano-stimulants, and nano-pesticides for enhancing crop yields, improving crop resistance, promoting crop seed germination, and controlling crop diseases. Besides, the paper concluded the potential impact of copper-based nanomaterials on the soil micro-environment, including soil physicochemical properties, enzyme activities, and microbial communities. Additionally, the potential mechanisms were proposed underlying the interactions between copper-based nanomaterials, pathogenic microorganisms, and crops. Furthermore, the review summarized the factors affecting the application of copper-based nanomaterials, and highlighted the advantages and limitations of employing copper-based nanomaterials in agriculture. Finally, insights into the future research directions of nano-agriculture were put forward. The purpose of this review is to encourage more researches and applications of copper-based nanomaterials in agriculture, offering a novel and sustainable strategy for agricultural development.

Toxic effects and mechanisms of engineered nanoparticles and nanoplastics on lettuce (Lactuca sativa L.)

Engineered nanoparticles (ENPs) and nanoplastics (NPs) are typical nanoparticles in terrestrial environments. Till now, few studies have compared their toxicity and mechanism to plants. Here we investigated the effects of CuO, nZVI ENPs and polystyrene (PS) NPs on lettuce growth, metabolic functions, and microbial community structure. Results showed that low concentrations of nanoparticles decreased root biomass and promoted photosynthetic indicators, whereas increased reactive oxygen species (ROS) were detected in roots exposed to high concentrations of nanoparticles. High-dose CuO ENP exposure significantly raised the MDA content by 124.6 % compared to CK, causing the most severe membrane damage in the roots among the three types of nanoparticles. Although linoleic acid metabolism was down-regulated, the roots alleviated CuO stress by up-regulating galactose metabolism. Uptake of PS by roots similarly caused ROS production and activated the oxidative stress system by altering amino acid and vitamin metabolism. Faster microbial responses to nanoparticles were observed in the nZVI and PS networks. The root toxicity was indirectly mediated by ion release, NP uptake, or ROS generation, ultimately impacting root cell metabolism, rhizospheric microorganism and plant growth. These findings provide theoretical basis for assessing environmental impact of nanoparticles and their possible ecological risks.

Formulation of Zinc oxide/Gum acacia nanocomposite as a novel slow-release fertilizer for enhancing Zn uptake and growth performance of Spinacia oleracea L

Zinc (Zn) deficiency has caused nutritional disorders in 17% of the world's population; thus, producing Zn-enriched plants as a dietary source is necessary. Recently, nanofertilizers have gained much attention as a substitute for conventional fertilizers; however, soil application of polymer-coated Zn-based nanofertilizer has not been explored much. The present study depicts the green synthesis of ZnO nanoparticles using Melia azedarach L. leaf extract, whose phytoconstituents have reducing abilities. The synthesized nanoparticles were combined with gum acacia (GA) to form a ZnOGA nanocomposite. The structural and morphological properties of ZnOGA were studied using XRD, FTIR, FESEM, and EDX. A pot experiment study was carried out with Spinacia oleracea L. at various doses (3, 5, and 10 mg/kg) of the synthesized ZnOGA to evaluate its effectiveness as a slow-release fertilizer and was compared with a commercial Zn fertilizer. The plant growth studies revealed a significant increase in the phyto-morphological traits of the plants fertilized with ZnOGA compared to commercial fertilizer. The plants also displayed significantly higher contents of protein (17-47%), phenols (25-60%), proline (82-94%), total soluble sugar (20-31%), DPPH activity (70-72%), and Zn uptake (91-106%). The doses of ZnOGA played an imperative role in determining the growth and productivity of the plant. Soil column studies showed that ZnOGA reduces Zn leaching by 52% compared to commercial Zn fertilizer. This study signifies the potential of ZnOGA to be applied as an eco-friendly and sustainable substitute for conventional Zn fertilizer minimizing Zn losses and Zn deficiency-related health problems in human populations.

Layered Double Hydroxides for Regulating Phosphate in Water to Achieve Long-Term Nutritional Management

Hunger and undernourishment are increasing global challenges as the world's population continuously grows. Consequently, boosting productivity must be implemented to reach the global population's food demand and avoid deforestation. The current promising agricultural practice without herbicides and pesticides is fertilizer management, particularly that of phosphorus fertilizers. Layered double hydroxides (LDHs) have recently emerged as favorable materials in phosphate removal, with practical application possibilities in nanofertilizers. This review discusses the fundamental aspects of phosphate removal/recycling mechanisms and highlights the current endeavors on the development of phosphate-selective sorbents using LDH-based materials. Specific emphasis is provided on the progress in designing LDHs as the slow release of phosphate fertilizers reveals their relevance in making agro-practices more ecologically sound. Relevant pioneering efforts have been briefly reviewed, along with a discussion of perspectives on the potential of LDHs as green nanomaterials to improve food productivity with low eco-impacts.

Discovery of rosin-based acylhydrazone derivatives as potential antifungal agents against rice Rhizoctonia solani for sustainable crop protection

BACKGROUND

The use of fungicides to protect crops from diseases is an effective method, and novel environmentally friendly plant-derived fungicides with enhanced performance and low toxicity are urgent requirements for sustainable agriculture.

RESULTS

Two kinds of rosin-based acylhydrazone compounds were designed and prepared. Based on the antifungal activity assessment against Rhizoctonia solani, Fusarium oxysporum, Phytophthora capsici, Sclerotinia sclerotiorum, and Botrytis cinerea, acylhydrazone derivatives containing a thiophene ring were screened and showed an inhibitory effect on rice R. solani. Among them, Compound 4n, with an electron-withdrawing group on the benzene ring structure attached to the thiophene ring, showed optimal activity, and the EC₅₀ value was 0.981 mg L^-1 , which was lower than that of carbendazim. Furthermore, it was indicated that 4n could affect the mycelial morphology, cell membrane permeability and microstructure, cause the generation of reactive oxygen species in fungal cells, and damage the nucleus and mitochondrial physiological function, resulting in the cell death of R. solani. Meanwhile, Compound 4n exhibited a better therapeutic effect on in vivo rice plants. However, the induction activity of 4n on the defense enzyme in rice leaf sheaths showed that 4n stimulates the initial resistance of rice plants by removing active oxygen, thereby protecting the cell membrane or enhancing the strength of the cell wall. Through the quantitative structure-activity relationship study, the quantitative chemical and electrostatic descriptors significantly affect the binding of 4n with the receptor, which improves its antifungal activity.

CONCLUSION

This study provides a basis for exploiting potential rosin-based fungicides in promoting sustainable crop protection. © 2022 Society of Chemical Industry.

ZnO nanoparticles as potential fertilizer and biostimulant for lettuce

Zn is an indispensable nutrient for crops that usually presents low bioavailability. Different techniques have been proposed to improve the bioavailability of Zn, including the use of nanofertilizers. The objective of the study was to evaluate the applications of drench (D) and foliar (F) ZnO nanoparticles (NZnO) compared to those of ionic Zn²⁺ (ZnSO₄) in lettuce. The plants cv. Great Lakes 407 was produced in pots of 4 L with perlite-peat moss (1:1) under greenhouse conditions. The treatments consisted of NZnO applications that replaced the total Zn provided with a Steiner solution, as follows: Zn²⁺ (100%D) (control); Zn²⁺ (50%D+50%F); NZnO (100%D); NZnO (50%D+50%F); NZnO (75%D); NZnO (50%D); NZnO (75%F) and NZnO (50%F). Four applications of Zn were made with a frequency of 15 days. 75 days after transplant (DAP), the fresh and dry biomass, chlorophyll a, b, and β-carotene, phenolics, flavonoids, antioxidant capacity, vitamin C, glutathione, H₂O₂, total protein, and enzymatic activity of PAL, CAT, APX, and GPX were evaluated. The mineral concentrations (N, P, K, Ca, Mg, S, Cu, Fe, Mn, Mo, Zn, Ni, and Si) in the leaves and roots of plants were also determined. The results showed that, compared to Zn²⁺, NZnO promoted increases in biomass (14-52%), chlorophylls (32-69%), and antioxidant compounds such as phenolics, flavonoids, and vitamin C. The activity of enzymes like CAT and APX, as well as the foliar concentration of Ca, Mg, S, Fe, Mn, Zn, and Si increased with NZnO. A better response was found in the plants for most variables with foliar applications of NZnO equivalent to 50-75% of the total Zn²⁺ applied conventionally. These results demonstrate that total replacement of Zn²⁺ with NZnO is possible, promoting fertilizer efficiency and the nutraceutical quality of lettuce.

Efficacy of metallic nanoparticles in attenuating the accumulation and toxicity of chromium in plants: Current knowledge and future perspectives

Nanoparticles have emerged as cutting-edge technology for the improvement of crops yield and safe cultivation of agricultural plants, especially in peripheral areas impaired with toxic heavy metals including chromium (Cr). The uncontrolled release of Cr mainly from anthropogenic factors is substantially polluting the surrounding environment, thereby extensively accumulated in soil-plant system. The excessive Cr-accretion in plant tissues disturbed the morph-physiological, biochemical, cellular, metabolic and molecular processes, and impaired the plants functionality. Therefore, it is obligatory to restrict the accumulation and toxic effects of Cr in plant organs. Recent studies on metallic nanoparticles (MNPs) such as iron oxide, silicon dioxide, copper oxide and zinc oxide have approved their efficacy as potent pool to curb the Cr-induced phytotoxicities and improved the plant tolerance. MNPs attenuated the bioaccumulation and phytotoxicity of Cr by utilizing key mechanisms such as improved photosynthetic machinery, regulation of cellular metabolites, greater chelation capacity to bind with Cr, release of corresponding metallic ions, upsurge in the uptake of essential nutrients, activation of antioxidants (enzymatic and non-enzymatic), reduction in oxidative stress, and cellular injuries, thus improvement in plant growth performances. We have briefly discussed the current knowledge and research gaps in existing literature along with possible recommendations for future research. Overall, Cr-detoxification by MNPs may depends upon the target plant species, Cr speciation, plant growth stages (seedling, vegetative and ripening etc.), treatment methods (foliar spray, seed priming and nutrient solution etc.), type, size, dose and coating of applied MNPs, and conditions (hydroponic and soil environment etc.). This review would help plant scientists to develop MNPs based strategies such as nano-fertilizers to alleviate the Cr-accumulation and its toxic impacts. This may leads to safe and healthy food production. The review outcomes can provide new horizons for research in the applications of MNPs for the sustainable agriculture.

Potential of metal and metal oxide nanoparticles in plant disease diagnostics and management: Recent advances and challenges

Plant diseases caused by phytopathogens are a severe threat to global food production. Management of plant diseases mostly rely on the application of pesticides which have several adverse effects on the ecosystem. Innovative and high-performance diagnostic tools are useful for the early detection of phytopathogens. Emerging role of metal and metal oxides nanoparticles (NPs) in plant disease diagnostics to combat crop diseases has been described. These NPs constitute new weapons against plant pathogens and facilitate the early diagnosis/management of crop diseases specifically in resource-poor conditions. The interactions between NPs, phytopathogens and plants showed great diversity and multiplicity which reduces chances of the development of resistant pathogen strains. The present article discusses the available literature as well as challenges and research gaps that are essential in the successful utilization of metal and metal oxide NPs for precise and timely detection and management of plant diseases.

Nano-Fe2O3 as a tool to restore plant growth in contaminated soils - Assessment of potentially toxic elements (bio)availability and redox homeostasis in Hordeum vulgare L

This work aimed to evaluate the potential of Fe₂O₃ nanoparticles (nano-Fe₂O₃) to alleviate potentially toxic elements (PTEs) - induced stress in barley plants (Hordeum vulgare L.), focusing on bioaccumulation patterns and on plant growth and redox homeostasis. To achieve this goal, plants grew in two agricultural soils, contaminated by different levels of PTEs, collected from an industrial area, previously amended, or not, with 1% (w/w) nano-Fe₂O₃. After 14 d of growth, biometric parameters were evaluated, along with the analysis of PTEs bioaccumulation and biochemical endpoints. After exposure to contaminated soils, plant development was greatly affected, as evidenced by significant decreases in root length and biomass production. However, upon co-treatment with nano-Fe₂O₃, lower inhibitory effects on biometric parameters were observed. Regarding the oxidative damage, both soils led to increases in lipid peroxidation and superoxide anion concentration, though hydrogen peroxide levels were only increased in the most contaminated soil. In general, these changes in the oxidative stress markers were accompanied by an upregulation of different antioxidant mechanisms, whose efficiency was even more powerful upon soil amendment with nano-Fe₂O₃, thus lowering PTEs-induced oxidative damage. Altogether, the present study revealed that nano-Fe₂O₃ can protect the growth of barley plants under contaminated soils.

Influence of Copper Oxide Nanoparticles on Gene Expression of Birch Clones In Vitro under Stress Caused by Phytopathogens

Recently, metal oxide nanoparticles (NPs) have attracted attention as promising components for the protection and stimulation of plant microclones in tissue culture in vitro. However, the effect of NPs on the genetic mechanisms underlying plant adaptive responses remains poorly understood. We studied the effect of column-shaped CuO NPs 50 nm in diameter and 70–100 nm in length at a concentration of 0.1–10 mg/L on the development of phytopathogenic fungi Alternaria alternata, Fusarium oxysporum, and Fusarium avenaceum in culture, as well as on the infection of downy birch micro-clones with phytopathogens and the level of genes expression associated with the formation of plant responses to stress induced by microorganisms. CuO NPs effectively suppressed the development of colonies of phytopathogenic fungi A. alternata and F. avenaceum (up to 68.42% inhibition at 10 mg/L CuO NPs) but not the development of a colony of F. oxysporum. Exposure to the NPs caused multidirectional responses at the level of plant genes transcription: 5 mg/L CuO NPs significantly increased the expression level of the LEA8 and MYB46 genes and decreased the expression of DREB2 and PAL. Infection with A. alternata significantly increased the level of MYB46, LEA8, PAL, PR-1, and PR-10 transcripts in birch micro-clones; however, upon exposure to a medium with NPs and simultaneous exposure to a phytopathogen, the expression of the MYB46, PR-1, and PR-10 genes decreased by 5.4 times, which is associated with a decrease in the pathogenic load caused by the effect of NPs and the simultaneous stimulation of clones in vitro. The results obtained can be used in the development of preparations based on copper oxide NPs for disinfection and stimulation of plant phytoimmunity during clonal micropropagation of tree crops.

Titanium dioxide nanoparticles mitigate cadmium toxicity in Coriandrum sativum L. through modulating antioxidant system, stress markers and reducing cadmium uptake

Anthropogenic activities are the foremost reason of metal pollution in soils of the cultivated areas, resulting abnormal physiochemical processes in plants. Among metals contaminants, cadmium (Cd) is one of the most injurious contaminants that deleteriously affect physiological activities, growth and yield of the crop plants. Keeping in view the stress mitigation potential of titanium dioxide (TiO₂), the existing research work was premeditated to inspect the beneficial role of seed priming with titanium dioxide nanoparticles (TiO₂-NPs) on biochemical, morphological and physiological characteristics of Coriandrum sativum L. (coriander) plants under Cd stress. For this purpose, C. sativum seeds were primed with 0, 40, 80 and 160 mg L^-1 TiO₂-NPs. Cadmium stress triggered a significant decrease in chlorophyll a content (49%), chlorophyll b content (44%), photosynthetic rate (62%) and plant growth (51%) as compared with control. Tanium dioxide nanoparticles treated seedlings exhibited reduced Cd contents besides improved agronomic traits (seedlings biomass, number of seeds and yield). The TiO₂-NPs treatment declined the magnitude of EL and MDA by 1.5 fold and 1.71 fold, respectively. Furthermore, TiO₂-NPs diminished oxidative injuries in plants exposed to Cd stress. Additionally, TiO₂-NPs enhanced the biosynthesis of osmatic regulators (proline) by 47% which helped in the mitigation of Cd persuaded toxicity in plants. Briefly, treatment of 80 mg L^-1 TiO₂-NPs perhaps ameliorates the deleterious influence of Cd stress and enhance the yield of coriander.

Effect of Fe3O4 and CuO Nanoparticles on Morphology, Genotoxicity, and miRNA Expression on Different Barley (Hordeum vulgare L.) Genotypes

Metal nanoparticles (NPs) have an influence on plant growth and development. They can alter plant shoot and root length, fresh biomass production, and even influence the genome. Nanoparticles are also able to affect expression levels of plant microRNAs. MicroRNAs are able to protect plants from biotic stress, including pathogens which cause powdery mildew. In this study, Hordeum vulgare L. varieties "Marthe" and "KWS Olof" were grown in hydroponics with magnetic iron oxide (Fe3O4) and copper oxide (CuO) NPs added at 17, 35, and 70 mg/L. Plant morphology, genotoxicity, and expression of miR156a were investigated. The Fe3O4 and CuO NPs demonstrated different effects on the barley varieties, namely, Fe3O4 nanoparticles increased plant shoot and root lengths and fresh biomass, while CuO nanoparticles decreased them. CuO NPs presence caused larger changes on barley genome compared to Fe3O4 NPs. Thus, Fe3O4 NPs reduced genome stability to 72% in the "Marthe" variety and to 76.34% in the "KWS Olof" variety, while CuO NPs reduced genome stability to 53.33% in "Marthe" variety and in the "KWS Olof" variety to 68.81%. The miR156a expression levels after Fe3O4 NPs treatment did not change in the "Marthe" variety, but increased in the "KWS Olof" variety, while CuO NPs treatment increased miRNA expression levels in the "Marthe" variety but decrease them in the "KWS Olof" variety. As NPs are able to influence miRNA expression and miRNAs can affect the plant resistance, obtained results suggest that tested NPs may alter plant resistance response to pathogens.

Abiotic stressors impact outer membrane vesicle composition in a beneficial rhizobacterium: Raman spectroscopy characterization

Outer membrane vesicles (OMVs) produced by Gram-negative bacteria have roles in cell-to-cell signaling, biofilm formation, and stress responses. Here, the effects of abiotic stressors on OMV contents and composition from biofilm cells of the plant health-promoting bacterium Pseudomonas chlororaphis O6 (PcO6) are examined. Two stressors relevant to this root-colonizing bacterium were examined: CuO nanoparticles (NPs)-a potential fertilizer and fungicide- and H₂O₂-released from roots during plant stress responses. Atomic force microscopy revealed 40–300 nm diameter OMVs from control and stressed biofilm cells. Raman spectroscopy with linear discriminant analysis (LDA) was used to identify changes in chemical profiles of PcO6 cells and resultant OMVs according to the cellular stressor with 84.7% and 83.3% accuracies, respectively. All OMVs had higher relative concentrations of proteins, lipids, and nucleic acids than PcO6 cells. The nucleic acid concentration in OMVs exhibited a cellular stressor-dependent increase: CuO NP-induced OMVs > H₂O₂-induced OMVs > control OMVs. Biochemical assays confirmed the presence of lipopolysaccharides, nucleic acids, and protein in OMVs; however, these assays did not discriminate OMV composition according to the cellular stressor. These results demonstrate the sensitivity of Raman spectroscopy using LDA to characterize and distinguish cellular stress effects on OMVs composition and contents.

Can the properties of engineered nanoparticles be indicative of their functions and effects in plants?

The extensive applicability of engineered nanoparticles (ENPs) in various fields such as environment, agriculture, medicine or biotechnology has mostly been attributed to their better physicochemical properties as compared with conventional bulk materials. However, functions and biological effects of ENPs change across different scenarios which impede the progress in their risk assessment and safety management. This review thus intends to figure out whether properties of ENPs can be indicators of their behavior through summarizing and analyzing the available literature and knowledge. The studies have indicated that size, shape, solubility, specific surface area, surface charge and surface reactivity constitute a more accurate measure of ENPs functions and toxic effects in addition to mass concentration. Effects of ENPs are also highly dependent on dose metrics, species and strains of organisms, environmental conditions, exposure route and duration. Searching correlations between properties and functions or biological effects may serve as an effective way in understanding positive and negative impacts of ENPs. This will ensure safe design and sustainable future use of ENPs.

Effect of Zinc Priming on Salt Response of Wheat Seedlings: Relieving or Worsening?

In an attempt to alleviate salt-induced damage, the application of ZnO nanoparticles has been suggested. As the use of these particles has also been associated with phytotoxicity, to better clarify the effect of zinc and its possible mitigation of salt stress, we treated wheat seedlings with ZnO (nanoparticles or their bulk-scale counterparts, amended either in the growth medium, NPs and B, or sprayed on the leaves, SPNPs and SPB) with or without subsequent treatment with salt. Growth, photosynthetic parameters, zinc and ion concentration, and in situ and biochemical determination of oxidative stress in wheat leaves and/or in roots were considered. Both Zn and NaCl significantly inhibited growth and induced severe alterations in root morphology. Oxidative stress and damage decreased or increased under ZnO treatment and in saline conditions depending on the organ and on the size and mode of application of particles. In spite of the higher stress conditions often recorded in treated leaves, neither pigment concentration nor photochemical efficiency were decreased. A large variability in the effects of ZnO treatment/priming on seedling salt response was recorded; however, the presence of a cumulative negative effect of priming and salt stress sometimes observed calls for caution in the use of ZnO in protection from saline stress.

Zinc-Based Nanomaterials for Diagnosis and Management of Plant Diseases: Ecological Safety and Future Prospects

A facet of nanorenaissance in plant pathology hailed the research on the development and application of nanoformulations or nanoproducts for the effective management of phytopathogens deterring the growth and yield of plants and thus the overall crop productivity. Zinc nanomaterials represent a versatile class of nanoproducts and nanoenabled devices as these nanomaterials can be synthesized in quantum amounts through economically affordable processes/approaches. Further, these nanomaterials exhibit potential targeted antimicrobial properties and low to negligible phytotoxicity activities that well-qualify them to be applied directly or in a deviant manner to accomplish significant antibacterial, antimycotic, antiviral, and antitoxigenic activities against diverse phytopathogens causing plant diseases. The photo-catalytic, fluorescent, and electron generating aspects associated with zinc nanomaterials have been utilized for the development of sensor systems (optical and electrochemical biosensors), enabling quick, early, sensitive, and on-field assessment or quantification of the test phytopathogen. However, the proficient use of Zn-derived nanomaterials in the management of plant pathogenic diseases as nanopesticides and on-field sensor system demands that the associated eco- and biosafety concerns should be well discerned and effectively sorted beforehand. Current and possible utilization of zinc-based nanostructures in plant disease diagnosis and management and their safety in the agroecosystem is highlighted.

Potential application of titanium dioxide nanoparticles to improve the nutritional quality of coriander (Coriandrum sativum L.)

TiO₂ nanoparticles (nTiO₂) have been widely used in many disciplines. However, whether they can be used to improve crops growth and nutritional quality is unknown. In this study, coriander (Coriandrum sativum L.) was treated with 0, 50, 100, 200, and 400 mg/L nTiO₂ to evaluate their possible benefit to plant growth and nutritional quality under hydroponic conditions. Our observations showed that 50 mg/L nTiO₂ only slightly but insignificantly increased the root and shoot fresh biomass by 13.2 % and 4.1 %, respectively, relative to the control. nTiO₂ at this level promoted shoot K, Ca, Mg, Fe, Mn, Zn, and B accumulation, while spatial distribution of K, Ca, Fe, Mn, Cu and Zn in coriander leaves was not affected. No nTiO₂ internalization or translocation to shoots occurred. 400 mg/L nTiO₂ significantly reduced root fresh biomass by 15.8 % and water content by 6.7 %. Moreover, this high dose induced root cell membrane wrinkling, attributable to their aggregation and adsorption on root surfaces. At 100-400 mg/L, antioxidant defense systems (SOD, CAT and APX) in plant were triggered to alleviate oxidative stress. At an appropriate dose (50 mg/L), nTiO₂ can improve nutrient quality of edible tissues without exerting toxicity to plant or posing health risk to consumers.

Hormesis Effects of Nano- and Micro-sized Copper Oxide

The concerns about the possible risk of manufactured nanoparticles (NPs) have been raised recently. Nano- and micro-sized copper oxide (CO and CONP) are widely used in many industries. In this regard, in-vitro studies have demonstrated that CONP is a toxic compound in different cell lines. Despite their unique properties, NPs possess unexpected toxicity profiling relative to the bulk materials. This study was designed to examine and compare the toxic effects of CO and CONPs in-vivo and in isolated rat mitochondria. Male Wistar albino rats received 50 to 1000 mg/kg CO or CONP by gavage and several toxicological endpoints including biochemical indices and oxidative stress markers. Then, the pathological parameters in the multiple organs such as liver, brain, spleen, kidney, and intestine were assessed. Mitochondria were isolated from the rat liver and several mitochondrial indices were measured. The results of this study demonstrated that CO and CONP exhibited biphasic dose-response effects. CONPs showed higher toxicity compared with the bulk material. There were no significant changes in the results of CONP and CO in isolated rat liver mitochondria. The present studies provided more information regarding the hormetic effects of CO and CONPs in-vivo and in isolated rat mitochondria.

Effects of copper oxide nanoparticles on growth of lettuce (Lactuca sativa L.) seedlings and possible implications of nitric oxide in their antioxidative defense

Copper oxide nanoparticles (CuO NPs) have been extensively explored for use in agriculture. Previous studies have indicated that application of CuO NPs might be promising for development and conservation of plants, pest control, and for the recovery of degraded soils. However, depending on the applied concentration copper can cause phytotoxic effects. In this work, biosynthesized CuO NPs (using green tea extract) were evaluated on their effects on lettuce (Lactuca sativa L.) seedling growth, which were exposed at concentrations ranged between 0.2 and 300 μg mL-1. From the biosynthesized were obtained ultra-small CuO NPs (~ 6.6 nm), with high stability in aqueous suspension. Toxicity bioassays have shown that at low concentrations (up to 40 μg mL-1), CuO NPs did not affect or even enhanced the seed germination. At higher concentrations (higher than 40 μg mL-1), inhibition of seed germination and radicle growth ranging from 35 to 75% was observed. With the increase of CuO NPs concentrations, nitrite and S-nitrosothiols levels in radicles increased, whereas superoxide dismutase and total antioxidant activities decreased. The nitrite and S-nitrosothiols levels in lettuce radicles showed a direct dose response to CuO NP application, which may indicate nitric oxide-dependent signaling pathways in the plant responses. Therefore, the results demonstrated that at low concentrations (≤ 20 μg mL-1) of CuO NPs, beneficial effects are obtained from seedlings, enhancing plant growth, and the involvement of nitric oxide signaling in the phytotoxic effects induced by high concentration of this formulation. Graphical abstract.

Bacteria-nanoparticle interactions in the context of nanofouling

The attachment of microbial communities to surfaces is a well-known problem recognized to be involved in a variety of critical issues in the sectors of food processing, chronic wounds, infection from implants, clogging of membranes and corrosion of equipment. Considering the importance of the detrimental impact of biofouling, it has received much attention in the scientific community and from concerned stakeholders. With the development of nanotechnology and the nowadays widespread use of engineered nanoparticles (ENPs), concerns have been raised regarding their fate in terrestrial and aquatic environments. Safety aspects and public health issues are critical in the management of handling nanomaterials and their nanowastes. The interactions of various types of nanoparticles (NPs) with planktonic bacteria have also received attention due to their antimicrobial properties. However, their behavior in regard to biofilms is not well understood although, in the environment, most of the bacteria prefer living in sessile communities. The question appears relevant considering the need to build knowledge on the fate of nanoparticles and the fact that no one can exclude the risk of accumulation of nanoparticles in biofilms and on surfaces leading to a form of nanofouling involving both engineered nanoparticles (ENPs) and nanoplastics. The present analysis of recent research accounts allows in identifying that (1) research activities related to water remediation systems have been mostly oriented on the impact of NPs on pre-existing biofilms, (2) experimental designs are restricted to few scenarios of exposure, usually limited to relative short-time periods although nanofouling could favour the development of multi-resistant bacterial species through sub-lethal exposures over prolong periods of time (3) nanofouling in other systems in which biofilms develop remains to be addressed, and (4) new research directions are required for investigating the mechanisms involved and the subsequent impact of nanofouling on bacterial consortium responses encountered in a variety of environments such as those prevailing in food production/processing settings. Finally, this review aims at providing recent information and insights on nanoparticle-bacterial interactions in the context of biofilms in order to supply an updated outlook of research perspectives that could help establish the framework for production, use and fate of nanomaterials as well as future research directions.

Facile Coating of Urea With Low-Dose ZnO Nanoparticles Promotes Wheat Performance and Enhances Zn Uptake Under Drought Stress

Zinc oxide nanoparticles (ZnO-NPs) hold promise as novel fertilizer nutrients for crops. However, their ultra-small size could hinder large-scale field application due to potential for drift, untimely dissolution or aggregation. In this study, urea was coated with ZnO-NPs (1%) or bulk ZnO (2%) and evaluated in wheat (Triticum aestivum L.) in a greenhouse, under drought (40% field moisture capacity; FMC) and non-drought (80% FMC) conditions, in comparison with urea not coated with ZnO (control), and urea with separate ZnO-NP (1%) or bulk ZnO (2%) amendment. Plants were exposed to ≤ 2.17 mg/kg ZnO-NPs and ≤ 4.34 mg/kg bulk-ZnO, indicating exposure to a higher rate of Zn from the bulk ZnO. ZnO-NPs and bulk-ZnO showed similar urea coating efficiencies of 74-75%. Drought significantly (p ≤ 0.05) increased time to panicle initiation, reduced grain yield, and inhibited uptake of Zn, nitrogen (N), and phosphorus (P). Under drought, ZnO-NPs significantly reduced average time to panicle initiation by 5 days, irrespective of coating, and relative to the control. In contrast, bulk ZnO did not affect time to panicle initiation. Compared to the control, grain yield increased significantly, 51 or 39%, with ZnO-NP-coated or uncoated urea. Yield increases from bulk-ZnO-coated or uncoated urea were insignificant, compared to both the control and the ZnO-NP treatments. Plant uptake of Zn increased by 24 or 8% with coated or uncoated ZnO-NPs; and by 78 or 10% with coated or uncoated bulk-ZnO. Under non-drought conditions, Zn treatment did not significantly reduce panicle initiation time, except with uncoated bulk-ZnO. Relative to the control, ZnO-NPs (irrespective of coating) significantly increased grain yield; and coated ZnO-NPs enhanced Zn uptake significantly. Zn fertilization did not significantly affect N and P uptake, regardless of particle size or coating. Collectively, these findings demonstrate that coating urea with ZnO-NPs enhances plant performance and Zn accumulation, thus potentiating field-scale deployment of nano-scale micronutrients. Notably, lower Zn inputs from ZnO-NPs enhanced crop productivity, comparable to higher inputs from bulk-ZnO. This highlights a key benefit of nanofertilizers: a reduction of nutrient inputs into agriculture without yield penalities.

Effect of metal oxide nanoparticles on amino acids in wheat grains (Triticum aestivum) in a life cycle study

Engineered nanoparticles (NPs) are now used as additives in pesticides and fungicides and as novel fertilizers in agriculture so there is an urgent need to explore their effects on crop yield and quality in a full life cycle study. In the present study, three widely used NPs (TiO₂, Fe₂O₃ and CuO NPs applied at doses of 50 and 500 mg/kg) were selected to investigate their long-term impact on wheat growth. TiO₂ NPs did not affect the growth and development of wheat, but Fe₂O₃ NPs promoted wheat precocity and CuO NPs inhibited the growth and development of the wheat grains. The Cu content in grains treated with CuO NP increased by 18.84%-30.45% compared with the control. However, the contents of Fe and Zn were both significantly lower in the CuO NP treatments. Univariate and multivariate analyses were used to analyze the effect of different NPs on the composition of amino acids in wheat grains. Exposure to TiO₂ NPs at dose of 500 mg/kg increased the overall amino acid nutrition in the edible portion of wheat. Fe₂O₃ NPs at both doses increased the contents of cysteine (Cys) and tyrosine (Tyr). The addition of CuO NPs reduced the level of some essential amino acids in wheat grains, isoleucine (Ile), leucine (Leu), threonine (Thr) and histidine (His). Overall, evaluation of the potential impacts of metal-based NPs on the nutritional quality of wheat grains could provide important information for their safe use when incorporated into agrichemicals in sustainable agriculture.

Antimicrobial Zn-Based "TSOL" for Citrus Greening Management: Insights from Spectroscopy and Molecular Simulation

Huanglongbing (HLB), also known as citrus greening, is a bacterial disease that poses a devastating threat to the citrus industry worldwide. To manage this disease efficiently, we developed and characterized a ternary aqueous solution (TSOL) that contains zinc nitrate, urea, and hydrogen peroxide. We report that TSOL exhibits better antimicrobial activity than commercial bactericides for growers. X-ray fluorescence analysis demonstrates that zinc is delivered to citrus leaves, where the bacteria reside. FTIR and Raman spectroscopy, molecular dynamics simulations, and density functional theory calculations elucidate the solution structure of TSOL and reveal a water-mediated interaction between Zn²⁺ and H₂O₂, which may facilitate the generation of highly reactive hydroxyl radicals contributing to superior antimicrobial activity of TSOL. Our results not only suggest TSOL as a potent antimicrobial agent to suppress bacterial growth in HLB-infected trees, but also provide a structure-property relationship that explains the superior performance of TSOL.

Opportunities and challenges for nanotechnology in the agri-tech revolution

Current agricultural practices, developed during the green revolution, are becoming unsustainable, especially in the face of climate change and growing populations. Nanotechnology will be an important driver for the impending agri-tech revolution that promises a more sustainable, efficient and resilient agricultural system, while promoting food security. Here, we present the most promising new opportunities and approaches for the application of nanotechnology to improve the use efficiency of necessary inputs (light, water, soil) for crop agriculture, and for better managing biotic and abiotic stress. Potential development and implementation barriers are discussed, emphasizing the need for a systems approach to designing proposed nanotechnologies.

Nanotoxicity of engineered nanomaterials (ENMs) to environmentally relevant beneficial soil bacteria - a critical review

Deposition of engineered nanomaterials (ENMs) in various environmental compartments is projected to continue rising exponentially. Terrestrial environments are expected to be the largest repository for environmentally released ENMs. Because ENMs are enriched in biosolids during wastewater treatment, agriculturally applied biosolids facilitate ENM exposure of key soil micro-organisms, such as plant growth-promoting rhizobacteria (PGPR). The ecological ramifications of increasing levels of ENM exposure of terrestrial micro-organisms are not clearly understood, but a growing body of research has investigated the toxicity of ENMs to various soil bacteria using a myriad of toxicity end-points and experimental procedures. This review explores what is known regarding ENM toxicity to important soil bacteria, with a focus on ENMs which are expected to accumulate in terrestrial ecosystems at the highest concentrations and pose the greatest potential threat to soil micro-organisms having potential indirect detrimental effects on plant growth. Knowledge gaps in the fundamental understanding of nanotoxicity to bacteria are identified, including the role of physicochemical properties of ENMs in toxicity responses, particularly in agriculturally relevant micro-organisms. Strategies for improving the impact of future research through the implementation of in-depth ENM characterization and use of necessary experimental controls are proposed. The future of nanotoxicological research employing microbial ecoreceptors is also explored, highlighting the need for continued research utilizing bacterial isolates while concurrently expanding efforts to study ENM-bacteria interactions in more complex environmentally relevant media, e.g. soil. Additionally, the particular importance of future work to extensively examine nanotoxicity in the context of bacterial ecosystem function, especially of plant growth-promoting agents, is proposed.

Nano-based smart pesticide formulations: Emerging opportunities for agriculture

The incorporation of nanotechnology as a means for nanopesticides is in the early stage of development. The main idea behind this incorporation is to lower the indiscriminate use of conventional pesticides to be in line with safe environmental applications. Nanoencapsulated pesticides can provide controlled release kinetics, while efficiently enhancing permeability, stability, and solubility. Nanoencapsulation can enhance the pest-control efficiency over extended durations by preventing the premature degradation of active ingredients (AIs) under harsh environmental conditions. This review is thus organized to critically assess the significant role of nanotechnology for encapsulation of AIs for pesticides. The smart delivery of pesticides is essential to reduce the dosage of AIs with enhanced efficacy and to overcome pesticide loss (e.g., due to leaching and evaporation). The future trends of pesticide nanoformulations including nanomaterials as AIs and nanoemulsions of biopesticides are also explored. This review should thus offer a valuable guide for establishing regulatory frameworks related to field applications of these nano-based pesticides in the near future.

Multimodal Generally Recognized as Safe ZnO/Nanocopper Composite: A Novel Antimicrobial Material for the Management of Citrus Phytopathogens

Copper (Cu) bactericides/fungicides are used extensively for crop protection in agriculture. Concerns for Cu accumulation in soil, Cu leaching into the surrounding ecosystem, and development of Cu resistance in phytopathogenic bacteria are evident. While there is no suitable alternative to Cu available to date for agricultural uses, it is possible to reduce Cu per application by supplementing with Zn and improving Cu bioavailability using nanotechnology. We have prepared a non-phytotoxic composite material consisting of generally recognized as safe ZnO 800 particles and nanocopper-loaded silica gel (ZnO-nCuSi). The morphology of the ZnO-nCuSi material was characterized using scanning electron microscopy, showing ZnO particles dispersed in the silica gel matrix. ZnO-nCuSi demonstrated strong in vitro antimicrobial properties against several model plant bacterial species. Two consecutive year field efficacy results showed that agri-grade ZnO-nCuSi was effective in controlling citrus canker disease at less than half the metallic rate of the commercial cuprous oxide/zinc oxide pesticide.

Uptake of Engineered Nanoparticles by Food Crops: Characterization, Mechanisms, and Implications

With the rapidly increasing demand for and use of engineered nanoparticles (NPs) in agriculture and related sectors, concerns over the risks to agricultural systems and to crop safety have been the focus of a number of investigations. Significant evidence exists for NP accumulation in soils, including potential particle transformation in the rhizosphere and within terrestrial plants, resulting in subsequent uptake by plants that can yield physiological deficits and molecular alterations that directly undermine crop quality and food safety. In this review, we document in vitro and in vivo characterization of NPs in both growth media and biological matrices; discuss NP uptake patterns, biotransformation, and the underlying mechanisms of nanotoxicity; and summarize the environmental implications of the presence of NPs in agricultural ecosystems. A clear understanding of nano-impacts, including the advantages and disadvantages, on crop plants will help to optimize the safe and sustainable application of nanotechnology in agriculture for the purposes of enhanced yield production, disease suppression, and food quality.

Differential Expression of Mitochondrial Manganese Superoxide Dismutase (SOD) in Triticum aestivum Exposed to Silver Nitrate and Silver Nanoparticles

Background: The increasing use of nanoparticles (NPs) may have negative impacts on both organisms and the environment. Objectives: The differential expression of mitochondrial manganese superoxide dismutase (MnSOD) gene in wheat in response to silver nitrate nanoparticles (AgNPs) and AgNO₃ was investigated. Materials and Methods: A quantitative Real-Time RT-PCR experiment was carried out with MnSOD gene using RNAs isolated from wheat shoots treated for 0, 2, 6, 12, and 24 h with 100 mg.L^-1 of either AgNO ₃ or AgNPs. Results: The results of this study showed that both treatments cause changes in the expression pattern of the MnSOD gene. While 2 and 6 h following the beginning of the stress, MnSOD expression was up-regulated significantly, in response to AgNO ₃ (1.4 and 2.8 fold, respectively), in response to AgNPs, it was up-regulated significant only after 6 h (1.6 fold), compared with the control. The gene expression, after 12 h in response to AgNO₃ and AgNPs were downregulated significantly (0.7 and 0.8 fold, respectively), and in the next 12 h , the expression appeared to be similar to the control. Conclusion: Exposure to both AgNPs and Ag ions led to a significant increase in MnSOD expression, but AgNO ₃ changed the MnSOD expression faster than AgNPs. Therefore, it is suggested that AgNO₃ has greater penetrability and effectiveness.