Foliar absorption and field herbicidal studies of atrazine-loaded polymeric nanoparticles

Efficient delivery of the herbicide quinclorac by nanosuspension for enhancing deposition, uptake and herbicidal activity

BACKGROUND

The presence of barnyardgrass poses a threat to global food security by reducing rice yields. Currently, herbicides are primarily applied for weed management. However, the effectiveness of herbicide deposition and uptake on barnyardgrass is limited as a consequence of the high wax content on leaves, low water solubility and extreme lipophilicity of herbicides. Therefore, it is imperative to develop novel formulations for efficient delivery of herbicides to improve herbicidal activity and reduce dosage.

RESULTS

We successfully prepared nanosuspension(s) (NS) of quinclorac through the wet media milling technique. This NS demonstrates excellent physical stability and maintains nanoscale during dose transfer. The deposition concentration and uptake concentration of NS on barnyardgrass were 3.84-4.47- and 2.11-2.58-fold greater than those traditional formulations, respectively. Moreover, the NS exhibited enhanced herbicidal activity against barnyardgrass at half the dosage required by conventional formulations without compromising rice safety.

CONCLUSIONS

These findings suggest that NS can effectively facilitate the delivery of hydrophobic and poorly water-soluble herbicide active ingredients, thereby enhancing their deposition, uptake and bioactivity. This study expands the potential application of NS in pesticide delivery, which can provide valuable support for optimizing pesticide utilization, improving economic efficiency and mitigating environmental risks. © 2024 Society of Chemical Industry.

Chitosan Coating as a Strategy to Increase Postemergent Herbicidal Efficiency and Alter the Interaction of Nanoatrazine with Bidens pilosa Plants

The atrazine nanodelivery system, composed of poly(ε-caprolactone) (PCL+ATZ) nanocapsules (NCs), has demonstrated efficient delivery of the active ingredient to target plants in previous studies, leading to greater herbicide effectiveness than conventional formulations. Established nanosystems can be enhanced or modified to generate new biological activity patterns. Therefore, this study aimed to evaluate the effect of chitosan coating of PCL+ATZ NCs on herbicidal activity and interaction mechanisms with Bidens pilosa plants. Chitosan-coated NCs (PCL/CS+ATZ) were synthesized and characterized for size, zeta potential, polydispersity, and encapsulation efficiency. Herbicidal efficiency was assessed in postemergence greenhouse trials, comparing the effects of PCL/CS+ATZ NCs (coated), PCL+ATZ NCs (uncoated), and conventional atrazine (ATZ) on photosystem II (PSII) activity and weed control. Using a hydroponic system, we evaluated the root absorption and shoot translocation of fluorescently labeled NCs. PCL/CS+ATZ presented a positive zeta potential (25 mV), a size of 200 nm, and an efficiency of atrazine encapsulation higher than 90%. The postemergent herbicidal activity assay showed an efficiency gain of PSII activity inhibition of up to 58% compared to ATZ and PCL+ATZ at 96 h postapplication. The evaluation of weed control 14 days after application ratified the positive effect of chitosan coating on herbicidal activity, as the application of PCL/CS+ATZ at 1000 g of a.i. ha-1 resulted in better control than ATZ at 2000 g of a.i. ha-1 and PCL+ATZ at 1000 g of a.i. ha-1. In the hydroponic experiment, chitosan-coated NCs labeled with a fluorescent probe accumulated in the root cortex, with a small quantity reaching the vascular cylinder and leaves up to 72 h after exposure. This behavior resulted in lower leaf atrazine levels and PSII inhibition than ATZ. In summary, chitosan coating of nanoatrazine improved the herbicidal activity against B. pilosa plants when applied to the leaves but negatively affected the root-to-shoot translocation of the herbicide. This study opens avenues for further investigations to improve and modify established nanosystems, paving the way for developing novel biological activity patterns.

Smart controlled-release nanopesticides based on metal-organic frameworks

The practical utilization rates of conventional pesticide formulations by target organisms are very low, which results in the pollution of ecological environments and the formation of pesticide residues in agricultural products. Water-based nanopesticide formulations could become alternative and effective formulations to eventually resolve the main issues of conventional pesticide formulations. In this feature article, we describe the design concept of smart (stimuli-responsive) controlled-release nanopesticides, which are created toward hierarchical targets (pests, pathogens, and foliage) in response to multidimensional stimuli from physiological and environmental factors (such as sunlight) of target organisms and plants, for achieving enhanced insecticidal and fungicidal efficacies. The pore sizes and functionalities of metal-organic frameworks (MOFs) can be fine-tuned through the choice of metal-containing units and organic ligands. Tailor-made MOF nanoparticles with large microporous or mesoporous sizes, as well as good biocompatibility and high thermal, mechanical, and chemical durabilities, are used to load pesticides within these pores followed by coating of plant polyphenols and natural polymers for stimuli-responsive controlled pesticide release. This feature article highlights our works on smart controlled-release MOF-based nanopesticides and also includes related works from other laboratories. The future challenges and promising prospects of smart controlled-release MOF-based nanopesticides are also discussed.

Critical Review: Uptake and Translocation of Organic Nanodelivery Vehicles in Plants

Nanodelivery vehicles (NDVs) are engineered nanomaterials (ENMs) that, within the agricultural sector, have been investigated for their ability to improve uptake and translocation of agrochemicals, control release, or target specific tissues or subcellular compartments. Both inorganic and organic NDVs have been studied for agrochemical delivery in the literature, but research on the latter has been slower to develop than the literature on the former. Since the two classes of nanomaterials exhibit significant differences in surface chemistry, physical deformability, and even colloidal stability, trends that apply to inorganic NDVs may not hold for organic NDVs, and vice versa. We here review the current literature on the uptake, translocation, biotransformation, and cellular and subcellular internalization of organic NDVs in plants following foliar or root administration. A background on nanomaterials and plant physiology is provided as a leveling ground for researchers in the field. Trends in uptake and translocation are examined as a function of NDV properties and compared to those reported for inorganic nanomaterials. Methods for assessing fate and transport of organic NDVs in plants (a major bottleneck in the field) are discussed. We end by identifying knowledge gaps in the literature that must be understood in order to rationally design organic NDVs for precision agrochemical nanodelivery.

Investigating the effects of mesotrione/atrazine-based herbicide on honey bee foragers

A mixture of the herbicides mesotrione and atrazine (Calaris®) is a widely used herbicide in agriculture in several countries. However, the possible toxicological effects of this formulation on non-target organisms require investigation. In this study, the effects of acute oral exposure to Calaris® were evaluated in Apis mellifera foragers. The effect of seven different concentrations of Calaris® on survival and sucrose consumption was studied, while the recommended concentration for field use (FC) and its 10× dilution (0.1 FC) were used to assess overall locomotor activity, respiratory rate, flight, midgut morphology, oxidative and nitrosative stresses, and hemocyte counting. The exposure to FC or 0.1 FC decreased locomotor activity and induced damage to the midgut epithelium. Additionally, the two tested concentrations reduced superoxide dismutase activity, nitric oxide levels, and total hemocyte count. FC also increased malondialdehyde content and 0.1 FC increased respiratory rate and decreased the proportion of prohemocytes. Overall, our findings evidenced significant harmful effects on A. mellifera foragers resulting from the ingestion of the Calaris® herbicide.

Ecotoxicity studies of two atrazine nanoformulations: From the evaluation of stability in media to the effects on aquatic organisms

In the field of agriculture, nanopesticides have been developed as an alternative to the conventional pesticides, being more efficient for pest control. However, before their widespread application it is essential to evaluate their safe application and no environmental impacts. In this paper, we evaluated the toxicological effects of two kinds of atrazine nanoformulations (ATZ NPs) in different biological models (Raphidocelis subcapitata, Danio rerio, Lemna minor, Artemia salina, Lactuca sativa and Daphnia magna) and compared the results with nanoparticle stability over time and the presence of natural organic matter (NOM). The systems showed different characteristics for Zein (ATZ NPZ) (184 ± 2 nm with a PDI of 0.28 ± 0.04 and zeta potential of (30.4 ± 0.05 mV) and poly(epsilon-caprolactone (ATZ PCL) (192 ± 3 nm, polydispersity (PDI) of 0.28 ± 0.28 and zeta potential of -18.8 ± 1.2 mV) nanoparticles. The results showed that there is a correlation between nanoparticles stability and the presence of NOM in the medium and Environmental Concentrations (EC) values. The stability loss or an increase in nanoparticle size result in low toxicity for R. subcapitata and L. minor. For D. magna and D. rerio, the presence of NOM in the medium reduces the ecotoxic effects for ATZ NPZ nanoparticles, but not for ATZ NPs, showing that the nanoparticles characteristics and their interaction with NOM can modulate toxic effects. Nanoparticle stability throughout the evaluation must be considered and become an integral part of toxicity protocol guidelines for nanopesticides, to ensure test quality and authentic results regarding nanopesticide effects in target and non-target organisms.

Availability of Metribuzin-Loaded Polymeric Nanoparticles in Different Soil Systems: An Important Study on the Development of Safe Nanoherbicides

Nanoformulations have been used to improve the delivery of fertilizers, pesticides, and growth regulators, with a focus on more sustainable agriculture. Nanoherbicide research has focused on efficiency gains through targeted delivery and environmental risk reduction. However, research on the behavior and safety of the application of these formulations in cropping systems is still limited. Organic matter contained in cropping systems can change the dynamics of herbicide−soil interactions in the presence of nanoformulations. The aim of this study was to use classical protocols from regulatory studies to understand the retention and mobility dynamics of a metribuzin nanoformulation, compared to a conventional formulation. We used different soil systems and soil with added fresh organic material. The batch method was used for sorption−desorption studies and soil thin layer chromatography for mobility studies, both by radiometric techniques. Sorption parameters for both formulations showed that retention is a reversible process in all soil systems (H~1.0). In deep soil with added fresh organic material, nanoformulation was more sorbed (14.61 ± 1.41%) than commercial formulation (9.72 ± 1.81%) (p < 0.05). However, even with the presence of straw as a physical barrier, metribuzin in nano and conventional formulations was mobile in the soil, indicating that the straw can act as a barrier to reduce herbicide mobility but is not impeditive to herbicide availability in the soil. Our results suggest that environmental safety depends on organic material maintenance in the soil system. The availability can be essential for weed control, associated with nanoformulation efficiency, in relation to the conventional formulation.

Development of a Preemergent Nanoherbicide: From Efficiency Evaluation to the Assessment of Environmental Fate and Risks to Soil Microorganisms

Nanoparticles based on biodegradable polymers have been shown to be excellent herbicide carriers, improving weed control and protecting the active ingredient in the crop fields. Metribuzin is often found in natural waters, which raises environmental concerns. Nanoencapsulation of this herbicide could be an alternative to reduce its losses to the environment and improve gains in its efficiency. However, there is a paucity of information about the behavior of nanoformulations of herbicides in environmental matrices. In this study, the stability of nanoencapsulated metribuzin in polymeric nanoparticles (nanoMTZ) was verified over time, as well as its dissipation in different soils, followed by the effects on soil enzymatic activity. The physiological parameters and control effects of nanoMTZ on Ipomoea grandifolia plants were investigated. No differences were verified in the half-life of nanoencapsulated metribuzin compared to a commercial formulation of the herbicide. Moreover, no suppressive effects on soil enzymatic activities were observed. The retention of nanoMTZ in the tested soils was lower compared to its commercial analogue. However, the mobility of nanoencapsulated metribuzin was not greatly increased, reflecting a low risk of groundwater contamination. Weed control was effective even at the lowest dose of nanoMTZ (48 g a.i. ha^-1), which was consistent with the higher efficiency of nanoMTZ compared to the conventional herbicide in inhibiting PSII activity and decreasing pigment levels. Overall, we verified that nanoMTZ presented a low environmental risk, with increased weed control.

Post-emergence herbicidal activity of nanoatrazine against Alternanthera tenella Colla plants compared to other weed species

The encapsulation of atrazine into poly(epsilon-caprolactone) nanocapsules has been shown to improve the efficiency of the herbicide and decrease its environmental impacts. In the current work, we evaluated the efficiency of nanoatrazine in the post-emergence control of Alternanthera tenella Colla plants and performed a meta-analysis to compare the results with studies already published with other weeds. The first experiment was carried out in the field, where we observed that nanoatrazine (at 200 g a. i. ha⁻¹) induced higher inhibition of the maximum quantum efficiency of photosystem II (up to 39%) than conventional atrazine at the same concentration. However, nanoencapsulation did not improve the visually-determined weed control by atrazine. To better understand the response of A. tenella plants to nanoatrazine, a second experiment was carried out in a greenhouse with four-leaf stage plants treated with nano and conventional atrazine at 200, 500, 1000, and 2000 g a. i. ha⁻¹. Nanoatrazine showed higher efficiency (up to 33%) than commercial atrazine in inhibiting photosystem II activity at all doses until 48 h after application. Again, weed control and plant dry mass did not differ between formulations. From the meta-analysis, it was observed that A. tenella plants showed a response to nanoatrazine that differs from other target species, as the gain in efficiency resulting from the nanoencapsulation was restricted to the short-term analysis, and did not result in better weed control. These results reinforce that the efficiency of nanoatrazine is dependent on the studied species.

Interaction of Nanoatrazine and Target Organism: Evaluation of Fate and Photosystem II Inhibition in Hydroponically Grown Mustard (Brassica juncea) Plants

Poly(epsilon-caprolactone) nanoparticles are an efficient carrier system for atrazine. However, there is a gap regarding the effects of nanoencapsulation on herbicide-plant interactions. Here, we evaluate the fate and photosystem II inhibition of nano and commercial atrazine in hydroponically grown mustard (Brassica juncea) plants whose roots were exposed to the formulations. In addition, to quantify the endogenous levels of atrazine in plant organs, we measured the inhibition of photosystem II activity by both formulations. Moreover, the fluorescently labeled nanoatrazine was tracked in plant tissues using confocal microscopy. The nanoencapsulation induced greater inhibition of photosystem II activity as well as higher accumulation of atrazine in roots and leaves. The nanoparticles were quickly absorbed by the roots, being detected in the vascular tissues and the leaves. Overall, these results provide insights into the mechanisms involved in the enhanced preemergent herbicidal activity of nanoatrazine against target plants.

Nitric oxide-releasing nanomaterials: from basic research to potential biotechnological applications in agriculture

Nitric oxide (NO) is a multifunctional gaseous signal that modulates the growth, development and stress tolerance of higher plants. NO donors have been used to boost plant endogenous NO levels and to activate NO-related responses, but this strategy is often hindered by the relative instability of donors. Alternatively, nanoscience offers a new, promising way to enhance NO delivery to plants, as NO-releasing nanomaterials (e.g. S-nitrosothiol-containing chitosan nanoparticles) have many beneficial physicochemical and biochemical properties compared to non-encapsulated NO donors. Nano NO donors are effective in increasing tissue NO levels and enhancing NO effects both in animal and human systems. The authors believe, and would like to emphasize, that new trends and technologies are essential for advancing plant NO research and nanotechnology may represent a breakthrough in traditional agriculture and environmental science. Herein, we aim to draw the attention of the scientific community to the potential of NO-releasing nanomaterials in both basic and applied plant research as alternatives to conventional NO donors, providing a brief overview of the current knowledge and identifying future research directions. We also express our opinion about the challenges for the application of nano NO donors, such as the environmental footprint and stakeholder's acceptance of these materials.

Nano-enabled agrochemicals/materials: Potential human health impact, risk assessment, management strategies and future prospects

Nanotechnology is a rapidly developing technology that will have a significant impact on product development in the next few years. The technology is already being employed in cutting-edge cosmetic and healthcare products. Nanotechnology and nanoparticles have a strong potential for product and process innovation in the food industrial sector. This is already being demonstrated by food product availability made using nanotechnology. Nanotechnologies will have an impact on food security, packaging materials, delivery systems, bioavailability, and new disease detection materials in the food production chain, contributing to the UN Millennium Development Goals targets. Food products using nanoparticles are already gaining traction into the market, with an emphasis on online sales. This means that pre- and post-marketing regulatory frameworks and risk assessments must meet certain standards. There are potential advantages of nanotechnologies for agriculture, consumers and the food industry at large as they are with other new and growing technologies. However, little is understood about the safety implications of applying nanotechnologies to agriculture and incorporating nanoparticles into food. As a result, policymakers and scientists must move quickly, as regulatory systems appear to require change, and scientists should contribute to these adaptations. Their combined efforts should make it easier to reduce health and environmental impacts while also promoting the economic growth of nanotechnologies in the food supply chain. This review highlighted the benefits of a number of nano enabled agrochemicals/materials, the potential health impacts as well as the risk assessment and risk management for nanoparticles in the agriculture and food production chain.

Zein and lignin-based nanoparticles as soybean seed treatment: translocation and impact on seed and plant health

Zein nanoparticles (ZNPs) were synthesized with a cationic surfactant, didodecyldimethylammonium bromide (122.9 ± 0.8 nm, + 59.7 ± 4.4 mV) and a non-ionic surfactant, Tween 80 (118.7 ± 1.7 nm, + 26.4 ± 1.1 mV). Lignin-graft-poly(lactic-co-glycolic) acid nanoparticles (LNPs) were made without surfactants (52.9 ± 0.2 nm, − 54.9 ± 0.5 mV). Both samples were applied as antifungal seed treatments on soybeans, and their impact on germination and plant health was assessed. Treated seeds showed high germination rates (> 90% for all treatment groups), similar to the control group (100%). Root and stem lengths and the dry biomass of treated seeds were not statistically distinguishable from the control. Foliage from seed-treated plants was fed to larvae of Chrysodeixis includens with no differences in mortality between treatments. No translocation of fluorescently tagged particles was observed with fluorescence microscopy following seed treatment and germination. Nano-delivered azoxystrobin provided ~ 100% protection when LNPs were used. Results suggest ZNPs and LNPs are safe and effective delivery systems of active compounds for seed treatments.

Development of Phosphatidylcholine/Tween 80 based biocompatible clove oil-in-water nanoemulsion as a green nanocarrier for controlled herbicide delivery

Recently, the development of ecofriendly and biocompatible agrochemical delivery systems has garnered widespread attention because of their great potential in sustainable agri-food applications. Atrazine (ATZ) is a globally used herbicide used to control weeds, but it suffers from poor aqueous solubility, poor efficacy, and environmental loss. Herein, we report a novel, eco-friendly and biocompatible clove oil-based nanoemulsion as a green nanocarrier to enhance the solubility, bioavailability, and control release of ATZ. Food grade surfactants, Tween 80 and Phosphatidylcholine (PC) were used to formulate clove oil nanoemulsion with size <200 nm using ultrasonic emulsification technique, without any use of organic solvent. The ATZ encapsulation efficiency in NEm was greater than 95%. DLS confirms the nanosize (106 nm) and monodispersity of NEm. HRTEM reveals the spherical morphology of the nanodroplets. FTIR and DSC confirm the successful incorporation of ATZ inside the NEm oil droplet core. ATZ loaded NEm showed excellent thermal and storage stability, low Ostwald ripening rate, slow and sustained herbicide release behavior, which is of vital importance for an herbicide formulation. The release rate was better than commercial ATZ and free ATZ formulations. Results from herbicidal activity assays demonstrate that ATZ NEm exhibited excellent herbicidal activity even at low concentrations as compared to commercial ATZ analogs. In consideration of biocompatible excipients, free of organic solvent, and a simple fabrication process, ATZ loaded clove oil NEm can hold great potential in weed control and sustainable agri-food applications.

The Differences between the Effects of a Nanoformulation and a Conventional Form of Atrazine to Lettuce: Physiological Responses, Defense Mechanisms, and Nutrient Displacement

The rapid development of nanotechnology influences the developments within the agro-sector. An example is provided by the production of nanoenabled pesticides with the intention to optimize the efficiency of the pesticides. At the same time, it is important to collect information on the unintended and unwanted adverse effects of emerging nanopesticides on nontarget plants. Currently, this information is limited. In the present study, we compared the effects of a nanoformulation of atrazine (NPATZ) and the nonencapsulated atrazine formulation (ATZ) on physiological responses, defense mechanisms, and nutrient displacement in lettuce over time with the applied concentrations ranging from 0.3 to 3 mg atrazine per kg soil. Our results revealed that both NPATZ and ATZ induced significant decreases in plant biomass, chlorophyll content, and protein content. Additionally, exposure to NPATZ and ATZ caused oxidative stress to the lettuce plant and significantly elevated the activities of the tested ROS scavenger enzymes in plant tissues. These results indicate that NPATZ and ATZ cause distinct adverse impacts on lettuce plants. When comparing the adverse effects in plants after exposure to NPATZ and ATZ, no obvious differences in plant biomass and chlorophyll content were observed between NPATZ and ATZ treatments at the same exposure concentration regardless of exposure duration. An enhanced efficiency of the active ingredient of the nanopesticide as compared to the conventional formulation was observed after long-term exposure to the high concentration of NPATZ, as it induced higher impacts on plants in terms of the end points of the contents of protein, superoxide anion (O2̇-), and MDA, and the activities of stress-related enzymes as compared to the same concentration of ATZ. Furthermore, exposure to both NPATZ and ATZ disrupted the uptake of mineral nutrients in plants, and the differences in the displacement of nutrients between the NPATZ and ATZ treatments depended on the element type, plant organ, exposure concentration, and time. Overall, the application dose of a nanopesticide should balance their increased herbicidal efficiency with the long-term adverse effects in order to maximize the desired impact while minimizing adverse impacts; only then will we be able to understand the potential impact of nanopesticides on the environment.