Efficiency of Biodegradable and pH-Responsive Polysuccinimide Nanoparticles (PSI-NPs) as Smart Nanodelivery Systems in Grapefruit: In Vitro Cellular Investigation

Optimized nanopesticide delivery of thiamethoxam to cowpeas (Vigna unguiculata) controls thrips (Megalurothrips usitatus) and reduces toxicity to non-target worker bees (Apis mellifera)

Thrips [Megalurothrips usitatus (Bagnall)] (Thysanoptera: Thripidae) is a pest that poses a serious challenge to global crop production and food supply, especially to the cowpea industry. Nano-delivery systems have broad application prospects in the prevention and control of pests in agriculture. Herein, three types of amino acid (AA) modified polysuccinimide nano-delivery carriers (PSI-GABA, PSI-ASP and PSI-GLU) were constructed with a diameter of approximately 150 nm to load thiamethoxam (THX), which enhanced THX effective distribution and use with cowpea plants. Significantly, the PSI-GLU nanocarrier effectively delivered THX to cowpea plant tissues following 6 h of soil application. Compared with commercial THX suspension (SC), the THX content in the leaves of cowpea plants was increased by 2.3 times. Confocal laser scanning microscopy revealed that the FITC-labeled PSI-GLU nanocarrier reached the leaves through the vascular system after being absorbed by the roots of cowpea plants. The PSI-GLU nanocarrier decreased the LC50 of THX from 11.45 to 7.79 mg/L and significantly enhanced the insecticidal effect. The PSI-GLU nanocarrier also improved the safety of THX to worker bees at 48 h, and moreover showed a growth-promoting effect on cowpea seedlings. These results demonstrated that the PSI-GLU nano-delivery carrier has promising uses on improving the effective utilization of THX for the sustainable control of thrips and reducing the risk to non-target pollutions.

Enhancing plant biotechnology by nanoparticle delivery of nucleic acids

Plant biotechnology plays a crucial role in developing modern agriculture and plant science research. However, the delivery of exogenous genetic material into plants has been a long-standing obstacle. Nanoparticle-based delivery systems are being established to address this limitation and are proving to be a feasible, versatile, and efficient approach to facilitate the internalization of functional RNA and DNA by plants. The nanoparticle-based delivery systems can also be designed for subcellular delivery and controlled release of the biomolecular cargo. In this review, we provide a concise overview of the recent advances in nanocarriers for the delivery of biomolecules into plants, with a specific focus on applications to enhance RNA interference, foreign gene transfer, and genome editing in plants.

A Pyr-loaded polymer microparticle for effectively controlling Solenopsis invicta (Hymenoptera: Formicidae) in the nest

Human interference and incorrect use of pesticides are easy to induce red imported fire ant (RIFA) escape and migrate from a nest, resulting in ineffective control of RIFA. In order to avoid RIFA alert, we designed an amphiphilic PSI-mPEG-Boc-DAH loaded Pyr to make the microparticles with effective controlled release. The investigation showed that the quantity of Pyr released by Pyr@PSI-mPEG-Boc-DAH under acidic environment was only 36.40 ± 1.90% at 48 h, whereas the release rate of original Pyr was 75.23 ± 5.71%. And the RIFA mortality rate of 1 ppm Pyr in Pyr@PSI-mPEG-Boc-DAH microparticles at 48 h was only 7.78%, which was significantly lower than that of the Pyr (47.78%). Futhermore, the death rate increased sharply after 48 h, and reached 95.84% within a week after using Pyr@PSI-mPEG-Boc-DAH microparticles. Moreover, PSI-mPEG-Boc-DAH carriers could be absorbed and even transported to crop of the RIFA for subsequent trophallaxis by using fluorescence tracking. In the field experiment, the reduction rate of Pyr@PSI-mPEG-Boc-DAH treatment was achieved 99.89% after 7 d. Pyr@PSI-mPEG-Boc-DAH didn't cause RIFA to be alarmed within 48 h and could kill nearly all of ants in the nest after 7 d, which showed a very good control effect in the field experiment. This work provided a new idea and guidance for the effective control RIFA and the development of sustainable agriculture.

Priming of Pisum sativum seeds with stabilized Pluronic P85 nanomicelles: effects on seedling development and photosynthetic function

Natural and synthetic polymers are widely explored for improving seed germination and plant resistance to environmental constraints. Here, for the first time, we explore stabilized nanomicelles composed of the biocompatible triblock co-polymer Pluronic P85 (SPM) as a priming agent for Pisum sativum (var. RAN-1) seeds. We tested a wide concentration range of 0.04-30 g(SPM) L-1. Applying several structural and functional methods we revealed that the utilized nanomicelles can positively affect root length, without any negative effects on leaf anatomy and photosynthetic efficiency at 0.2 g L-1, while strong negative effects were recorded for 10 and 30 g(SPM) L-1 concerning root length, leaf histology, and photoprotection capability. Our data strongly suggest that SPM can safely be utilized for seed priming at specific concentrations and are suitable objects for further loading with plant growth regulators.

Huanglongbing Pandemic: Current Challenges and Emerging Management Strategies

Huanglongbing (HLB, aka citrus greening), one of the most devastating diseases of citrus, has wreaked havoc on the global citrus industry in recent decades. The culprit behind such a gloomy scenario is the phloem-limited bacteria "Candidatus Liberibacter asiaticus" (CLas), which are transmitted via psyllid. To date, there are no effective long-termcommercialized control measures for HLB, making it increasingly difficult to prevent the disease spread. To combat HLB effectively, introduction of multipronged management strategies towards controlling CLas population within the phloem system is deemed necessary. This article presents a comprehensive review of up-to-date scientific information about HLB, including currently available management practices and unprecedented challenges associated with the disease control. Additionally, a triangular disease management approach has been introduced targeting pathogen, host, and vector. Pathogen-targeting approaches include (i) inhibition of important proteins of CLas, (ii) use of the most efficient antimicrobial or immunity-inducing compounds to suppress the growth of CLas, and (iii) use of tools to suppress or kill the CLas. Approaches for targeting the host include (i) improvement of the host immune system, (ii) effective use of transgenic variety to build the host's resistance against CLas, and (iii) induction of systemic acquired resistance. Strategies for targeting the vector include (i) chemical and biological control and (ii) eradication of HLB-affected trees. Finally, a hypothetical model for integrated disease management has been discussed to mitigate the HLB pandemic.

Biopolymer-based nanocarriers for sustained release of agrochemicals: A review on materials and social science perspectives for a sustainable future of agri- and horticulture

Devastating plant diseases and soil depletion rationalize an extensive use of agrochemicals to secure the food production worldwide. The sustained release of fertilizers and pesticides in agriculture is a promising solution to the eco-toxicological impacts and it might reduce the amount and increase the effectiveness of agrochemicals administration in the field. This review article focusses on carriers with diameters below 1 μm, such as capsules, spheres, tubes and micelles that promote the sustained release of actives. Biopolymer nanocarriers represent a potentially environmentally friendly alternative due to their renewable origin and biodegradability, which prevents the formation of microplastics. The social aspects, economic potential, and success of commercialization of biopolymer based nanocarriers are influenced by the controversial nature of nanotechnology and depend on the use case. Nanotechnology's enormous innovative power is only able to unfold its potential to limit the effects of climate change and to counteract current environmental developments if the perceived risks are understood and mitigated.

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.

Phytotoxic Effects of Polyethylene Microplastics on the Growth of Food Crops Soybean (Glycine max) and Mung Bean (Vigna radiata)

Accumulation of micro-plastics (MPs) in the environment has resulted in various ecological and health concerns. Nowadays, however, studies are mainly focused on toxicity of MPs on aquatic organisms, but only a few studies assess the toxic effects of micro-plastics on terrestrial plants, especially edible agricultural crops. The present study was aimed to investigate the adverse effects of polyethylene (PE) microplastics on the germination of two common food crops of China, i.e., soybean (Glycine max) and mung bean (Vigna radiata). Both the crops were treated with polyethylene microplastics (PE-MPs) of two sizes (6.5 μm and 13 μm) with six different concentrations (0, 10, 50, 100, 200, and 500 mg/L). Parameters studied were (i) seed vigor (e.g., germination energy, germination index, vigor index, mean germination speed, germination rate); (ii) morphology (e.g., root length, shoot length) and (iii) dry weight. It was found that the phyto-toxicity of PE-MPs to soybean (Glycine max) was greater than that of mung bean (Vigna radiata). On the 3rd day, the dry weight of soybean was inhibited at different concentrations as compared to the control and the inhibition showed decline with the increase in the concentration of PE-MPs. After the 7th day, the root length of soybean was inhibited by PE-MPs of 13 μm size, and the inhibition degree was positively correlated with the concentration, whereas the root length of mung bean was increased, and the promotion degree was positively correlated with the concentration. Present study indicated the necessity to explore the hazardous effects of different sizes of PE-MPs on the growth and germination process of agricultural crops. Additionally, our results can provide theoretical basis and data support for further investigation on the toxicity of PE-MPs to soybean and mung bean.

Transport and retention of polymeric and other engineered nanoparticles in porous media

Increasing applications of nanoparticles (NPs) in agriculture have raised potential risks to soil and aquatic ecosystems. A comparative study examining the transport of commonly used NPs in porous media is of critical significance for their application and regulation in agroecosystems. In this study, laboratory column leaching experiments were conducted to investigate the transport and retention of polysuccinimide NPs (PSI-NPs) in two saturated porous media with different grain sizes, as compared with multi-walled carbon nanotubes (MWCNTs), nano-Ag and nano-TiO₂. Zeta potential of the NPs was negative at pH_6.3 and decreased in an order of PSI-NPs > nano-TiO₂ > MWCNTs > nano-Ag. The coarse and fine sands used in this study had negative charges with similar zeta potentials. The movement of NPs was affected by grain size, with larger sizes facilitating mobility while finer sizes favoring retention of NPs in the porous matrix. The retention profile significantly varied between the two sand columns, with more NPs transported to deeper layers in the coarse sand than the fine sand. The relative percentage of NPs detected in leachate was found to be positively correlated with the zeta potential of NPs (r = 0.931). Among the NPs, nano-Ag had the most negative zeta potential, and therefore was the most mobile, followed by MWCNTs and nano-TiO₂. Having the least negative zeta potential, PSI-NPs had the lowest mobility, as compared with other NPs regardless of matrix grain size. This work reveals grain size and zeta potential of NPs are major factors that influence transport of NPs along the vertical porous profile, as well as demonstrating the relative unimportance of NP composition, which could serve as important guideline in nanomaterials application, risk assessment, and waste management in agroecosystems.

Preparation of p-amino salicylic acid-modified polysuccinimide as water-based nanocarriers for enhancing pesticide stability and insecticidal activity

Avermectin (AVM) is a biopesticide with low toxicity and high activity, but has limited use due to its poor water solubility and easy decomposition. A delivery system that can stabilize this biopesticide can play a significant role for improving its biological activity. Herein, water-dispersible functionalized polysuccinimide nanoparticles (PAD) were prepared by a ring-opening reaction and subsequently used to encapsulate AVM via self-assembly to form AVM@PAD nanoparticles with a loading ratio of 10.04 %. The half-life under UV radiation (300 W) of AVM@PAD was three times higher than that of free AVM, demonstrating the excellent protective ability of PAD. In addition, AVM@PAD nanoparticles could sustain the release of AVM for 70 h with a cumulative release rate of 70 %. AVM@PAD nanoparticles also showed a pH-responsive release, and their maximum cumulative release rate was at neutral pH. Moreover, the median lethal concentration (LC₅₀) value of AVM@PAD with respect to Plutella xylostella was 34.50 mg/L, while that of free AVM was 56.05 mg/L. These results showed that the AVM@PAD nanoparticles can potentially and effectively promote drug stability and biological activity in agriculture.

Phloem Delivery of Fludioxonil by Plant Amino Acid Transporter-Mediated Polysuccinimide Nanocarriers for Controlling Fusarium Wilt in Banana

Fusarium wilt disease poses a serious threat to the global production of bananas. The targeted delivery of fungicides to banana phloem tissues may offer new hope for controlling this hard-to-treat vascular disease. In this study, fludioxonil (FLU)-loaded glycine methyl ester-conjugated polysuccinimide nanoparticles (PGA) were prepared with a loading efficiency (LE) of 27.9%. The obtained nanoparticles (FLU@PGA) exhibited pH-sensitive controlled release, specifically under an alkaline pH in plant phloem. In vivo experiments in potted bananas demonstrated that FLU@PGA can achieve the downward delivery of FLU to banana rhizomes and roots after foliar application, reducing disease severity by 50.4%. The phloem transport studies showed that the phloem loading of FLU@PGA was involved in an active transport mechanism at the organ level (castor bean seedlings). The observation of fluorescein-5-isothiocyanate cadaverine-labeled PGA nanocarriers showed that they could be absorbed by mesophyll cells and loaded into vascular tissues through the symplastic pathway. Furthermore, the interaction of FLU@PGA with the plant amino acid transporter AtLHT1 was observed to enhance transmembrane uptake at the cellular level (Xenopus oocytes). These results suggested that the phloem-targeted delivery of fungicide by transporter-mediated nanocarriers could be a promising new strategy for the management of Fusarium wilt in bananas.

Use of polymeric nanoparticles to improve seed germination and plant growth under copper stress

Plant seedlings are susceptible to copper (Cu) toxicity. As copper levels in soil continue to rise with the use of Cu-based agrochemicals, alleviation of Cu stress is of paramount importance. Traditional approaches to allay Cu stress are well documented but are typically found to be either costly or inefficient. Given their small size, ionic character, and high biocompatibility, specific polymeric nanoparticles (NPs) may have the potential for mitigating metal toxicity to crops. In this pioneering study, we investigated the effects of newly synthesized polysuccinimide NPs (PSI-NPs) on corn (Zea mays L.) seed germination and seedling growth under different levels of Cu stress. The results showed that PSI-NPs influenced seed germination in a dose-dependent manner with an optimal rate of 200 mg L^-1. In addition, the positive effects of PSI-NPs on seed germination indexes were found to be positively correlated with enhanced seed imbibition (r = 0.82). The addition of PSI-NPs significantly mitigated Cu stress as indicated by improved growth of shoots and roots, and higher antioxidant enzyme activity observed with co-exposure to PSI-NPs as compared to Cu stress treatment only. Cu concentrations in seedling root and shoot significantly increased with increasing Cu treatment rate. Higher uptake of Cu by plant was observed in the Cu-PSI-NPs co-treatment than single Cu treatment. The alleviation effect of PSI-NPs could be explained by the enhanced antioxidant enzyme activities and storage of Cu as Cu-PSI complexes in plants with reduced phytotoxicity. These findings will open the opportunity of using PSI-NPs as a regulator to enhance seed germination and improve seedling growth under stress of heavy metals like Cu.

Plant hairy roots enable high throughput identification of antimicrobials against Candidatus Liberibacter spp

A major bottleneck in identifying therapies to control citrus greening and other devastating plant diseases caused by fastidious pathogens is our inability to culture the pathogens in defined media or axenic cultures. As such, conventional approaches for antimicrobial evaluation (genetic or chemical) rely on time-consuming, low-throughput and inherently variable whole-plant assays. Here, we report that plant hairy roots support the growth of fastidious pathogens like Candidatus Liberibacter spp., the presumptive causal agents of citrus greening, potato zebra chip and tomato vein greening diseases. Importantly, we leverage the microbial hairy roots for rapid, reproducible efficacy screening of multiple therapies. We identify six antimicrobial peptides, two plant immune regulators and eight chemicals which inhibit Candidatus Liberibacter spp. in plant tissues. The antimicrobials, either singly or in combination, can be used as near- and long-term therapies to control citrus greening, potato zebra chip and tomato vein greening diseases.

Development of stimuli-responsive nano-based pesticides: emerging opportunities for agriculture

Pesticides and fertilizers are widely used to enhance agriculture yields, although the fraction of the pesticides applied in the field that reaches the targets is less than 0.1%. Such indiscriminate use of chemical pesticides is disadvantageous due to the cost implications and increasing human health and environmental concerns. In recent years, the utilization of nanotechnology to create novel formulations has shown great potential for diminishing the indiscriminate use of pesticides and providing environmentally safer alternatives. Smart nano-based pesticides are designed to efficiently delivery sufficient amounts of active ingredients in response to biotic and/or abiotic stressors that act as triggers, employing targeted and controlled release mechanisms. This review discusses the current status of stimuli-responsive release systems with potential to be used in agriculture, highlighting the challenges and drawbacks that need to be overcome in order to accelerate the global commercialization of smart nanopesticides.

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.

Development of Multifunctional Avermectin Poly(succinimide) Nanoparticles to Improve Bioactivity and Transportation in Rice

Avermectin (AVM) as a nonsystemic pesticide possesses a low effective utilization rate. Studies of the multifunctional pesticide delivery system for improving biological activity are developing prosperously. In this study, multifunctional avermectin/polysuccinimide with glycine methyl ester nanoparticles (AVM-PGA) were prepared by the self-assembly process. The AVM loading capacity was up to 23.7%. After 24 h of UV irradiation, there was still about 70% of AVM remaining in PGA₄₂ nanocarriers, as opposed to less than 5% of the free-form AVM. The rising ambient pH promoted the release of AVM using an in vitro releasing test, revealing a favorable pH-responsively controlled-release property. The mortality rate of Plutella xylostella with 2.5 μg/mL of AVM content of AVM-PGA₄₂ was 96.3% after 48 h, while that of free AVM was only 51.5%. In addition, the AVM could be detected in stems and all leaves treated with AVM-PGA₄₂ nanoparticles, whereas rare AVM was detected only in treated leaves for the free-form AVM, which achieved the transportation of nanocarriers carrying AVM in rice for the first time. Furthermore, the PGA nanoparticles performed a good growth promoting effect on rice. These results show that the AVM-PGA₄₂ nanopesticides have a great potential application prospect to control the pest and improve the drug utilization efficiency on agriculture.