Efficient polymer-mediated delivery system for thiocyclam: Nanometerization remarkably improves the bioactivity toward green peach aphids

Self-assembled co-delivery nanoplatform for increasing the broad-spectrum susceptibility of fall armyworm toward insecticides

INTRODUCTION

Unscientific application of insecticides has led to severe resistance of pests to almost all classes of insecticides. Enhanced detoxification is the most common mechanism for this kind of resistance.

OBJECT

Fall armyworm (FAW) has developed insecticide resistance, which is often linked to the overexpression of detoxification genes. Herein, a multicomponent nano-pesticide is designed to increase its broad-spectrum susceptibility toward insecticides.

METHOD

Regulatory function of nuclear factor erythroid 2-related factor 2 (Nrf2) in detoxification was confirmed using transcriptome sequencing, quantitative real-time PCR and enzyme activity measurement. A star polycation (SPc) was adopted to construct the pesticide/SPc/complex, whose self-assembly mechanism and characterization were examined using isothermal titration calorimetry, dynamic light scattering and transmission electron microscope. The delivery efficiency of SPc-loaded dsRNA was examined in vitro and in vivo using fluorescent tracer technique. A multicomponent nano-pesticide was created through the integration of bacterial expression system and nano-delivery system, and its bioactivity was tested in laboratory and field.

RESULTS

We confirmed the crucial role of Nrf2 in regulating the detoxification in FAW, and silencing Nrf2 could decrease detoxification gene expression and increase insecticide susceptibility. We then applied the SPc to self-assemble a nanoplatform for delivering Nrf2 double-stranded RNA (dsRNA) and pesticide simultaneously. Nano-sized pesticide/SPc/dsRNA complex exhibited high delivery efficiency in vitro and in vivo. Excitingly, the insecticidal activities of pesticide/SPc/dsNrf2 complexes were remarkably improved with the normalized synergistic ratios of 5.43-6.25 for chlorantraniliprole, 4.45-15.00 for emamectin benzoate, and 6.75-15.00 for spinetoram. Finally, we developed a multicomponent nano-pesticide (pesticide/SPc/dsNrf2 complex) using a bacterial expression system and nano-delivery system. This approach exhibited excellent leaf protection and pest control efficacy.

CONCLUSION

The integration between the pesticide nanometerization and insecticide susceptibility improvement offers a promising strategy to increase insecticidal activity. Our study provides a revolutionary and universal strategy to increase insecticidal activity and decease application doses.

Efficient Polyamine-Based Nanodelivery System for Proline: Enhanced Uptake Improves the Drought Tolerance of Tobacco

Drought stress is one of the most unfavorable factors affecting plant growth and productivity among various environmental stresses. Nanotechnology is expected to enhance the effectiveness of conventional biostimulants. Herein, the current study constructed an efficient proline (Pro) nanodelivery system based on a star polyamine (SPc). The hydroxyl groups of Pro could assemble with carbonyl groups of SPc, and the self-assembly of Pro with SPc formed the nanoscale particles of the Pro/SPc complex. Compared to Pro alone, the contact angle of SPc-loaded Pro decreased, and its retentivity and plant uptake increased. Importantly, the tobacco (Nicotiana benthamiana) seeds and seedlings treated with Pro/SPc complex exhibited stronger drought tolerance. RNA-Seq analysis indicated that the SPc-loaded Pro could further upregulate photosynthesis-related genes and endocytosis-related genes. The current study constructed an efficient nanodelivery system for improving the bioactivity of biostimulants, which has broad application prospects in the agricultural field.

Efficient nanoparticle-based CRISPR-Cas13d induced mRNA disruption of an eye pigmentation gene in the white-backed planthopper, Sogatella furcifera

The discovery of the clustered regularly interspaced short palindromic repeat (CRISPR) system has driven gene manipulation technology to a new era with applications reported in organisms that span the tree of life. The utility of CRISPR-mediated editing was further expanded to mRNA following identification of the RNA-targeting Cas13 family of smaller endonuclease proteins. Application of this family to insect research, however, has been more limited. In this study, the smallest Cas13 family member, Cas13d, and guide RNAs (gRNAs) were complexed with a versatile nanomaterial (star polycation, SPc) to generate a proof-of-concept RNA-editing platform capable of disrupting mRNA expression of the eye pigmentation gene tryptophan 2,3-dioxygenase (SfTO) in white-backed planthoppers (WBPHs). The resulting red-eye phenotype was present in 19.76% (with SPc) and 22.99% (without SPc) of the treatment groups and was comparable to the red-eye phenotype generated following conventional RNA interference knockdown (22.22%). Furthermore, the Cas13/gRNA phenotype manifested more quickly than RNA interference. Consistent with the expected Cas13d mechanism, SfTO transcript levels were significantly reduced. Taken together, the results indicate that the SPc-CRISPR-Cas13d/gRNA complex negatively impacted expression of the target gene. These findings confirm the utility of this novel mRNA disruption system in insects and lay the foundation for further development of these tools in the implementation of green agricultural pest management tactics.

Star Polymer-Based Nanodelivery System for Pesticides: Enhanced Broad-Spectrum Toxicity and Selective Toxicity

The application of nanotechnology in agriculture can break through many traditional problems of synthetic pesticides, especially for increasing bioactivity and reducing application amount. However, the safety and selective toxicity of nanocarrier-loaded pesticides should be clarified toward natural predators. In this context, an efficient spirotetramat nanodelivery system was successfully constructed based on a star polymer (SPc). Spirotetramat could complex with SPc through hydrogen bonding and van der Waals forces spontaneously. The self-assembly of the spirotetramat/SPc complex decreased the particle size of spirotetramat from 1292 to 710 nm. After the complexation with SPc, the lethal concentration 50 (LC50) values of spirotratemat decreased from 252.064 to 108.871 and 332.079 to 189.257 mg/L toward target pest Frankliniella occidentalis and nontarget predator Orius sauteri with the synergic ratios of 2.315 and 1.755, respectively. The possible reason might be due to the enhancement of the broad-spectrum toxicity of SPc-loaded pesticides. Importantly, the selective toxicity ratio (STR) of spirotetramat increased from 1.32 to 1.73 with the help of SPc, indicating the higher selectivity of the spirotratemat/SPc complex toward predators. Meanwhile, the safety coefficient (SC) of spirotratemat was not significantly changed after complexation with SPc, and the spirotratemat/SPc complex belonged to the medium risk pesticide. Overall, the assembly with SPc could not only improve the control efficacy of spirotetramat but also increase its selectivity as well as alleviate its negative effects on predators. The current study is beneficial for understanding the enhancement of broad-spectrum toxicity and the selective toxicity of nanocarrier-loaded pesticides.

Nano-based smart formulations: A potential solution to the hazardous effects of pesticide on the environment

Inefficient usage, overdose, and post-application losses of conventional pesticides have resulted in severe ecological and environmental issues, such as pesticide resistance, environmental contamination, and soil degradation. Advances in nano-based smart formulations are promising novel methods to decrease the hazardous impacts of pesticide on the environment. In light of the lack of a systematic and critical summary of these aspects, this work has been structured to critically assess the roles and specific mechanisms of smart nanoformulations (NFs) in mitigating the adverse impacts of pesticide on the environment, along with an evaluation of their final environmental fate, safety, and application prospects. Our study provides a novel perspective for a better understanding of the potential functions of smart NFs in reducing environmental pollution. Additionally, this study offers meaningful information for the safe and effective use of these nanoproducts in field applications in the near future.

Nanodelivery System Alters an Insect Growth Regulator's Action Mode: From Oral Feeding to Topical Application

Insect growth regulators (IGRs) guide animal development through injection, oral feeding, or topical application. Among them, lufenuron is a widely used insect cuticle inhibitor but only shows a gastric toxic effect. Lacking contact toxicity limits the effective utilization when spraying the lufenuron pesticide. To overcome this shortcoming, a nanocarrier (star polycation, SPc)-based transdermal delivery system was applied to improve the penetrability and contact toxicity of lufenuron. The fluoride groups in lufenuron could interact with the tertiary amines in the branch-chain of the SPc through electrostatic interaction to form a lufenuron/SPc complex. The above interaction reduced the particle size of lufenuron from 933 to 70 nm. Interestingly, the contact toxicity of SPc-loaded lufenuron was remarkably improved with effects of higher larval mortality and lower egg hatching rate of the devastating pest fall armyworm. The physiological and molecular toxic mechanism was revealed by RNA-Seq analysis. The SPc-loaded lufenuron apparently down-regulated cuticle-related genes and thus inhibited insect cuticle formation. Such contact toxicity was achieved by the transdermal nanodelivery of lufenuron, which up-regulated endocytosis-related genes for drug uptake. This study is the first successful application of a nanoparticle-mediated transdermal delivery system to explore the contact toxicity of an IGR, which alters the IRG's action mode from oral feeding to topical application.

A Preparation Method of Nano-Pesticide Improves the Selective Toxicity toward Natural Enemies

Various nano-delivery systems have been designed to deliver synthetic/botanical pesticides for improved bioactivity. However, the enhanced toxicity of nanocarrier-loaded pesticides may injure the natural enemies, and their selective toxicity should be evaluated before the large-scale application. In this context, a star polymer (SPc)-based cyantraniliprole (CNAP) nano-delivery system was constructed, and its selective toxicity was evaluated using pest Frankliniella occidentalis (WFT) and predator Orius sauteri. The amide NH of CNAP could assemble with carbonyl groups or tertiary amines of SPc through hydrogen bonds to form CNAP/SPc complex spontaneously. The above self-assembly decreased the particle size of CNAP from 808 to 299 nm. With the help of SPc, the lethal concentration 50 (LC₅₀) values of CNAP decreased from 99 to 54 mg/L and 230 to 173 mg/L toward WFTs and O. sauteri due to the enhancement of broad-spectrum bioactivity. Interestingly, the toxicity selective ratio (TSR) of CNAP increased from 2.33 to 3.23 with the help of SPc, revealing the higher selectivity of SPc-loaded CNAP. To our knowledge, it was the first successful exploration of the selective toxicity of nanocarrier-loaded pesticides, and the higher selective toxicity of SPc-loaded CNAP was beneficial for alleviating the negative impacts on predators.

A Star Polyamine-Based Nanocarrier Delivery System for Enhanced Avermectin Contact and Stomach Toxicity against Green Peach Aphids

The unscientific application of synthesized/botanical pesticides has not only brought the resistance of plant pathogens and pests, but also led to serious environmental pollution. In recent years, various nano-delivery systems have been used for the development of environmental-friendly pesticides with improved efficacy. Herein, the current study constructed an efficient avermectin B1a (AVM) nano-delivery system based on a star polyamine (SPc) and focused on the characterization and bioactivity of SPc-loaded AVM at various mass ratios. The hydroxyl groups of AVM could assemble with carbonyl groups of SPc through hydrogen bond and van der Waals forces, and the self-assembly of AVM and SPc formed nearly spherical particles of AVM/SPc complex with nanoscale size. The contact angle of SPc-loaded AVM decreased with the increasing mass ratio of SPc, revealing the easier distribution and spreading of the AVM/SPc complex. Furthermore, the stomach and contact toxicity of AVM/SPc complex also increased along with the increasing SPc mass ratio, which could be attributed to the enhanced systemic transportation in plants, enlarged contact area to insect pests and stronger permeability across the insect cuticle. The current study provides an efficient nano-delivery system for increasing stomach and contact toxicity of pesticides with wide applications in the agricultural field.

Calcium nutrition nanoagent rescues tomatoes from mosaic virus disease by accelerating calcium transport and activating antiviral immunity

As an essential structural, metabolic and signaling element, calcium shows low remobilization from old to young tissues in plants, restricting the nutrient-use efficiency and control efficacy against mosaic virus disease. Nanotechnology has been applied to prevent/minimize nutrient losses and improve the accessibility of poorly-available nutrients. Herein, the current study applied a star polycation (SPc) to prepare a calcium nutrition nanoagent. The SPc could assemble with calcium glycinate through hydrogen bond and Van der Waals force, forming stable spherical particles with nanoscale size (17.72 nm). Transcriptomic results revealed that the calcium glycinate/SPc complex could activate the expression of many transport-related genes and disease resistance genes in tomatoes, suggesting the enhanced transport and antiviral immunity of SPc-loaded calcium glycinate. Reasonably, the calcium transport was accelerated by 3.17 times into tomato leaves with the help of SPc, and the protective effect of calcium glycinate was remarkably improved to 77.40% and 67.31% toward tomato mosaic virus with the help of SPc after the third and fifth applications. Furthermore, SPc-loaded calcium glycinate could be applied to increase the leaf photosynthetic rate and control the unusual fast growth of tomatoes. The current study is the first success to apply nano-delivery system for enhanced calcium transport and antiviral immunity, which is beneficial for increasing nutrient-use efficiency and shows good prospects for field application.