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

Regenerated SERS substrate based on Ag/AuNPs-TiO2-oxidized carbon cloth for detection of imidacloprid

Imidacloprid (IMI) are widely used in modern tea industry for pest control, but IMI residues pose a great threat to human health. Herein, we propose a regeneration metal-semiconductor SERS substrate for IMI detection. We fabricated the SERS sensor through the in-situ growth of a nano-heterostructure incorporating a semiconductor (TiO2) and plasmonic metals (Au, Ag) on oxidized carbon cloth (OCC). Leveraging the high-density hot spots, the formed Ag/AuNPs-TiO2-OCC substrate exhibits higher enhancement factors (1.92 × 108) and uniformity (RSD = 7.68%). As for the detection of IMI on the substrate, the limit of detection was lowered to 4.1 × 10-6 μg/mL. With a hydrophobic structure, the Ag/AuNPs-TiO2-OCC possessed excellent self-cleaning performance addressing the limitation of single-use associated with traditional SERS substrates, as well as the degradation capability of the substrate under ultraviolet (UV) light. Accordingly, Ag/AuNPs-TiO2-OCC showcases outstanding SERS sensing and regenerating properties, making it poised for extensive application in the field of food safety assurance.

Triacontanol delivery by nano star shaped polymer promoted growth in maize

Plant Growth Regulators (PGRs) are functional compounds known for enhancing plant growth and development. However, their environmental impact is a concern due to poor water solubility and the need for substantial organic solvents. Recently, nano-delivery systems have emerged as a solution, offering a broad range of applications for small molecule compounds. This study introduces a nano-delivery system for Triacontanol (TA), utilizing a star polymer (SPc), aimed at promoting maize growth and improving physiological indicators. The system forms nearly spherical nanoparticles through TA's hydroxyl group and SPc's tertiary amine group. The TA/SPc nano-complex notably outperforms separate TA or SPc treatments in maize, increasing biomass, chlorophyll content, and nutrient absorption. It elevates chlorophyll content by 16.4%, 10.0%, and 6.2% over water, TA, and SPc treatments, respectively, and boosts potassium and nitrate ion uptake by up to 2 and 1.6 times compared to TA alone, leading to enhanced plant height and leaf growth. qRT-PCR analysis further demonstrated that the nano-complex enhanced cellular uptake through the endocytosis pathway by up-regulating endocytosis-related gene expression. The employment of TEM to observe vesicle formation during the internalization of maize leaves furnishes corroborative evidence for the participation of the endocytosis pathway in this process. This research confirms that SPc is an effective carrier for TA, significantly enhancing biological activity and reducing TA dosage requirements.

Potential of Streptomyces avermitilis: A Review on Avermectin Production and Its Biocidal Effect

Secondary metabolites produced by the fermentation of Streptomyces avermitilis bacterium are powerful antiparasitic agents used in animal health, agriculture and human infection treatments. Avermectin is a macrocyclic lactone with four structural components (A1, A2, B1, B2), each of them containing a major and a minor subcomponent, out of which avermectin B1a is the most effective parasitic control compound. Avermectin B1a produces two homologue avermectins (B1 and B2) that have been used in agriculture as pesticides and antiparasitic agents, since 1985. It has a great affinity with the Cl-channels of the glutamate receptor, allowing the constant flow of Cl- ions into the nerve cells, causing a phenomenon of hyperpolarization causing death by flaccid paralysis. The purpose of this work was to gather information on the production of avermectins and their biocidal effects, with special emphasis on their role in the control of pests and phytopathogenic diseases. The literature showed that S. avermitilis is an important producer of macrocyclic lactones with biocidal properties. In addition, avermectin contributes to the control of ectoparasites and endoparasites in human health care, veterinary medicine and agriculture. Importantly, avermectin is a compound that is harmless to the host (no side effects), non-target organisms and the environment.

Perfect cooperative pest control via nano-pesticide and natural predator: High predation selectivity and negligible toxicity toward predatory stinkbug

The improper use of synthetic pesticides has caused adverse effects on global ecosystems and human health. As a part of sustainable pest management strategy, natural predators, along with nano-pesticides, have made significant contributions to ecological agriculture. The cooperative application of both approaches may overcome their limitations, substantially reducing pesticide application while controlling insect pests efficiently. Herein, the current study introduced a cationic star polymer (SPc) to prepare two types of nano-pesticides, which were co-applied with predatory stinkbugs Picromerus lewisi to achieve perfect cooperative pest control. The SPc exhibited nearly no toxicity against predatory stinkbugs at the working concentration, but it led to the death of predatory stinkbugs at extremely high concentration with the lethal concentration 50 (LC50) value of 13.57 mg/mL through oral feeding method. RNA-seq analysis revealed that the oral feeding of SPc could induce obvious stress responses, leading to stronger phagocytosis, exocytosis, and energy synthesis to ultimately result in the death of predatory stinkbugs. Then, the broflanilide and chlorobenzuron were employed to prepare the self-assembled nano-pesticides via hydrogen bond and Van der Waals force, and the complexation with SPc broke the self-aggregated structures of pesticides and reduced their particle sizes down to nanoscale. The bioactivities of prepared nano-pesticides were significantly improved toward common cutworm Spodoptera litura with the corrected mortality increase by approximately 30%. Importantly, predatory stinkbugs exhibited a strong predation selectivity for alive common cutworms to reduce the exposure risk of nano-pesticides, and the nano-pesticides showed negligible toxicity against predators. Thus, the nano-pesticides and predatory stinkbugs could be applied simultaneously for efficient and sustainable pest management. The current study provides an excellent precedent for perfect cooperative pest control via nano-pesticide and natural predator.

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.

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.

A nano-delivery system expands the insecticidal target of thiamethoxam to include a devastating pest, the fall armyworm

Nano-delivery systems have been applied to deliver various synthetic/botanical pesticides to increase the efficiency of pesticide use and reduce the volumes of pesticides applied. Previous studies have supported the hypothesis that the nanocarriers can help expand the insecticidal target of pesticides to include non-target pests. However, the potential mechanism underlying this interesting phenomenon remains unclear. Herein, a widely applied star polycation (SPc) nanocarrier was synthesized to construct a thiamethoxam (TMX) nano-delivery system. The SPc-based delivery system could promote the translocation of exogenous substances across the membrane of Sf9 cells, increase the cytotoxicity of TMX against Sf9 cells by nearly 20%, and expand the insecticidal target of TMX to include Spodoptera frugiperda (the fall armyworm), with a 27.5% mortality increase at a concentration of 0.25 mg/mL. Moreover, the RNA-seq analysis demonstrated that the SPc could upregulate various transport-related genes, such as Rab, SORT1, CYTH, and PIKfyve, for the enhanced cellular uptake of TMX. Furthermore, enhanced cell death in larvae treated with the TMX-SPc complex was observed through changes in the expression levels of death-related genes, such as Casp7, BIRC5, MSK1, and PGAM5. The SPc-based nano-delivery system improved the cellular uptake of TMX and expanded its insecticidal target by adjusting the expression levels of death-related genes. The current study mainly identified the transport and cell death genes related to nanocarrier-based insecticidal target expansion, which is beneficial for understanding the bioactivity enhancement of the nano-delivery system.

Multifunctional Nanoparticles and Nanopesticides in Agricultural Application

The unscientific application of pesticides can easily cause a series of ecological environmental safety issues, which seriously restrict the sustainable development of modern agriculture. The great progress in nanotechnology has allowed the continuous development of plant protection strategies. The nanonization and delivery of pesticides offer many advantages, including their greater absorption and conduction by plants, improved efficacy, reduced dosage, delayed resistance, reduced residues, and protection from natural enemies and beneficial insects. In this review, we focus on the recent advances in multifunctional nanoparticles and nanopesticides. The definition of nanopesticides, the types of nanoparticles used in agriculture and their specific synergistic mechanisms are introduced, their safety is evaluated, and their future application prospects, about which the public is concerned, are examined.

Fluorescent Nanoparticle-RNAi-Mediated Silencing of Sterol Carrier Protein-2 Gene Expression Suppresses the Growth, Development, and Reproduction of Helicoverpa armigera

Helicoverpa armigera is a polyphagous destructive lepidopteran pest with strong Bacillus thuringiensis (Bt) resistance. Cholesterol, a vital component for insect growth, can only be obtained from food, and its transfer and metabolism are regulated by sterol carrier protein-2 (SCP-2). This study examined whether H. armigera SCP-2 (HaSCP-2) gene expression, involved in cholesterol absorption, can be silenced by nanocarrier fluorescent nanoparticle-RNA interference (FNP-RNAi) by larval feeding and whether the silencing affected H. armigera development. Fluorescence microscopy showed that nanoparticle-siRNA was distributed in Ha cells and the larval midgut. FNP-HaSCP-2 siRNA suppressed HaSCP-2 expression by 52.5% in H.armigera Ha cells. FNP can effectively help deliver siRNA into cells, protect siRNA, and is not affected by serum. FNP-siRNA in vivo biological assays showed that HaSCP-2 transcript levels were inhibited by 70.19%, 68.16%, and 67.66% in 3rd, 4th, and 5th instar larvae, leading to a decrease in the cholesterol level in the larval and prepupal fatbodies. The pupation rate and adult emergence were reduced to 26.0% and 56.52%, respectively. This study demonstrated that FNP could deliver siRNA to cells and improve siRNA knockdown efficiency. HaSCP-2 knockdown by FNP-siRNA in vivo hindered H. armigera growth and development. FNP could enhance RNAi efficiency to achieve pest control by SCP-2-targeted FNP-RNAi.

Construction of Prochloraz-Loaded Hollow Mesoporous Silica Nanoparticles Coated with Metal-Phenolic Networks for Precise Release and Improved Biosafety of Pesticides

Currently, environmental-responsive pesticide delivery systems have become an essential way to improve the effective utilization of pesticides. In this paper, by using hollow mesoporous silica (HMS) as a nanocarrier and TA-Cu metal-phenolic networks as a capping agent, a pH-responsive controlled release nano-formulation loaded with prochloraz (Pro@HMS-TA-Cu) was constructed. The structure and properties of Pro@HMS-TA-Cu were adequately characterised and analysed. The results showed that the loading content of Pro@HMS-TA-Cu nanoparticles was about 17.7% and the Pro@HMS-TA-Cu nanoparticles exhibited significant pH-responsive properties. After a coating of the TA-Cu metal-phenolic network, the contact angle and adhesion work of Pro@HMS-TA-Cu nanoparticles on the surface of oilseed rape leaves after 360 s were 59.6° and 107.2 mJ·m^-2, respectively, indicating that the prepared nanoparticles possessed excellent adhesion. In addition, the Pro@HMS-TA-Cu nanoparticles demonstrated better antifungal activity against Sclerotinia sclerotiorum and lower toxicity to zebrafish compared to prochloraz technical. Hence, the pH-responsive nanoparticles prepared with a TA-Cu metal-phenolic network as a capping agent are highly efficient and environmentally friendly, providing a new approach for the development of new pesticide delivery systems.

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.