Preparation of thermosensitive buprofezin-loaded mesoporous silica nanoparticles by the sol-gel method and their application in pest control

Construction and biological effects of a redox-enzyme dual-responsive lufenuron nano-controlled release formulation

BACKGROUND

Pesticide formulations based on nanotechnology can effectively improve the efficiency of pesticide utilization and reduce pesticide residues in the environment. In this study, mesoporous silica nanoparticles containing disulfide bonds were synthesized by the sol-gel method, carboxylated and adsorbed with lufenuron, and grafted with cellulose to obtain a lufenuron-loaded nano-controlled release formulation (Luf@MSNs-ss-cellulose).

RESULTS

The structure and properties of Luf@MSNs-ss-cellulose were characterized. The results showed that Luf@MSNs-ss-cellulose exhibits a regular spherical shape with 12.41% pesticide loading. The highest cumulative release rate (73.46%) of this pesticide-loaded nanoparticle was observed at 7 days in the environment of glutathione and cellulase, which shows redox-enzyme dual-responsive performance. As a result of cellulose grafting, Luf@MSNs-ss-cellulose had a small contact angle and high adhesion work on corn leaves, indicating good wetting and adhesion properties. After 14 days of spraying with 20 mg L-1 formulations in the long-term control efficacy experiment, the mortality of Luf@MSNs-ss-cellulose against Ostrinia furnacalis larvae (56.67%) was significantly higher than that of commercial Luf@EW (36.67%). Luf@MSNs-ss-cellulose is safer for earthworms and L02 cells.

CONCLUSION

The nano-controlled release formulation obtained in this study achieved intelligent pesticide delivery in time and space under the environmental stimulation of glutathione and cellulase, providing an effective method for the development of novel pesticide delivery systems. © 2023 Society of Chemical Industry.

A Novel Fluorescent Aptasensor Based on Mesoporous Silica Nanoparticles for Selective and Sensitive Detection of Saxitoxin in Shellfish

Background:

Saxitoxin (STX) stands as one of the most potent marine biotoxins, exhibiting high lethality. Despite its severity, current treatments remain ineffective, and existing detection techniques are limited due to ethical concerns and technical constraints.

Methods:

Herein, an innovative approach was constructed for STX detection, utilizing mesoporous silica nanoparticles (MSN) as a foundation. This innovative, easy, and label-free aptamer (Apt)- sensor was fabricated. Apts were employed as molecular identification probes and "gated molecules," while rhodamine 6G was encapsulated within particles to serve as a signal probe. In a lack of STX, Apts immobilized on an MSN surface kept a "gate" closed, preventing signal probe leakage. Upon the presence of STX, the "gate" opened, allowing a particular binding of Apts to STX and a subsequent release of a signal probe.

Results:

Experimental results demonstrated a positive correlation between fluorescence intensity and concentrations of STX within a range of 1 to 80 nM, with an exceptional limit of detection of 0.12 nM. Furthermore, the selectivity and stability of a biosensor were rigorously evaluated, validating its reliability.

Conclusion:

This newly developed sensing strategy exhibits remarkable performance in STX detection. Its success holds significant promise for advancing portable STX detection equipment, thereby addressing a pressing need for efficient and ethical detection methods in combating marine biotoxin contamination.

Deposition and water repelling of temperature-responsive nanopesticides on leaves

Pesticides are widely used to increase agricultural productivity, however, weak adhesion and deposition lead to low efficient utilization. Herein, we prepare a nanopesticide formulation (tebuconazole nanopesticides) which is leaf-adhesive, and water-dispersed via a rapid nanoparticle precipitation method, flash nanoprecipitation, using temperature-responsive copolymers poly-(2-(dimethylamino)ethylmethylacrylate)-b-poly(ε-caprolactone) as the carrier. Compared with commercial suspensions, the encapsulation by the polymer improves the deposition of TEB, and the contact angle on foliage is lowered by 40.0°. Due to the small size and strong van der Waals interactions, the anti-washing efficiency of TEB NPs is increased by 37% in contrast to commercial ones. Finally, the acute toxicity of TEB NPs to zebrafish shows a more than 25-fold reduction as compared to commercial formulation indicating good biocompatibility of the nanopesticides. This work is expected to enhance pesticide droplet deposition and adhesion, maximize the use of pesticides, tackling one of the application challenges of pesticides.

Silica nanoparticles mediated insect pest management

Silicon is known for mitigating the biotic and abiotic stresses of crop plants. Many studies have proved beneficial effects of bulk silicon against biotic stresses in general and insect pests in particular. However, the beneficial effects of silica nanoparticles in crop plants against insect pests were barely studied and reported. By virtue of its physical and chemical nature, silica nanoparticles offer various advantages over bulk silicon sources for its applications in the field of insect pest management. Silica nanoparticles can act as insecticide for killing target insect pest or it can act as a carrier of insecticide molecule for its sustained release. Silica nanoparticles can improve plant resistance to insect pests and also aid in attracting natural enemies via enhanced volatile compounds emission. Silica nanoparticles are safe to use and eco-friendly in nature in comparison to synthetic pesticides. This review provides insights into the applications of silica nanoparticles in insect pest management along with discussion on its synthesis, side effects and future course of action.

Bioactivity, Uptake, and Distribution of Prothioconazole Loaded on Fluorescent Double-Hollow Shelled Mesoporous Silica in Soybean Plants

Prothioconazole (PTC) has been widely utilized for plant fungal disease control, but its metabolite prothioconazole-desthio (PTC-d) exhibits reproductive toxicity. In the present study, carbon quantum dot (CQD)-modified fluorescent double-hollow shelled mesoporous silica nanoparticles (FL-MSNs) loaded with PTC, referred to as PTC@FL-MSNs, were constructed with an average size of 369 nm and a loading capacity of 28.1 wt %, which could increase the antifungal efficiency of PTC. In addition, upright fluorescence microscope and UPLC-MS/MS studies showed that PTC@FL-MSNs could be effectively transported via root uptake and foliar spray in soybean plants. Compared to a 30% PTC dispersible oil suspension agent, the PTC@FL-MSN treatment group showed higher concentrations (leaves: 0.50 > 0.48 mg/kg), longer half-lives for degradation (leaves: 3.62 > 3.21 d; roots: 3.39 > 2.82 d), and fewer metabolites. These findings suggest that sustained pesticide release and toxicity reduction are potential applications for PTC nanofungicide delivery technology.

Fluorescent aptamer-modified mesoporous silica nanoparticles for quantitative acetamiprid detection

Acetamiprid (ACE) is widely used to control aphids, brown planthoppers, and other pests in agricultural production. However, ACE is difficult to degrade in the environment, resulting in excessive residue, which causes acute and chronic toxicity to human beings and non-target organisms. Therefore, the development of a rapid, convenient, and highly sensitive method to quantify ACE is essential. In this study, aminated mesoporous silica nanoparticles (MSNs-NH₂) were synthesized by one-pot method, and 6-carboxyl fluorescein modified aptamers (FAM-Apt) of ACE were adsorbed on the surface of MSNs-NH₂ by electrostatic interaction. Finally, a simple and sensitive fluorescence analysis method for the rapid detection of ACE was established. In the absence of ACE, the negatively charged FAM-Apt was electrostatically bound to the positively charged MSNs-NH₂, followed by centrifugation to precipitate MSNs-NH₂@FAM-Apt, and no fluorescent signal was detected in the supernatant. In the presence of ACE, the specific combination of FAM-Apt with ACE was greater than its electrostatic interaction with MSNs-NH₂, so that FAM-Apt was separated from MSNs-NH₂, and the supernatant had strong fluorescence signal after centrifugation. For ACE detection, the linear concentration range was 50-1100 ng/mL, and the detection limit (LOD) was 30.26 ng/mL. The method exhibited high sensitivity, selectivity and reproducibility, which is suitable for practical sample analysis and provides guidance for rapid detection of pesticide residues.

Advances in stimuli-responsive systems for pesticides delivery: Recent efforts and future outlook

Effective pest management for enhanced crop output is one of the primary goals of establishing sustainable agricultural practices in the world. Pesticides are critical in preventing biological disasters, ensuring crop productivity, and fostering sustainable agricultural production growth. Studies showed that crops are unable to properly utilize pesticides because of several limiting factors, such as leaching and bioconversion, thereby damaging ecosystems and human health. In recent years, stimuli-responsive systems for pesticides delivery (SRSP) by nanotechnology demonstrated excellent promise in enhancing the effectiveness and safety of pesticides. SRSP are being developed with the goal of delivering precise amounts of active substances in response to biological needs and environmental factors. An in-depth analysis of carrier materials, design fundamentals, and classification of SRSP were provided. The adhesion of SRSP to crop tissue, absorption, translocation in and within plants, mobility in the soil, and toxicity were also discussed. The problems and shortcomings that need be resolved to accelerate the actual deployment of SRSP were highlighted in this review.

Environmentally Friendly Zr-Based MOF for Pesticide Delivery: Ultrahigh Loading Capacity, pH-Responsive Release, Improved Leaf Affinity, and Enhanced Antipest Activity

The stimuli responsive pesticide delivery system (PDS) has drawn increasing attention in recent years, a system which can effectively improve the utilization of pesticides. In the current research, we report a pH responsive PDS by using carboxymethyl cellulose (CMC) modified Zr-based metal organic frameworks (UiO-66-NH₂) as the nanocarrier for acetamiprid (ATP). UiO-66-NH₂-CMC possesses a large surface area and abundant pores, which can effectively load ATP, and the loading rate is as high as 90.79%. Compared with free ATP, the ATP@UiO-66-NH₂-CMC nanopesticide exhibits pH responsive controlled release behavior, and the pesticide can sustained release to the medium. In addition, it also shows improved leaf affinity, which makes it easier to wet the leaf surface and improve the utilization of pesticide. Therefore, ATP@UiO-66-NH₂-CMC displays better antipest activity against aphids than free ATP does. Meanwhile, ATP@UiO-66-NH₂-CMC shows no negative effects on the germination and growth of maize, showing good biosafety. Moreover, the ATP@UiO-66-NH₂-CMC nanopesticide does not contain any toxic organic solvents or additives. Therefore, we hope that it can be a suitable candidate for plant protection and sustainable agriculture.

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.

Discovery of Novel Triazolothiadiazines as Fungicidal Leads Targeting Pyruvate Kinase

Pyruvate kinase (PK) was discovered as a potent new target for novel fungicide development. A series of novel triazolothiadiazine derivatives were rationally designed and synthesized by a ring expansion strategy and computer-aided pesticide design using the 3D structure of Rhizoctonia solani PK (RsPK) obtained by homology modeling as a receptor and our previously discovered lead YZK-C22 as a ligand. The in vitro bioassay results indicated that compounds 4g, 6h, 6m, 6n, 6o, and 6p exhibited good activity against R. solani with the EC₅₀ values falling between 10.99 and 72.76 μM. Especially, 6m showed similar potency to YZK-C22 (10.99 vs 11.97 μM of the EC₅₀ value, respectively). The in vivo bioassay results suggested that 6m against R. solani at a concentration of 200 μg/mL displayed a numerically higher inhibition than YZK-C22 (70 vs 60%, respectively). A field experiment validated that 6m at an application rate of 120 g ai/ha showed comparable efficacy against R. solani to thifluzamide at an application rate of 80 g ai/ha (77.80 vs 84.5%, respectively). Enzymatic inhibition suggested that the potency of 6m was about twofold lower than that of YZK-C22 (67.30 vs 32.64 μM of IC₅₀, respectively). Fluorescence quenching studies validated that RsPK was quenched by both 6m and YZK-C22, implying that they both might act at the same target site of PK. A possible binding conformation of 6m in the RsPK active site was depicted by molecular docking. Our studies suggest that 6m could be a fungicidal lead targeting PK.