A leaf adhesion nano-pesticide drug delivery system based on anti-solvent precipitation method and construction method and application thereof

Abstract

The application relates to the technical field of functional pesticide preparation development, in particular to a leaf surface adhesion nano-pesticide drug delivery system based on an anti-solvent precipitation method and a construction method and application thereof; and the construction method of the leaf surface adhesion nano-pesticide drug delivery system based on the anti-solvent precipitation method comprises the following steps: dropping a mixed solution of a pesticide and a slow-release carrier material into an anti-solvent, stirring, rotary evaporation, drying and the like to prepare nano-pesticide drug delivery particles; dispersing the nano-pesticide drug delivery particles in a buffer solution containing plant polyphenols, stirring, centrifuging, washing and drying and the like to prepare a composite nano-pesticide drug delivery system; the composite nano-pesticide drug delivery system prepared in the application not only has good slow-release performance and anti-photolysis performance, but also has excellent plant leaf surface adhesion performance, can significantly improve pesticide utilization rate and reduce the negative influence of pesticide use on the ecological environment.

Description

Technical Field

[0001] This application relates to the technical field of functional pesticide formulation development, and in particular to a leaf-adhesive nanopesticide delivery system based on antisolvent precipitation method, its construction method and application. Background Technology

[0002] Pesticides play a crucial role in ensuring safe agricultural production. However, traditional pesticide formulations generally suffer from poor leaf adhesion and the easy loss of active ingredients due to rain washout, resulting in low actual utilization rates. This not only increases application costs but also poses a potential threat to non-target organisms and the ecological environment. Especially under rainfall or irrigation conditions, pesticide formulations rapidly detach due to the lack of strong adhesion to the plant leaf surface, becoming one of the key bottlenecks restricting the efficient use of pesticides. Therefore, improving the adhesion and retention capacity of pesticides on the leaves of target crops is of great significance for improving pesticide utilization efficiency and reducing environmental residues.

[0003] In recent years, nanotechnology-based nanoparticle-based drug delivery systems have been considered an effective strategy for improving pesticide utilization efficiency. By encapsulating pesticide active ingredients in functionalized carriers, controlled release, enhanced leaf surface affinity, and resistance to environmental stress can be achieved. Among these, the introduction of specific functional groups or materials to enhance the interaction between nanoparticles and the leaf surface has attracted widespread attention. For example, utilizing the adhesive properties of polyphenols, the anchoring ability of the carrier on the leaf surface can be enhanced through hydrogen bonding, hydrophobic interactions, or electrostatic interactions. Patent CN110050787A describes a method for preparing a tannic acid-modified leaf-adhesive pesticide, which utilizes the complexation of tannins and ferric iron to form a rough solid, increasing leaf surface anchoring ability. However, the use of metal particles is not environmentally friendly and the process is complex. Other research has imitated the adhesion mechanisms of natural organisms to construct pesticide delivery systems resistant to rain washout. Dopamine adhesion is also used, but dopamine itself is expensive, hindering large-scale application in the agrochemical field. In the construction of nanopesticide systems, CN115581229B describes a method for preparing tannic acid-modified imazalil ethyl cellulose nanoparticles and their antibacterial applications. While ethyl cellulose is used to construct nanoparticles via solvent evaporation, this method suffers from low production efficiency and the potential generation of toxic liquids and gases. Antisolvent precipitation, as a mild, simple, and controllable method for preparing nanomaterials, has shown significant advantages in pesticide formulation research in recent years. This method utilizes rapid mixing between the solvent and antisolvent, and achieves controllable construction of nanoparticles by controlling precipitation kinetics, avoiding the need for high temperatures, high pressures, or violent chemical reactions.

[0004] Therefore, developing a nanopesticide delivery system based on antisolvent precipitation combined with interface modification technology, which has high loading efficiency, stable dispersion and excellent adhesion to plant leaves, is of great significance for improving pesticide utilization and reducing environmental loss. Summary of the Invention

[0005] To address the shortcomings of existing technologies, this application provides a leaf-adhesive nanopesticide delivery system based on antisolvent precipitation, its construction method, and its application.

[0006] This application presents a leaf-adhesive nano-drug delivery system based on antisolvent precipitation, overcoming the problems of poor leaf adhesion, susceptibility to rain washout, and low utilization rate of traditional pesticide formulations. This delivery system combines excellent plant leaf adhesion, resistance to photodegradation, and sustained-release properties, enhancing pesticide retention and absorption at the target site, thereby improving pesticide utilization efficiency and reducing environmental risks.

[0007] In a first aspect, this application provides a method for constructing a leaf-adhesive nanopesticide delivery system based on antisolvent precipitation, employing the following technical solution: A method for constructing a leaf-adhesive nanopesticide delivery system based on antisolvent precipitation includes the following steps: dropping a mixture of pesticide and slow-release carrier material into an antisolvent to obtain nanoparticles; then modifying the interface of the nanoparticles with plant polyphenols to obtain a composite nanoparticle delivery system.

[0008] Preferably, the sustained-release carrier material includes at least one of ethyl cellulose and polylactic acid-glycolic acid copolymer.

[0009] Preferably, the pesticide includes at least one of macrolides, diamides, and triazoles.

[0010] Preferably, the plant polyphenols include at least one of tannic acid, gallic acid, and tea polyphenols.

[0011] Preferably, the antisolvent is water.

[0012] Preferably, the mass ratio of the slow-release carrier material to the pesticide is 1:0.5 to 1:2.

[0013] Preferably, the concentration of the mixture is 20~50 mg / mL.

[0014] Preferably, the volume ratio of the mixture to the antisolvent is 1:5 to 1:8.

[0015] Preferably, a method for constructing a leaf-adhesive nanopesticide delivery system based on antisolvent precipitation includes the following steps: (1) Dissolve the pesticide and the slow-release carrier material in an organic solvent to obtain a mixture; (2) The mixture is added dropwise into the antisolvent, stirred to form a suspension, and after the solvent is removed, it is separated by solid-liquid separation and dried to obtain nano-drug-loaded particles; (3) Add the drug-loaded nanoparticles to a buffer solution containing plant polyphenols and stir. After solid-liquid separation and drying, a composite drug-loaded nanoparticle system is obtained.

[0016] Preferably, in step (1), the organic solvent includes at least one of ethanol, methanol, and N,N-dimethylformamide.

[0017] Preferably, in step (2), the mixture is added dropwise to the antisolvent at a rate of 3 to 9 mL / min.

[0018] Preferably, in step (2), the stirring speed is 400~600 r / min during the stirring process.

[0019] Preferably, in step (2), the reaction temperature during the solvent removal process is 40~50℃.

[0020] Preferably, in step (3), the buffer solution containing plant polyphenols is Tris-HCl buffer solution with a concentration of 50~150mM and a pH of 8.0~9.0.

[0021] Preferably, in step (3), the concentration of plant polyphenols in the buffer solution containing plant polyphenols is 0.5~2 mg / mL.

[0022] Preferably, in step (3), the stirring temperature is 20~30℃ and the stirring time is 10~14 hours.

[0023] Preferably, in step (3), the solid-liquid separation process is carried out by centrifugation equipment, with a centrifugation speed of 9000~10000 rpm and a centrifugation time of 15~25 min.

[0024] By adopting the above technical solution, this application uses a slow-release carrier material as the base carrier and loads pesticide active ingredients through an antisolvent precipitation method, which is simple to operate and operates under mild conditions. Furthermore, through interfacial modification with plant polyphenols, the abundant phenolic hydroxyl structures in plant polyphenol molecules endow the nanoparticles with excellent interfacial affinity. They can interact with plant leaf surfaces through hydrogen bonds and hydrophobic interactions, thereby significantly enhancing their adhesion to leaf surfaces and improving their resistance to rain erosion. Simultaneously, the coating of the slow-release carrier material and plant polyphenols effectively shields ultraviolet light, improves the photostability of the pesticide, and achieves sustained drug release, extending the duration of efficacy.

[0025] The nanopesticide prepared in this application has two key advantages. First, the plant polyphenols in its outer shell are rich in polyphenol hydroxyl structures, which can firmly bind to the waxy layer of plant leaves through hydrogen bonds, hydrophobic interactions, and electrostatic interactions, significantly enhancing leaf adhesion and effectively resisting rain erosion. Second, the slow-release carrier material forms a dense hydrophobic network structure that can effectively encapsulate the active ingredients of the pesticide, slow down the drug release rate, and shield the drug from direct ultraviolet radiation, reducing photolysis loss. The slow-release carrier material forms a dense hydrophobic nanoskeleton, providing a spherical, uniform nanomorphology, a small size, and a large specific surface area. It adheres to leaf wrinkles through physical interlocking, serving as the carrier basis for the adhesion effect of plant polyphenols. The synergistic effect of these two components not only improves the retention capacity of pesticides on the leaves of target crops but also achieves long-term slow-release of the drug, thereby significantly improving pesticide utilization efficiency, reducing environmental runoff, and mitigating potential risks to non-target organisms and ecosystems.

[0026] Secondly, this application provides a leaf-adhesive nanopesticide delivery system based on antisolvent precipitation, employing the following technical solution: A leaf-adhesive nanopesticide delivery system based on antisolvent precipitation method was constructed using the method described above.

[0027] The leaf-adhesive nanopesticide delivery system prepared in this application, based on the antisolvent precipitation method, combines slow-release properties, resistance to photodegradation, and leaf adhesion.

[0028] Thirdly, this application provides an application of a leaf-adhesive nanopesticide delivery system based on antisolvent precipitation in the preparation of pesticide formulations for the control of plant diseases and pests, employing the following technical solution: Application of a leaf-adhesive nanopesticide delivery system based on antisolvent precipitation in the preparation of pesticide formulations for the control of plant diseases and pests.

[0029] This invention does not impose any special limitations on the plants and diseases mentioned herein, and the plants and diseases mentioned correspond to the pesticides loaded in this application.

[0030] In summary, this application includes at least one of the following beneficial technical effects: 1. This application employs an antisolvent precipitation method combined with plant polyphenol interface modification to successfully construct a composite nano-drug delivery system. This method is mild and easy to operate, avoiding the need for high temperature, high pressure or violent chemical reactions. 2. In the construction of the nano-drug delivery system, this application loads pesticides onto a slow-release carrier material and then modifies it through the interface of plant polyphenols. By utilizing the polyphenol structure of plant polyphenols, multiple interactions occur with the plant leaf surface through hydrogen bonds, hydrophobic interactions, or electrostatic interactions, thereby enhancing the adhesion and retention capacity of nanoparticles on the leaf surface. As a result, the prepared composite nano-drug delivery system has excellent wettability and rain erosion resistance. 3. The nanoparticle drug delivery system prepared in this application has excellent sustained-release characteristics. Compared with unmodified nanoparticle drug delivery particles, the encapsulation with plant polyphenols effectively slows down the burst release of the drug, prolongs the duration of drug action, and reduces the amount of pesticide used. Attached Figure Description

[0031] The present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments, and the advantages of the present invention above and in other aspects will become clearer.

[0032] Figure 1 SEM image of the tannic acid-coated drug-loaded nanoparticles prepared in Example 1; Figure 2 SEM image of the uncoated tannic acid nanoparticles prepared in Comparative Example 2; Figure 3 The graphs show the fluorescence retention rates of the nanopesticides prepared in Example 1 and Comparative Example 2 on the surface of cabbage leaves after different rinsing cycles. The first row of the graphs shows the fluorescence retention rate of the nanopesticides prepared in Comparative Example 2, and the second row shows the fluorescence retention rate of the nanopesticides prepared in Example 1. Figure 4 The cumulative release curves of the nano-pesticides prepared in Example 1, Comparative Example 1, and Comparative Example 2 in 30% methanol aqueous solution are shown.

[0033] Figure 5 The images show the residue of nanoparticles on the surface of cabbage leaves after different rinsing cycles for the nanopesticides in Example 1, Comparative Example 1, and Comparative Example 2. Detailed Implementation

[0034] The technical solutions of this application are further illustrated by specific embodiments below. These specific embodiments do not represent a limitation on the scope of protection of this application. Any non-essential modifications and adjustments made by others based on the concept of this application still fall within the scope of protection of this application.

[0035] In the embodiments of this application, the experimental methods described are conventional methods unless otherwise specified; the reagents described are commercially available unless otherwise specified.

[0036] Reagents and sources: Abamectin was provided by Jiangsu Aijin Agricultural Technology Service Co., Ltd.; Ethyl cellulose (EC), purchased from Shanghai Aladdin Biochemical Technology Co., Ltd.; Tannic acid (TA), purchased from Shanghai Lingfeng Chemical Reagent Co., Ltd. Tris(hydroxymethyl)aminomethane was purchased from Shanghai Maclean Biotechnology Co., Ltd. Rhodamine B, purchased from Tianjin Chemical Reagent Research Institute; Methanol and ethanol were both purchased from Wuxi Yisheng Chemical Co., Ltd. Polylactic acid-glycolic acid copolymer, purchased from Evonik, model RESOMER ® RG 502 H; Tea polyphenols were purchased from Shanghai Aladdin Biochemical Technology Co., Ltd., product number: T418534. The deionized water was prepared in the laboratory.

[0037] The present application will be further described in detail below with reference to embodiments and comparative examples.

[0038] A method for constructing a leaf-adhesive nanopesticide delivery system based on antisolvent precipitation includes the following steps: an organic solution containing pesticide and slow-release carrier material is added dropwise to an antisolvent, stirred, solvent removed, and dried to obtain nanoparticles; the obtained nanoparticles are dispersed in a buffer solution containing plant polyphenols, and a composite nanoparticle delivery system is obtained through stirring, solid-liquid separation, washing, and drying.

[0039] In one specific feasible implementation, a method for preparing a leaf-adhesive nano-drug delivery system based on anti-solvent precipitation includes the following steps: (1) Dissolve the pesticide and the slow-release carrier material in an organic solvent to form a mixture; (2) The mixture is added dropwise into the antisolvent, stirred to form a suspension, the solvent is removed, and then solid-liquid separation and drying are performed to obtain nano-drug-loaded particles; (3) Add the drug-loaded nanoparticles to a buffer solution containing plant polyphenols and stir. After solid-liquid separation, washing and drying, a composite drug-loaded nanoparticle system is obtained.

[0040] Preferably, in step (1), the pesticide includes at least one of macrolides, diamides, and triazoles.

[0041] Preferably, in step (1), the sustained-release carrier material includes at least one of ethyl cellulose and polylactic acid-hydroxyacetic acid copolymer.

[0042] Preferably, in step (1), the organic solvent includes at least one of ethanol, methanol, and N,N-dimethylformamide; more preferably, the organic solvent is ethanol.

[0043] Preferably, in step (1), the mass ratio of the slow-release carrier material to the pesticide is 1:0.5 to 1:2; for example, the mass ratio is 1:0.5, 1:0.6, 1:0.7, 1:0.8, 1:0.9, 1:1, 1:1.1, 1:1.2, 1:1.3, 1:1.4, 1:1.5, 1:1.6, 1:1.7, 1:1.8, 1:1.9 or 1:2.

[0044] Preferably, in step (1), the concentration of the mixture is 20~50 mg / mL; for example, the concentration is 20 mg / mL, 21 mg / mL, 22 mg / mL, 23 mg / mL, 24 mg / mL, 25 mg / mL, 26 mg / mL, 27 mg / mL, 28 mg / mL, 29 mg / mL, 30 mg / mL, 31 mg / mL, 32 mg / mL, 33 mg / mL, 33.33 mg / mL, 34 mg / mL, 35 mg / mL, 36 mg / mL, 37 mg / mL, 38 mg / mL, 39 mg / mL, 40 mg / mL, 41 mg / mL, 42 mg / mL, 43 mg / mL, 44 mg / mL, 45 mg / mL, 46 mg / mL, 47 mg / mL, 48 mg / mL, 49 mg / mL or 50 mg / mL.

[0045] Preferably, in step (2), the antisolvent is water.

[0046] Preferably, in step (2), the volume ratio of the mixture to the antisolvent is 1:5 to 1:8, for example, the volume ratio is 1:5, 1:6, 1:6.7, 1:7 or 1:8.

[0047] Preferably, in step (2), the mixture is added dropwise to the antisolvent at a rate of 3 to 9 mL / min; for example, the dropwise rate is 3 mL / min, 4 mL / min, 5 mL / min, 6 mL / min, 7 mL / min, 8 mL / min or 9 mL / min.

[0048] Preferably, in step (2), the stirring speed is 400~600 r / min, for example, the stirring speed is 400 r / min, 410 r / min, 420 r / min, 430 r / min, 440 r / min, 450 r / min, 460 r / min, 470 r / min, 480 r / min, 490 r / min, 500 r / min, 510 r / min, 520 r / min, 530 r / min, 540 r / min, 550 r / min, 560 r / min, 570 r / min, 580 r / min, 590 r / min or 600 r / min.

[0049] Preferably, in step (2), the reaction temperature during the solvent removal process is 40~50℃; for example, the reaction temperature is 40℃, 41℃, 42℃, 43℃, 44℃, 45℃, 46℃, 47℃, 48℃, 49℃ or 50℃.

[0050] More preferably, the organic solvent is removed by rotary evaporation during the solvent removal process.

[0051] Preferably, in step (2), the drying is freeze drying, and the temperature is -80~-40℃, for example, the temperature is -80℃, -70℃, -60℃, -50℃ or -40℃.

[0052] Preferably, in step (2), the drying is freeze drying for 40 to 50 hours; for example, the time is 40 hours, 41 hours, 42 hours, 43 hours, 44 hours, 45 hours, 46 hours, 47 hours, 48 ​​hours, 49 hours or 50 hours.

[0053] Preferably, in step (3), the plant polyphenols include at least one of tannic acid, gallic acid, and tea polyphenols.

[0054] Preferably, in step (3), the buffer solution containing plant polyphenols is a Tris-HCl buffer solution with a concentration of 50~150mM, for example, the concentration of Tris-HCl buffer solution is 50mM, 60mM, 70mM, 80mM, 90mM, 100mM, 110mM, 120mM, 130mM, 140mM or 150mM.

[0055] Preferably, in step (3), the buffer solution containing plant polyphenols is a Tris-HCl buffer solution with a pH of 8.0 to 9.0, for example, pH 8.0, 8.1, 8.2, 8.3, 8.4, 8.5, 8.6, 8.7, 8.8, 8.9 or 9.0.

[0056] Preferably, in step (3), the concentration of plant polyphenols in the buffer solution containing plant polyphenols is 0.5~2 mg / mL; for example, the concentration of plant polyphenols is 0.5 mg / mL, 0.6 mg / mL, 0.7 mg / mL, 0.8 mg / mL, 0.9 mg / mL, 1.0 mg / mL, 1.1 mg / mL, 1.2 mg / mL, 1.3 mg / mL, 1.4 mg / mL, 1.5 mg / mL, 1.6 mg / mL, 1.7 mg / mL, 1.8 mg / mL, 1.9 mg / mL or 2.0 mg / mL.

[0057] Preferably, in step (3), the stirring temperature is 20~30℃ during the stirring process; for example, the stirring temperature is 20℃, 21℃, 22℃, 23℃, 24℃, 25℃, 26℃, 27℃, 28℃, 29℃ or 30℃.

[0058] Preferably, in step (3), the stirring time is 10 to 14 hours; for example, the stirring time is 10 hours, 11 hours, 12 hours, 13 hours or 14 hours.

[0059] Preferably, in step (3), the solid-liquid separation process is carried out by centrifugation equipment, and the centrifugation speed is 9000~10000 rpm; for example, the centrifugation speed is 9000 rpm, 9100 rpm, 9200 rpm, 9300 rpm, 9400 rpm, 9500 rpm, 9600 rpm, 9700 rpm, 9800 rpm, 9900 rpm or 10000 rpm.

[0060] Preferably, in step (3), the solid-liquid separation process is carried out by centrifugation equipment, and the centrifugation time is 15~25min, for example, the centrifugation time is 15min, 16min, 17min, 18min, 19min, 20min, 21min, 22min, 23min, 24min or 25min.

[0061] Example 1: A leaf-adhesive nano-drug delivery system based on antisolvent precipitation was prepared using the following steps: (1) Preparation of ethyl cellulose nanoparticles loaded with emamectin benzoate (EB@EC) The antisolvent precipitation method was used: 1.0 g of emamectin benzoate and 1.0 g of ethyl cellulose were added to 30 mL of ethanol and dissolved by ultrasonication to form a mixture with a concentration of 33.33 mg / mL. Then, 3 mL of the mixture was added dropwise to 20 mL of deionized water using a constant flow pump at a rate of 6 mL / min, and stirred at a rate of 500 rpm to form a suspension. Next, the suspension was evaporated at 45 °C using a rotary evaporator to remove the ethanol. Finally, the ethanol-free suspension was centrifuged and freeze-dried at -60 °C for 48 hours to obtain EB@EC powder. (2) Preparation of tannic acid-modified abamectin nanocarrier system (EB@EC-TA) The EB@EC nanoparticles obtained in step (1) were dispersed in 20 mL of Tris−HCl buffer (100 mM, pH 8.5) containing 1 mg / mL tannic acid (TA). After sonication for 5 min, the mixture was stirred at 500 rpm and 25 °C for 12 h. Finally, the reaction product was collected, centrifuged at 10000 rpm and 16 °C for 20 min, and washed three times with ultrapure water. The collected EB@EC-TA nanoparticles were freeze-dried to obtain the tannic acid-modified emamectin benzoate nanoparticle drug delivery system (EB@EC-TA).

[0062] Examples 2-5:

[0063] The preparation methods of Examples 2-5 are basically the same as those of Example 1, except that the mass ratio of abamectin to ethyl cellulose and the concentration of the mixed solution are different in step (1); the specific parameters are shown in Table 1.

[0064] Table 1. Preparation parameters for Examples 2-5

[0065] Examples 6-9:

[0066] The preparation methods of Examples 6-9 are basically the same as those of Example 1, except that the concentration of tannic acid, the pH of the buffer solution or the reaction time are different in step (2); the specific parameters are shown in Table 2.

[0067] Table 2 Preparation parameters for Examples 6-9

[0068] Example 10:

[0069] The preparation method is basically the same as that in Example 1, except that ethyl cellulose is replaced with an equal mass of polylactic acid-glycolic acid copolymer.

[0070] Example 11:

[0071] The preparation method is basically the same as that in Example 1, except that tannic acid is replaced with an equal mass of gallic acid.

[0072] Example 12:

[0073] The preparation method is basically the same as that in Example 1, except that tannic acid is replaced with an equal mass of tea polyphenols.

[0074] Example 13:

[0075] The preparation method is basically the same as that in Example 1, except that abamectin is replaced with an equal mass of chlorantraniliprole.

[0076] Example 14:

[0077] The preparation method is basically the same as that in Example 1, except that abamectin is replaced with an equal mass of tebuconazole.

[0078] Comparative Example 1:

[0079] Abamectin technical grade (EB): Abamectin technical grade without any treatment was used as a control.

[0080] Comparative Example 2:

[0081] Unmodified emamectin methyl ethyl cellulose nanoparticles (EB@EC) were prepared using only the method in step (1) of Example 1, without the tannic acid interface modification in step (2).

[0082] Comparative Example 3:

[0083] A method for preparing ethyl cellulose nanoparticles loaded with emamectin benzoate includes the following steps: (1) Organic phase preparation Weigh 1.0 g of abamectin and 1.0 g of ethyl cellulose, and dissolve them together in 80 mL of dichloromethane. Stir magnetically at room temperature until completely dissolved to obtain a clear and transparent organic phase.

[0084] (2) Aqueous phase preparation 2.4 g of polyvinyl alcohol (PVA) was dissolved in 400 mL of deionized water, heated in a water bath at 60 °C and stirred until completely dissolved. After cooling to room temperature, a PVA aqueous solution with a mass fraction of 0.6% was obtained as the aqueous phase.

[0085] (3) Preparation of ethyl cellulose nanoparticles loaded with emamectin benzoate The organic phase obtained in step (1) and the aqueous phase obtained in step (2) are mixed at a volume ratio of 1:4 and magnetically stirred at a speed of 800 r / min for 5 minutes at room temperature to obtain the colostrum.

[0086] A beaker containing colostrum was placed in an ice bath and subjected to ultrasonic treatment using a probe-type ultrasonic emulsifier. The ultrasonic power was set to 400W and the ultrasonic time was 5 minutes to obtain a stable nanoemulsion.

[0087] The obtained nanoemulsion was transferred to a beaker and magnetically stirred continuously at 500 rpm for 4 hours at room temperature to allow the dichloromethane to completely evaporate. After the organic solvent evaporated, the solidified nanoparticle suspension was centrifuged at 9000 rpm for 25 minutes at 25°C, and the precipitate was collected. The precipitate was resuspended and washed with deionized water, repeated 4 times to remove unencapsulated emamectin benzoate and free PVA.

[0088] Finally, the washed precipitate was freeze-dried at -60°C for 48 hours to obtain ethyl cellulose nanoparticles (EB@EC) powder loaded with emamectin benzoate.

[0089] Performance testing methods:

[0090] 1. SEM detection: The morphology of the samples was observed using a cold field emission scanning electron microscope (SEM, Regulus 8100, Hitachi, Japan).

[0091] Table 3. SEM images of the examples and comparative examples under a scanning electron microscope.

[0092] Based on the test results in Table 3, it can be seen that the EB@EC nanoparticles prepared using the method of this application, after being coated with tannic acid to obtain the composite nanoparticle drug-carrying system EB@EC-TA, still maintain a regular spherical structure, but a distinct flocculent coating layer appears on the surface, and the average particle size is larger than before coating. This indicates that tannic acid was successfully coated on the surface of the EB@EC nanoparticles. Figure 1 As shown.

[0093] Comparative Example 1's emamectin benzoate technical grade exhibits an irregular blocky or flaky crystal structure with uneven particle size distribution and a rough surface. Comparative Example 2 (uncoated drug-loaded nanoparticles EB@EC) has the same morphology as the drug-loaded nanoparticles EB@EC prepared in step (1) of Example 1, appearing as regular spheres with a uniform particle size distribution, such as... Figure 2 As shown in the figure; Comparative Example 3 (EB@EC) prepared ethyl cellulose nanoparticles loaded with abamectin by ultrasonic emulsification-solvent evaporation method, which have a regular spherical shape and uniform particle size distribution.

[0094] A comparison of the test results from Examples 1 to 5 shows that when the mass ratio of abamectin to ethyl cellulose is 1:1, the concentration of the mixed solution is 33.33 mg / mL, and the volume ratio of the mixed solution to the antisolvent is 1:6.7 (i.e., Example 1), the resulting nanoparticles have the best morphology, exhibiting regular spherical shapes and good dispersibility. When the proportion of abamectin is increased (Example 2, 1:0.5), the particle morphology remains good, but the flocculent coating layer on the particle surface is slightly thinner; when the proportion of ethyl cellulose is increased (Example 3, 1:1.5), the particle morphology is good, but the flocculent coating layer on the particle surface is slightly thinner; when the concentration of the mixed solution is reduced to 20 mg / mL (Example 4), the particle morphology is good, but the flocculent coating layer on the particle surface is slightly thinner; when the concentration of the mixed solution is increased to 50 mg / mL (Example 5), slight agglomeration occurs on the particle surface, indicating that excessively high concentrations are not conducive to the uniform dispersion of particles.

[0095] A comparison of the detection results from Examples 1 and 6-9 shows that the tannic acid coating conditions have a significant impact on particle morphology. When the tannic acid concentration is reduced to 0.5 mg / mL (Example 6), the flocculent coating layer on the particle surface is less; when the tannic acid concentration is increased to 2.0 mg / mL (Example 7), the flocculent coating layer on the particle surface is thicker, but no obvious adhesion occurs between particles. When the buffer pH is reduced to 8.0 (Example 8), the coating effect is still good; when the buffer pH is increased to 9.0 and the reaction time is shortened to 10 h (Example 9), the flocculent coating layer on the particle surface is slightly thinner, indicating that alkaline conditions and reaction time have a certain influence on the adsorption efficiency of tannic acid.

[0096] The test results of Examples 10-12 show that the type of carrier material and plant polyphenols have a certain influence on the coating effect. When PLGA is used instead of ethyl cellulose as the carrier material (Example 10), the particles still maintain a regular spherical shape after tannic acid modification, and a flocculent coating layer is formed on the surface, indicating that this interface modification strategy has a certain applicability to different carrier materials. In Example 11, gallic acid was used instead of tannic acid for interface modification, and the resulting flocculent coating layer on the particle surface was slightly thinner, indicating that the self-polymerization ability of gallic acid is weaker than that of tannic acid. In Example 12, tea polyphenols were used for modification, and although a thicker coating layer was visible on the particle surface, the uniformity was poor, indicating that the coating controllability of tea polyphenols is not as good as that of tannic acid.

[0097] 2. Drug loading and encapsulation efficiency: The drug loading and encapsulation efficiency of the composite nano-drug delivery system (EB@EC-TA) were determined using a high-speed centrifugation filtration method. The specific method is as follows: 1 mL of the composite nano-drug delivery system (EB@EC-TA) was accurately pipetted into 3 mL of methanol solution. After ultrasonic demulsification, the solution was filtered through a 0.22 μm filter membrane. The absorbance was then measured at 245 nm using a UV-Vis spectrophotometer. The emamectin benzoate concentration was calculated using the emamectin benzoate standard curve to obtain the total drug content C0. Separately, 1 mL of the composite nano-drug delivery system (EB@EC-TA) was added to a 1.5 mL centrifuge tube and centrifuged at 15000 rpm for 10 min. The supernatant was filtered through a 0.22 μm filter membrane, and three times the volume of methanol solution was added. The absorbance was then measured at 245 nm using a UV-Vis spectrophotometer. The emamectin benzoate concentration was calculated using the emamectin benzoate standard curve to obtain the free drug content C1. Drug loading content (DLC) and encapsulation efficiency (EE) are calculated using the following formulas: Encapsulation efficiency (EE%) formula: EE% = (1 - C1 / C0) × 100%; Drug loading percentage (DLC%) formula: DLC% = (M emamectin benzoate × EE%) / (M emamectin benzoate + M ethyl cellulose) × 100%; Table 4. Encapsulation efficiency and pesticide loading results of nano-pesticides

[0098] As shown in Table 4, the composite nano-drug delivery system (EB@EC-TA) prepared by the method of this application has good encapsulation efficiency and drug loading capacity, and can be used to encapsulate pesticides.

[0099] 3. Leaf fluorescence retention rate determination: Rhodamine B (1 mM) was added to a suspension of the composite nanoparticle drug delivery system (EB@EC-TA) to obtain a stained micelle solution. The stained micelle solution (2 μL) was dropped onto the surface of Chinese cabbage leaves, and the leaves were allowed to air dry at room temperature. Images of the droplets before immersion in deionized water were recorded using an Eclipse NI-E fluorescence microscope (Nikon, Japan). The Chinese cabbage leaves were then immersed in deionized water for 5 min. After removal, the leaves were allowed to air dry at room temperature. Fluorescence images before and after rinsing were taken using a fluorescence microscope, and the coverage area of ​​fluorescent nanoparticles on the Chinese cabbage leaves was measured using IMAGE J software. To determine the change in the coverage area of ​​the fluorescent nanoparticles, the initial image before rinsing was used as a control, and the image after rinsing was compared with the initial image.

[0100] Table 5. Fluorescence retention rate of cabbage leaf surface after different rinsing cycles of nano-pesticides

[0101] Combined with Table 5 and Figure 3 The test results showed that, without rinsing (0 times), both the EB@EC nanoparticles of Comparative Example 2 and the EB@EC-TA composite nanoparticle drug delivery system of Example 1 exhibited complete fluorescent coverage (100%) on the surface of cabbage leaves. After one simulated rain wash, the fluorescence retention rate of EB@EC decreased to 60.73%, while EB@EC-TA maintained a relatively high level of 85.69%. After three washes, the fluorescence retention rate of EB@EC further decreased to 21.47%, while EB@EC-TA remained as high as 75.21%. After 10 washes, the fluorescence retention rate of EB@EC was only 2.05%, almost completely lost; while the fluorescence retention rate of EB@EC-TA still reached 14.61%, more than 7 times that of EB@EC. This demonstrates that the tannic acid coating significantly enhanced the adhesion of the composite nanoparticle drug delivery system EB@EC-TA to the surface of cabbage leaves, exhibiting stronger resistance to rain wash and better adhesion performance.

[0102] A comparison of Comparative Example 2 (EB@EC) and Example 1 (EB@EC-TA) shows that EB@EC-TA exhibits significantly higher fluorescence retention after each rinse than uncoated EB@EC, with the advantage becoming more pronounced with increasing rinse counts. This is mainly attributed to the fact that tannic acid molecules are rich in phenolic hydroxyl groups, enabling them to form hydrogen bonds with hydroxyl groups and other functional groups on the waxy surface of cabbage leaves. Simultaneously, the polyphenolic structure of tannic acid can also generate multiple interactions with the microstructure of the leaf surface, thereby enhancing the anchoring ability of the nanoparticles.

[0103] The comparison between Comparative Example 3 (EB@EC) and Example 1 (EB@EC-TA) shows that the fluorescence retention rate of EB@EC-TA prepared in Example 1 after each rinsing is significantly higher than that of EB@EC prepared in Comparative Example 3. This indicates that the composite nano-drug delivery system EB@EC-TA prepared by the anti-solvent precipitation method in this application exhibits stronger adhesion to the surface of cabbage leaves, demonstrating stronger resistance to rain rinsing and better adhesion performance.

[0104] Based on the test results of Examples 1-5, it can be seen that the fluorescence retention rate (i.e., adhesion performance) is affected by the preparation conditions. When the mass ratio of abamectin to ethyl cellulose is 1:1, the stock solution concentration is 33.33 mg / mL, and the volume ratio of the mixed solution to the antisolvent is 1:6.7 (Example 1), the obtained EB@EC nanoparticles have uniform particle size and smooth surface, which is conducive to the uniform coating of tannic acid, thus obtaining the best adhesion performance and the best fluorescence retention rate. If the proportion of ethyl cellulose is too high (Example 3, 1:1.5), although the particle morphology still maintains a regular spherical shape, the excessive ethyl cellulose may change the physicochemical properties of the particle surface, affecting the deposition efficiency of tannic acid on the particle surface, resulting in a slightly thinner flocculent coating layer and a slight decrease in fluorescence retention rate; if the concentration of the mixed solution is too high (Example 5, 50 mg / mL), the particles may agglomerate or have uneven particle size, affecting the coating effect of tannic acid and thus reducing the fluorescence retention rate. If the proportion of abamectin is too high (Example 2, 1:0.5), the drug loading increases but the encapsulation efficiency decreases, the flocculent coating layer on the particle surface is slightly thinner, the adhesion performance is slightly reduced, and the fluorescence retention rate decreases.

[0105] Based on the detection results of Examples 1 and 6-9, it can be seen that under the tannic acid coating conditions, when the tannic acid concentration is 1 mg / mL, the buffer pH is 8.5, and the stirring time is 12 h (Example 1), the resulting EB@EC-TA surface coating layer is uniform and the fluorescence retention rate is the highest. If the tannic acid concentration is too low (Example 6, 0.5 mg / mL), the coating layer is incomplete, the adhesion performance decreases, and the fluorescence retention rate decreases; if the tannic acid concentration is too high (Example 7, 2.0 mg / mL), although the coating layer is thick, it may cause slight adhesion between particles, affecting dispersibility, and may instead reduce the effective adhesion area, resulting in a slight decrease in the fluorescence retention rate. When the buffer pH is reduced to 8.0 (Example 8), the coating efficiency decreases slightly, the adhesion performance decreases, and the fluorescence retention rate decreases; when the pH is increased to 9.0 and the stirring time is shortened to 10 h (Example 9), the coating layer becomes thinner, the adhesion performance decreases, and the fluorescence retention rate decreases.

[0106] 4. Cumulative release rate: Drug release profiles were determined using dialysis. 5 mg of EB@EC nanoparticles and the EB@EC-TA composite nanoparticle drug delivery system were dispersed in 2 mL of a methanol / water (30 / 70, v / v) mixture, then transferred to a dialysis bag with a 14 kDa cutoff. The bag was placed in a brown capped sample vial, and the release medium was added to a final volume of 100 mL. The vial containing the dialysis bag was then placed on a shaker at 25 °C and a shaking rate of 100 rpm. At regular intervals, 4 mL of the release medium was pipetted, and an equal volume of fresh medium was added. The EB content in the solution was measured using a UV spectrophotometer. The cumulative release rate of EB was calculated using the following formula:

[0107] in This indicates the amount of EB loaded in the sample; This indicates the total volume of the released medium (V=100mL). This indicates the volume of the release medium extracted within a certain time period (v=4mL). (mg / mL) represents the concentration of EB in the release medium from time t-1 to t.

[0108] Table 6. Release of nano-pesticides in 30% methanol aqueous solution

[0109] Combined with Table 6, Figure 4 The test results show that the nano-drug delivery system prepared in this application has excellent sustained-release characteristics; the release kinetics study shows that the composite nano-drug delivery system (EB@EC-TA) can still achieve continuous drug release within 100 hours, and the release behavior conforms to the Ritger-Peppas model, which is Fick diffusion.

[0110] Combined with Table 6, Figure 4 The test results showed that, when the release time reached 24 hours, the cumulative release rate of Comparative Example 1 (EB technical grade) was 80.89%, with the fastest release rate; the cumulative release rate of Comparative Example 2 (EB@EC) was 66.89%, which was slower than that of EB technical grade, indicating that the ethyl cellulose carrier has a certain sustained-release effect on emamectin benzoate; the cumulative release rate of Comparative Example 3 (EB@EC) was 68.53%, which was faster than that of Example 1, indicating that the composite nano-drug delivery system EB@EC-TA prepared by the antisolvent precipitation method in this application has excellent sustained-release characteristics.

[0111] Example 1 (the composite nano-drug delivery system EB@EC-TA) exhibited the lowest cumulative release rate, at only 46.55%, significantly lower than that of the original EB drug and EB@EC without TA coating. This indicates that tannic acid coating further mitigates the burst release effect of the drug and achieves prolonged release.

[0112] A comparison of Comparative Example 2 (EB@EC) and Example 1 (EB@EC-TA) shows that, after coating with tannic acid, the release rate of EB@EC-TA after 24 hours was reduced by approximately 20.34 percentage points compared to EB@EC. This is mainly attributed to the dense coating layer formed by tannic acid on the surface of EB@EC, which increases the resistance to drug diffusion, thereby slowing down the release rate of abamectin from the nanoparticles. This sustained-release characteristic is beneficial for prolonging the duration of drug action and reducing the frequency and dosage of pesticide application.

[0113] Based on the test results of Examples 1 and 6-9, it can be seen that for tannic acid coating conditions, when the tannic acid concentration is 1 mg / mL, the buffer pH is 8.5, and the stirring time is 12 h (Example 1), the resulting composite nano-drug delivery system EB@EC-TA has a uniform and dense surface coating layer, resulting in the best sustained-release effect. If the tannic acid concentration is too low (Example 6, 0.5 mg / mL), the coating layer is incomplete, and the release rate is relatively fast; if the tannic acid concentration is too high (Example 7, 2.0 mg / mL), the coating layer is too thick, which may lead to slow initial release, but may result in burst release later due to uneven coating layer. When the buffer pH is decreased to 8.0 (Example 8) or increased to 9.0 and the stirring time is shortened to 10 h (Example 9), the coating efficiency decreases, and the release rate increases compared to Example 1, further confirming the importance of optimal coating conditions.

[0114] 5. Adhesion of plant leaves: A simulated rain test was conducted: EB (1 mg / mL), EB@EC nanoparticles, and the EB@EC-TA composite nanoparticle drug delivery system solution were uniformly sprayed onto the surface of cabbage leaves. After the solutions on the leaves air-dried, the leaves were tilted at 45°, and deionized water was dripped onto the leaves at a rate of 5 mL / min for 2 min. After air-drying again, the residue of nanoparticles on the surface of the cabbage leaves was observed using a cold field emission scanning electron microscope (SEM, Regulus 8100, Hitachi, Tokyo, Japan).

[0115] Table 7. Residual nanoparticles on the surface of cabbage leaves after different rinsing cycles.

[0116] Combined with Table 7, Figure 5 The test results showed that, without rinsing (0 times), the EB technical grade of Comparative Example 1, the EB@EC nanoparticles of Comparative Example 2, and the EB@EC-TA composite nanoparticle system of Example 1 were all widely distributed on the surface of cabbage leaves. After 5 simulated rain washes, the EB technical grade particles of Comparative Example 1 were significantly lost, with only scattered distribution remaining; some EB@EC particles of Comparative Example 2 detached, but many spherical particles remained attached; only a small amount of EB@EC-TA particles of Example 1 detached, with a large number of particles still attached to the leaf surface. After 10 washes, the leaf surface of the EB technical grade group of Comparative Example 1 had almost no particle residue; the leaf surface of the EB@EC grade group of Comparative Example 2 still had a small amount of particle residue, but the distribution area was small; while the leaf surface of the EB@EC-TA grade group of Example 1 still had a large number of particles adhering, mainly distributed in the folded areas of the leaves, indicating that it has excellent rain wash resistance.

[0117] A comparison of Comparative Example 2 (EB@EC) and Example 1 (EB@EC-TA) shows that, after being coated with tannic acid, the composite nano-drug-carrying system EB@EC-TA exhibits significantly higher adhesion on the leaf surface than the unmodified nano-drug-carrying particles EB@EC, with a larger distribution area and significantly enhanced resistance to rain erosion. This is mainly attributed to two factors: firstly, the surface of Chinese cabbage leaves contains numerous wrinkled structures, and EB@EC-TA is primarily distributed in these areas, indicating that it can utilize the microstructure of the leaf surface to enhance adhesion performance; secondly, the waxy layer of Chinese cabbage leaves is rich in hydroxyl groups, while the surface of EB@EC-TA contains multiple phenolic hydroxyl groups, which can interact through hydrogen bonds, further enhancing its adhesion to the leaf surface.

[0118] 6. Standard Curve: First, weigh 5 mg of EB technical and dilute to a 50 mL volumetric flask with methanol to obtain an EB-methanol stock solution with a concentration of 100 mg / L. Then, dilute the stock solution to prepare a series of standard solutions with concentrations of 5 mg / L, 10 mg / L, 15 mg / L, 20 mg / L, and 25 mg / L. Measure the absorbance of the standard solutions at 245 nm using a UV-2450 spectrophotometer (Shimadzu Enterprise Management Co., Ltd., China) to plot a standard curve for EB.

[0119] Table 8. Standard curve of abamectin in 100% methanol

[0120] 7. Contact angle detection: The contact angle was measured using the seated drop method with a Krüss DSA100 contact angle meter at room temperature (25±1°C) and relative humidity (50%±5%). Fresh cabbage leaves were cut into 2cm×2cm squares, fixed to glass slides with double-sided tape, and the surfaces were kept flat. The samples from the comparative and example studies were prepared into suspensions of 0.5 mg / mL with deionized water, ultrasonically dispersed for 5 min, and then 2 μL of the test droplet was drawn up using a microsyringe and dropped vertically onto the surface of the cabbage leaf (avoiding the veins). Images of the droplet were captured at the instant of contact (0s) and 150s later. The contact angle was calculated by fitting the droplet profile based on the Young-Laplace equation using the instrument's software. Each sample was measured five times at different locations on the leaf, and the average value was taken as the final contact angle. The change in contact angle during dynamic spreading was also recorded. ( ) to evaluate the wetting and spreading behavior of each sample on the leaf surface.

[0121] Table 9 Contact Angle Test Results

[0122] The composite nanoparticle drug delivery system prepared in this application (Example 1) showed a contact angle on the cabbage leaf surface that decreased from an initial 54.27° to 47.13° after 150 s, less than 50°, significantly lower than that of Comparative Example 1 (82.30°) of emamectin benzoate technical grade and Comparative Example 2 (65.20°) of unmodified EB@EC nanoparticles. The contact angle data indicates that tannic acid interface modification endows the nanoparticle drug delivery system with excellent leaf wettability and dynamic spreading ability. This not only facilitates uniform coverage of the drug solution on the target leaf surface but also provides a direct physicochemical basis for its resistance to rain washout. The smaller the contact angle and the more complete the spreading, the stronger the interaction between the nanoparticles and the leaf surface, and the higher the drug retention rate. These results are highly consistent with simulated rain washout experiments, confirming the significant advantages of this nanoparticle drug delivery system in efficient leaf delivery.

[0123] The contact angle test results above show that the nano-drug delivery system prepared in this invention exhibits excellent wettability and rain erosion resistance on the surface of Chinese cabbage leaves. Its wettability is significantly better than that of the EB technical material in Comparative Example 1 and the unmodified EB@EC in Comparative Example 2.

[0124] 8. Light stability test Each sample was diluted with deionized water to a bacitracin concentration of 1000 mg / L. 1 mL of this diluted solution was evenly spread onto a 9 cm diameter glass petri dish and allowed to air dry in a dark environment. The petri dishes were then irradiated 30 cm directly below a 36W UV lamp. Samples were taken before irradiation (0 h) and at 12 h, 24 h, 40 h, 60 h, 100 h, and 120 h after irradiation. The residual active ingredient in the petri dishes was eluted with methanol and extracted. Its content was determined by high-performance liquid chromatography (HPLC), and the photodegradation rate of bacitracin was calculated using the formula.

[0125] Photodegradation rate (%) = (Active component content before irradiation - Active component content after irradiation) / Active component content before irradiation × 100%; Table 10 Results of photostability tests for nano-pesticides

[0126] The experimental results show that the photodegradation rate of the composite nano-drug delivery system EB@EC-TA (prepared in Example 1) prepared in this application after irradiation with ultraviolet light for 12h, 24h, 40h, 60h, 100h and 120h is significantly lower than that of Comparative Example 1 and Comparative Example 2. Among them, after 120h of ultraviolet light irradiation, the photodegradation rate of Example 1 is only 42.0%, which is much lower than that of Comparative Example 2 (78.0%) and Comparative Example 1 (93.0%), indicating that the tannic acid interface modified emamectin benzoate nano-drug delivery system prepared in this application has excellent photostability.

[0127] Application Example 1: Field efficacy trial for controlling fall armyworm Experimental location: Selected areas with concentrated Chinese cabbage planting, where the soil fertility is uniform and water and fertilizer management is consistent.

[0128] The test crop was Chinese cabbage (Brassica rapa L.), which had grown to the rosette stage.

[0129] The tested pest was the 2nd to 3rd instar larvae of the fall armyworm (Spodoptera frugiperda), which occurred naturally in the field with a uniform population density.

[0130] Experimental design: There were 3 treatment groups (Example 1, Comparative Example 1, Comparative Example 2) and 1 water blank control. Each treatment was repeated 3 times, for a total of 12 plots, arranged in randomized block design, with each plot area of ​​20m².

[0131] Application method: Use a backpack sprayer to spray evenly. The effective ingredient dosage for each treatment is 15 g ai / hm². Apply once at the early stage of fall armyworm larval emergence (peak of the 2nd to 3rd instar). During the experiment, record the temperature, precipitation, and wind speed daily. There was no rainfall within 24 hours after application, and the average temperature was comparable to that of the same period in previous years.

[0132] Survey method: Ten cabbages were surveyed at a fixed point in each plot, and the number of live insects was recorded. The initial insect population was surveyed before the pesticide was applied, and the number of remaining live insects was surveyed 1 day, 3 days, 7 days, and 14 days after the pesticide was applied.

[0133] Calculation formula: Insect population reduction rate (%) = (Number of live insects before treatment - Number of live insects after treatment) / Number of live insects before treatment × 100%; Control efficacy (%) = (Pest population reduction rate in the treated area - Pest population reduction rate in the blank control area) / (100 - Pest population reduction rate in the blank control area) × 100%; Table 11 Results of field efficacy trials of nano-pesticides for controlling fall armyworm.

[0134] The composite nano-loaded drug delivery system EB@EC-TA (prepared in Example 1) prepared in this application showed higher control efficacy than Comparative Example 1 and Comparative Example 2 at 1 day, 3 days, 7 days and 14 days after application, indicating that the composite nano-loaded drug delivery system prepared in this application has better field insecticidal effect.

[0135] Application Example 2: Field efficacy trial for controlling beet armyworm Test crop: Lettuce (Lactuca sativa L.), from rosette stage to vigorous growth stage; The tested pests were 2nd to 3rd instar larvae of the beet armyworm, which occurred naturally in the field with a uniform population density. Experimental design: Three treatments (Example 1, Comparative Example 1, Comparative Example 2) and one water control were set up. Each treatment was repeated three times in a randomized block design with a plot area of ​​20 m². Application method: Spray evenly using a backpack sprayer. The dosage of active ingredient for each treatment was 15 g ai / hm². During the experiment, temperature, precipitation, and wind speed were recorded daily. There was no rainfall within 24 hours after application, and the average temperature was comparable to that of the same period in previous years.

[0136] Survey method: Ten plants were surveyed at each plot, and the number of live insects was recorded. The initial insect population was surveyed before the pesticide was applied, and the number of remaining live insects was surveyed 1 day, 3 days, 7 days, and 14 days after the pesticide was applied. Calculation formula: Same as in application example 1; Table 12 Results of field efficacy trials of nano-pesticides for controlling beet armyworm

[0137] The composite nano-loaded drug delivery system EB@EC-TA (prepared in Example 1) prepared in this application showed higher control efficacy than Comparative Example 1 and Comparative Example 2 at 1 day, 3 days, 7 days and 14 days after application, indicating that the composite nano-loaded drug delivery system prepared in this application has better field insecticidal effect.

[0138] Application Example 3: Field efficacy trial for controlling cabbage caterpillars Experimental location: Celery growing area, a region where cabbage caterpillars occur year-round.

[0139] The test crop was celery (Apium graveolens L.) during its vigorous growth period.

[0140] The tested pest was the cabbage caterpillar (Pieris rapae) 3rd-4th instar larvae, which occurred naturally in the field with a uniform population density.

[0141] Experimental design: Three treatments (Comparative Example 1, Comparative Example 2, and Example 1) and one water control were set up. Each treatment was repeated three times in a randomized block design with an area of ​​20 m² per plot.

[0142] Application method: A backpack sprayer was used for uniform spraying. The effective ingredient dosage for each treatment was 15 g ai / hm². One application was made during the peak larval stage of the cabbage caterpillar. Temperature, precipitation, and wind speed were recorded daily during the experiment. No rainfall occurred within 24 hours after application, and the average temperature was comparable to the same period in previous years.

[0143] Survey method: Five samples were taken from each plot, and 10 celery plants were surveyed to count the number of live insects on each plant. The initial insect population was surveyed before the pesticide was applied, and the number of remaining live insects was surveyed 1, 3, 7 and 14 days after the pesticide was applied.

[0144] Calculation formula: Same as in application example 1; Table 13 Results of field efficacy trials of nano-pesticides for controlling cabbage caterpillars

[0145] The composite nano-loaded drug delivery system EB@EC-TA (prepared in Example 1) prepared in this application showed higher control efficacy than Comparative Example 1 and Comparative Example 2 at 1 day, 3 days, 7 days and 14 days after application, indicating that the composite nano-loaded drug delivery system prepared in this application has better field insecticidal effect.

[0146] Application Example 4: Field efficacy trial for controlling corn borer Experiment location: Corn-growing areas, regions where corn borers occur year-round.

[0147] The tested crop was maize (Zea mays L.), from the tasseling stage to the heading stage.

[0148] The tested pest was the larvae of the corn borer (Ostrinia nubilalis), which occurred naturally in the field.

[0149] Experimental design: Three treatments (Comparative Example 1, Comparative Example 2, and Example 1) and one water control were set up. Each treatment was repeated three times in a randomized block design with a plot area of ​​30 m².

[0150] Application method: Use a backpack sprayer to evenly spray the whorl and ear of corn. The effective ingredient dosage for each treatment is 15 g ai / hm². Apply once during the peak hatching period of corn borer eggs to the early larval stage. Record temperature, precipitation, and wind speed daily during the experiment. There was no rainfall within 24 hours after application, and the average temperature was similar to that of the same period in previous years.

[0151] Survey method: Five samples were taken from each plot, and 50 corn plants were surveyed. The number of live insects remaining was investigated before, 1 day, 3 days, 7 days and 14 days after the application of pesticide.

[0152] Calculation formula: Same as in application example 1; Table 14 Results of field efficacy trials of nano-pesticides for controlling corn borers

[0153] The composite nano-loaded drug delivery system EB@EC-TA (prepared in Example 1) prepared in this application showed higher control efficacy than Comparative Example 1 and Comparative Example 2 at 1 day, 3 days, 7 days and 14 days after application, indicating that the composite nano-loaded drug delivery system prepared in this application has better field insecticidal effect.

[0154] Application Example 5: Chlorantraniliprole for the control of diamondback moth Experimental subject: Diamondback moth (Plutella xylostella); Test reagent: The test reagent was the nano-pesticide prepared in Example 13, with water as a blank control; Application method: Dilute the test agent to 1000 times and spray it evenly on both sides of the cabbage leaves; Investigation methods: Before applying pesticides, the baseline insect population was investigated. After applying pesticides, the number of remaining live insects was investigated at 1, 3, 7 and 14 days. The insect population reduction rate and control effect were calculated.

[0155] Table 15 Results of field efficacy trials of nano-pesticides for controlling diamondback moth.

[0156] The composite nano-drug delivery system CAP@EC-TA (prepared in Example 13) prepared in this application has good field insecticidal effect.

[0157] Application Example 6: Tebuconazole for the control of powdery mildew Test subject: Wheat powdery mildew; Test reagent: The test reagent was the nano-pesticide prepared in Example 14, with water as a blank control; Application method: Dilute the test agent to a 3000-fold dilution, and spray it with water at the early stage of powdery mildew disease. Repeat the application twice at 7-day intervals. Investigation method: Disease index was investigated 1 day, 3 days, 7 days and 14 days after the last application of the drug, and the control effect was calculated; Table 16 Results of field efficacy trials of nano-pesticides for controlling diamondback moth

[0158] The composite nano-drug delivery system TEB@EC-TA (prepared in Example 14) prepared in this application has good field insecticidal effect.

[0159] This application provides a leaf-based adhesive nano-drug delivery system based on antisolvent precipitation, its preparation method, and its application. Many methods and approaches exist for implementing this technical solution; the above description is merely a preferred embodiment of the invention. It should be noted that those skilled in the art can make various improvements and modifications without departing from the principles of the invention, and these improvements and modifications should also be considered within the scope of protection of this invention. All components not explicitly stated in this embodiment can be implemented using existing technologies.

Claims

1. A method for constructing a leaf-adhesive nanopesticide delivery system based on antisolvent precipitation, characterized in that: Includes the following steps: A mixture of pesticide and slow-release carrier material is dropped into an antisolvent to obtain drug-loaded nanoparticles; then, plant polyphenols are used to modify the interface of the drug-loaded nanoparticles to obtain a composite drug-loaded nanoparticle system.

2. The method for constructing a leaf-adhesive nanopesticide delivery system based on antisolvent precipitation according to claim 1, characterized in that: The sustained-release carrier material includes at least one of ethyl cellulose and polylactic acid-glycolic acid copolymer; The pesticide includes at least one of macrolides, diamides, and triazoles; The antisolvent is water.

3. The method for constructing a leaf-adhesive nanopesticide delivery system based on antisolvent precipitation according to claim 1, characterized in that: The plant polyphenols include at least one of tannic acid, gallic acid, and tea polyphenols.

4. The method for constructing a leaf-adhesive nanopesticide delivery system based on antisolvent precipitation according to claim 1, characterized in that: The mass ratio of the slow-release carrier material to the pesticide is 1:0.5 to 1:2; The concentration of the mixture is 20~50 mg / mL; The volume ratio of the mixture to the antisolvent is 1:5 to 1:

8.

5. A method for constructing a leaf-adhesive nanopesticide delivery system based on antisolvent precipitation according to any one of claims 1-4, characterized in that: Includes the following steps: (1) Dissolve the pesticide and the slow-release carrier material in an organic solvent to obtain a mixture; (2) The mixture is added dropwise into the antisolvent, stirred to form a suspension, and after the solvent is removed, it is separated by solid-liquid separation and dried to obtain nano-drug-loaded particles; (3) Add the drug-loaded nanoparticles to a buffer solution containing plant polyphenols and stir. After solid-liquid separation and drying, a composite drug-loaded nanoparticle system is obtained.

6. The method for constructing a leaf-adhesive nanopesticide delivery system based on antisolvent precipitation according to claim 5, characterized in that: In step (1), the organic solvent includes at least one of ethanol, methanol, and N,N-dimethylformamide.

7. The method for constructing a leaf-adhesive nanopesticide delivery system based on antisolvent precipitation according to claim 5, characterized in that: In step (2), the mixture is added dropwise to the antisolvent at a rate of 3-9 mL / min; During the stirring process, the stirring speed is 400~600 r / min; During the solvent removal process, the reaction temperature is 40~50℃.

8. The method for constructing a leaf-adhesive nanopesticide delivery system based on antisolvent precipitation according to claim 5, characterized in that: In step (3), the buffer solution containing plant polyphenols is Tris-HCl buffer solution with a concentration of 50~150mM and a pH of 8.0~9.

0. The concentration of plant polyphenols in the buffer solution containing plant polyphenols is 0.5~2 mg / mL; During the stirring process, the stirring temperature is 20~30℃ and the stirring time is 10~14 hours; During the solid-liquid separation process, a centrifuge is used for separation, with a centrifugation speed of 9000~10000 rpm and a centrifugation time of 15~25 min.

9. A leaf-adhesive nanopesticide delivery system based on antisolvent precipitation, characterized in that: It is constructed by the method described in any one of claims 1-8.

10. The application of the leaf-adhesive nanopesticide delivery system based on antisolvent precipitation method as described in claim 9 in the preparation of pesticide formulations for the control of plant diseases and pests.

Images