A method for preparing tannic acid-amino acid nano-pesticide microcapsules by ultrasonic-assisted emulsification cross-linking and application

Abstract

The application discloses a method for preparing tannic acid-amino acid nano pesticide microcapsules by using ultrasonic wave assisted emulsification cross-linking method and application thereof, and belongs to the technical field of pesticide preparation processing and pest control. In the application, tannic acid, amino acid and sodium dodecyl sulfate are dissolved in deionized water to prepare an aqueous phase. Then, an organic solvent is used to dissolve a pesticide active ingredient, and the pesticide active ingredient is added into the aqueous phase. After ultrasonic treatment, glutaraldehyde is added under magnetic stirring to perform cross-linking reaction. Finally, centrifugation, washing and freeze-drying are performed, and the nano pesticide microcapsules are obtained. Compared with traditional pesticide preparations, the nano pesticide microcapsules have uniform particle size, simple synthesis equipment, small amount of organic auxiliary agent, and can slowly release the pesticide active ingredient. The nano pesticide microcapsules have excellent control effect on rice sheath blight and diamondback moth and other pests, can prolong the pesticide effective period, reduce the pesticide application frequency and amount, and have a wide application prospect in pest control.

Description

Technical Field

[0001] This invention relates to the field of pesticide formulation processing and pest and disease control technology, and more specifically to a method and application for preparing tannic acid-amino acid nanopesticide microcapsules using an ultrasonic-assisted emulsification crosslinking method. Background Technology

[0002] Pesticide formulations play an irreplaceable role in agricultural production, with traditional formulations such as emulsifiable concentrates, suspension concentrates, and powders long dominating the market. However, these formulations have significant limitations: on the one hand, the active ingredients are easily degraded by environmental factors (sunlight, rainwater erosion), resulting in a short duration of effectiveness, requiring frequent application to maintain efficacy; high doses and frequent application not only increase the risk of crop damage and residues but also accelerate the evolution of resistance in pathogenic microorganisms such as sheath blight and pests such as diamondback moths. On the other hand, the large amounts of organic solvents or adjuvants in formulations can easily cause environmental pollution and pesticide residue risks, posing potential threats to the environment and the health of operators, and are no longer able to meet the urgent needs of modern agriculture for green, efficient, and low-carbon plant protection technologies.

[0003] To overcome the aforementioned drawbacks, microencapsulation technology has gradually attracted attention. Current microcapsules mostly use synthetic polymer materials (such as polyurea, polyamide, cyclodextrin, and melamine resin) as wall materials. While these can delay pesticide release, they suffer from poor biocompatibility, uncontrollable degradation cycles, and low deposition rates at target sites due to poor leaf surface affinity. In recent years, attempts have been made to introduce biomaterials (such as proteins and polysaccharides), but these methods suffer from complex preparation processes, uneven particle size, and low drug loading rates.

[0004] Therefore, how to develop a novel microcapsule system that is environmentally friendly and has controllable release behavior is a technical problem that urgently needs to be solved by those skilled in the art. Summary of the Invention

[0005] In view of this, the present invention provides a method and application for preparing tannic acid-amino acid nanopesticide microcapsules using an ultrasonic-assisted emulsification crosslinking method.

[0006] However, achieving the above goals faces several technical challenges: First, the cross-linking reaction conditions between tannic acid and amino acids are demanding, and conventional stirring and emulsification are insufficient to form stable and uniform nanoscale wall materials; second, traditional microcapsule preparation often relies on large amounts of organic solvents and cumbersome solvent replacement steps, which not only increases the environmental burden but also easily leads to wide particle size distribution and poor batch repeatability; third, how to endow microcapsules with controllable pH-responsive release behavior while ensuring high drug loading rate without using synthetic polymer materials is a bottleneck that has not yet been solved by existing technologies. To address these challenges, this invention creatively employs an ultrasonic-assisted emulsification cross-linking method. Utilizing the instantaneous strong shear force and microjets generated by ultrasonic cavitation, the size of the emulsion droplets is significantly reduced and a narrow distribution is achieved, while simultaneously promoting rapid cross-linking of tannic acid and amino acids into a shell under mild conditions. This method requires only a small amount of organic solvent to dissolve and disperse pesticides, eliminating the need for complex replacement steps. It overcomes the dependence of traditional cross-linking reactions on stringent conditions, making the preparation process of nanocapsules simple, controllable, and environmentally friendly, and endowing the microcapsules with excellent pH-sensitive release characteristics.

[0007] This invention provides a rapid, mild method for preparing nanopesticide microcapsules without complex solvent replacement steps, addressing the problems of cumbersome preparation processes, large amounts of organic solvents, and poor biocompatibility of wall materials in existing nanopesticide microcapsule technologies. The nanopesticide microcapsules of this invention exhibit pH-sensitive properties, significantly extending the duration of action and reducing the frequency of application while enhancing the control efficacy against multiple targets (diseases and pests), thus overcoming the limitations of both traditional pesticide formulations and existing microcapsule technologies.

[0008] This invention utilizes the cavitation effect of ultrasound and the shear force of magnetic stirring to disperse an organic oil phase containing pesticides into nanoscale droplets, and uses sodium dodecyl sulfate in the aqueous phase as an emulsifier to stabilize the emulsion. Tannic acid and amino acids dissolved in the aqueous phase undergo two covalent reactions under the cross-linking action of glutaraldehyde: ① the aldehyde group of glutaraldehyde forms a Schiff base with the amino group of the amino acid; ② the aldehyde group of glutaraldehyde undergoes phenol-aldehyde condensation with the active hydrogen on the phenolic ring of tannic acid. These two cross-linking reactions preferentially occur at the oil-water interface, rapidly forming an insoluble, three-dimensionally cross-linked "tannic acid-amino acid" copolymer shell on the surface of the oil droplets. This shell completely encapsulates the internal pesticide oil phase. Subsequent centrifugal washing removes unreacted substances and organic solvents, and freeze-drying yields nanocapsules with a core-shell structure for pesticides.

[0009] To solve the above-mentioned technical problems, the present invention adopts the following technical solution: A method for preparing tannic acid-amino acid nanopesticide microcapsules using ultrasound-assisted emulsification crosslinking includes the following steps: (1) Dissolve tannic acid powder, amino acid powder and sodium dodecyl sulfate powder in deionized water and stir thoroughly until completely dissolved to obtain an aqueous phase; (2) Dissolve the active ingredient of the pesticide in an organic solvent, add it to the aqueous phase described in step (1), and sonicate to obtain an oil-in-water nanoemulsion; (3) Under magnetic stirring conditions, add glutaraldehyde aqueous solution to the water-in-oil nanoemulsion described in step (2) to carry out cross-linking reaction, stir magnetically, then centrifuge, wash, freeze dry to obtain nano-pesticide microcapsules.

[0010] Furthermore, in step (1), the concentration of tannic acid is 8 mmol / L to 10 mmol / L, the concentration of amino acids is 32 mmol / L to 100 mmol / L, and the concentration of sodium dodecyl sulfate is 0.3% to 0.6%; the reaction temperature is 20 to 40 ℃, and the stirring speed is 600 to 1000 r / min.

[0011] Furthermore, in step (2), the ultrasonic treatment time is 3 to 6 minutes.

[0012] Furthermore, the amino acid is one or more selected from glutamine, phenylalanine, cysteine, asparagine, glycine, and aminobutyric acid.

[0013] Furthermore, the active ingredient of the pesticide is a fungicide or an insecticide; The fungicide is one or more of the following: tebuconazole, azoxystrobin, thifluzamide, carbendazim, difenoconazole, and isoprothiolane; The insecticide is one or more of the following: indoxacarb, chlorfenapyr, chlorantraniliprole, emamectin benzoate, lambda-cyhalothrin, and lufenuron.

[0014] Furthermore, the organic solvent is one or more of dichloromethane, xylene, and ethyl acetate.

[0015] Furthermore, the amount of glutaraldehyde added is 1 wt% to 2 wt% of the solution mass ratio in step (1), and the concentration of glutaraldehyde is 5% to 20%.

[0016] Furthermore, the magnetic stirring parameters in step (3) are: stirring time of 30 min to 4 h and stirring speed of 600 to 1200 r / min.

[0017] Nanopesticide microcapsules prepared by the above method.

[0018] The above-mentioned application of nano-pesticide microcapsules in the prevention and control of pests and diseases.

[0019] As can be seen from the above technical solution, compared with the prior art, the present invention has the following beneficial effects: (1) The nano-pesticide microcapsules of the present invention are prepared by ultrasonic-assisted emulsification and interfacial cross-linking, which is simple in preparation process, low in production cost, uniform in particle size and high in pesticide loading.

[0020] (2) The shell formed by covalent cross-linking, rather than physical adsorption or hydrogen bond assembly, provides strong encapsulation of pesticides and significantly reduces the problem of burst release during storage and use.

[0021] (3) The tannic acid cross-linked amino acid used has pH-sensitive properties in the capsule wall, which can control the release of the drug, reduce the unnecessary release of pesticide active ingredients on crop leaves, and achieve precise release in the body of pests or the site of pathogen infection, thereby prolonging the duration of effect.

[0022] (4) The nano-pesticide microcapsules of the present invention can be loaded with a variety of poorly soluble pesticides. By loading fungicides or insecticides, they can achieve efficient control of diseases such as sheath blight and pests such as diamondback moth. They have broad application prospects in the field of green pest control. Attached Figure Description

[0023] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on the provided drawings without creative effort.

[0024] Figure 1 The images show scanning electron microscope (SEM) images of the nanocapsules prepared in Examples 1 to 6 of Experiment 1 of this invention. Specifically, a is the tannic acid-glycine nanocapsule prepared in Example 1; b is the tannic acid-glycine-loaded tebuconazole nanocapsule prepared in Example 2; c is the tannic acid-phenylalanine-loaded azoxystrobin nanocapsule prepared in Example 3; d is the tannic acid-aminobutyric acid-loaded chlorfenapyr nanocapsule prepared in Example 4; e is the tannic acid-glutamine-loaded indoxacarb nanocapsule prepared in Example 5; and f is the tannic acid-aminobutyric acid-loaded lambda-cyhalothrin nanocapsule prepared in Example 6.

[0025] Figure 2 This is a scanning electron microscope image of the nanopesticide microcapsules prepared in Comparative Example 1 of this invention.

[0026] Figure 3 This is a scanning electron microscope image of the nanopesticide microcapsules prepared in Comparative Example 2 of this invention.

[0027] Figure 4 The cumulative release rate of the tannic acid-glutamine nanopesticide microcapsules synthesized in Example 5 of Experiment 5 of this invention is measured under pH 5, pH 7, and pH 9 conditions. Detailed Implementation

[0028] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0029] Example 1 A method for preparing tannic acid-glycine nanocapsules (without loading pesticide active ingredients) using ultrasound-assisted emulsification crosslinking, the specific steps of which are as follows: (1) Dissolve tannic acid powder (0.5 mmol), L-glycine powder (2 mmol), and sodium dodecyl sulfate powder (0.2 g) in 50 mL of deionized water. Stir at 600 r / min at 25 °C until completely dissolved to obtain an aqueous solution containing tannic acid (concentration 10 mmol / L), L-glycine (concentration 40 mmol / L), and sodium dodecyl sulfate (concentration 0.4%).

[0030] (2) Under magnetic stirring at 600 r / min, 0.5 mL of dichloromethane was slowly added to the aqueous phase obtained in step (1), and ultrasonic treatment was performed for 5 min to form a stable oil-in-water nanoemulsion.

[0031] (3) Slowly add 5 mL of glutaraldehyde (10% concentration) to the water-in-oil nanoemulsion in step (2) for crosslinking, and stir at 600 r / min for 60 min at 25 ℃. Then, centrifuge at 15000 r / min for 3 min to collect the nanocapsule particles, wash with deionized water and centrifuge 3 times, and then dry using a freeze dryer to obtain nanocapsules.

[0032] Example 2 A method for preparing tannic acid-glycine-supported tebuconazole nanopesticide microcapsules using ultrasound-assisted emulsification crosslinking, the specific steps of which are as follows: (1) Dissolve tannic acid powder (0.5 mmol), L-glycine powder (2 mmol), and sodium dodecyl sulfate powder (0.2 g) in 50 mL of deionized water. Stir at 600 r / min at 25 °C until completely dissolved to obtain an aqueous solution containing tannic acid (concentration 10 mmol / L), L-glycine (concentration 40 mmol / L), and sodium dodecyl sulfate (concentration 0.4%).

[0033] (2) Dissolve 0.2 g of tebuconazole technical in 0.5 mL of dichloromethane to form an oil phase; under magnetic stirring at 600 r / min, slowly add the oil phase to the aqueous phase obtained in step (1) and sonicate for 5 min to form a stable oil-in-water nanoemulsion.

[0034] (3) Slowly add 5 mL of glutaraldehyde (10% concentration) to the water-in-oil nanoemulsion in step (2) for crosslinking, and stir at 600 r / min for 60 min at 25 ℃. Then, centrifuge at 15000 r / min for 3 min to collect the nanocapsule particles, wash with deionized water and centrifuge 3 times, and then dry using a freeze dryer to obtain nano-pesticide microcapsules.

[0035] The nanopesticide microcapsules prepared in this embodiment can be used for the prevention and control of rice sheath blight. Example 3

[0036] A method for preparing tannic acid-phenylalanine-loaded azoxystrobin nanopesticide microcapsules using an ultrasound-assisted emulsification crosslinking method, the specific steps of which are as follows: (1) Dissolve tannic acid powder (0.4 mmol), L-phenylalanine powder (1.6 mmol), and sodium dodecyl sulfate powder (0.15 g) in 50 mL of deionized water. Stir at 800 r / min at 40 °C until completely dissolved to obtain an aqueous solution containing tannic acid (concentration 8 mmol / L), L-phenylalanine (concentration 32 mmol / L), and sodium dodecyl sulfate (concentration 0.3%).

[0037] (2) Dissolve 0.3 g of azoxystrobin technical in 0.5 mL of dichloromethane to form an oil phase; under magnetic stirring at 800 r / min, slowly add the oil phase to the aqueous phase obtained in step (1) and sonicate for 3 min to form a stable oil-in-water nanoemulsion.

[0038] (3) Slowly add 5 mL of glutaraldehyde (concentration of 20%) to the water-in-oil nanoemulsion in step (2) for crosslinking, and stir at 800 r / min for 30 min at 25 ℃. Then, centrifuge at 15000 r / min for 3 min to collect the nanocapsule particles, wash with deionized water and centrifuge 3 times, and then dry using a freeze dryer to obtain nano-pesticide microcapsules.

[0039] The nanopesticide microcapsules prepared in this embodiment can be used for the prevention and control of rice sheath blight. Example 4

[0040] A method for preparing tannic acid-aminobutyric acid-loaded chlorfenapyr nanopesticide microcapsules using ultrasound-assisted emulsification crosslinking, the specific steps of which are as follows: (1) Dissolve tannic acid powder (0.5 mmol), γ-aminobutyric acid powder (3 mmol), and sodium dodecyl sulfate powder (0.3 g) in 50 mL of deionized water. Stir at 600 r / min at 20 °C until completely dissolved to obtain an aqueous solution containing tannic acid (concentration 10 mmol / L), γ-aminobutyric acid (concentration 60 mmol / L), and sodium dodecyl sulfate (concentration 0.6%).

[0041] (2) Dissolve 0.2 g of chlorfenapyr technical in 0.5 mL of ethyl acetate to form an oil phase; under magnetic stirring at 600 r / min, slowly add the oil phase to the aqueous phase obtained in step (1) and sonicate for 3 min to form a stable oil-in-water nanoemulsion.

[0042] (3) Slowly add 10 mL of glutaraldehyde (5% concentration) to the water-in-oil nanoemulsion in step (2) for crosslinking, and stir at 600 r / min for 60 min at 25 ℃. Then, centrifuge at 15000 r / min for 3 min to collect the nanocapsule particles, wash with deionized water and centrifuge 3 times, and then dry using a freeze dryer to obtain nano-pesticide microcapsules.

[0043] The nanopesticide microcapsules prepared in this embodiment can be used for the control of diamondback moth. Example 5

[0044] A method for preparing tannic acid-glutamine-loaded indoxacarb nanopesticide microcapsules using ultrasound-assisted emulsification crosslinking, the specific steps of which are as follows: (1) Dissolve tannic acid powder (0.4 mmol), L-glutamine powder (2 mmol), and sodium dodecyl sulfate powder (0.2 g) in 50 mL of deionized water. Stir at 800 r / min at 30 °C until completely dissolved to obtain an aqueous solution containing tannic acid (concentration 8 mmol / L), L-glutamine (concentration 40 mmol / L), and sodium dodecyl sulfate (concentration 0.4%).

[0045] (2) Dissolve 0.2 g of indoxacarb technical in 1 mL of dichloromethane to form an oil phase; under magnetic stirring at 400 r / min, slowly add the oil phase to the aqueous phase obtained in step (1) and sonicate for 6 min to form a stable oil-in-water nanoemulsion.

[0046] (3) Slowly add 10 mL of glutaraldehyde (10% concentration) to the water-in-oil nanoemulsion in step (2) for crosslinking, and stir at 600 r / min for 4 h at 25 ℃. Then, centrifuge at 15000 r / min for 3 min to collect the nanocapsule particles, wash with deionized water and centrifuge 3 times, and then dry using a freeze dryer to obtain nano-pesticide microcapsules.

[0047] The nanopesticide microcapsules prepared in this embodiment can be used for the control of diamondback moth. Example 6

[0048] A method for preparing tannic acid-aminobutyric acid-loaded high-efficiency cyhalothrin nanopesticide microcapsules using ultrasound-assisted emulsification crosslinking, the specific steps of which are as follows: (1) Dissolve tannic acid powder (0.5 mmol), γ-aminobutyric acid powder (5 mmol), and sodium dodecyl sulfate powder (0.25 g) in 50 mL of deionized water. Stir at 1000 r / min at 20 °C until completely dissolved to obtain an aqueous solution containing tannic acid (concentration 10 mmol / L), γ-aminobutyric acid (concentration 100 mmol / L), and sodium dodecyl sulfate (concentration 0.5%).

[0049] (2) Dissolve 0.2 g of high-efficiency cyhalothrin technical material in 1 mL of ethyl acetate to form an oil phase; under magnetic stirring at 1200 r / min, slowly add the oil phase to the aqueous phase obtained in step (1) and sonicate for 6 min to form a stable oil-in-water nanoemulsion.

[0050] (3) Slowly add 5 mL of glutaraldehyde (10% concentration) to the water-in-oil nanoemulsion in step (2) for crosslinking, and stir at 1200 r / min for 30 min at 25 ℃. Then, centrifuge at 15000 r / min for 3 min to collect the nanocapsule particles, wash with deionized water and centrifuge 3 times, and then dry using a freeze dryer to obtain nano-pesticide microcapsules.

[0051] The nanopesticide microcapsules prepared in this embodiment can be used for the control of diamondback moth.

[0052] Experiment 1

[0053] Electron microscopy was performed on the nanocapsules prepared in Examples 1 to 6, and the results are as follows: Figure 1As shown in the figure. SEM results indicate that the nanopesticide microcapsules formed by the self-assembly of tannic acid with different types of amino acids (e.g., L-glycine, L-phenylalanine, γ-aminobutyric acid, L-glutamine) all exhibit a uniform spherical morphology, but the morphology size and surface roughness vary slightly depending on the amino acid composition. Under the same conditions, the unloaded pesticide (Example 1) and pesticide-loaded (Example 2) microcapsules are spherical in shape and similar in size, indicating that drug loading does not affect the formation of the microcapsules.

[0054] Comparative Example 1

[0055] Only the glutaraldehyde concentration was changed; all other operations were the same as in Example 3. Details are as follows: In step (3), 5 mL of glutaraldehyde (concentration of 2.5%) is slowly added to the water-in-oil nanoemulsion of step (2) for crosslinking.

[0056] Because the concentration of added glutaraldehyde is low, irregularly shaped nanopesticide microcapsules are obtained, existing in irregular sheet-like, dendritic, and aggregated forms. The particle edges are uneven and the outline is tortuous, with some particles interconnected to form a porous aggregate network. Figure 2 ).

[0057] Comparative Example 2

[0058] Only the concentration of L-phenylalanine was changed; all other operations were the same as in Example 3. Specifically: In step (1), tannic acid powder (0.4 mmol), L-phenylalanine powder (0.75 mmol), and sodium dodecyl sulfate powder (0.15 g) were dissolved in 50 mL of deionized water and stirred thoroughly at 800 r / min until completely dissolved to obtain an aqueous solution containing tannic acid (concentration of 8 mmol / L), L-phenylalanine (concentration of 15 mmol / L), and sodium dodecyl sulfate (concentration of 0.3%).

[0059] Because the concentration of added L-phenylalanine was low, the resulting nanopesticide microcapsules had uneven particle sizes. Although there were a large number of spherical nanopesticide microcapsules, there were also many micron-sized sheet-like particles with uneven edges. Figure 3 ).

[0060] Experiment 2

[0061] Accurately weigh 20 mg of the lyophilized nanocapsule sample, add 20 mL of methanol, and sonicate to fully release the encapsulated pesticide into the solvent. After centrifugation and filtration through a 0.22 μm filter membrane, determine the pesticide concentration in the filtrate using high-performance liquid chromatography (HPLC). Substitute the results into a standard curve to calculate the pesticide mass. Calculate the pesticide loading rate of the nanocapsules prepared in Examples 2-6 according to the following formula.

[0062] Pesticide loading rate (%) = (mass of pesticide in microcapsules / total mass of microcapsules) × 100%.

[0063] The results are shown in Table 1.

[0064] This invention systematically measured the drug loading capacity of nanopesticide microcapsules under different preparation processes. The results showed that the drug loading capacity of each treatment remained at a high level, ranging from 19.82% to 23.27%, fully demonstrating the high drug loading capacity of this nanopesticide loading system. Example 6 showed the highest drug loading capacity, reaching 23.27 ± 0.39%, which was superior to other treatment groups, indicating that its preparation process had optimal efficiency in drug encapsulation and loading. The small standard deviation of the data for each group indicated that the experimental results had good repeatability and reliability, providing a solid material foundation for subsequent research on pesticide controlled-release performance and field applications.

[0065] Table 1. Drug loading rates of different nanopesticide microcapsules

[0066] Experiment 3 Field trials were conducted at the experimental field of Hainan University Danzhou Campus, Danzhou City, Hainan Province. The nano-pesticide microcapsules prepared in Examples 2 and 3, along with a commercially available brand of 43% tebuconazole suspension and 25% azoxystrobin suspension, were used to control rice sheath blight. Deionized water treatment served as a blank control group. Each plot was 30 m². 2 Each plot is separated by a 1-meter buffer zone.

[0067] Application method: The rice growth period is from jointing to booting stage. For Examples 2 and 3, the dosage of 43% tebuconazole suspension and 25% azoxystrobin suspension, calculated based on the active ingredient, is 96.75 g ha. -1 225 g ha -1 96.75 g ha -1 225 g ha -1 The effective ingredient of the nano-pesticide microcapsules was calculated according to the loading amount in Examples 2 and 3. The pesticide was applied once using a conventional electric sprayer. Each plot was a completely randomized design, repeated three times. No other insecticides or fungicides were applied during the experiment.

[0068] Investigation method: The five-point sampling method was used to investigate the number of diseased plants and the disease severity before application of the pesticide, and 7 days, 14 days and 21 days after application. A total of 25 clumps were investigated in each plot.

[0069] Disease grading standards: Grade 0: The entire plant is disease-free; Grade 1: Disease occurs on the fourth leaf and all leaf sheaths and leaves below it; Grade 3: Disease occurs on the third leaf and all leaf sheaths and leaves below it; Level 5: Disease occurs on the second leaf and all leaf sheaths and leaves below it; Level 7: Disease occurs on the sword-shaped leaf blade and all leaf sheaths and leaves below it; Level 9: The entire plant becomes infected and dies.

[0070] Disease index and prevention and control efficacy were calculated according to GB / T17980.20-2000 standard. The calculation method is as follows: Disease index = ∑(number of diseased plants at each level × corresponding value at each level) / (total number of diseased plants investigated × 9) × 100; Prevention and control effect (%) = [1 - (CK0 × PT1) / (CK1 × PT0)] × 100, where, CK0 and CK1 represent the disease indices before and after drug administration in the blank control area, respectively, while PT0 and PT1 represent the disease indices before and after drug administration in the treatment area, respectively.

[0071] Table 2 shows the disease index of rice sheath blight after treatment with 43% tebuconazole suspension and 25% azoxystrobin suspension in Examples 2 and 3.

[0072] Table 2 Disease Index

[0073] Note: The disease index data in the table were analyzed using one-way ANOVA combined with Tukey's HSD test. p < 0.05), data represent mean ± standard error (n=3).

[0074] Table 3 shows the control effects of Example 2, Example 3, 43% tebuconazole suspension, and 25% azoxystrobin suspension on rice sheath blight.

[0075] Table 3 Prevention and control effects

[0076] Note: The prevention and control effect data in the table were analyzed using one-way ANOVA combined with Tukey's HSD test. p < 0.05), data represent mean ± standard error (n=3).

[0077] As shown in Table 2, there was no significant difference in the disease index among the treatment groups before the drug was applied, and the groups were comparable. The disease index of the blank control group continued to rise over time, while all drug treatment groups could effectively inhibit the development of the disease. Among them, the disease index of the nano-pesticide microcapsule group (Example 2 and Example 3) increased much less than that of 43% tebuconazole suspension and 25% azoxystrobin suspension, and remained at a low level over time.

[0078] As shown in Table 3, in terms of control efficacy, Examples 2 and 3 are significantly superior to the two conventional agents. They not only demonstrated a high level of control at 7 days but also maintained a stable and efficient control effect from 14 to 21 days. In contrast, the efficacy of conventional suspension concentrates decreased to varying degrees over time, with the 25% azoxystrobin suspension concentrate showing the most significant decline. In summary, the nano-pesticide microcapsule formulation exhibits superior disease suppression ability and more sustained control effect in the control of rice sheath blight, significantly outperforming conventional suspension concentrates and possessing higher value for field application.

[0079] Experiment 4

[0080] Field trials were conducted at the experimental field of Hainan University Danzhou Campus, Danzhou City, Hainan Province. The nano-pesticide microcapsules prepared in Examples 4-6 were used, along with commercially available 10% chlorfenapyr suspension concentrate, 30% indoxacarb suspension concentrate, and 2.5% high-efficiency cyhalothrin emulsifiable concentrate, to control diamondback moths on cabbage under field conditions. Deionized water treatment served as a blank control group. Each plot was 30 m². 2 Each plot is separated by a 1-meter buffer zone.

[0081] Application method: During the cabbage's heading stage, the application dosages for Examples 4, 5, and 6, 10% chlorfenapyr suspension concentrate, 30% indoxacarb suspension concentrate, and 2.5% lambda-cyhalothrin emulsifiable concentrate, calculated based on the active ingredient, were 75 g / ha. -1 45 g ha -1 15 g ha -1 75 g ha -1 45 g ha -1 15 g ha -1 The effective ingredient loading of the nano-pesticide microcapsules was calculated according to the loading rates in Examples 4, 5, and 6. The pesticide was applied once using a conventional electric sprayer. Each plot was a completely randomized design, replicated three times. No other insecticides or fungicides were applied during the experiment.

[0082] Survey Method: After delineating each plot, a zigzag five-point sampling method was used to investigate the number of diamondback moths at each point. Twenty plants were randomly sampled from each plot, and the number of diamondback moths was recorded. The efficacy was calculated according to GB / T17980.13-2000 standard. Insect population reduction rate (%) = (Number of live insects before application - Number of live insects after application) / Number of live insects before application × 100; Prevention and control effect (%) = [(PT-CK) / (100-CK)] × 100, where, PT represents the insect population reduction rate in the pesticide-treated area; CK represents the insect population reduction rate in the blank control area.

[0083] The insect population reduction rate after treatment is shown in Table 4.

[0084] Table 4. Insect population reduction rate after treatment

[0085] Note: The insect population decline rate data in the table were analyzed using one-way ANOVA combined with Tukey's HSD test. p < 0.05), data represent mean ± standard error (n=3).

[0086] Table 5. Control efficacy against diamondback moth

[0087] Note: The data on prevention and control effectiveness in the table were analyzed using one-way ANOVA combined with Tukey's HSD test. p < 0.05), data represent mean ± standard error (n=3).

[0088] This invention evaluated the control effect of high-load nano-pesticide microcapsules on diamondback moth by measuring insect population reduction rate and field control efficacy. The results are shown in Tables 4 and 5. Three days after application, the insect population reduction rate in each nano-pesticide microcapsule treatment group reached 82.48%–88.33%, and the control efficacy reached 85.25%–90.54%. Example 5 showed the best performance, exceeding the control efficacy of three commercial pesticide formulations against diamondback moth. Seven days after application, the insect population reduction rate in the nano-pesticide microcapsule group stabilized at 88.79%–92.58%, and the control efficacy increased to 93.16%–95.40%. Examples 4 and 5 were significantly higher than the control efficacy of the three commercial pesticide formulations against diamondback moth. At 14 days, the insect population reduction rates of Examples 4, 5, and 6 reached 83.34%–95.98%, with control efficacy as high as 91.15%–97.88%. In contrast, the insect population reduction rates of commercially available pesticide formulations were only 58.55%–74.74%, and the control efficacy was only 78.35%–86.87%, both significantly lower than the examples treated with the same pesticide. In summary, compared with the control treatment, the nano-pesticide microcapsules prepared in Examples 4–6 significantly improved the control effect and duration of action against diamondback moth, providing technical support for pesticide reduction with increased efficiency and delayed resistance development, and demonstrating good prospects for field application.

[0089] Experiment 5

[0090] The cumulative release rate of the nanopesticide microcapsules prepared in Example 5 was evaluated under pH 5, pH 7, and pH 9 conditions using an RC-6 dissolution tester. For each experiment, 100 mg of microcapsules were suspended in 500 mL of ethanol-phosphate buffer (20:80, v / v) and stirred at 100 rpm. At time points 1, 2, 4, 8, 12, 16, 24, 36, and 48 h, 1.0 mL of sample was collected, and an equal volume of fresh medium was immediately added. The collected samples were centrifuged at 15000 rpm for 3 min, and the supernatant was used for quantitative determination by high-performance liquid chromatography (HPLC). Each condition was repeated three times. The cumulative release rate at time t was calculated using a formula with liquid replenishment correction.

[0091] Where V1 is the total volume of the release medium (500 mL), V2 is the volume of each sample (1 mL), Ct is the drug concentration in the sample taken at time t, and M is the total amount of drug loaded in a 100 mg sample.

[0092] The results are as follows Figure 4 As shown.

[0093] Figure 4 The cumulative release rate curve of the tannic acid-glutamine nanopesticide microcapsules synthesized in Example 5 over time shows that it has significant pH-responsive release characteristics. In an acidic environment (pH 5), the drug release rate is the fastest, with the cumulative release rate continuously increasing, reaching a maximum of 52.90% at 48 h, indicating the most vigorous release process. In a weakly alkaline environment (pH 9), the release rate is second fastest, with the cumulative release rate steadily increasing, significantly higher than in a neutral environment. In a neutral environment (pH 7), the release rate is the slowest, with the cumulative release rate increasing gradually and remaining at a low level of only 18.91%. Overall, the nanopesticide microcapsules release the fastest and largest amount under acidic conditions, followed by weakly alkaline conditions, and the slowest under neutral conditions, exhibiting obvious pH-sensitive characteristics. This gives it potential advantages in controlled-release applications targeting acidic microenvironments (such as the infection sites of plant pathogens) or alkaline environments (such as the midgut of lepidopteran insects).

[0094] In summary, the nano-pesticide microcapsules of the present invention, by using tannic acid and amino acid materials as slow-release agents and glutaraldehyde as a cross-linking agent, solve the problems of low drug loading capacity, complex preparation process, and uncontrollable drug burst release or release cycle in the prior art. While improving the control effect on multiple targets (diseases and pests), they significantly extend the effective period and reduce the frequency of application, effectively improving the utilization rate of pesticides.

[0095] The various embodiments in this specification are described in a progressive manner, with each embodiment focusing on the differences from other embodiments. The same or similar parts between the various embodiments can be referred to each other.

[0096] The above description of the disclosed embodiments enables those skilled in the art to make or use the invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the invention. Therefore, the invention is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A method for preparing tannic acid-amino acid nanopesticide microcapsules using ultrasound-assisted emulsification crosslinking, characterized in that, Includes the following steps: (1) Dissolve tannic acid powder, amino acid powder and sodium dodecyl sulfate powder in deionized water and stir thoroughly until completely dissolved to obtain an aqueous phase; (2) Dissolve the active ingredient of the pesticide in an organic solvent, add it to the aqueous phase described in step (1), and sonicate to obtain an oil-in-water nanoemulsion; (3) Under magnetic stirring conditions, add glutaraldehyde aqueous solution to the water-in-oil nanoemulsion described in step (2) to carry out cross-linking reaction, stir magnetically, then centrifuge, wash, freeze dry to obtain nano-pesticide microcapsules.

2. The method as described in claim 1, characterized in that, In step (1), the concentration of tannic acid is 8 mmol / L to 10 mmol / L, the concentration of amino acids is 32 mmol / L to 100 mmol / L, and the concentration of sodium dodecyl sulfate is 0.3% to 0.6%; the reaction temperature is 20 to 40 ℃, and the stirring speed is 600 to 1000 r / min.

3. The method as described in claim 1, characterized in that, In step (2), the ultrasonic treatment time is 3 to 6 minutes.

4. The method as described in claim 1, characterized in that, The amino acid is one or more of glutamine, phenylalanine, cysteine, asparagine, glycine, and aminobutyric acid.

5. The method as described in claim 1, characterized in that, The active ingredient of the pesticide is a fungicide or an insecticide; The fungicide is one or more of the following: tebuconazole, azoxystrobin, thifluzamide, carbendazim, difenoconazole, and isoprothiolane; The insecticide is one or more of the following: indoxacarb, chlorfenapyr, chlorantraniliprole, emamectin benzoate, lambda-cyhalothrin, and lufenuron.

6. The method as described in claim 1, characterized in that, The organic solvent is one or more of dichloromethane, xylene, and ethyl acetate.

7. The method as described in claim 1, characterized in that, The amount of glutaraldehyde active ingredient added is 1 wt%~2 wt% of the mass ratio of the solution in step (1), and the concentration of glutaraldehyde is 5%~20%.

8. The method as described in claim 1, characterized in that, The magnetic stirring parameters in step (3) are: stirring time of 30 min to 4 h and stirring speed of 600 to 1200 r / min.

9. Nanopesticide microcapsules prepared by any one of claims 1 to 8.

10. The application of the nano-pesticide microcapsules according to claim 9 in the prevention and control of pests and diseases.

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