Insecticidal and fungicidal microcapsules with anti-photolysis and pH response performance and preparation method thereof

Abstract

The application belongs to the field of pesticide preparation research and development, and discloses an insecticidal and bacteriostatic microcapsule with anti-photolysis and pH response performance and a preparation method thereof.The preparation steps are as follows: taking abamectin as a core medicine, assembling sodium lignosulfonate and polylysine through electrostatic assembly to form a capsule shell, and further solidifying the capsule shell by FeCl3 to obtain an abamectin microcapsule.The prepared microcapsule has an encapsulation rate of more than 90%, a drug loading rate of more than 10%, good anti-photolysis and pH response release performance, and insecticidal and bacteriostatic activity, and realizes multifunctionalization of the microcapsule.

Description

Technical Field

[0001] This invention belongs to the field of pesticide formulation application, specifically relating to an insecticidal and antibacterial microcapsule with resistance to photosynthesis and pH response, and its preparation method. Background Technology

[0002] Pesticides are a crucial guarantee for modern agricultural production, effectively reducing the impact of plant diseases and pests on crops and increasing yields. However, traditional pesticide formulations suffer from problems such as high organic solvent content, dust drift, environmental instability, and low utilization rates, leading to environmental pollution and food safety concerns. Controlled-release technology utilizes the physiological and biochemical characteristics of the target organism and the application environment to purposefully design and regulate the release rate and amount of pesticides, thereby reducing pesticide usage and improving targeting and safety. Pesticide microcapsules, as an important sustained-release formulation, encapsulate and fix the active ingredient using capsule wall materials, leveraging the membrane properties to achieve controlled drug release. This improves pesticide stability and utilization rates, reduces environmental pressure, and aligns with the green development requirements of pesticide formulations.

[0003] Avermectin is a widely used biological pesticide effective against various pests, but its poor photostability reduces its efficacy. Sodium lignosulfonate, rich in sulfonic acid groups and negatively charged, is commonly used as an anionic encapsulation material in microcapsules. Polylysine, a food-grade cationic amino acid, possesses excellent antimicrobial activity and thermal stability, and is frequently used as a preservative. Studies have shown it also exhibits good activity against the agricultural disease gray mold. This invention utilizes the opposite charge properties of sodium lignosulfonate and polylysine to prepare avermectin-loaded microcapsules using an electrostatic assembly method. This imparts UV resistance, adhesion properties, and pH responsiveness to the microcapsules, improving avermectin's stability while simultaneously providing both insecticidal and antibacterial activity, resulting in good residual efficacy in field applications. Summary of the Invention

[0004] To achieve the above-mentioned technical effects, the present invention provides the following technical solution: An insecticidal and antibacterial microcapsule with anti-photolysis and pH-responsive properties and its preparation method are disclosed. The core drug is avermectin technical, and sodium lignosulfonate and polylysine are used as coating materials. The microcapsules are prepared by electrostatic assembly.

[0005] The method for preparing avermectin microcapsules includes the following steps: (1) Weigh an appropriate amount of avermectin technical, dissolve it completely in cyclohexanone, and add an emulsifier to form an oil phase; (2) Weigh an appropriate amount of sodium lignosulfonate and dissolve it completely in deionized water to form an aqueous phase; (3) Under the condition of a shear rate of 15000 rpm, the oil phase prepared in step (1) is slowly added to the aqueous phase prepared in step (2) to form an oil-in-water emulsion system. (4) Add polylysine aqueous solution dropwise while stirring at 300 r / min, continue stirring for 20 min, then add FeCl3 aqueous solution dropwise, adjust the pH to 5, continue stirring for 30 min, centrifuge, wash with deionized water and centrifuge again, freeze dry to obtain avermectin microcapsules.

[0006] The method for preparing abamectin microcapsules includes the following: the amount of abamectin is 1%-2% of the total weight; the amount of sodium lignosulfonate is 0.5%-1% of the total weight, preferably 0.8%; the emulsifier is one or more of OP-10, Tween-80, YB-125, NP-10-P, agricultural emulsion 500#, and agricultural emulsion 1600#, and the amount is 1%-5%, preferably 3%; the ratio of oil phase to water phase is 1:4 to 1:8, preferably 1:6; the amount of polylysine is 0.5-1.5% of the total weight, preferably 1.0%; and the concentration of FeCl3 solution is 0.5 g / L, with an addition amount of 2%.

[0007] The insecticidal and antibacterial microcapsules have an average particle size of 400-600 nm, an encapsulation rate of over 90%, a drug loading rate of over 10%, and exhibit good UV resistance, pH responsiveness, and sustained insecticidal and antibacterial activity.

[0008] The present invention has the following beneficial effects: The abamectin microcapsules prepared by the method described above in this invention use environmentally friendly natural polymer materials for encapsulation. The preparation process is simple, and the method improves the photostability of abamectin, achieves pH-responsiveness, enhances adhesion, and also possesses insecticidal and antibacterial activity, thus improving the control effect. This invention aligns with the national green agriculture development strategy, helps improve pesticide utilization, reduces pesticide use, and provides a guarantee for environmental ecology, food safety, and sustainable agricultural development. Attached Figure Description

[0009] Figure 1 Electron micrographs of insecticidal and antibacterial microcapsules Figure 2 Release performance (pH response performance) of insecticidal and antibacterial microcapsules. Figure 3 Insecticidal and anti-photodegradation properties of insecticidal and antibacterial microcapsules Figure 4 Insecticidal and antibacterial microcapsules exhibit antibacterial activity against Botrytis cinerea. Detailed Implementation

[0010] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of the 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. In the present invention, unless otherwise specified, the equipment and raw materials used can be purchased from the market or are commonly used in the art. Unless otherwise specified, the methods in the following embodiments are conventional methods in the art. Specifically: Example

[0011] This embodiment provides an abamectin microcapsule with resistance to photolysis and pH response, and its preparation method, the steps of which are as follows: Weigh 1 g of avermectin technical grade, 5 g of cyclohexanone, and 1.5 g of OP-10 and mix them to form the oil phase; dissolve 1 g of SL in 34 g of water to form the aqueous phase; shear at 15,000 rpm for 3 min, slowly adding the oil phase dropwise to the aqueous phase during the shearing process to obtain an oil-in-water (O / W) emulsion, and continue stirring at 300 rpm. While stirring, add polylysine solution (1% of the total weight) dropwise; after 20 min, add 1 ml of FeCl3 aqueous solution (0.5 g / L) dropwise, make up to 50 g with water, adjust the pH to 5, continue stirring for 20 min, wash three times with deionized water, centrifuge and freeze-dry to obtain avermectin microcapsules. Example

[0012] This embodiment provides an abamectin microcapsule with resistance to photolysis and pH response, and its preparation method, the steps of which are as follows: Weigh 0.5 g of avermectin technical grade, 5 g of cyclohexanone, and 1.5 g of Tween-80 and mix them to form the oil phase; dissolve 1 g of sodium lignin sulfonate in 27 g of water to form the aqueous phase; shear at 15,000 rpm for 3 min, slowly adding the oil phase dropwise to the aqueous phase during the shearing process to obtain an oil-in-water (O / W) emulsion, and continue stirring at 300 rpm. While stirring, add 5 g of polylysine solution (1% of the total weight) dropwise; after 20 min, add 1 ml of FeCl3 aqueous solution (0.5 g / L) dropwise, make up to 50 g with water, adjust the pH to 5, continue stirring for 20 min, wash three times with deionized water, centrifuge and freeze-dry to obtain avermectin microcapsules. Example

[0013] This embodiment provides an insecticidal and antibacterial microcapsule with anti-photolysis and pH-responsive properties, and its preparation method, the steps of which are as follows: Weigh 0.5 g of avermectin technical grade, 5 g of cyclohexanone, and 1.5 g of OP-10 and mix them to form the oil phase; dissolve 1 g of SL in 29 g of water to form the aqueous phase; shear at 15,000 rpm for 3 min, slowly adding the oil phase dropwise to the aqueous phase during the shearing process to obtain an oil-in-water (O / W) emulsion, and continue stirring at 300 rpm. While stirring, add 5 g of polylysine solution (1% of the total weight) dropwise; after 20 min, add 1 ml of FeCl3 aqueous solution (0.5 g / L) dropwise, make up to 50 g with water, adjust the pH to 5, continue stirring for 20 min, wash three times with deionized water, centrifuge and freeze-dry to obtain avermectin microcapsules.

[0014] Example 4: Taking Example 1 as an example, the insecticidal and antibacterial microcapsules with anti-photolysis and pH-responsive properties were evaluated. 1. Experimental methods and procedures (1) Morphological and structural characterization The microcapsules were diluted with water by a certain factor, and their particle size and span were measured using a laser particle size analyzer. The morphology of the samples was examined using a scanning electron microscope (SEM).

[0015] (2) Encapsulation efficiency and release performance test The free drug in the microcapsule suspension was extracted using n-hexane as a solvent. 1 g of the microcapsule suspension was weighed into a glass sample vial, 10 mL of n-hexane was added, and the vial was stirred on a magnetic stirrer. 0.5 mL of the upper n-hexane solution was filtered through a 0.22 μm organic filter membrane, and the drug concentration was determined using high-performance liquid chromatography (HPLC). Simultaneously, the free drug concentration in the microcapsule suspension was calculated. The encapsulation efficiency (E) of the microcapsule suspension was calculated using formula (1), and the free concentration (R) of avermectin in the microcapsule suspension was calculated using formula (2).

[0016] E / % = [1−(C1×V1) / m1]×100 .....(1) R / % = 100−E............. (2) In the formula, C1 is the mass concentration of avermectin in n-hexane, mg / L; V1 is the volume of n-hexane, L; and m1 is the total mass of avermectin in the microcapsule suspension, mg.

[0017] The release performance of drug-loaded microcapsules was determined using a rapid release buffer. The microcapsule suspension was diluted to 450 mg / L with deionized water. 10 mL of the diluted solution was placed in a glass sample vial, and 80 mL of n-hexane and 10 mL of methanol were added sequentially, followed by standing. At 10, 20, 30, 45, 60, 80, 100, 120, 150, 180, 240, and 300 min, 0.5 mL of the supernatant n-hexane solution was collected, filtered through a 0.22 μm organic filter membrane, and the drug content was determined by HPLC. An equal volume of n-hexane was added after each sampling to maintain a constant total amount of n-hexane in the release system.

[0018] Chromatographic conditions: The chromatographic column was a C18 stainless steel column (250 mm × 4.6 mm); the mobile phase was acetonitrile:water (formic acid) = 90:10 (0.1%); the flow rate was 1.0 mL / min; the column temperature was 25 ℃; the detection wavelength was 230 nm; the injection volume was 20 μL; the chromatographic column was Shimadzu ODS-3 250*4.6; the quantitative loop was 5 μL; the sample volume was approximately 30 mg (accurate to 0.002 g) and dissolved in acetonitrile to make up to volume.

[0019] The cumulative release rate (ε) is obtained using formula (3).

[0020] ε / % = (C2×V2) / m2×100−R.....(3) In the formula, C2 is the mass concentration of the drug in n-hexane, mg / L; V2 is the volume of n-hexane, mL; and m2 is the total mass of the drug in the microcapsule suspension dilution, mg.

[0021] (4) Insecticidal activity assay method Second-instar diamondback moth larvae were used as the test pests, and commercially available abamectin emulsifiable concentrate was used as the control agent. The insecticidal activity of the prepared abamectin microcapsules was compared. At the same time, the insecticidal activity was measured after the agent was treated with ultraviolet light to evaluate the anti-ultraviolet properties of the abamectin microcapsules.

[0022] (5) Method for determining bactericidal activity The antibacterial activity of the insecticidal and antifungal microcapsules was determined using the mycelial growth rate method. Chloramphenicol-containing glucose-potato agar was sterilized, and solutions of the insecticidal and antifungal microcapsules at different concentrations were prepared and added to the culture medium. Deionized water and acetone were used as blank controls. Botrytis cinerea (5 mm in diameter) mycelial cakes were inoculated onto the drug-treated culture medium. The petri dishes were placed in an incubator at 25 ℃ and 90% relative humidity. When the diameter of the control group reached 2 / 3 of the petri dish, the colony diameter was recorded, and the inhibition rate was calculated.

[0023] 2. Experimental Results and Analysis (1) The results of the determination of morphology, particle size, drug loading rate and encapsulation rate of avermectin microcapsules are shown in Appendix. Figure 1 See Table 1. It can be seen that the avermectin microcapsules have a uniform shape and a smooth, non-porous membrane shell, with an average particle size of approximately 463 nm and a span of 1.469 nm, classifying them as nanoscale microcapsules. Table 1 shows that the encapsulation efficiency of the microcapsules is 90.2%, and the drug loading is approximately 10.4%.

[0024] Table 1. Average particle size and span of microcapsules 463 1.469 90.2 10.4 (2) pH-responsive release performance of insecticidal and antibacterial microcapsules From the appendix Figure 2 It can be seen that avermectin microcapsules exhibit pH-responsive characteristics, releasing slowly under alkaline conditions and rapidly under acidic conditions. This is because under acidic conditions, the sulfonic acid groups of sodium lignin sulfonate hydrolyze more quickly, disrupting the stability of the microcapsules and leading to rapid release. Under alkaline conditions, the sulfonic acid groups form stable sulfate ions, which react with Fe... 3+ The system forms a stable complex through complexation, thus slowing down the release of abamectin. Its acid-responsive characteristics match the microenvironment of acidic substances released by pathogens after crop infection, which is beneficial for improving bioavailability.

[0025] (3) Insecticidal and antibacterial microcapsules: insecticidal activity and UV protection properties Appendix Figure 3 This relates to the insecticidal activity and UV protection properties of the prepared avermectin microcapsules. Figure 3 It can be seen that the prepared abamectin microcapsules have a longer-lasting effect compared with commercially available abamectin emulsifiable concentrate. Even 4 days after application, the mortality rate of diamondback moth was still higher than that of abamectin emulsifiable concentrate. After UV irradiation treatment, the insecticidal effect of the abamectin microcapsules was higher than that of the control and abamectin emulsifiable concentrate, with a mortality rate still as high as 63%, while the mortality rate of abamectin emulsifiable concentrate was only 37%, indicating that the photolytic stability of the abamectin microcapsules was improved.

[0026] (4) Antibacterial activity of insecticidal and antibacterial microcapsules Appendix Figure 4 These are the results of indoor activity tests on the insecticidal and antibacterial microcapsules against Botrytis cinerea. It can be seen that the addition of polylysine enhances the antibacterial activity of the microcapsules against Botrytis cinerea. Compared to lignin microcapsules without polylysine, the antibacterial activity is increased by 3.7 times, demonstrating the multifunctional insecticidal and antibacterial advantages of microcapsules.

[0027] The above embodiments are preferred embodiments of the present invention. However, it is understood that those skilled in the art can make equivalent substitutions or changes based on the technical solutions and concepts of the present invention, and all such substitutions or changes should fall within the protection scope of the appended claims.

Claims

1. An insecticidal and antibacterial microcapsule with anti-photolysis and pH-responsive properties and its preparation method, wherein the core drug is avermectin technical, sodium lignosulfonate and polylysine are the coating materials, and the microcapsule is prepared by electrostatic assembly.

2. The method for preparing insecticidal and antibacterial microcapsules with anti-photolysis and pH-responsive properties according to claim 1, comprising the following steps: (1) Weigh an appropriate amount of avermectin technical, dissolve it completely in cyclohexanone, and add an emulsifier to form an oil phase; (2) Weigh an appropriate amount of sodium lignosulfonate and dissolve it completely in deionized water to form an aqueous phase; (3) Under the condition of a shear rate of 15000 rpm, the oil phase prepared in step (1) is slowly added to the aqueous phase prepared in step (2) to form an oil-in-water emulsion system. (4) Add polylysine aqueous solution dropwise while stirring at 300 r / min, continue stirring for 20 min, then add FeCl3 aqueous solution dropwise, adjust the pH to 5, continue stirring for 30 min, centrifuge, wash with deionized water and centrifuge again, freeze dry to obtain avermectin microcapsules.

3. The method for preparing insecticidal and antibacterial microcapsules according to claim 2, characterized in that, The amount of abamectin is 1%-2% of the total weight.

4. In the method for preparing avermectin microcapsules according to claim 2, the amount of sodium lignosulfonate is 0.5%-1% of the total weight, preferably 0.8%.

5. The method for preparing insecticidal and antibacterial microcapsules with anti-photolysis and pH-responsive properties according to claim 2, wherein the emulsifier is one or more of OP-10, Tween-80, YB-125, NP-10-P, agricultural emulsion 500#, and agricultural emulsion 1600#, and the dosage is 1%-5%, particularly, the optimized dosage is 3%.

6. The method for preparing insecticidal and antibacterial microcapsules with anti-photolysis and pH-responsive properties according to claim 2, wherein the ratio of oil phase to water is 1:4 to 1:8, and particularly, the optimized ratio of oil phase to water phase is 1:

6.

7. The method for preparing insecticidal and antibacterial microcapsules with anti-photolysis and pH-responsive properties according to claim 2, wherein the amount of polylysine is 0.5-1.5% of the total weight, preferably 1.0%.

8. The method for preparing insecticidal and antibacterial microcapsules with anti-photolysis and pH-responsive properties according to claim 2, wherein the FeCl3 solution concentration is 0.5 g / L and the amount added is 2%.

9. The insecticidal and antibacterial microcapsules with anti-photolysis and pH-responsive properties according to claims 1-8, characterized in that, The prepared microcapsules have an average particle size of 400-600 nm, an encapsulation rate of over 90%, a drug loading rate of over 10%, and exhibit good photostability, pH responsiveness, and sustained insecticidal and antibacterial activity.

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