Foliar adhesion type nano pesticide based on self-assembly technology as well as preparation method and application of foliar adhesion type nano pesticide

Abstract

The invention discloses a foliar adhesion type nano pesticide based on a self-assembly technology as well as a preparation method and application of the foliar adhesion type nano pesticide. The foliar adhesion type nano pesticide carrier is prepared from a pesticide with amino and chlorogenic acid through self-assembly. Natural chlorogenic acid molecules are used as a carrier, the natural chlorogenic acid molecules and pesticide molecules are subjected to a self-assembly process, the nano pesticide is prepared under low-speed stirring, the nano pesticide is good in biocompatibility and has good adhesiveness with leaf surfaces, the bioavailability of the pesticide is improved, the pesticide application cost is reduced, the environmental pollution is relieved, and the economic value of the pesticide is improved.

Description

Technical Field

[0001] The invention belongs to the technical field of pesticide preparations, and in particular relates to a leaf surface-adhesive nanopesticide based on a self-assembly technology, and a preparation method and application thereof. Background Art

[0002] Pesticides play a vital role in controlling the spread of plant diseases, insects, and weeds, and increasing crop yields. However, excessive use of pesticides causes resistance to pests and diseases, and also causes serious environmental problems, such as high residues, ecological imbalance, and decreased biodiversity. During agricultural applications, more than 90% of pesticide molecules will be lost or diffused into the surrounding environment due to bouncing, leaching, photodegradation, and transpiration during spraying. Pesticide molecules in the environment pose a risk to human health and the survival of plants and animals, and reducing loss pathways and increasing bioavailability can significantly improve the efficiency of pesticide application. Therefore, it is very important to enhance the deposition of pesticides on crop leaves and extend the duration of action of pesticides.

[0003] As a new type of pesticide formulation, nanopesticides have the advantages of small size, large specific surface area, etc., which are extremely advantageous in improving the bioavailability of pesticides, droplet coverage efficiency, drug deposition and dosage transmission efficiency.

[0004] Leaf adhesion is a key factor in determining the retention capacity of a pesticide slow-release system. Increasing the leaf adhesion of pesticides can significantly increase the retention rate of pesticides on plant leaves and improve the utilization rate of pesticides. Studies on traditional pesticides have shown that due to low adhesion and poor hydrophilicity, less than 0.1% of pesticides act on harmful biological targets. Nanopesticides have small particle sizes and strong targeting, and are expected to become an important method to solve these problems.

[0005] Leaf-adhesive nanopesticides can interact with the micro-nanostructure of the leaf surface, allowing the liquid pesticide to adhere to the leaf surface, avoiding the loss of liquid pesticide caused by rain erosion, and increasing the retention of pesticides on the leaf surface. Therefore, enhancing the deposition and adhesion of nanopesticides on the surface of crops is particularly critical to improving the effective utilization rate of pesticides, which is also an important strategy for achieving sustainable and green development of pesticides.

[0006] However, the existing preparation process of leaf-adhesive nanopesticides has the following defects and still faces many challenges in actual application, making its mass production difficult.

[0007] 1. The preparation process is complicated, sometimes requiring multiple chemical reactions and a large amount of toxic solvents, causing environmental pollution.

[0008] 2. In order to improve the leaf permeability and adhesion of pesticides, various additives and surfactants are often added to the water phase during the preparation process, which can easily cause adverse effects on the environment.

[0009] 3. The carrier in the preparation process is inorganic material or non-degradable organic material, which results in the inability to completely release the pesticide, resulting in low pesticide use efficiency and large pesticide residues. Summary of the invention

[0010] In order to solve the above technical problems, improve the bioavailability of traditional pesticides, reduce residual pesticides in the environment, and reduce agricultural production costs, the present invention provides the following technical solutions.

[0011] In a first aspect, the present invention provides a leaf-adhesive nanopesticide based on self-assembly technology, wherein the leaf-adhesive nanopesticide-loaded particles are prepared by self-assembly of an amino-carrying pesticide and chlorogenic acid.

[0012] Preferably, the pesticide includes but is not limited to any one or a combination of two or more of emamectin benzoate, spinosad, spinetoram, matrine or veratridine.

[0013] Preferably, the molar ratio of the pesticide to the chlorogenic acid is in the range of 1:1 to 10, for example: 1:1, 1:2.3, 1:25, 1:2.8, 1:3.3, 1:3.4, 1:4.6, 1:6.9, 1:8, 1:10.

[0014] Preferably, the particle size of the nanopesticide is 40-120 nm, for example: 40 nm, 50 nm, 60 nm, 70 nm, 80 nm, 90 nm, 101 nm, 104 nm, 105 nm, 108 nm, 112 nm, 115 nm, 120 nm.

[0015] Furthermore, the particle size of the nanopesticide is 70-120 nm.

[0016] In a second aspect, the present invention provides a method for preparing the leaf-adhesive nanopesticide according to the first aspect, comprising the following steps: (1) dissolving the pesticide in ethanol to obtain a pesticide ethanol solution; (2) dissolving chlorogenic acid in water to obtain a chlorogenic acid solution; (3) Slowly adding the pesticide ethanol solution to the chlorogenic acid solution, and obtaining the leaf-adhesive nanopesticide through stirring, dialyzing, and drying.

[0017] Preferably, in step (1), the mass percentage concentration of the pesticide ethanol solution is 2-10%, for example: 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10%.

[0018] Preferably, in step (2), the mass percentage concentration of the chlorogenic acid solution is 4-12%, for example: 4%, 5%, 6%, 7%, 8%, 9%, 10%, 11%, 12%.

[0019] Preferably, in step (2), the pH of the chlorogenic acid solution is 6.2-6.8, for example: 6.2, 6.4, 6.5, 6.6, 6.8.

[0020] Preferably, in step (3), the stirring speed is 400-1000 rpm, for example: 400 rpm, 500 rpm, 600 rpm, 700 rpm, 800 rpm, 900 rpm, 1000 rpm.

[0021] Preferably, in step (3), the stirring time is 2-4 h, for example, 2 h, 2.5 h, 3 h, 3.5 h, 4 h.

[0022] Preferably, the temperature conditions in steps (1), (2) and (3) are 50-60°C, for example, 50°C, 52°C, 55°C, 58°C, 60°C.

[0023] In a third aspect, the present invention provides the use of the leaf-adhesive nanopesticide described in the first aspect in preventing and controlling crop diseases and insect pests.

[0024] Preferably, the pests and diseases include but are not limited to cabbage loopers, aphids, diamondback moths or thrips, and more preferably aphids.

[0025] Beneficial effects of the present invention: 1. The present invention uses chlorogenic acid and amino-containing pesticides as raw materials. The two molecules self-assemble to form nanoparticles through electrostatic, hydrophobic and hydrogen bonding effects, forming nanoparticles with a hydrophobic core and a hydrophilic outer layer. The self-assembly process is simple, and leaf-adhesive nanopesticides can be prepared only under low-speed stirring.

[0026] 2. The present invention makes full use of the characteristics of the natural adhesive molecules of chlorogenic acid, reduces the various additives added during the use of traditional pesticides to improve leaf permeability and adhesion, and reduces production and application costs.

[0027] 3. The leaf-adhesive nanopesticide of the present invention can be completely degraded under natural conditions, is environmentally friendly, has low pesticide residues, high efficacy, and high bioavailability, and provides a new research and development idea and technical basis for the development of new nanopesticide formulations. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 Shown is the hydrated particle size diagram of leaf-adhesive avermectin nanopesticide; Figure 2Shown is a scanning electron microscope image of avermectin nanopesticide adhered to the leaf surface; Figure 3 Shown is a transmission electron microscope image of avermectin nanopesticide adhered to the leaf surface; Figure 4 Shown are the sustained-release curves of leaf-adhesive avermectin nanopesticide and commercially available suspension concentrate; Figure 5 Shown are the photolysis curves of leaf-adhesive avermectin nanopesticide and commercial suspension concentrate; Figure 6 The figure shows the change of leaf retention rate of leaf-adhesive avermectin nanopesticide and commercial suspension after simulated rainwater flushing; Figure 7 Shown is the change in leaf retention rate of leaf-adhesive avermectin nanopesticide after flushing with 2.5% NaCl and 2.5% urea solution. DETAILED DESCRIPTION

[0029] The technical scheme of the present invention is described clearly and completely below in conjunction with the embodiments and drawings. The described embodiments are only a part of the embodiments of the present invention, rather than all of the embodiments. Based on the embodiments of the present invention, other embodiments obtained by ordinary technicians in this field without creative work belong to the scope of protection of the present invention.

[0030] It should be noted that the experimental methods used in the following examples are conventional methods in the art unless otherwise specified. Example 1 Preparation of pesticide solution

[0031] A certain amount of pesticide (emamectin benzoate, spinosad, spinetoram, matrine, and veratridine) powder was weighed and dissolved in a certain amount of ethanol solution at 50-60°C to prepare 1.0 L of pesticide solution with a mass percentage concentration of 2-10%. Example 2 Preparation of chlorogenic acid solution

[0032] Weigh a certain amount of chlorogenic acid, dissolve it in a certain amount of aqueous solution at 50-60°C to prepare 1.0 L of aqueous solution with a mass percentage concentration of 4-12%. Example 3 Preparation of leaf-adhesive avermectin nanopesticide sample 1

[0033] 50 mL of 5% avermectin benzoate solution prepared in Example 1 was slowly added dropwise to 50 mL of 4% chlorogenic acid aqueous solution prepared in Example 2, the molar ratio of avermectin benzoate to chlorogenic acid was 1:2.3, the temperature was maintained at 50-60°C, the pH was adjusted to 6.5, and the mixture was stirred at 500 rmp for 2 h. After filtration, dialysis and drying, a leaf-adhesive avermectin nanopesticide sample 1 was obtained. The particle size was about 100 nm as measured by a laser particle size analyzer. Example 4 Preparation of leaf-adhesive avermectin nanopesticide sample 2

[0034] 50 mL of 5% avermectin benzoate solution prepared in Example 1 was slowly added dropwise to 100 mL of 4% chlorogenic acid solution prepared in Example 2, the molar ratio of avermectin benzoate to chlorogenic acid was 1:4.6, the temperature was maintained at 50-60°C, the pH was adjusted to 6.5, and the mixture was stirred at 500 rpm for 2 h. After filtration, dialysis and drying, the leaf-adhesive avermectin nanopesticide sample 2 was obtained. The particle size was about 105 nm as measured by a laser particle size analyzer, and scanning and transmission electron microscopy samples were prepared after dilution. Example 5 Preparation of leaf-adhesive avermectin nanopesticide sample 3

[0035] 50 mL of 5% avermectin benzoate solution prepared in Example 1 was slowly added dropwise to 150 mL of 4% chlorogenic acid solution prepared in Example 2, the molar ratio of avermectin benzoate to chlorogenic acid was 1:6.9, the temperature was maintained at 50-60°C, the pH was adjusted to 6.5, and the mixture was stirred at 500 rmp for 2 h. After filtration, dialysis and drying, the leaf-adhesive avermectin nanopesticide sample 3 was obtained. The particle size was measured by a laser particle size analyzer to be approximately 112 nm. Example 6 Preparation of leaf-adhesive spinosad nanopesticide samples

[0036] 50 mL of the 5% spinosad solution prepared in Example 1 was slowly added dropwise to 100 mL of the 5% chlorogenic acid solution prepared in Example 2, the molar ratio of spinosad to chlorogenic acid was 1:3.3, the temperature was maintained at 50-60°C, the pH was adjusted to 6.5, and the mixture was stirred at 500 rmp for 2 h. After filtration, dialysis and drying, a leaf-adhesive spinosad nanopesticide sample 1 was obtained. The particle size was measured by a laser particle size analyzer to be approximately 104 nm. Example 7 Preparation of Leaf-adhesive Spinetoram Nanopesticide Sample

[0037] 50 mL of the 5% spinetoram solution prepared in Example 1 was slowly added dropwise to 100 mL of the 5% chlorogenic acid solution prepared in Example 2, the molar ratio of spinetoram to chlorogenic acid was 1:3.4, the temperature was maintained at 50-60°C, the pH was adjusted to 6.5, and the mixture was stirred at 500 rmp for 2 h. After filtration, dialysis and drying, a leaf-adhesive spinetoram nanopesticide sample 1 was obtained. The particle size was measured by a laser particle size analyzer to be approximately 108 nm. Example 8 Preparation of leaf-adhesive matrine nanopesticide samples

[0038] 50 mL of 5% matrine solution prepared in Example 1 was slowly added dropwise to 180 mL of 5% chlorogenic acid solution prepared in Example 2, the molar ratio of matrine to chlorogenic acid was 1:2.5, the temperature was maintained at 50-60°C, the pH was adjusted to 6.5, and the mixture was stirred at 500 rpm for 2 h. After filtration, dialysis and drying, a leaf-adhesive matrine nanopesticide sample 1 was obtained. The particle size was measured by a laser particle size analyzer to be approximately 101 nm. Example 9 Preparation of leaf-adhesive veratridine nanopesticide samples

[0039] 50 mL of 5% veratridine solution prepared in Example 1 was slowly added dropwise to 120 mL of 5% chlorogenic acid solution prepared in Example 2, the molar ratio of matrine to chlorogenic acid was 1:2.8, the temperature was maintained at 50-60°C, the pH was adjusted to 6.5, and the mixture was stirred at 500 rpm for 2 h. After filtration, dialysis and drying, a leaf-adhesive veratridine nanopesticide sample 1 was obtained. The particle size was measured by a laser particle size analyzer to be approximately 101 nm. Example 10 Performance test of leaf-adhesive avermectin nanopesticide sample 2

[0040] 10.1 Particle size and morphology Weigh 2 mg of leaf-adhesive avermectin nanopesticide sample 2, dissolve it in 5.0 mL of water, sonicate for 5 min, take 1.0 mL and inject it into the dynamic light scattering sample cell. The hydrated particle size is 105 nm (see Figure 1 ).

[0041] 50 μL of the leaf-adhesive avermectin nanopesticide sample 2 prepared in Example 4 was taken and added to 5.0 mL of deionized water. After ultrasonic dispersion, 5.0 μL was taken and spotted on a silicon wafer. After natural drying, its morphology was observed using a scanning electron microscope. The results are shown in FIG. Figure 2 .

[0042] 50 μL of leaf-adhesive avermectin nanopesticide sample 2 was taken and added to 5.0 mL of deionized water. After ultrasonic dispersion, 5.0 μL was taken and spotted on a copper grid. After natural drying, the morphology was observed using a transmission electron microscope. The results are shown in Table 1. Figure 3 .

[0043] Depend on Figure 2 and Figure 3 The results show that the leaf-adhesive avermectin nanopesticide is spherical in shape with a particle size of about 100 nm.

[0044] 10.2 Sustained-release effect of leaf-adhesive avermectin nanopesticide sample 2 5 mL of leaf-adhesive avermectin nanopesticide sample 2 solution (pesticide content of 5 mg / mL) was placed in a dialysis bag (MWCO: 3500 Da) and immersed in 10 mL of 30% acetonitrile aqueous solution. The solution was shaken and released at 25°C for 48 h. 1 mL of the sustained-release medium was drawn at 0 h, 0.5 h, 1 h, 2 h, 3 h, 5 h, 7 h, 9 h, 11 h, 15 h, 19 h, 24 h, 30 h, 36 h, 42 h, and 48 h, and the corresponding volume of sustained-release medium was quickly added to the dialysis system. The concentration of avermectin in the samples taken at each time point was determined by high-performance liquid chromatography. At the same time, the avermectin benzoate suspension solution (content of 5 mg / mL) was used as a control to calculate the cumulative release curve comparison of the two. The results are shown in the figure. Figure 4 .

[0045] like Figure 4 As shown in the figure, the release rate of the leaf-adhesive avermectin nanopesticide sample 2 gradually slowed down over time, following a slow diffusion mode, with a cumulative release of about 62.3% in 48 hours, and had good sustained-release performance. The cumulative release rate of the control suspension sample exceeded 98.4% within 24 hours, and the sustained-release performance was poor. This shows that the leaf-adhesive avermectin nanopesticide of the present invention has good lasting performance.

[0046] 10.3 Photodegradation experiment Take 50 mL of avermectin nanopesticide sample 2 and commercial avermectin suspension (pesticide content is 25 mg / mL) respectively, place them in a xenon arc lamp irradiation incubator at 25°C and 250 W for continuous illumination, take 2.0 mL of sample at 0 h, 12 h, 24 h, 36 h and 48 h respectively, completely dissolve in methanol, ultrasonicate for 15 min to completely release the pesticide, and use high performance liquid chromatography to determine the content of the original drug in the filtrate obtained after filtration. The results are shown in Table 2. Figure 5 .

[0047] from Figure 5 It can be seen that after 48 h of illumination, the avermectin nanopesticide was degraded by less than 40%, while the commercially available suspension concentrate was degraded by more than 80%, indicating that the nanopesticide formed after self-assembly can significantly reduce the photodegradation rate of avermectin and improve its photostability.

[0048] 10.4 Evaluation of the adhesion performance of leaf-adhesive avermectin nanopesticide sample 2 Take 500 μL of leaf-adhesive avermectin nanopesticide sample 2 and avermectin benzoate suspension solution (content 5 mg / mL), spray them evenly on cucumber leaves with a high-pressure spray gun, and then carefully divide the leaf surface into two parts after natural air drying. One part was rinsed with 50 mL of deionized water to simulate rain erosion, and then these parts were quickly frozen in liquid nitrogen, ground into powder, and then 5.0 mL of acetonitrile was used to extract avermectin. The avermectin content was quantified by high-performance liquid chromatography (HPLC), and the retention rate of avermectin was determined by comparing the changes before and after rinsing, so as to evaluate the leaf adhesion performance. The results are shown in Figure 6 .

[0049] In order to study the leaf adhesion mechanism of avermectin nanopesticide samples, another part of the leaves were washed with 2.5% NaCl and 2.5% urea solutions instead of deionized water to destroy the electrostatic interaction or hydrogen bonding, respectively. The results are shown in Figure 7 .

[0050] Depend on Figure 6 It can be seen that the leaf-adhesive avermectin nanopesticide has a strong ability to resist rain erosion. After simulated rain erosion, the pesticide retention rate on the leaf surface exceeded 80%, while the retention rate of the suspension sample after erosion was less than 30%. These results show that after the introduction of the adhesive molecule chlorogenic acid through self-assembly, the leaf adhesion of the avermectin nanopesticide is significantly enhanced.

[0051] like Figure 7 As shown, electrostatic and hydrogen bonding effects are mainly involved in the adhesion mechanism of nanopesticides and leaf surfaces.

[0052] 10.5 Indoor toxicity test of melon aphid The spray method was used to compare the endotoxicity of leaf-adhesive avermectin nanopesticide and commercial avermectin benzoate suspension on cucumber aphids indoors. Leaf-adhesive avermectin nanopesticide, commercial suspension and emulsion were prepared in equal proportions to prepare 7 series of concentration gradients (ppm): 500, 250, 125, 67.5, 34, 17, 8.5 for standby use. The cucumber leaves that had not been exposed to the pesticide were beaten into discs with a diameter of 7.5 cm, sprayed with a spray tower, and then taken out and dried naturally indoors. About 2 mm agar solution was poured into a culture dish, and the back of the leaf was attached to the culture dish after cooling. Cucumber seedlings with a large number of insects were collected in the field, and wingless adult aphids were picked with a brush and attached to the leaves. 30 heads were attached to each dish, which was sealed with plastic wrap. 15-20 small holes were pierced on the film with an insect needle. The experiment was repeated 4 times. The treated test insects were placed in the insect breeding room for normal feeding under the conditions of L / D=14:10, T=(25±2)℃, RH=(75±5)%, and three biological replicates were established. The number of dead and live insects was checked after 48 h, and the mortality rate was calculated. LC was calculated using SPSS software. 50 , the results are shown in Table 1.

[0053] Table 1 Results of indoor toxicity tests of avermectin nanopesticide and commercial suspension concentrate

[0054] It can be seen from the results in Table 1 that the leaf-adhesive avermectin nanopesticide prepared by the method of the present invention has stronger toxicity to aphids than the commercially available suspension concentrate.

[0055] 10.6 Zebrafish toxicity assay The toxicity of leaf-adhesive avermectin nanopesticide sample 2 to zebrafish was evaluated using a static method, and a commercially available avermectin benzoate suspension was used as a control group. The two pesticide preparations were diluted into different concentrations of liquid with deionized water, and 20 zebrafish (length 2-3 cm) were placed in a container of a certain capacity. Deionized water was used as a blank control. Three biological replicates were set up, and the mortality rate of zebrafish after 96 h in the liquid was recorded. SPSS software was used to calculate the LC 50 , the results are shown in Table 2.

[0056] Table 2 Results of toxicity test of avermectin nanopesticide and commercial emulsion on zebrafish

[0057] As can be seen from Table 2, after 96 hours of pesticide incubation, the LC values ​​of avermectin nanopesticide and commercial suspension on zebrafish were 50They were 2.08 μg / mL and 1.14 μg / mL respectively, indicating that the toxicity of Emamectin was significantly reduced after self-assembly, its safety to non-target organisms was significantly improved, and its environmental friendliness was enhanced.

[0058] The above descriptions are merely embodiments of the present invention and are not intended to limit the patent scope of the present invention. Any equivalent structural transformations made using the contents of the present invention specification, or directly or indirectly applied in other related technical fields, are also included in the patent protection scope of the present invention.

Claims

1. A leaf-adhesive nanopesticide based on self-assembly technology, characterized in that: The leaf-adhesive nanopesticide-loaded particles are prepared by self-assembly of amino-containing pesticides and chlorogenic acid.

2. The leaf-adhesive nanopesticide according to claim 1, characterized in that: The pesticide includes any one of emamectin benzoate, spinosad, spinetoram, matrine or veratridine, or a combination of two or more thereof.

3. The leaf-adhesive nanopesticide according to claim 1, characterized in that: The molar ratio of the pesticide to the chlorogenic acid is 1:1-10.

4. The leaf-adhesive nanopesticide according to claim 1, characterized in that: The particle size of the nanopesticide is 40-120 nm.

5. The method for preparing the leaf-adhesive nanopesticide according to claim 1, characterized in that: The following steps are involved: (1) dissolving the pesticide in ethanol to obtain a pesticide ethanol solution; (2) dissolving chlorogenic acid in water to obtain a chlorogenic acid solution; (3) Slowly adding the pesticide ethanol solution to the chlorogenic acid solution, and obtaining the leaf-adhesive nanopesticide through stirring, dialyzing, and drying.

6. The preparation method according to claim 5, characterized in that: In step (1), the mass percentage concentration of the pesticide ethanol solution is 2-10%.

7. The preparation method according to claim 5, characterized in that: In step (2), the mass percentage concentration of the chlorogenic acid solution is 4-12%, and the pH of the chlorogenic acid solution is 6.2-6.

8.

8. The preparation method according to claim 5, characterized in that: In step (3), the stirring speed is 400-1000 rpm and the time is 2-4 h.

9. The preparation method according to claim 5, characterized in that: The temperature conditions in steps (1), (2) and (3) are 50-60°C.

10. Use of the leaf-adhesive nanopesticide according to any one of claims 1 to 4 in preventing and controlling crop diseases and insect pests.

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