Nano pesticide as well as preparation method and application thereof

Abstract

According to the nano pesticide and the preparation method and application thereof, pH response type nano particles ZIF-90 serve as a carrier, azoxystrobin is loaded to serve as a medicine, and the nano pesticide is used for preventing and treating rice sheath blight disease caused by rhizoctonia solani. When the rhizoctonia solani infects rice, oxalic acid can be generated to reduce the pH around an infected area, so that the ZIF-90 carrier skeleton and the hyaluronic acid coating are decomposed to release azoxystrobin, and the rhizoctonia solani is inhibited in a targeted manner. It is further found that ZIF-90 and azoxystrobin have synergistic bacteriostatic activity, the EC50 value of azoxystrobin to rhizoctonia solani can be greatly reduced, after ZIF-90 carrier encapsulation and hyaluronic acid end capping, the photolysis stability of azoxystrobin can be improved, the adhesive force of azoxystrobin on rice leaves can be enhanced, and the ZIF-90 and azoxystrobin compound has important application in agricultural disease control.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of nano-pesticide, and particularly to a nano-pesticide, a preparation method and application thereof. BACKGROUND

[0002] At present, nanotechnology provides a variety of application potential strategies for reducing the amount of pesticide and improving the utilization rate of pesticide. The controlled release system realizes on-demand and site-specific response release by encapsulating pesticides in nano-carriers under the stimulation of microenvironment (such as pH, temperature, light, glutathione and enzyme), so as to realize the efficient utilization of pesticides. In addition, this technology can also enhance the leaf affinity, promote plant growth, and minimize the environmental risk.

[0003] Therefore, the pesticide controlled release preparation based on nano-carriers has broad application prospects in agricultural production. Among the numerous nano-carrier materials, metal organic framework (MOFs) material shows great potential in agricultural applications due to its high porosity, high loading rate, easy functionalization of surface and good biocompatibility.

[0004] Generally speaking, the naked MOF-based nano-pesticide has the defects of easy drug leakage, poor controlled release performance, weak adhesion and poor water dispersibility, which significantly reduces the utilization rate of the pesticide. In addition, the synergistic fungicidal effect of the nano-carrier and the pesticide is beneficial to improve the control effect, reduce the amount of pesticide, and alleviate the generation of pesticide resistance. However, most of the nano-pesticide carriers reported at present do not have antifungal activity or have weak antifungal activity. Azoxystrobin (Azo) as an antifungal drug is limited in its application in the field environment due to its high photolysis and high toxicity to non-target organisms. SUMMARY

[0005] The present application provides a nano-pesticide, a preparation method and application thereof, to solve the defects of MOF-based nano-pesticide in the prior art, such as easy drug leakage, poor controlled release performance, weak adhesion, easy photolysis of azoxystrobin, and high toxicity to non-target organisms, and to provide a nano-pesticide with pH responsiveness, high fungicidal activity, high light stability and high adhesion capacity.

[0006] In a first aspect, the present application provides a nano-pesticide, which comprises: a carrier, wherein the carrier is ZIF-90 nanoparticles; a drug, wherein the drug is encapsulated in the nano-carrier, and the drug has the effect of killing or inhibiting bacteria and / or fungi; an end-capping agent, wherein the end-capping agent is used to seal the pores of the ZIF-90 nanoparticles.

[0007] Zeolitic imidazolate framework-90 (ZIF-90) is a kind of material synthesized by Zn 2+MOF nanoparticles composed of ZIF-90 and imidazole-2-carboxaldehyde (2-ICA) have the advantages of high loading efficiency, simple preparation, large surface area, and good biocompatibility. ZIF-90 nanoparticles are easily decomposed under acidic conditions, making them suitable for designing pH-responsive pesticide release systems to achieve precise targeted delivery of active ingredients.

[0008] The present invention loads ZIF-90 nanoparticles with antibacterial drugs and uses a capping agent to seal the pores of ZIF-90 to develop a pH-responsive nanopesticide. It can combine the acidic microenvironment generated during the infection of some pathogens with the acid-sensitive properties of the carrier to construct an intelligent responsive pesticide controlled-release system.

[0009] Preferably, the drug in the above-mentioned nanopesticide is azoxystrobin, pyraclostrobin, trifloxystrobin, kresoxim-methyl, fluopyram, or flutoxamid, preferably azoxystrobin.

[0010] Azoxystrobin (Azo) is a highly effective, broad-spectrum strobilurin fungicide with excellent activity against nearly all fungal diseases, including powdery mildew, rust, glumeman blight, web blotch, downy mildew, and rice blast. However, it is susceptible to light degradation and has strong permeability, which can easily cause leaf aging. Using the aforementioned ZIF-90 particles to load Azo significantly improves its photostability, exhibits pH-responsive release, and reduces its phytotoxicity.

[0011] Preferably, the capping agent in the above-mentioned nanopesticide is one or more selected from hyaluronic acid (HA), chitosan, tannic acid-metal ion complex, pectin, and polydopamine, preferably hyaluronic acid.

[0012] In addition to encapsulating Azo within the ZIF-90 nanoparticles, hyaluronic acid also absorbs ultraviolet light, further enhancing the nanomedicine's photostability. The hyaluronic acid coating also improves the nanoparticles' wettability and adhesion to the rice leaf surface. Furthermore, the hyaluronic acid coating readily decomposes in acidic environments, allowing it to effectively release Azo when combined with the ZIF-90 nanoparticles.

[0013] Preferably, the nanopesticide is in the form of powder, granule, spray, suspension, microcapsule or suspension.

[0014] In a second aspect, the present invention provides a method for preparing the above-mentioned nanopesticide, comprising the following steps: (1) The ZIF-90 nanoparticles were resuspended in a methanol solution of azoxystrobin, stirred for 10-14 h, and then centrifuged and resuspended in methanol for washing three times. The precipitate was freeze-dried in vacuum for 20-28 h to obtain Azo@ZIF-90 nanoparticles; (2) Dissolve the Azo@ZIF-90 nanoparticles and hyaluronic acid in ultrapure water respectively to form an Azo@ZIF-90 solution and a hyaluronic acid solution, slowly add the hyaluronic acid solution into the Azo@ZIF-90 solution under stirring, ultrasonic for 20-25 min, stirring at room temperature for 10-14 h, centrifugal resuspension washing for 3 times, vacuum freeze-drying the precipitate for 20-28 h to obtain the Azo@ZIF-90 nanoparticles.

[0015] The ZIF-90 nanoparticles used in the above preparation method can be prepared by any existing technology, for example, in the embodiment of the present application, the preparation method is as follows: (1) Dissolve imidazole-2-formaldehyde in N,N-dimethylformamide solution to obtain solution 1, disperse (CH3COO)2·Zn·2H2O in a mixed solution of N,N-dimethylformamide and ultrapure water with a volume ratio of 3:1-1:1 to obtain solution 2; (2) After adding solution 2 into solution 1 under stirring for 10-20 min, centrifugal resuspension washing is sequentially performed with N,N-dimethylformamide, ethanol and ultrapure water, and the precipitate is vacuum freeze-dried for 20-28 h to obtain the ZIF-90 nanoparticles.

[0016] The ZIF-90 nanoparticles prepared by the above method have a particle size of about 500-700 nm.

[0017] Preferably, the mass ratio of the ZIF-90 nanoparticles to the azoxystrobin in step (3) of the above preparation method is 1:2-2:1, preferably 1:1.

[0018] Preferably, the mass ratio of the Azo@ZIF-90 nanoparticles to the hyaluronic acid in step (4) of the above preparation method is 15:1-25:1, preferably 20:1.

[0019] Preferably, the centrifugal speed of the centrifugal resuspension in the above preparation method is 8000-12000 rpm, and the centrifugal time is 3-7 min.

[0020] In a third aspect, the present application provides the ZIF-90 nanoparticles and / or the above nano-pesticide for use in inhibiting the growth of Rhizoctonia solani. Rhizoctonia solani ) and / or the above nano-pesticide for use in inhibiting the growth of Rhizoctonia solani.

[0021] Rhizoctonia solani is a plant pathogenic fungus that can release oxalic acid to create acidic environmental conditions, so that the Azo in the above nano-pesticide can be released. The present application finds that the ZIF-90 nanoparticles themselves also have an inhibitory effect on the growth of Rhizoctonia solani, and the loading of Azo on ZIF-90 can synergistically enhance the inhibitory effect of Azo on Rhizoctonia solani, which can reduce the EC 50 value of Azo from 7.5 mg / L to 0.6 mg / L.

[0022] In a fourth aspect, the present invention provides a method for treating or preventing rice sheath blight, specifically, applying the above-mentioned nanopesticide to a rice field, wherein the rice sheath blight is caused by Rhizoctonia solani.

[0023] The nanopesticide Azo@ZIF-90@HA provided by the present invention can protect Azo through the ZIF-90 nanoparticle carrier and the capping agent HA, thereby improving its light resistance. The nanopesticide itself has good adhesion ability, which can effectively resist rain erosion and increase the drug's lasting effect. The release of Azo in the acidic environment caused by Rhizoctonia solani effectively inhibits its growth, and its EC for the growth of Rhizoctonia solani hyphae is 50 The value was 2.3 μg / mL, which could significantly reduce the diameter of rice sheath blight lesions in the application group.

[0024] The nanopesticide Azo@ZIF-90@HA provided by the present invention is a ZIF-90 nanoparticle loaded with antifungal drug Azo, which is sealed with hyaluronic acid. It has pH responsiveness and excellent antibacterial activity, light resistance and adhesion. Its drug release rate can reach 100% in 70 hours at a pH of 5, and it has an EC of 100% for the growth of Rhizoctonia solani hyphae. 50 The value was 2.3 μg / mL. After 50 h of irradiation, its photolysis rate was 55.1%. The photolysis half-life was 1.7 times higher than that of Azo alone. It had a smaller contact angle on the surface of rice leaves. After rainwater washing, its residual rate was 24.4% higher than that of Azo alone. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] In order to more clearly illustrate the technical solutions in the present invention or the prior art, a brief introduction is given below to the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0026] Figure 1 The morphology of the Azo@ZIF-90@HA nanoparticles and their intermediates provided by the present invention is characterized, wherein Figure 1 AC are the scanning electron microscopy images of ZIF-90, Azo@ZIF-90 and Azo@ZIF-90@HA, respectively; Figure 1 D and E are transmission electron microscopy images of Azo@ZIF-90 and Azo@ZIF-90@HA.

[0027] Figure 2 The particle size distribution of the Azo@ZIF-90@HA nanoparticles and their intermediates provided by the present invention is Figure 2The ACs are the particle size distributions of ZIF-90, Azo@ZIF-90 and Azo@ZIF-90@HA, respectively.

[0028] Figure 3 This is the release rate curve result of the Azo@ZIF-90@HA nanoparticles provided by the present invention under different pH conditions.

[0029] Figure 4 These are the anti-photolysis performance results of the Azo, Azo@ZIF-90 and Azo@ZIF-90@HA nanoparticles provided by the present invention.

[0030] Figure 5 The adhesion performance results of Azo SC, Azo@ZIF-90 and Azo@ZIF-90@HA nanoparticles provided by the present invention are as follows: Figure 5 A is the blade contact angle measurement result, Figure 5 B is the residual rate of resistance to rainwater erosion.

[0031] Figure 6 The results are as follows: the inhibition rate of the Azo@ZIF-90@HA nanoparticles and their intermediates on the mycelial growth of Rhizoctonia solani provided by the present invention, wherein Figure 6 A is the inhibition rate of Azo, Azo@ZIF-90 and Azo@ZIF-90@HA nanoparticles. Figure 6 B is the inhibition rate results of ZIF-90@HA, ZIF-90@, HA.

[0032] Figure 7 The results of the inhibition rate of mycelial growth of Rhizoctonia solani by different concentrations of Azo provided by the present invention in the presence of ZIF-90 are shown in FIG. Figure 7 A is the apparent result. The Azo concentrations of the culture dishes from left to right are 0.625, 1.25, 2.5, 5, and 10 mg / L. Figure 7 B is the statistical result.

[0033] Figure 8 These are the therapeutic effect results of the Azo SC, Azo@ZIF-90 and Azo@ZIF-90@HA nanoparticles provided by the present invention on rice sheath blight at 5 and 7 days. DETAILED DESCRIPTION

[0034] To make the objectives, technical solutions, and advantages of the present invention more clear, the technical solutions of the present invention will be clearly and completely described below in conjunction with the accompanying drawings. Obviously, the embodiments described are only some of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts shall fall within the scope of protection of the present invention.

[0035] Example 1 Synthesis of Azo@ZIF-90@HA This example provides the synthesis of Azo@ZIF-90@HA nanoparticles.

[0036] First, ZIF-90 particles were synthesized. The specific steps are as follows: (1) Dissolve 961 mg of imidazole-2-carboxaldehyde (2-ICA) in 200 mL of N,N-dimethylformamide solution and stir magnetically at room temperature for 15 min. (2) Disperse 0.55 g (CH3COO)2·Zn·2H2O in 100 mL of a mixed solution of N,N-dimethylformamide and ultrapure water (volume ratio 3:2); (3) The (CH3COO)2·Zn·2H2O solution was then added dropwise to the imidazole-2-carboxaldehyde solution under stirring. After magnetic stirring at room temperature for 15 min, the solution was centrifuged and resuspended with N,N-dimethylformamide, ethanol, and ultrapure water, respectively. Ultrasonic resuspension was used for each resuspension, followed by centrifugation at 10,000 rpm for 5 min. Finally, ZIF-90 nanoparticles were obtained after vacuum freeze-drying for 24 h.

[0037] Then, Azo@ZIF-90 particles were synthesized as follows: (1) The prepared ZIF-90 nanoparticles (250 mg) were suspended in a 20 mg / mL azoxystrobin methanol solution (12.5 mL). The Azo@ZIF-90 solution was obtained after magnetic stirring at room temperature for 12 h. The solution was then centrifuged and resuspended in methanol and washed three times, each time using ultrasound-assisted resuspension. The solution was then centrifuged at 10,000 rpm for 5 min, and finally freeze-dried in vacuum for 24 h to obtain the Azo@ZIF-90 nanoparticles.

[0038] Finally, Azo@ZIF-90@HA particles were synthesized by the following steps: (1) Disperse 1 g of Azo@ZIF-90 nanoparticles in 20 mL of ultrapure water and dissolve 50 mg of hyaluronic acid in 10 mL of ultrapure water; (2) The hyaluronic acid solution was slowly added to the Azo@ZIF-90 solution under magnetic stirring at room temperature. Ultrasonication was performed for 20 min, stirring was performed at room temperature for 12 h, and the solution was resuspended and washed three times by centrifugation in ultrapure water, each time using ultrasound-assisted resuspension and centrifugation at 10,000 rpm for 5 min. Finally, Azo@ZIF-90@HA nanoparticles were obtained by vacuum freeze drying for 24 h.

[0039] Example 2 Characterization of Azo@ZIF-90@HA This example provides morphological characterization of ZIF-90, Azo@ZIF-90, and Azo@ZIF-90@HA nanoparticles.

[0040] An appropriate amount of sample powder was added to a centrifuge tube filled with deionized water to prepare a 250 μg / mL suspension. The suspension was then placed in an ultrasonic disruptor (500 W power, 30 minutes) for sonication to uniformly disperse the sample powder in the deionized water.

[0041] 5 μL of the sample suspension was pipetted onto the grid and air-dried at room temperature for 12 hours to fix the nanoparticles on the grid. The prepared sample was stored in a desiccator to prevent moisture and other contamination. The micromorphology of the sample was observed and photographed using scanning and transmission electron microscopy. The results are shown in Figure 2. Figure 1 The particle size distribution of the nanoparticles was analyzed using GraphPad software, and the results are shown in Figure 2 shown.

[0042] Depend on Figure 1 It can be seen that both Azo@ZIF-90 and Azo@ZIF-90@HA have good monodispersity and regular cubic crystal morphology. The surface of Azo@ZIF-90 is relatively smooth, while the surface of Azo@ZIF-90@HA with the introduction of hyaluronic acid is relatively rough with obvious protrusions.

[0043] Depend on Figure 2 The particle size distribution calculated from scanning electron microscopy images of the samples revealed average particle sizes of 642 nm for ZIF-90, 780 nm for Azo@ZIF-90, and 850 nm for Azo@ZIF-90@HA, respectively. The increased particle sizes of Azo@ZIF-90 and Azo@ZIF-90@HA compared to ZIF-90 demonstrate successful azoxystrobin loading and hyaluronic acid encapsulation.

[0044] Example 3 Release performance of Azo@ZIF-90@HA This example studies the cumulative release rate of azoxystrobin from Azo@ZIF-90@HA nanoparticles under different pH conditions.

[0045] Azo@ZIF-90@HA nanoparticles were placed in a dialysis bag (MWCO, 3500Da) and placed in phosphate buffer solutions at pH 5, 7, and 9. At specific time intervals, 1 mL of release solution was removed and the same volume of release solution was added simultaneously to ensure a constant volume of release medium. The cumulative release rate of the sample was calculated as follows: Where Ve is the volume of the extracted solution at time n (1 mL); Cn (mg / L) is the concentration of the sample in the extracted solution at time n; V0 is the total volume of the release medium (200 mL); and mp is the loading mass of azoxystrobin in Azo@ZIF-90@HA (mg).

[0046] The samples were analyzed by high performance liquid chromatography. The mobile phase was acetonitrile and 0.1% formic acid in water (80:20, v / v). The flow rate was 1 mL / min and the UV detector wavelength was 235 nm. Figure 3 shown.

[0047] Depend on Figure 3 The release rate of Azo@ZIF-90@HA increased with decreasing pH, attributed to the decomposition of the ZIF-90 framework and hyaluronic acid coating under acidic conditions. Compared with neutral (pH 7) and alkaline (pH 9) conditions, the cumulative release rate of Azo@ZIF-90@HA increased by 35.9% and 128.7%, respectively, after 60 h of treatment in an acidic environment (pH 5). At pH 5, the cumulative release rates of both Azo@ZIF-90 and Azo@ZIF-90@HA reached 100% after approximately 70 h, demonstrating their acid-responsive release properties. This allows for on-demand release of active ingredients upon disease occurrence, enabling targeted delivery of active ingredients and improving the effective utilization of pesticides.

[0048] Example 4 Drug loading efficiency of Azo@ZIF-90@HA This example tests the drug loading efficiency of Azo@ZIF-90@HA nanoparticles.

[0049] 15 mg of Azo@ZIF-90@HA nanoparticles were placed in a 25 mL volumetric flask and 200 μL of phosphoric acid was added to dissolve the Azo@ZIF-90@HA nanoparticles. Methanol was then added to the volume to 25 mL, and the mixture was sonicated for 5 min. 1 mL of the final solution was filtered through a 0.22 μm filter and placed in a vial. The azoxystrobin content was determined by high-performance liquid chromatography. The mobile phase consisted of acetonitrile and 0.1% formic acid in water (80:20, v / v). The flow rate was 1 mL / min, and the UV detector wavelength was 235 nm. The experiment was repeated three times. The drug loading efficiency was calculated as follows: Where C (mg / mL) is the concentration of azoxystrobin, V (25 mL) is the total volume of the final solution, and W (mg) is the exact weight of the nanoparticles. Testing showed that the drug loading efficiency of Azo@ZIF-90@HA was 22.2%.

[0050] Example 5 Photolytic stability and adhesion properties of Azo@ZIF-90@HA This example tested the photolytic stability of azoxystrobin technical Azo, Azo@ZIF-90, and Azo@ZIF-90@HA nanoparticles, as well as the adhesion properties of azoxystrobin suspension concentrate Azo SC (Nantong Taihe Chemical Co., Ltd., registration number PD20131922), Azo@ZIF-90, and Azo@ZIF-90@HA nanoparticles.

[0051] Photolytic Stability: Samples of azoxystrobin (Azo), Azo@ZIF-90, and Azo@ZIF-90@HA nanoparticles were diluted with deionized water to a relative concentration of 100 mg / L of the active ingredient Azo. Subsequently, 200 μL of each diluted solution was evenly applied to a 2 × 4 cm glass slide. After evaporation of the water, the slide was exposed to ultraviolet light at an average irradiance of 25 MW / cm. The slide was removed at intervals and placed in a 50 mL centrifuge tube. Acetonitrile was then added and ultrasonically extracted for 15 min. 5 mL of the extract was transferred to a 10 mL centrifuge tube, 1 g of NaCl was added, and the tube was vortexed for 5 min. Centrifuged at 4000 rpm for 5 min, and 1 mL of the supernatant was filtered through a 0.22 μm filter into a vial. The azoxystrobin content was determined by high-performance liquid chromatography. The photolytic residue was calculated as follows: Where C t is the concentration of azoxystrobin at time t; C0 is the initial concentration of azoxystrobin, and the measurement results are as follows: Figure 4 shown.

[0052] Leaf Adhesion Performance: The dynamic contact angle of the nanoparticles on rice leaves was measured using a contact angle meter to evaluate the wettability of Azo@ZIF-90@HA. The rice leaves were washed with ultrapure water and air-dried on a glass slide. Subsequently, 5 μL of each sample solution was dropped onto the rice leaf surface. The contact angle was measured after 0, 15, 45, and 60 seconds to analyze the wetting process. The results are shown in Figure 2. Figure 5 As shown in A. Rice leaves were cut into long strips and soaked in a sample diluent with a concentration of 200 mg / L for 30 seconds. After natural drying, each leaf was tilted 30° relative to the ground. To simulate rainwater washing, 20 mL of deionized water was dripped onto the leaves at a rate of 20 mL / min. The washing liquid was collected, extracted and concentrated, and the content of azoxystrobin was determined by high-performance liquid chromatography. The results are shown in Figure 2. Figure 5 As shown in B.

[0053] Depend on Figure 4After 50 hours of irradiation, the photolysis rates of Azo@ZIF-90 and Azo@ZIF-90@HA were 62.1% and 55.1%, respectively, lower than those of Azo (88.7%). Furthermore, Azo@ZIF-90@HA exhibited superior UV protection against pesticides to Azo@ZIF-90, attributed to the presence of a hyaluronic acid coating on its shell, which shielded the system from UV rays.

[0054] Depend on Figure 5 As shown by A, Azo@ZIF-90@HA exhibited a smaller contact angle on rice leaf surfaces compared to Azo SC and Azo@ZIF-90. After 60 s, the contact angle of Azo@ZIF-90@HA decreased by 49.6% and 49.7% compared to Azo@ZIF-90 and Azo, respectively, indicating that the introduction of HA enhanced the wetting properties of the nanoparticles on the rice leaf surface. This is likely due to the good dispersibility of Azo@ZIF-90@HA in aqueous solution, which allowed it to evenly distribute and diffuse on the leaf surface.

[0055] Depend on Figure 5 As shown in Figure B, the residual rate of Azo@ZIF-90@HA increased by 24.4% compared to Azo SC, indicating that Azo@ZIF-90@HA has better leaf adhesion properties, thereby reducing pesticide losses under rainfall conditions. In addition, compared with Azo@ZIF-90, the residual rate of Azo@ZIF-90@HA increased by 48.6%, indicating that the introduction of hyaluronic acid can significantly improve the adhesion properties of nanoparticles and enhance the adhesion of nanoparticles to the leaf surface.

[0056] Example 6 Inhibitory effect of Azo@ZIF-90@HA on hyphal growth of Rhizoctonia solani and synergistic activity of the carrier In this example, the inhibitory effects of Azo, Azo@ZIF-90, Azo@ZIF-90@HA, ZIF-90@HA, ZIF-90, and HA on the mycelial growth of Rhizoctonia solani were determined by the mycelial growth rate method. The specific steps are as follows: Potato dextrose agar (PDA) media containing Azo, Azo@ZIF-90, and Azo@ZIF-90@HA at concentrations of 0, 0.625, 1.25, 2.5, 5, and 10 mg / L, as well as PDA media containing ZIF-90, HA, and ZIF-90@HA at concentrations of 25, 50, 100, 200, and 400 mg / L, respectively, were prepared.

[0057] After culturing Rhizoctonia solani (Rhizoctonia solani used for cake preparation was provided by the Institute of Plant Protection, Chinese Academy of Agricultural Sciences) in a 9 cm diameter Petri dish (PDA solid medium) for 48 h, a 5 mm diameter cake was punched out from the edge of the medium using a hole punch. The cake was placed in the center of each group of PDA medium, with three replicate Petri dishes used for each test. All Petri dishes were placed in a constant temperature incubator at 25°C for 48 h. The colony diameter was measured using the cross-hatch method, and the antibacterial activity was calculated using the following formula: Figure 6 shown.

[0058] PDA culture medium with Azo concentrations of 0, 0.625, 1.25, 2.5, 5, and 10 mg / L was prepared, as well as the above-mentioned PDA culture medium containing Azo added with ZIF-90 at a final concentration of 100 mg / L. The above-mentioned antibacterial experiment was carried out again to evaluate the synergistic inhibitory effect of ZIF-90 and Azo on Rhizoctonia solani. The results are shown in FIG. Figure 7 shown.

[0059] Depend on Figure 6 It can be seen from the A that Azo, Azo@ZIF-90 and Azo@ZIF-90@HA have the highest EC value against Rhizoctonia solani after treatment for 48 h. 50 The values ​​were 4.0, 2.8 and 2.3 mg / L, respectively. Compared with Azo, the EC values ​​of Azo@ZIF-90 and Azo@ZIF-90@HA against Rhizoctonia solani were 50 The values ​​were reduced by 30.7% and 41.2%, respectively, indicating that the antibacterial ability of azoxystrobin was improved after being loaded by nanocarriers. Figure 6 As shown in Figure 2, the nanocarriers ZIF-90 and ZIF-90@HA also showed antibacterial activity against Rhizoctonia solani. After 48 h of treatment, their EC 50 The values ​​were 82.3 mg / L and 86.6 mg / L respectively. Hyaluronic acid also has very low antibacterial activity against Rhizoctonia solani, but its EC 50 The value is greater than 600 mg / L.

[0060] Depend on Figure 7 It can be seen that after 72 h of treatment, Azo treatment alone had an effect on the EC 50 The value was 7.5 mg / L, and after adding 100 mg / L of ZIF-90 to the Azo solution at each concentration, the EC 50 The value dropped to 0.6 mg / L, and its EC 50 The value was about 11.0 times lower than that of Azo treatment alone, indicating that ZIF-90 and azoxystrobin had synergistic antibacterial activity and could enhance the biological activity against Rhizoctonia solani, thus playing a synergistic role.

[0061] Example 7 Treatment activity of Azo@ZIF-90@HA against rice sheath blight In this example, the method of rice in vitro leaf inoculation was used to evaluate the control effect of Azo@ZIF-90@HA nanoparticles on rice sheath blight.

[0062] Rice was planted in pots in a greenhouse (25℃ / 20℃, day / night temperature, 8:00-18:00 supplemental lighting, 70% relative humidity) and fresh rice leaves were cut after growing for about two months, washed with sterile water and placed on the surface of water agar medium. Azo SC, Azo@ZIF-90 and Azo@ZIF-90@HA were diluted with 0.1% Tween-80 aqueous solution so that the concentration of active ingredients was 200 mg / L. Rhizoctonia solani was inoculated on rice leaves, and 48 h later, the sample solution was uniformly sprayed on the rice leaves to study its treatment activity against Rhizoctonia solani. Cultivation was carried out in a constant temperature light incubator (25℃, 12 / 12 h: light / dark, 75% humidity), and the lesion diameters were measured in two perpendicular directions after 5 days and 7 days of cultivation. Sterile water was used as a blank control group, and there were 15 rice leaves in each treatment, and each treatment was repeated 5 times. The control effect was calculated as follows: where D and d are the lesion diameters of the control group and the treatment group, respectively, and the results are shown in Figure 8 .

[0063] As can be seen from Figure 8 , after 5 days and 7 days of treatment, the treatment activity of Azo@ZIF-90@HA against rice sheath blight was significantly higher than that of Azo SC and Azo@ZIF-90. At 7 days, the control effect of Azo@ZIF-90@HA against rice sheath blight was increased by 195.4% and 68.6% compared with Azo SC and Azo@ZIF-90, respectively, indicating that Azo@ZIF-90@HA has better sustained control effect on rice sheath blight, thereby prolonging the efficacy period of azoxystrobin.

[0064] Finally, it should be noted that the above examples are only used to illustrate the technical solutions of the present application, and not to limit them; although the present application has been described in detail with reference to the foregoing examples, those skilled in the art should understand that they can still modify the technical solutions described in the foregoing examples, or make equivalent substitutions for some of the technical features; and these modifications or substitutions do not make the essence of the corresponding technical solutions deviate from the spirit and scope of the technical solutions of the embodiments of the present application.

Claims

1. A nanopesticide, characterized in that: The nanopesticides include: A carrier, wherein the carrier is ZIF-90 nanoparticles; A drug encapsulated in the nanocarrier, wherein the drug has an effect of killing or inhibiting bacteria and / or fungi; A capping agent is used to seal the pores of the ZIF-90 nanoparticles.

2. The nanopesticide according to claim 1, characterized in that The drug is azoxystrobin, pyraclostrobin, trifloxystrobin, kresoxim-methyl, fluopyram, or flutoxapyram, preferably azoxystrobin.

3. The nanopesticide according to claim 1 or 2, characterized in that The capping agent is one or more selected from hyaluronic acid, chitosan, tannic acid-metal ion complex, pectin, and polydopamine, preferably hyaluronic acid.

4. The nanopesticide according to any one of claims 1 to 3, characterized in that It is in the form of powder, granule, spray, microcapsule, and suspension.

5. The method for preparing the nanopesticide according to any one of claims 1 to 4, characterized in that: The following steps are involved: (1) ZIF-90 nanoparticles were resuspended in a methanol solution of azoxystrobin, stirred for 10-14 h, and then centrifuged and resuspended in methanol and washed three times. The precipitate was freeze-dried in vacuum for 20-28 h to obtain Azo@ZIF-90 nanoparticles. (2) The Azo@ZIF-90 nanoparticles and hyaluronic acid were dissolved in ultrapure water to form an Azo@ZIF-90 solution and a hyaluronic acid solution, respectively. The hyaluronic acid solution was slowly added to the Azo@ZIF-90 solution under stirring, and ultrasonicated for 20 to 25 minutes. The mixture was stirred at room temperature for 10 to 14 hours, and the mixture was resuspended and washed three times by centrifugation in ultrapure water. The precipitate was freeze-dried in vacuum for 20 to 28 hours.

6. The preparation method according to claim 5, characterized in that The mass ratio of the ZIF-90 nanoparticles to the azoxystrobin in step (3) is 1:2 to 2:1, preferably 1:

1.

7. The preparation method according to claim 5, characterized in that In step (4), the mass ratio of the Azo@ZIF-90 nanoparticles to the hyaluronic acid is 15:1 to 25:1, preferably 20:

1.

8. The preparation method according to any one of claims 5 to 7, characterized in that The centrifugal resuspension is performed at a centrifugal speed of 8000-12000 rpm and a centrifugal time of 3-7 min.

9. Use of ZIF-90 nanoparticles and / or the nanopesticide according to any one of claims 1 to 4 in inhibiting the growth of Rhizoctonia solani.

10. A method for treating or preventing rice sheath blight, characterized in that: The nanopesticide according to any one of claims 1 to 4 is applied to a rice field, wherein the rice sheath blight is caused by Rhizoctonia solani.

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