CN115005218A - Preparation of a pH-responsive controlled-release nanopesticide based on hydroxyapatite carrier - Google Patents

Abstract

The invention discloses the preparation of a hydroxyapatite carrier pH-responsive controlled-release nano-pesticide. The present invention adopts nano-hydroxyapatite with a particle size of 200nm to load two pesticides, promethazine and atrazine, and then wraps the nanoparticles with sodium alginate to prepare gel microspheres (with a particle size of about 1mm). The controlled release effect under neutral alkaline conditions is better than that under acidic conditions and is basically not affected by light and temperature. Meanwhile, the release of orthophosphate in nano-hydroxyapatite can also provide phosphorus source for microorganisms and plants in soil. The material of the invention has low cost and environmental friendliness, can improve soil fertility while exerting medicinal effect, and has wide application prospects.

Description

Preparation of a pH-responsive controlled-release nanopesticide based on hydroxyapatite carrier

technical field

The invention designs the field of novel pesticides, in particular to the preparation of a pH-responsive controlled-release nano-pesticide based on a hydroxyapatite carrier and its controlled-release effect.

Background technique

my country is a big grain-producing country, but also a big country in the production and application of pesticides. Pesticides are widely used because of their effective insect and weed control capabilities. In general, pesticides have a recommended dosage, but due to the development of collective agriculture and the driving of economic interests, the application frequency has been increasing, so that the amount used in the actual production process is 2 times or more than the recommended dosage. As a result, a large part of pesticides cannot be consumed and remain in the soil environment. The water environment, the atmospheric environment and the soil environment are closely linked. When there is an excess of pesticides in the soil, the excess pesticides may be transferred to the atmospheric environment and the water environment through atmospheric transpiration and rainfall leaching. The ecological environment system may have excessive pesticide content. Human activities and the ecological environment influence each other and restrict each other. Human activities affect the ecological environment, and the ecological environment in turn affects and restricts human activities. Therefore, when the pesticide content in the ecological environment exceeds the standard, the normal life activities of human beings will also be affected. affected.

Because of its slow and controlled release effect, nano-pesticides are an important direction of current research, which can reduce the residual amount of pesticides in the soil and reduce the accumulation of pesticides in the human body. The soil environment is very complex compared to water. Therefore, whether we prepare pesticides or phosphate fertilizers, it needs to have good stability in the complex environment of the soil. Such as pH changes, temperature changes, and changes in light conditions do not significantly change the properties of the applied drug.

The present invention uses nano-hydroxyapatite as a pesticide carrier, considering that nano-hydroxyapatite will release phosphorus under acidic conditions, and the material of nano-hydroxyapatite itself is relatively natural, and will not harm humans or animals and plants under normal circumstances. There are side effects. Therefore, nano-hydroxyapatite is a good natural carrier. On the one hand, loading it with pesticides can reduce the application amount of pesticides, and on the other hand, it can release phosphorus necessary for plant growth, and has a good application prospect. In addition, the microspheres are coated with sodium alginate, which makes the nano pesticides have a good ability to control the release. While prolonging the action time of the pesticides, for farmers, when using pesticides, this product reduces the direct contact with the human body. Toxic effect. Pesticide in the state of solid micro-particles also reduces the probability of rain leaching to pollute the water environment and transpiration to pollute the atmospheric environment, and also reduces the amount of pesticide application and enhances the effect of precise pesticide application.

SUMMARY OF THE INVENTION

The invention prepares an organophosphorus nano pesticide, which aims to prolong the action time of the pesticide, reduce the pesticide application amount, and enhance the effect of precise pesticide application through the loading of nano-hydroxyapatite and the wrapping of sodium alginate. To a certain extent, it effectively solves the environmental problems caused by pesticide residues and accumulation, and provides a good development prospect for nano-pesticides. At the same time, nano-hydroxyphosphorus can provide phosphorus source for microorganisms and plants in the soil while controlling the release of pesticides. It is a nano-pesticide that can both weed and provide phosphorus source.

In order to realize the above-mentioned purpose of the invention, the technical route adopted in the present invention is as follows:

(1) The nano-hydroxyapatite with a particle size of 200nm was stirred with the ethanol solution of Promethazine and the aqueous solution of atrazine for 24h, and then filtered and dried, and an ultraviolet spectrophotometer was used to measure the Promethazine in the supernatant, respectively. The contents of net and atrazine were calculated to obtain 20.8% loading of Promethazine nanospheres and 8.1% loading of atrazine nanoparticles, respectively.

(3) adding sodium alginate and the nano-hydroxyapatite loaded with pesticides into the centrifuge tube, and then using a syringe to drop it into the _CaCl solution after ultrasonic vibration, and then through the processing procedure of cleaning and pre-winter drying to obtain alginic acid Sodium-coated microspheres.

(4) The controlled release effects of the two kinds of nano-microspheres under different temperature, pH and light conditions were studied, and it was concluded that: (1) In neutral and alkaline environments, the sodium alginate gel spheres would rupture, and the release rate would also decrease. higher than the acidic conditions; ② the temperature had little effect on the release of pesticides; ③ ultraviolet light could stimulate the release of promethazine, which may be due to the easy degradation of promethazine under ultraviolet light irradiation. However, the two environments of normal light and dark light have basically no effect on the release of Promethazine. The three light conditions had little effect on the release of atrazine.

(5) Scanning electron microscopy (SEM) and energy dispersive analysis (EDS) were used to characterize nano-hydroxyapatite, pesticide-loaded hydroxyapatite and gel microspheres formed by encapsulating sodium alginate, respectively. The pesticide was successfully loaded on the nano-hydroxyapatite, and the nano-hydroxyapatite loaded with the pesticide was also successfully encapsulated by sodium alginate.

Description of drawings

Figure 1: (a) is the SEM image of the nano-hydroxyapatite, (b) is the SEM image of the nano-hydroxyapatite loaded with promethazine, (c) is the SEM image of the promethazine gel microspheres, and (d) is the The EDX image of nano-hydroxyapatite, (e) is the EDX image of the nano-hydroxyapatite loaded with Promethazine, and (f) is the EDX image of the Propodazone gel microspheres;

Figure 2: (a) SEM image of nano-hydroxyapatite, (b) SEM image of atrazine-loaded nano-hydroxyapatite, (c) SEM image of atrazine gel microspheres, (d) ) is the EDX image of nano-hydroxyapatite, (e) is the EDX image of atrazine-loaded nano-hydroxyapatite, and (f) is the EDX image of atrazine gel microspheres;

Figure 3: (a) is the actual picture of the nano-hydroxyapatite loaded with Promethazine, (b) is the actual picture of the nano-hydroxyapatite loaded with atrazine

Figure 4: (a) is the cumulative release curve of Protozam nano-microspheres with pH changes, (b) is the cumulative release curve of Protozam nano-microspheres with temperature changes, (c) is Cumulative release curves of light changes;

Figure 5: (a) is the cumulative release curve of atrazine nanospheres with pH, (b) is the cumulative release curve of atrazine nanospheres with temperature, (c) is atrazine nanospheres Cumulative release curve of microspheres with changes in light;

Figure 6: (a) is the release curve of phosphorus from nano-hydroxyapatite, (b) is the release curve of phosphorus from hydroxyapatite nanospheres, (c) is the nano-hydroxyapatite gel microspheres loaded with pesticides Phosphorus release profile from spheres.

specific implementation

Through the following embodiments, those skilled in the art can better understand the present invention, effectively improve the precision of pesticide application, and reduce pesticide residues in the environment. The basic research has been laid for the popularization of nano pesticides.

Embodiment 1: Loading of pesticides

(1) Loading of Promethazine: Prepare 10 ml of 1mg/ml Promethazine ethanol solution, add 1g of nano-hydroxyapatite to the solution, put a rotor in the conical flask and seal it with plastic wrap, put it in Stir with a magnetic stirrer for 24 hours. After 24 hours, use a suction filter to filter the nano-hydroxyapatite loaded with pesticides with a small amount of ethanol. multiples, and its absorbance was measured with a UV spectrophotometer. Put the material on the filter paper into a clean beaker, seal it with plastic wrap, poke pores on the plastic wrap, and put it into a 60-degree negative pressure oven to dry for 24 hours to obtain a protoprazine-loaded product. Nano-hydroxyapatite powder.

As shown in Fig. 1(d)(e), the characteristic elements of promethazine containing N and S are compared, indicating that promethazine was successfully loaded on the nano-hydroxyapatite.

(2) Atrazine load: configure 10 ml of 1 mg/ml atrazine acetone solution, add 1 g of finished nano-hydroxyapatite to the solution, put a rotor in the conical flask and seal it with plastic wrap Then put it into a magnetic stirrer and stir for 24 hours. After 24 hours, use a suction filter to filter the nano-hydroxyapatite loaded with the pesticide with a small amount of acetone for 2-3 times. A certain multiple is used to measure its absorbance with a UV spectrophotometer. Put the material on the filter paper into a clean beaker, seal it with plastic wrap, prick the pores with a needle on the plastic wrap, and put it in a negative pressure oven at 60 degrees to dry for 24 hours to get the atrazine loaded. of nano-hydroxyapatite powder.

As shown in Figure 2(d)(e), the two characteristic elements of atrazine containing N and Cl are compared, indicating that atrazine is successfully loaded on the nano-hydroxyapatite.

Figure 3 is the physical map of the two nano-pesticide.

Embodiment 2: Encapsulation of sodium alginate

Add 25ml of water, 0.1g of sodium alginate and 0.25g of pesticide-loaded nano-hydroxyapatite into a 50ml centrifuge tube, sonicate it until no large solid particles are seen, and then shake it with a vortex shaker. The solution is poured from the tail of the syringe, so that it can drip continuously from the head of 1mm, and the dripping liquid is added dropwise to 100ml, 0.1mol/l _CaCl2 solution, it can be observed that the dripping liquid is in the White spherical particles formed in the _CaCl2 solution. After all the dropwise additions are completed, the solution is allowed to stand for 30 minutes, the particles floating on the liquid surface are poured out, and the remaining solution and particles are filtered with filter paper and washed with distilled water for 2-3 times. Pour the particle microspheres on the filter paper into a clean conical flask, cover with plastic wrap, and pre-freeze in a refrigerator at -20 degrees for 30 minutes. After 30 minutes, prick the plastic wrap on the conical Dryer for 24h. The obtained product is the pesticide-loaded nano-hydroxyapatite wrapped with sodium alginate.

As shown in Figure 1(c), it can be clearly seen that sodium alginate successfully encapsulated the drug-loaded nano-hydroxyapatite, and in Figure 1(f), there are two characteristic elements of promethazine, N and S, which further proves that the encapsulated nano-hydroxyapatite success.

As shown in Figure 2(c), it is obvious that sodium alginate successfully encapsulated the drug-loaded nano-hydroxyapatite, and in Figure 2(f) the two characteristic elements of atrazine, N and Cl, still exist, which further proves the encapsulation. of success.

Embodiment 3: Exploration on the controlled release effect of two nano-pesticide

(1) Controlled release effect of promethazine nano-microspheres

①: The effect of different pH on the controlled release effect of Prometraz nanospheres

First prepare 1/16 mol sodium dihydrogen phosphate solution and 1/16 disodium hydrogen phosphate solution, and prepare 3 bottles of slow-release solution with pH 5.5, 7.0, and 8.5 of the two solutions according to a certain ratio. Fill each bottle with 50ml of slow-release solution 0.05g of Protozafloxacin nano-microspheres, make 3 parallels for each pH, and measure the absorbance of 1ml of the supernatant by UV spectrophotometry at regular intervals, and take samples after sampling. Then 1 ml of the corresponding sustained-release solution was added.

As shown in Figure 4(a), the release rate is the highest under alkaline conditions and the lowest under acidic conditions, but in general, the difference is not significant.

②: The effect of different temperatures on the controlled release effect of Prometraz nanospheres

Put 25ml of ethanol and 0.25g of Promethazine nanospheres into the bottle, set 3 temperature gradients of 5°C, 25°C, and 45°C, and take 1ml of supernatant at regular intervals to measure its absorbance by UV spectrophotometry. And add 1 ml of absolute ethanol after sampling.

As shown in Fig. 4(b), the controlled release effect of the nano-microspheres is relatively stable with the change of temperature, and the effect of temperature on it is not obvious.

③: The effect of different light conditions on the controlled release effect of Prometraz nanospheres

Put 10ml of ethanol and 0.01g of Prozafon nano-microspheres into the bottle, set three light irradiation conditions of normal light, dark light and ultraviolet light, set 3 parallels for each condition, and take the supernatant at regular intervals The absorbance was measured by ultraviolet spectrophotometry, and 1 ml of absolute ethanol was added after sampling.

As shown in Figure 4(c), under different lighting conditions, the release effect is consistent under normal light and dark conditions. However, the release rate was higher than normal light and dark conditions due to the sensitivity of Promethazine to UV light.

(2) Controlled release effect of atrazine nanospheres

①: Effect of different pH on the controlled release effect of atrazine nanospheres

First, 1/16 mol of sodium dihydrogen phosphate solution and 1/16 of disodium hydrogen phosphate solution were prepared, and the two solutions were prepared in a certain proportion to prepare a slow-release solution with pH of 5.5, 7.0, and 8.5. Fill each bottle with 50ml of slow-release solution and 0.05g of atrazine nano-microspheres, make 3 parallels for each pH, and measure the absorbance of 1ml of the supernatant by ultraviolet spectrophotometry at regular intervals. After sampling, 1 ml of the corresponding slow-release solution was added, and three parallels were set for each group of data.

As shown in Figure 5(a), the cumulative release curves of atrazine nanospheres at pH 5.5 and 7.0 are almost the same, while the cumulative release rate is higher at pH 8.5, but the overall difference is not large, it can be concluded that the pH It has little effect on the release of atrazine nanospheres.

②: The effect of different temperatures on the controlled release of atrazine nanospheres

Put 25ml of deionized water and 0.25g of atrazine nanospheres in the bottle, set 3 temperature gradients of 5°C, 25°C, and 45°C, and take 1ml of the supernatant at intervals and measure it by UV spectrophotometry Its absorbance, and add 1 ml of deionized water after sampling, each set three parallel.

As shown in Figure 5(b), the cumulative release concentration curves of atrazine at different temperatures are basically the same, so the temperature basically does not affect the release of atrazine.

③: The effect of different light conditions on the controlled release of atrazine nanospheres

Put 10ml of deionized water and 0.01g of atrazine nano-microspheres in the bottle, set 3 conditions of normal light, dark light, and ultraviolet light, and set 3 parallels for each condition, and take the top at regular intervals. The absorbance of the supernatant was measured by UV spectrophotometry, and 1 ml of deionized water was added after sampling.

As shown in Figure 5(c), the cumulative release rate of atrazine nanospheres is the highest under no-light conditions, followed by normal light, and the lowest under UV conditions, but in general the three are not much different, so it can be concluded that different Light conditions had no significant effect on the cumulative release of atrazine.

Embodiment 4: Release of Phosphorus

Weigh a certain mass of nano-hydroxyapatite, gel spheres containing the same mass of nano-hydroxyapatite, and pesticide gel microspheres containing the same mass of nano-hydroxyapatite. Put into buffer solutions with pH 5.5, 7.0, 8.5. The solution was taken out at intervals to measure the content of orthophosphate, and an equal volume of buffer solution was added, and three parallels were set for each experimental group.

As shown in Figure 6, the release of orthophosphate was measured under the three pH conditions, and the release rate of orthophosphate under acidic conditions was greater than that of neutral and alkaline conditions. It is indicated that the prepared pH-responsive controlled-release gel microspheres can provide the required phosphorus source for microorganisms and plants in soil.

Claims (4)

1. The invention discloses a preparation method of a pH response controlled release type nano pesticide based on a hydroxyapatite carrier.

2. The preparation method of the pH response controlled release type nano pesticide according to claim 1 is characterized in that:

(1) weighing nano-hydroxyapatite with the particle size of 200nm at normal temperature, and loading the atrazine solution and the prometryn solution on the nano-hydroxyapatite by stirring;

(2) sodium alginate is used for wrapping the nano-hydroxyapatite loaded with the pesticide, and a calcium chloride solution is dripped into the nano-hydroxyapatite to prepare the gel microsphere.

3. The preparation method of the pH response controlled release type nano pesticide according to claim 1 is characterized in that:

(1) the load rate of prometryn is 20.8%, and the load rate of atrazine is 8.1%;

(2) the prometryn nano microsphere can realize a pH response controlled release effect under the condition that the pH is 5.5, and the release of the prometryn nano microsphere is not influenced by the temperature. But it releases rapidly under uv light compared to darkness and normal light;

(3) the atrazine nano-microsphere can realize an intelligent controlled release effect under the condition that the pH value is 5.5, and the release process is not influenced by temperature and different illumination and is relatively stable;

(4) under normal experimental conditions, the release of orthophosphate can be measured under different pH conditions. And the release rate under the acidic condition is higher than that of neutral and alkaline.

4. The preparation method of the pH response controlled release type nano pesticide according to claim 1 is characterized in that:

(1) the nano-microspheres are characterized by means of a scanning electron microscope, energy spectrum scanning and the like, and show that the prometryn and the atrazine are successfully loaded on the nano-hydroxyapatite to successfully prepare the nano-pesticide gel microspheres.

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