CN115380897B

CN115380897B - Liquid-carrying gel and preparation method and application thereof

Info

Publication number: CN115380897B
Application number: CN202211050275.7A
Authority: CN
Inventors: 曹立冬; 陈慧萍; 黄啟良; 曹冲; 赵鹏跃
Original assignee: Institute of Plant Protection of Chinese Academy of Agricultural Sciences
Current assignee: Institute of Plant Protection of Chinese Academy of Agricultural Sciences
Priority date: 2022-08-31
Filing date: 2022-08-31
Publication date: 2023-07-21
Anticipated expiration: 2042-08-31
Also published as: CN115380897A

Abstract

The invention belongs to the technical field of agricultural pest control, and particularly relates to a liquid-carrying hydrogel and a preparation method and application thereof. The invention provides a water-carrying hydrogel, which comprises hydrogel and acaricide coated in the hydrogel; the hydrogel is obtained by crosslinking a hydroxyl-containing polymer and borax. In the invention, the hydrogel obtained by crosslinking the hydroxyl-containing polymer and borax coats the acaricide and can slowly release the acaricide; meanwhile, hydrogel obtained by crosslinking the hydroxyl-containing polymer and borax has good retention on the surface of the plant leaves, so that the retention period of the acaricide on the leaves is prolonged, and the utilization rate of the acaricide is improved.

Description

Liquid-carrying gel and preparation method and application thereof

Technical Field

The invention belongs to the technical field of agricultural pest control, and particularly relates to a liquid-carrying hydrogel and a preparation method and application thereof.

Background

Citrus is damaged by various insect pests during the growth process, with panonychus citri being one of the important pest mites of citrus. The prior means for controlling citrus pests mainly comprises floral control, and the prior means for controlling citrus whole-claw mites mainly comprises spraying and using the acaricide, wherein the dosage forms of the prior acaricide mainly comprise emulsifiable concentrate, suspending agent, wettable powder, aqueous emulsion or microemulsion. The pesticide can protect citrus fruits from being damaged by the panonychus citri by lower economic cost. However, in order to control the number of mites below the economic threshold of 3-5 mites/leaf during peak periods of serious mite damage, it is necessary to increase the frequency of application, even to spray the pesticide once a week, and frequent application of the pesticide not only easily causes the occurrence of drug resistance, but also adversely affects the environment. Therefore, developing a proper dosage form to effectively solve the problems of quick release, short duration, low utilization rate and the like of pesticide active ingredients is a technical problem to be solved.

Disclosure of Invention

In view of the above, the invention provides a drug-loaded hydrogel, a preparation method and application thereof, and the drug in the drug-loaded hydrogel has slow release performance and larger retention quantity on citrus leaves, so that the utilization rate of the drug is improved and the duration of the drug is prolonged.

In order to solve the technical problems, the invention provides a water-carrying gel, which comprises hydrogel and acaricide coated in the hydrogel;

the hydrogel is obtained by crosslinking a hydroxyl-containing polymer and borax.

Preferably, the mass ratio of the hydrogel to the acaricide is 1-2:1-2.

Preferably, the acaricide comprises cyenopyrafen, etoxazole, bifenazate or etoxazole.

Preferably, the hydroxyl-containing polymer comprises polyvinyl alcohol or hydroxypropyl guar.

Preferably, the hydroxyl group-containing polymer has an alcoholysis degree of 98.0 to 99.0%.

The invention also provides a preparation method of the liquid-carrying gel according to the technical scheme, which comprises the following steps:

mixing hydroxyl-containing polymer, acaricide solution, borax and water to obtain the aqueous gel.

Preferably, the acaricide solution is prepared according to the following method: dissolving acaricide in an organic solvent to obtain an acaricide solution;

the organic solvent comprises acetone, methanol, acetonitrile, dichloromethane or ethanol.

Preferably, the mixing comprises the steps of:

dispersing hydroxyl-containing polymer in part of water to obtain polymer solution;

dripping the acaricide solution into the polymer solution to obtain primary carrier hydrogel;

dissolving borax in the residual water to obtain borax solution;

and firstly mixing borax solution and the primary carrier hydrogel to obtain the carrier hydrogel.

Preferably, the mass concentration of the acaricide solution is 48-52 mg/mL; the mass concentration of the polymer solution is 11-13 mg/mL; the mass concentration of the borax solution is 2-3 mg/mL.

The invention also provides application of the liquid medicine-carrying gel in controlling the panonychus citri or the liquid medicine-carrying gel prepared by the preparation method in the technical scheme.

The invention provides a water-carrying hydrogel, which comprises hydrogel and acaricide coated in the hydrogel; the hydrogel is obtained by crosslinking a hydroxyl-containing polymer and borax. In the invention, the hydrogel obtained by crosslinking the hydroxyl-containing polymer and borax coats the acaricide and can slowly release the acaricide; meanwhile, hydrogel obtained by crosslinking the hydroxyl-containing polymer and borax has good retention on the surface of the plant leaves, so that the retention period of the acaricide on the leaves is prolonged, and the utilization rate of the acaricide is improved.

Drawings

FIG. 1 is an SEM image of a hydrogel SBG prepared in example 1 and a blank hydrogel Borax-co-HPG prepared in comparative example 2, where a is an SEM image of the Borax-co-HPG at 40 times, b is an SEM image of the Borax-co-HPG at 400 times, c is an SEM image of the SBG at 150 times, and d is an SEM image of the SBG at 450 times;

FIG. 2 is an infrared spectrum of the raw material of ethionazole nitrile (TC), SBG prepared in example 1, BORAX-co-HPG prepared in comparative example 2 and BORAX-HPG prepared in comparative example 3;

FIG. 3 is a thermogram of the bulk of ethionazole nitrile (TC), SBG prepared in example 1, borax-co-HPG prepared in comparative example 2, and HPG prepared in comparative example 4;

FIG. 4 is a comparative bar graph showing the retention of the drug on the leaves of the drugs prepared in example 1 and comparative example 5 at different mass concentrations;

FIG. 5 is a plot of swelling index for SBG prepared in example 1 at different pH values over time;

FIG. 6 is a graph showing the dotted line of the relative release rates of SBG and TC at different pH values at different times

FIG. 7 is a plot of the relative release rate of SBG at pH 7.1 at various temperatures;

FIG. 8 is a graph showing the transition of SBG sol-gel at different temperatures;

FIG. 9 is a bar graph showing fresh weight, stem length, root length of cotton after using different concentrations of TC and SBG, wherein CK is taken as a control group with applied water, TC-S is taken as a TC solution group with applied mass concentration of 80000mg/mL, TC-B is taken as a TC solution group with applied mass concentration of 136000mg/mL, SBG-S is taken as an SBG solution group with applied mass concentration of 80000mg/mL, and SBG-B is taken as an SBG solution group with applied mass concentration of 136000 mg/mL;

FIG. 10 is a bar graph comparing chlorophyll content in cotton leaves after using different concentrations of TC and SBG, wherein CK is applied water as a control group, TC-S is applied with a mass concentration of 80000mg/mL, TC-B is applied with a mass concentration of 136000mg/mL, SBG-S is applied with a mass concentration of 80000mg/mL, and SBG-B is applied with a mass concentration of 136000 mg/mL;

FIG. 11 is a bar graph comparing mortality after 24h using various concentrations of SG and SBG

Fig. 12 is a bar graph comparing mortality after 48h using various concentrations of SG and SBG.

Detailed Description

The invention provides a water-carrying hydrogel, which comprises hydrogel and acaricide coated in the hydrogel;

In the present invention, the acaricide preferably includes cyenopyrafen, etoxazole, bifenazate or etoxazole, more preferably etoxazole. In the invention, the etoxazole is preferably an etoxazole Technical (TC); the purity of the etoxazole nitrile crude drug is preferably 98%; the etoxazole nitrile drug substance is preferably purchased from Shenyang scientific chemical Co. The etoxazole mite original drug is a novel acrylonitrile acaricide, belongs to a non-systemic acaricide, has no cross resistance with the existing acaricide at present, and has good effect on controlling citrus panonychus citri.

In the present invention, the hydroxyl-containing polymer preferably comprises polyvinyl alcohol or hydroxypropyl guar, more preferably hydroxypropyl guar. In the present invention, the alcoholysis degree of the hydroxyl group-containing polymer is preferably 98.0 to 99.0%, more preferably 99%. In the present invention, the relative molecular mass of the polyvinyl alcohol is preferably 70000 to 80000. In the present invention, the purity of the hydroxypropyl guar is preferably 96%, and the hydroxypropyl guar is preferably purchased from protoleaf organisms limited. In the invention, the hydroxypropyl guar has biodegradability, good biocompatibility and biorenewability, and has good dissolution property and stability in water, and does not pollute the environment.

In the invention, borax is an important and effective cross-linking agent, can react with up to four hydroxyl groups, and can also carry out cross-linking reaction under low concentration, and meanwhile, borax is often used as a source of boron in agriculture, and boron is an important element required by plant growth. The hydrogel provided by the invention can regulate and control the release rate of pesticides to improve the pesticide utilization rate, and meanwhile, the hydrogel provided by the invention is easy to degrade and can not damage soil.

In the present invention, the mass ratio of the hydrogel to the acaricide is preferably 1 to 2:1 to 2, more preferably 1 to 2:1, and most preferably 1:1. In the present invention, the drug loading of the aqueous carrier gel is preferably 27.97 to 50.28%, more preferably 29.48 to 47.86%.

In the present invention, the mixing preferably includes the steps of:

dissolving borax in the residual water to obtain borax solution;

The invention disperses the polymer containing hydroxyl into partial water to obtain polymer solution. In the present invention, the mass concentration of the polymer solution is preferably 11 to 13mg/mL, more preferably 12 to 12.5mg/mL. The invention has no special requirement on the dispersion, so long as the dispersion is uniform.

After the polymer solution is obtained, the acaricide solution is dripped into the polymer solution to obtain the primary carrier hydrogel. In the present invention, the acaricide solution is preferably prepared according to the following method: dissolving acaricide in an organic solvent to obtain an acaricide solution; the organic solvent preferably comprises acetone, methanol, acetonitrile, dichloromethane or ethanol, more preferably methanol, acetonitrile or dichloromethane, most preferably methanol. In the present invention, the methanol is preferably chromatographically pure, and the methanol is preferably purchased from Fisher, inc. of America. The invention has no special requirement on the dissolution, so long as the dissolution is complete. The invention uses methanol as organic solvent to improve the drug-loading capacity and encapsulation efficiency of the drug-loading hydrogel. In the present invention, the mass concentration of the acaricide solution is preferably 48 to 52mg/mL, more preferably 50mg/mL. In the present invention, the volume ratio of the acaricide solution to the polymer solution is preferably 3:9 to 11, more preferably 3:10. In the present invention, the rate of the dropping is preferably 30 to 60 drops/min, more preferably 30 to 35 drops/min. In the present invention, the dropping is preferably accompanied by stirring; the invention has no special requirement on stirring, so long as the mite-killing agent can be uniformly dispersed in the system. According to the invention, the borax and the hydroxyl-containing polymer can be uniformly contacted by dropwise adding according to the dropwise adding rate, so that the crosslinking effect is improved, and meanwhile, the acaricide solution and the hydroxyl-containing polymer are uniformly contacted, so that the distribution uniformity is improved.

In the present invention, it is preferable that the method further comprises: stirring the system after dripping. In the invention, the rotation speed of the stirring is preferably 1000-1800 r/min, more preferably 1500-1600 r/min; the stirring time is preferably 1.8 to 2.2 hours, more preferably 2 to 2.1 hours; the temperature of the stirring is preferably room temperature. In the present invention, the temperature of the room temperature is preferably 20 to 35 ℃, more preferably 25 to 30 ℃.

The borax is dissolved in the residual water to obtain borax solution. In the present invention, the borax is preferably purchased from the company of the sciences of the ridge, inc. In the present invention, the mass concentration of the borax solution is preferably 2 to 3mg/mL, more preferably 2.4 to 2.8mg/mL, and most preferably 2.62mg/mL. The dissolution is not particularly limited as long as the dissolution is complete.

After borax solution and primary carrier hydrogel are obtained, the borax solution and the primary carrier hydrogel are mixed for the first time to obtain the carrier hydrogel. In the present invention, the volume ratio of the borax solution to the polymer solution is preferably 1:0.8-1.2, more preferably 1:1.

In the present invention, the first mixing is preferably to slowly pour the borax solution into the primary carrier hydrogel. In the present invention, the first mixing is preferably accompanied by stirring. In the invention, the rotation speed of the stirring is preferably 1000-1800 r/min, more preferably 1500-1600 r/min; the stirring time is preferably 1.8 to 3 hours, more preferably 2 to 2.6 hours; the temperature of the stirring is preferably 20 to 35 ℃, more preferably 25 to 30 ℃.

In the invention, borax is crosslinked with a polymer after being hydrolyzed in a first mixing process, and the hydrolysis equation is shown in the formulas 1 and 2:

Na ₂ B ₄ O ₇ +7H ₂ O→2B(OH) ₃ +2B(OH) ₄ ^- +2Na ⁺ formula 1;

in the invention, taking hydroxypropyl guar gum (HPG) as an example of hydroxyl-containing polymer, a hydrogel (box-co-HPG) obtained by crosslinking Borax and hydroxypropyl guar gum is shown as formula 3:

in the present invention, the first mixing preferably further comprises: washing and drying the product obtained after the first mixing, wherein the liquid-carrying gel is prepared. In the present invention, the washing preferably includes sequentially performing acetone washing and water washing. In the present invention, the acetone wash acetone is preferably analytically pure; the water for washing is preferably deionized water. In the present invention, the number of times of the acetone washing is preferably 2 to 4 times, more preferably 3 times; the number of times of the washing is preferably 2 to 4 times, more preferably 3 times. In the invention, the acetone washing can remove the unreacted mite-killing agent; the water washing can remove borax and residual acetone which are not reacted.

In the present invention, the drying is preferably vacuum drying, and the temperature of the vacuum drying is preferably 40 to 70 ℃, more preferably 60 to 65 ℃; the time for the vacuum drying is preferably 10 to 14 hours, more preferably 12 hours. The invention has no special requirement on the vacuum degree of the vacuum drying, so long as the product to be dried can be ensured not to contact with air.

The invention also provides application of the liquid medicine-carrying gel in controlling the panonychus citri or the liquid medicine-carrying gel prepared by the preparation method in the technical scheme. In the present invention, the application preferably includes the steps of:

dispersing the aqueous carrier gel in water to obtain a diluent;

spraying the diluent.

In the present invention, the mass ratio of the carrier hydrogel to water is preferably 1:5000-10000, more preferably 1:6000-9000. In the present invention, the spraying amount is preferably 6 to 12 g/mu, more preferably 6.7 to 10 g/mu.

The technical solutions provided by the present invention are described in detail below in conjunction with examples for further illustrating the present invention, but they should not be construed as limiting the scope of the present invention.

Example 1

The raw material TC of the ethionazole nitrile (with the concentration of 98%) purchased from Shenyang scientific chemical Co., ltd is dissolved in the methanol of chromatographic purity purchased from Fisher in the United states to obtain the methanol solution of the ethionazole nitrile with the mass concentration of 50 mg/mL;

hydroxypropyl guar with a purity of 96% purchased from source leaf biology company, is dissolved in water to obtain an aqueous hydroxypropyl guar solution with a mass concentration of 12.5 mg/mL;

3mL of the ethionazole nitrile methanol solution is dripped (with stirring) to 10mL of hydroxypropyl guar gum water solution according to the dripping rate of 30 drops/min, and stirring is carried out for 2h at the speed of 1500r/min at 25 ℃ after the dripping is completed, so as to obtain primary carrier hydrogel;

borax purchased from the company of the scientific sciences of the ridge is dissolved in water to obtain borax solution with the mass concentration of 2.62 mg/mL;

slowly adding 10mL of borax solution into the primary water-carrying gel, stirring for 3 hours at a rotating speed of 1500r/min, washing for 3 times by using acetone, washing for 3 times by using deionized water, and vacuum drying the washed product at 60 ℃ for 12 hours to obtain the water-carrying gel SYP-9625@Borax-co-HPG which is called SBG for short; the medicinal material ratio of SBG is 1:1; the medicinal material ratio is the mass ratio of the mite removing agent (ethionazole) and the borax-crosslinked hydroxypropyl guar gum hydrogel.

Example 2

A carrier hydrogel was prepared as in example 1, except that acetone was used as the organic solvent instead of methanol.

Example 3

A carrier hydrogel was prepared as in example 1, except that acetonitrile was used as an organic solvent in place of methanol.

Example 4

A carrier hydrogel was prepared as in example 1, except that methylene chloride was used as the organic solvent instead of methanol.

Example 5

A carrier hydrogel was prepared as in example 1, except that ethanol was used as the organic solvent instead of methanol.

Example 6

A carrier hydrogel was prepared as in example 1, except that the mass concentration of the hydroxypropyl guar aqueous solution was 25.0mg/mL, and the amount of borax solution was 10m L (concentration 2.62 mg/mL); the ratio of the traditional Chinese medicine materials of the prepared water-carrying gel is 1:2.

Example 7

A carrier hydrogel was prepared as in example 1, except that the mass concentration of the etoxazole nitrile methanol solution was 100mg/mL; the ratio of the traditional Chinese medicine materials of the prepared water-carrying gel is 2:1.

Comparative example 1

A carrier hydrogel was prepared as in example 1, except that no borax was used for crosslinking, and the resulting carrier hydrogel (primary carrier hydrogel in example 1) was abbreviated as SG.

Comparative example 2

A blank hydrogel was prepared according to the method of example 1, except that the step of dropping the etoxazole nitrile methanol solution into the hydroxypropyl guar aqueous solution was omitted without coating the mite-removing agent, and the obtained blank hydrogel was abbreviated as Borax-co-HPG.

Comparative example 3

And directly carrying out physical mixing and stirring on the hydroxypropyl guar gum and the Borax by using a glass rod without adding a solvent, so as to obtain a mixture of the hydroxypropyl guar gum and the Borax, which is called as a Borax-HPG for short.

Comparative example 4

The hydroxypropyl guar alone was used as a comparative example, and the hydroxypropyl guar was abbreviated as HPG.

Comparative example 5

The comparative example was trezepan (etoxazole) available from Shenyang scientific chemical Co., ltd at a mass concentration of 30%, abbreviated as MSC.

Test case

Characterization of the Carrier hydrogel

The hydrogel SBG prepared in example 1 and the blank hydrogel BORAX-co-HPG prepared in comparative example 2 were coated on a silicon wafer, freeze-dried (-55 ℃ C., 6 h) and then stuck on a conductive adhesive for metal spraying, and the morphology and structure of the hydrogel were observed by a scanning electron microscope (Scanning electron microscope, SEM) to obtain SEM images, as shown in FIG. 1, wherein a is an SEM image of BORAX-co-HPG at 40 times, b is an SEM image of BORAX-co-HPG at 400 times, c is an SEM image of SBG at 150 times, and d is an SEM image of SBG at 450 times. The scanning electron microscope used was Hitachi SU8000, available from Hitachi, japan.

As can be seen from FIG. 1, the surface of the Borax-co-HPG is smooth and has a porous structure, the surface of the SBG after loading the ethaboxam is relatively rough, the ethaboxam nitrile (TC) can be seen under high-power SEM, and the square circles in FIG. 1 are the ethaboxam nitrile.

The raw material of ethionazole nitrile (TC), SBG prepared in example 1, B-co-HPG prepared in comparative example 2 and B-HPG prepared in comparative example 3 were respectively mixed and tabletted to a resolution of 4cm ^-1 At 400cm ^-1 And 4000cm ^-1 Fourier transform infrared spectroscopy (Fourier transform infrared spectrometer, FTIR) detection was performed over the spectral range, resulting in an infrared spectrum as shown in fig. 2. The model of the fourier transform infrared spectrometer used was NICOLET 6700, available from the sammer technology in the united states.

As can be seen from FIG. 2, the box-co-HPG is 3428cm higher than the box-HPG ^-1 There is a small wavelength shift, probably because intermolecular hydrogen bonds are formed between the hydroxyl groups of the hydroxypropyl guar and Borax, covalent borate/glycol bonds are formed, whereas the physical mixture of hydroxypropyl guar and Borax (box-HPG) does not undergo such a reaction. SBG at 1750cm ^-1 And 2220cm ^-1 Peaks appearing at C=O stretching vibration and C≡N stretching vibration, respectively, demonstrate successful loading of the etoxazole onto the Borax-co-HPG material.

Thermogravimetric analysis was performed on the etoxazole nitrile crude drug (TC), SBG prepared in example 1, borex-co-HPG prepared in comparative example 2 and HPG prepared in comparative example 4 using a thermogravimetric analyzer (Thermogravimetric analysis, TGA) to give a thermogram as shown in fig. 3. Thermogravimetric analysis was performed under an inert gas nitrogen atmosphere at a heating rate of 10 ℃/min from 25 ℃ to 800 ℃. The thermogravimetric analyzer used was model SDT Q600, available from TA company of America.

FIG. 3 shows that the main skeleton degradation temperature region of HPG is 250-350 deg.C, and compared with HPG, the main degradation temperature region of Borax-co-HPG is 350-525 deg.C, so that it is known that crosslinked Borax can make hydrogel more stable. The main degradation temperature region of TC (etoxazole mite nitrile) is 160-290 ℃, and after the TC (etoxazole mite nitrile) is coated by crosslinked hydroxypropyl guar gum, the main degradation temperature region of SBG is 275-460 ℃. Obviously, the thermal stability of the hydrogel can be improved by crosslinking borax, and the thermal stability of the etoxazole-chlorfenapyr can be improved by crosslinking the hydrogel system of borax. As can be seen from fig. 3, the decomposition of SBG includes 3 stages, the first stage is the volatilization of moisture, i.e., 5.72%, the second stage is the mass loss of 18.67%, the third stage is the mass loss of 56.22%, and the main degradation temperatures of the second and third stages are 241 ℃ and 297 ℃, respectively. The main degradation temperature of SBG is shifted to low temperature compared to 273℃of TC and 291℃of Borax-co-HPG, resulting in possible incomplete thermal degradation in the second stage. The aqueous gel for carrying the water has higher thermal stability.

Drug loading and encapsulation efficiency determination

0.020g (accurate to 0.0001 g) of the aqueous carrier gel prepared in examples 1-5 was weighed and mixed with 15-20 mL of methanol, and after ultrasonic treatment at 150W power for 1 hour, the mixture was fixed to a 25mL volumetric flask, the solution was filtered through a 0.22 μm filter membrane, and the content of etoxazole was detected by using a high performance liquid chromatography instrument. The conditions for high performance liquid chromatography were Agilent extension-C18 column (5 μm. Times.4.6 mm. Times.250 mm), acetonitrile and water (90:10, v/v) as mobile phases, a flow rate of 1.0mL/min, a sample injection volume of 5.00. Mu.L, a column temperature of 30 ℃, a wavelength of 280nm, a retention time of 6.77min, and drug Loading (LC) and encapsulation efficiency (Encapsulation efficiency, EE) of the drug-loaded system were calculated according to formulas 4 and 5, and the results are shown in Table 1. The high performance liquid chromatograph used was Agilent 1260 available from american Agilent technologies.

Table 1 drug loading and encapsulation efficiency of drug-loaded hydrogel systems prepared in examples 1 to 5

From table 1, it can be seen that the organic solvent affects the drug-loading rate and encapsulation efficiency of the drug-loaded hydrogel, and methanol is used as the organic solvent to make the drug-loaded hydrogel have higher drug-loading rate and encapsulation efficiency.

The drug loading and encapsulation efficiency of the drug-loaded gels prepared in example 1 and examples 6 to 7 were measured as described above, and the results are shown in Table 2.

Table 2 drug loading and encapsulation efficiency of the drug-loaded hydrogel systems prepared in example 1 and examples 6 to 7

Examples	Ratio of medicinal materials	Drug loading (%)	Encapsulation efficiency (%)
				Example 1	1:1	50.28±0.47	84.70±0.79
Example 6	1:2	28.50±0.48	72.96±1.22
				Example 7	2:1	63.71±0.31	84.27±0.41

As is clear from table 2, the drug loading gradually increased with the increase of the active ingredient (the mite-killing agent), and the encapsulation efficiency did not change much.

Interface retention measurement

The MSC of comparative example 5 and SBG of example 1 were mixed with water to prepare suspensions having mass concentrations of 200mg/L, 100mg/L, 50mg/L and 25mg/L, and the liquid retention on the surface of citrus leaves was measured by the Wilhelmy method. The liquid sample and tweezers were placed in a beaker, weighed on a balance, and the reading W was recorded ₁ . The leaf was cut into squares (2X 2 cm), the area was measured and recorded as S. The leaf was immersed in the suspension, and the leaf was pulled out rapidly after being held with forceps for 20 seconds until no water drops were dropped. The forceps were then placed back into the beaker and the balance reading W was again recorded ₂ . The maximum stable retention of the blade is 1000X (W ₁ -W ₂ )/S(mg/cm ² ) The results are shown in Table 3.

TABLE 3 retention of the products of example 1 and comparative example 5 on the blade surface

A comparative bar graph of the retention of drug at different mass concentrations in the leaves is plotted according to table 3, as shown in fig. 4. As can be seen from a combination of Table 3 and FIG. 4, the cross-linked hydrogel solutions were more retained in the citrus leaves than commercial treasure Zhuo Rongye in four solutions of different concentrations, and the test results demonstrate that the carrier hydrogels provided by the present invention are prone to adhere to the citrus leaves. Meanwhile, the invention also indirectly shows that the aqueous gel is beneficial to improving the utilization rate of the etoxazole.

Swelling experiment

0.1g of SBG of example 1 was accurately weighed into a tea bag and soaked at 30.+ -. 2 ℃ in three buffer solutions of 150ml pH 3.4, 7.0 and 9.0 respectively to reach equilibrium. Taking out the tea bag in the buffer solution every 0.5h, and removing superfluous water on the surface by using chipless paper. These teabags were weighed and the swelling ratio (Q _H2O G/g) and the results are shown in Table 4.

Where Wx is the mass of the dry hydrogel and We is the mass of the hydrogel after swelling.

TABLE 4 swelling index of SBG of example 1 at different pH

A plot of swelling index at different pH values over time is plotted according to table 4, as shown in fig. 5. It can be seen from the combination of table 4 and fig. 5 that the porous structure of the aqueous carrier gel provided by the present invention can absorb a large amount of water, and the swelling ratio of the aqueous carrier gel provided by the present invention is affected by the pH of the swelling medium. At pH 3.4, SBG has a reduced swelling ratio and corrosion occurs due to free H in the swelling medium ⁺ The increase in ions results in a decrease in the swelling pressure of the ions in the hydrogel matrix. SBG has a significant tendency to swell at pH 9.0 compared to aqueous gels loaded under acidic and neutral conditions, probably due to an increase in ionic swelling pressure and an increase in hydrogen bonding under alkaline conditions leading to expansion of the crosslinks. The aqueous gel-coated etoxazole provided by the invention has very low solubility in water (namely containsIs a hydrophobic functional group), the pores of the hydrogel are filled by adding the raw material, and the erosion of the hydrogel is promoted.

Environmental responsive release performance assay

The release performance of the etoxazole nitrile (TC) and SBG at room temperature is studied by a dialysis bag method. A mass of the dried sample was dispersed in a dialysis bag (molecular weight cut-off 8000-14000) containing 2.0mL of release medium (V phosphate buffer: V ethanol: V tween-80=119:80:1), and the dialysis bag was then placed in a release medium containing 200 mL. The rotation speed of the constant temperature oscillator is set to be 150r/min, the temperature is 25+/-2 ℃, and the amplitude is 20mm. At intervals 0.6mL of supernatant (0.6 mL fresh buffer solution was added immediately after each sampling) was taken and the amount of ethionazole released was determined by HPLC. The environmental response release profile of SBG under different conditions was studied at different pH values (4.0, 7.1, 9.1) and temperatures (10, 25, 35 ℃ C.) respectively, with three replicates for each treatment. The cumulative amount of etoxazole released was calculated according to formula 7, and the results are shown in tables 5 and 6.

Wherein E is _r : accumulating the release amount; v (V) _e : volume per sample (0.6 mL); c (C) _i : concentration of released solution (mg/mL) at the ith sampling; v (V) ₀ : total volume of release medium (200 mL); c (C) _n : concentration of release solution (mg/mL) of nth sample; n: sampling times; m is m _pesticide : total mass (mg) of SBG active ingredient.

TABLE 5 relative release rates of SBG and TC at different pH' s

TABLE 6 SBG and Release Rate at different temperatures at pH 7.1

The plot of the relative release rates of SBG and TC at different pH values for different times is plotted according to table 5, as shown in fig. 6. The relative release rate plot of SBG at pH 7.1 at different temperatures was plotted according to table 6, as shown in fig. 7.

The SBG is circularly heated and cooled, the heating temperature is 60 ℃, and the cooled temperature is 20 ℃ to obtain a sol-gel transformation object diagram of the SBG under 10 cycles, as shown in figure 8.

According to the dual responsiveness of a polymer high polymer intelligent material, namely, a box-co-HPG, the influence of different pH values and temperatures on the release of the ethionazole nitrile hydrogel is studied, and in combination with tables 5-6 and figures 6-7, it is known that when the pH value is 7.1, the accumulated release amount in the first 48 hours is 34.8%, and the 132 hours are continuously increased to 85.7%. Whereas at pH 4.0 and 9.1, the cumulative release at 48h was 28.8% and 26.7%, respectively, and at 132h was 50.9% and 47.9%, respectively. The release amount of SBG under neutral conditions is higher than that of acidic and alkaline environments. The swelling experiment shows that the swelling rate of SBG is continuously reduced under the neutral condition, and the dissolution speed is faster, so that the release of the etoxazole is facilitated. In addition, compared with the original medicine, the SBG has obvious slow release function, and has good guiding function on reducing the medicine application amount and improving the utilization rate.

The temperature of the citrus main-producing area is often up to 35 ℃ or more in summer and often approaches 0 ℃ in winter. Experiments examine the effect of different temperatures on the release of the ethaboxam hydrogel at a pH of 7.1, and from FIG. 7, it can be seen that the release of ethaboxam in the hydrogel increases with increasing temperature, and the cumulative release amount of the hydrogel at 35℃is higher than 25℃and 10 ℃.

In addition this result is consistent with the transition of the etoxazole hydrogel with temperature sol-gel (fig. 8). FIG. 8 shows that SBG is in a sol state when heated to 60℃and in a gel state when cooled to 20 ℃. This phenomenon indicates that the hydrogels have good temperature swelling properties. The high molecular polymer network can be extended at a proper temperature, and the polymer network absorbs water at a high temperature, so that pesticides can be released in the process of balancing the chemical potentials inside and outside the hydrogel; along with the temperature reduction, the hydrogel network structure is compact, and the release of pesticides is limited.

Impact of hydrogel drug-carrying system on cotton growth

The experiment selects Ji 14 cotton seeds (provided by plant protection institute of national academy of agricultural sciences) as test cotton, the sowing depth is 3cm, the sowing amount is 15 seeds/basin, and tap water is used for irrigation during the growth process to ensure the humidity of the whole growth period of the cotton. All treatments were grown in a climatic chamber at 25.+ -. 2 ℃ (14 h for light and 10h for dark). After 7d, the raw materials of the etoxazole and the SBG are respectively adopted for spray treatment, the application concentrations of the active ingredients are 136mg/L and 80mg/L respectively, and blank control is arranged. After spraying the medicines for 7d, the fresh weight, the stem length, the root length and the chlorophyll content of cotton were measured, and the results thereof are shown in tables 7 and 8.

TABLE 7 fresh weight, shoot length and root length of cotton after application of TC and SBG at different concentrations

TABLE 8 chlorophyll content of cotton after use of different concentrations of TC and SBG

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A bar graph of fresh weight, stem length, root length of cotton after using various concentrations of TC and SBG and water (CK) is plotted according to Table 7, as shown in FIG. 9, wherein CK is taken as a control group with applied water, TC-S is a TC solution group with an applied mass concentration of 80000mg/mL, TC-B is a TC solution group with an applied mass concentration of 136000mg/mL, SBG-S is a SBG solution group with an applied mass concentration of 80000mg/mL, and SBG-B is a SBG solution group with an applied mass concentration of 136000 mg/mL.

A bar graph of chlorophyll content in cotton leaves after using various concentrations of TC and SBG and water (CK) is plotted according to Table 8, as shown in FIG. 10, wherein CK is taken as a control group with applied water, TC-S is a TC solution group with an applied mass concentration of 80000mg/mL, TC-B is a TC solution group with an applied mass concentration of 136000mg/mL, SBG-S is a SBG solution group with an applied mass concentration of 80000mg/mL, and SBG-B is a SBG solution group with an applied mass concentration of 136000 mg/mL.

As can be seen from tables 7 to 8 and FIGS. 9 to 10, the high concentration and low concentration aqueous carrier gel solutions have a root length acceleration rate of 19.22% and 24.22% respectively for cotton, whereas the high concentration etoxazole nitrile crude drug has an inhibition rate of 20.60% for cotton root length at low concentrations. The aqueous medicine gel solution with different concentrations and the ethirimole crude medicine have promotion effect on stem length, and compared with 136mg/L of aqueous medicine gel and the ethirimole crude medicine, 80mg/L of aqueous medicine gel has obvious effect on the influence on stem length. As for fresh weight, the aqueous gel solution of the carrier and the raw material of the ethionazole with different concentrations have promotion effects on fresh weight, the promotion rate of the hydrogel is 16.80 percent (80 mg/L) and 18.04 percent (136 mg/L) respectively, and the promotion rate of the raw material is 29.67 percent (80 mg/L) and 19.76 percent (136 mg/L) respectively. As can be seen from fig. 10, the chlorophyll content of both the aqueous carrier gel solution and the ethionazole original drug solution is increased compared with the clear water spray, and the chlorophyll content of the plant sprayed by the aqueous carrier gel solution is increased more than that of the original drug, especially the treatment of the hydrogel with the concentration of 136mg/L has significance. This shows that the spraying of boron fertilizer on the leaf surface can increase the chlorophyll content of the leaf.

Hydrogel drug-carrying system effect on growth of panonychus citri

The detection was carried out using a slightly modified leaf dipping method (YAMAMOTO et al, 1995). To prevent the water shortage of the leaves in vitro, the petioles were wrapped with wet cotton and filter paper and secured with tape. Kidney bean leaves not contacted with pesticide were randomly collected from greenhouse of plant protection institute of national academy of agricultural sciences. The leaves were immersed in the acaricide solution for 30s, and the acaricide was diluted with distilled water at 6 different concentrations (100 mg/L, 25mg/L, 6.25mg/L, 1.56mg/L, 0.39mg/L, 0.098 mg/L). Distilled water treated leaves and guar gum carrier hydrogels (SG) without borax cross-linking were used as controls. After the leaves were dried, they were placed in a petri dish (diameter 9 cm) together with filter paper. At the time of the test, 30 female adult mites (panonychus citri, provided by the university of southwestern citrus institute) were transferred to each leaf using a humped brush. Mortality and corrected mortality were calculated after 24 and 48h and the concentration in death was assessed (Lethal concentration, LC 50). Mites were noted as alive if they could shake after being stimulated by the brush, and as dead if they could not shake. Each treatment was repeated three times. After Abbott correction for natural mortality, the data were analyzed by probabilistic regression, the results of which are set forth in table 9.

TABLE 9 lethality of two acaricides SG and SBG at 24 and 48h after treatment at different concentrations

Bar graphs of mortality after 24h using various concentrations of SG and SBG were plotted according to table 9, as shown in fig. 11. A bar graph of mortality after 48h using various concentrations of SG and SBG was plotted according to table 9, as shown in fig. 12.

As a result of calculation, the LC50 values of SG and SBG were 1.501 and 0.196mg/L, respectively, at 24 hours, and 0.002 and 0.009mg/L, respectively, after 48 hours, in combination with Table 9 and FIGS. 11 to 12. The LC50 value of SBG gradually decreases with time, probably due to the blocking effect of the carrier material, which results in a slow release of the active ingredient of the drug substance. With the increase of pesticide active ingredients, the acaricidal activity of SBG on the panonychus citri tends to be increased. The Ducan new complex polar difference method is adopted to analyze the results of two acaricides, and as the active ingredients are increased, the different concentrations have obvious differences. Furthermore, at six concentrations, the acaricidal effect of sbg was significantly higher than SG treatment, either 24h or 48 h.

The invention uses hydroxypropyl guar gum cross-linked borax as carrier material to synchronously carry medicine to prepare the medicine-carrying hydrogel, and researches the surface morphology, formation mechanism and thermodynamic stability of the hydrogel by means of SEM, FTIR, TGA and other instruments. Meanwhile, the interfacial retention, swelling performance, release performance in a buffer solution and indoor toxicity of the panonychus citri are measured. The results show that the thermodynamic properties show that the hydrogel can improve the thermal stability of the etoxazole. Compared with commercial treponema, the aqueous carrier gel system has a greater retention in citrus leaves. Swelling tests show that the aqueous gel carrier has two processes of swelling and then corrosion under alkaline environment, and the aqueous gel carrier has corrosion phenomena under acidic and neutral environments. In addition, the pH and temperature sensitive properties of the carrier material give the hydrogel environment response release characteristics, and the etoxazole is released quickly in a neutral environment and at a higher temperature than a lower temperature. Compared with the original medicine, the slow release effect of the aqueous gel is more obvious. The potted cotton experiment shows that compared with clear water spray, the chlorophyll content of the aqueous gel solution and the original solution is increased; compared with the original medicine, the chlorophyll content of the plant sprayed by the aqueous carrier gel solution is increased more. The boron fertilizer is sprayed on the leaf surfaces, so that the chlorophyll content of the leaf surfaces can be increased, and the photosynthesis of plants can be promoted. Compared with guar gum solution without cross-linking agent borax, the acaricidal effect of SBG is obviously higher than that of SG treatment, whether 24h or 48h

Although the foregoing embodiments have been described in some, but not all, embodiments of the invention, it should be understood that other embodiments may be devised in accordance with the present embodiments without departing from the spirit and scope of the invention.

Claims

1. The aqueous gel is characterized by comprising hydrogel and etoxazole nitrile coated in the hydrogel;

the hydrogel is obtained by crosslinking hydroxypropyl guar gum and borax;

the mass ratio of the hydrogel to the acaricide is 1-2:1-2;

the preparation method of the liquid-carrying gel comprises the following steps:

dispersing hydroxypropyl guar in part of water to obtain an aqueous hydroxypropyl guar solution; the mass concentration of the hydroxypropyl guar gum aqueous solution is 11-13 mg/mL;

dissolving the etoxazole mite nitrile into methanol to obtain an etoxazole mite nitrile methanol solution; the mass concentration of the etoxazole nitrile methanol solution is 48-52 mg/mL;

dropwise adding the ethionazole nitrile methanol solution into the hydroxypropyl guar gum aqueous solution to obtain primary carrier hydrogel; the volume ratio of the etoxazole nitrile methanol solution to the hydroxypropyl guar gum solution is 3:9-11; the dropping speed is 30-60 drops/min; after the dripping is finished, the method further comprises the following steps: stirring the system after dripping, wherein the stirring speed is 1000-1800r/min, and the stirring time is 1.8-2.2 h;

dissolving borax in the residual water to obtain borax solution; the mass concentration of the borax solution is 2-3 mg/mL;

firstly mixing the borax solution and the primary carrier hydrogel to obtain the carrier hydrogel; the volume ratio of the borax solution to the hydroxypropyl guar gum solution is 1:0.8-1.2; the first mixing is to slowly pour the borax solution into primary carrying hydrogel; the first mixing is accompanied by stirring, the rotating speed of stirring is 1000-1800r/min, and the stirring time is 1.8-3 h.

2. The carrier hydrogel of claim 1, wherein the hydroxypropyl guar has an alcoholysis degree of 98.0-99.0%.

3. A method of preparing a loaded hydrogel according to claim 1 or 2, comprising the steps of:

4. Use of the aqueous carrier gel according to claim 1 or 2 or the aqueous carrier gel prepared by the preparation method according to claim 3 for controlling panonychus citri.