Multi-stage slow-release mosquito-repelling gel based on plant essential oil compound and preparation method thereof

Abstract

The application discloses a multi-stage slow-release mosquito-repelling gel based on plant essential oil compounding and a preparation method thereof, and relates to the technical field of health and insect prevention daily-use chemical industry. The gel comprises an inner slow-release unit and an outer gel coating layer; the inner slow-release unit is composed of a sodium alginate matrix, a beta-cyclodextrin inclusion compound and isopropyl myristate, wherein the beta-cyclodextrin inclusion compound comprises camphor tree leaf essential oil and beta-cyclodextrin; the outer gel coating layer is composed of a chitosan matrix, a quaternary compound plant essential oil nanoemulsion and isopropyl myristate, and the quaternary compound plant essential oil is compounded by orange peel essential oil, mosla essential oil, capillary wormwood essential oil and camphor tree leaf essential oil. The application constructs a triple multi-stage slow-release barrier of beta-cyclodextrin molecular inclusion + sodium alginate microsphere buffer layer + chitosan outer gel, significantly inhibits essential oil volatilization, and prolongs the effective protection time from 1-2 hours of traditional natural products to more than 3 days. Meanwhile, all-natural biodegradable polymer materials are adopted, and the mosquito-repelling gel does not contain chemical synthetic mosquito-repelling agents and stimulating solvents, has the advantages of long-acting slow release, high safety, low allergenicity and environmental friendliness, and is suitable for infants, young children and sensitive groups.

Description

Technical Field

[0001] This invention relates to the field of sanitary insect repellent daily chemical technology, specifically to a multi-stage slow-release mosquito repellent gel based on plant essential oils and its preparation method. Background Technology

[0002] Currently, the mainstream mosquito repellent gels on the market are mainly divided into two categories: chemically synthesized mosquito repellent gels and ordinary natural plant essential oil mosquito repellent gels. Both types of products have technical defects that cannot simultaneously achieve long-lasting mosquito repellency, skin safety, and environmental friendliness.

[0003] Existing chemically synthesized mosquito repellent gels use DEET, picaridin, or IR3535 as the core active mosquito repellent components. The formulation is usually composed of an aqueous thickening system, a chemical mosquito repellent functional phase, and an ethanol soothing auxiliary phase. Although these products can achieve stable mosquito repellency, they have several inherent technical defects: First, the formulation often contains solvents such as anhydrous ethanol and polyethylene glycol, which can irritate sensitive skin and broken skin. High concentrations of DEET can easily induce rashes and blisters, and excessive use may even pose a risk of neurological damage. Furthermore, it is strictly prohibited for use on infants under 2 months of age, limiting the applicable population. Second, chemical mosquito repellent components have poor biodegradability and a long residual period in the natural environment. Some components are potentially toxic to aquatic organisms and pets, and can easily cause environmental pollution after disposal. Third, the protection time of a single application is usually only 4 to 8 hours, requiring frequent reapplication in outdoor settings, making it inconvenient to use.

[0004] Existing natural plant essential oil mosquito repellent gels mostly use aloe vera gel, common plant hydrosols, or synthetic polymers as a base, adding plant essential oils such as citronella oil, lemon eucalyptus oil, and menthol through simple physical mixing, without constructing an effective sustained-release carrier system. Although the raw materials of this type of product are relatively natural, they have significant technical shortcomings: First, plant essential oils are highly volatile and lack a lock-in sustained-release structure, evaporating and being lost rapidly at room temperature, with an effective protection time often less than 1-2 hours. They fail even faster in high-temperature environments, requiring frequent reapplication; Second, some essential oils (such as citronellol in lemon eucalyptus oil) are themselves allergens, easily inducing contact dermatitis. The US Centers for Disease Control and Prevention explicitly restricts their use in infants under 3 years old, making them unsuitable for mothers, infants, and sensitive populations; Third, the gel thickening carriers of many commercially available products are still non-degradable synthetic polymer materials, generating "white pollution" after disposal; Fourth, they only use simple physical mixing and lack gradient release control methods, so essential oils with different evaporation rates cannot form a synergistic and long-lasting repellent effect, resulting in poor stability of mosquito repellent effect.

[0005] In summary, the existing two types of mosquito repellent gels cannot simultaneously meet the needs of long-lasting mosquito repellency, all-natural biodegradability, and low irritation suitable for specific populations. Therefore, this paper proposes a multi-stage slow-release mosquito repellent gel based on a compound of plant essential oils and its preparation method to address the aforementioned problems. Summary of the Invention

[0006] (a) Technical problems to be solved

[0007] To address the shortcomings of existing technologies, this invention provides a multi-stage sustained-release mosquito repellent gel based on plant essential oils and its preparation method. It has the advantages of being all-natural, biodegradable, and highly safe, with multi-stage synergistic long-lasting sustained release and low allergenicity suitable for sensitive populations. It solves the problems of traditional chemical mosquito repellent products being highly irritating and polluting the environment, natural essential oils evaporating too quickly and resulting in short-lasting protection, and existing carrier materials being non-degradable and causing white pollution.

[0008] (II) Technical Solution

[0009] To achieve the above objectives, the present invention provides the following technical solution: a multi-stage sustained-release mosquito repellent gel based on plant essential oil compound, comprising an inner sustained-release unit and an outer gel coating layer;

[0010] The inner layer sustained-release unit is composed of sodium alginate matrix, β-cyclodextrin inclusion complex and isopropyl myristate;

[0011] The outer gel coating layer is composed of chitosan matrix, quaternary compound plant essential oil nanoemulsion and isopropyl myristate;

[0012] The β-cyclodextrin inclusion complex contains camphor leaf essential oil and β-cyclodextrin;

[0013] The quaternary compound plant essential oil is composed of orange peel essential oil, sesame essential oil, turmeric essential oil and camphor leaf essential oil.

[0014] Preferably, in the quaternary compound plant essential oil, the volume ratio of orange peel essential oil, sesame essential oil, turmeric essential oil and camphor leaf essential oil is 1:1:0.5:0.5.

[0015] Preferably, in the β-cyclodextrin inclusion complex, the mass ratio of camphor leaf essential oil to β-cyclodextrin is 1:8.

[0016] Preferably, the preparation method of the quaternary compound plant essential oil nanoemulsion includes: mixing and emulsifying the quaternary compound plant essential oil with Tween 80; wherein the volume ratio of the quaternary compound plant essential oil to Tween 80 is 1:2.

[0017] Preferably, the mass fractions of each component in the gel are: sodium alginate 1.5-2.5 parts, chitosan 1.0-2.0 parts, β-cyclodextrin 0.4-0.6 parts, camphor leaf essential oil 0.4-0.6 parts, quaternary compound essential oil 0.4-0.6 parts, and isopropyl myristate 0.05-0.15 parts.

[0018] Preferably, the preparation process of the orange peel essential oil includes: scraping off the white pith from the inside of the orange peel, cutting it into strips, and then steam distilling it;

[0019] The preparation process of camphor tree leaf essential oil includes: collecting old camphor tree leaves, cutting them into small pieces, and then steam distilling them.

[0020] A method for preparing a multi-stage sustained-release mosquito repellent gel based on a compound of plant essential oils includes the following steps:

[0021] Step S1: Preparation of β-cyclodextrin inclusion complex: Dissolve camphor leaf essential oil in an organic solvent, slowly add it dropwise to an aqueous solution of β-cyclodextrin while stirring, stir at a constant temperature, refrigerate to crystallize, filter and dry to obtain inclusion complex powder;

[0022] Step S2: Preparation of inner layer microspheres: Sodium alginate is dissolved in water, and the inclusion complex powder obtained in step S1 and isopropyl myristate are added. After stirring evenly, the mixture is dropped into a calcium salt solution for cross-linking and curing to form inner layer microspheres.

[0023] Step S3: Preparation of outer gel solution: Dissolve chitosan in acidic aqueous solution, add quaternary compound plant essential oil nanoemulsion and isopropyl myristate, and stir evenly;

[0024] Step S4: Assembly: Mix the inner layer microspheres obtained in step S2 into the outer layer gel liquid obtained in step S3, drop them into the crosslinking agent solution for crosslinking and curing, and then clean and dry to obtain the final product.

[0025] Preferably, in step S1, the temperature of the constant temperature stirring is controlled at 60±2℃, and the stirring time is 2 hours; the refrigeration temperature is 4℃, and the time is 24 hours.

[0026] In step S2, the calcium salt solution is a 2% (w / w) calcium chloride solution, and the crosslinking time is 5 minutes;

[0027] In step S4, the crosslinking agent is sodium tripolyphosphate (TPP) solution, and the crosslinking time is 15 minutes.

[0028] This invention provides the application of the above-described multi-stage slow-release mosquito repellent gel based on plant essential oil compound in the preparation of mosquito repellent and mosquito prevention products.

[0029] (III) Beneficial Effects

[0030] Compared with the prior art, the present invention provides a multi-stage sustained-release mosquito repellent gel based on plant essential oil compound and its preparation method, which has the following beneficial effects:

[0031] 1. This invention constructs a triple multi-level sustained-release barrier consisting of β-cyclodextrin molecular inclusion, a sodium alginate microsphere buffer layer, and a chitosan outer gel layer: the β-cyclodextrin cavity structure molecules bind camphor leaf essential oil, reducing the intrinsic evaporation rate of the essential oil; the calcium alginate microspheres act as an intermediate buffer layer to delay the outward diffusion of active components; the outer chitosan gel forms secondary diffusion resistance, and the three-layer structure synergistically regulates the essential oil release kinetics; compared with the traditional single physical mixture of natural essential oil systems, it can significantly inhibit the rapid evaporation of essential oils, greatly increasing the effective protection time under a single waterless rinse from the existing natural products of 1-2 hours to more than 3 days, with the repellency rate still maintaining above 70% on the 3rd day, and the overall sustained-release rate reduced by 35%, demonstrating a significant improvement in long-lasting mosquito repellency.

[0032] 2. This invention completely abandons chemical mosquito repellent active ingredients such as DEET, picaridin, and IR3535. The matrix uses two natural biopolymers, sodium alginate and chitosan. All raw materials are food-grade biodegradable materials. The formula does not contain anhydrous ethanol or artificial preservatives. The finished product is non-irritating to the skin and has no risk of damage to the nervous system. In addition, the product can be completely degraded into carbon dioxide and water in the soil environment and has no ecotoxicity. It is suitable for special groups such as infants, pregnant women, and people with sensitive skin. It also solves the technical defects of chemical mosquito repellent products, such as difficulty in degradation and easy environmental pollution.

[0033] 3. This invention employs a compound system of orange peel essential oil, sesame essential oil, turmeric essential oil, and camphor tree leaf essential oil in a volume ratio of 1:1:0.5:0.5. Utilizing the differences in boiling points and evaporation rates among the four essential oils, a gradient relay release is achieved, targeting multiple points to synergistically repel mosquitoes with a synergy coefficient consistently greater than 1.5. Simultaneously, the invention incorporates a raw material pretreatment process that removes the white pith from the orange peel and selects fresh, mature camphor tree leaves to eliminate potentially allergenic impurities, reducing the risk of skin contact sensitization. This simultaneously improves the stability and safety of the mosquito repellent.

[0034] 4. In this invention, isopropyl myristate (IPM) is added to both the inner layer of calcium alginate microspheres and the outer layer of chitosan gel system. IPM acts as a co-solvent for the hydrophobic essential oil and the aqueous gel matrix, which can prevent the essential oil from separating and precipitating, and improve the physical uniformity of the formulation. At the same time, IPM evenly regulates the overall release curve, so that the release rate of essential oil is stable throughout the process, which significantly improves the long-term storage stability of the gel. In addition, the plant essential oil raw materials selected in this invention (such as Changsha local orange peel, Elsholtzia ciliata, etc.) are widely available and have low harvesting costs, eliminating the need to rely on imported mosquito repellent essential oils, which is conducive to achieving localization of raw materials and reducing the cost of large-scale production. Attached Figure Description

[0035] Figure 1These are the gel preparation processes and photographs of the four sets of comparative experiments of this invention; wherein: A is the preparation of a single-layer chitosan gel (Comparative Example 1); B is the preparation of a gel with added physically mixed cyclodextrin (Comparative Example 2); C is the preparation of bilayer microspheres (Comparative Example 3); and D is the finished multi-stage sustained-release gel of this invention (Example 1).

[0036] Figure 2 This is a schematic diagram comparing the mosquito repellent and protective effects of the multi-stage sustained-release mosquito repellent gel prepared in Example 1 of the present invention on human skin; wherein: the left figure is the group with gel applied, and the right figure is the control group without gel applied. Detailed Implementation

[0037] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0038] The plant essential oil raw material pretreatment method involved in this invention is as follows:

[0039] Orange peel essential oil: Select fresh local Changsha orange peel, scrape off the inner white spongy layer, cut into 2-3mm thin strips, extract orange peel essential oil using steam distillation, and collect the oil phase for later use.

[0040] Elsholtzia and Eupatorium fortunei essential oils: The whole plants of Elsholtzia and Eupatorium fortunei are collected from unpolluted areas in the wild in Changsha. After being rinsed with clean water, they are naturally dried in the shade and cut into 1-2cm pieces. The corresponding essential oils are extracted by steam distillation.

[0041] Camphor tree leaf essential oil: Fresh old leaves of camphor trees in Changsha are selected, washed with clean water, dried and chopped, and then steam distilled to obtain camphor tree leaf essential oil.

[0042] The general process for preparing quaternary compound plant essential oil nanoemulsions involved in this invention is as follows:

[0043] By volume ratio, orange peel essential oil: euphorbia essential oil: lavender essential oil: camphor tree leaf essential oil = 1:1:0.5:0.5 are mixed to obtain a quaternary compound essential oil; 1 mL of the quaternary compound essential oil is mixed thoroughly with 2 mL of Tween 80, shaken vigorously and stirred at low speed to obtain a milky white semi-transparent nanoemulsion for later use.

[0044] The general preparation process of the β-cyclodextrin-camphor leaf essential oil inclusion complex of the present invention is as follows: Prepare materials at a mass ratio of camphor leaf essential oil to β-cyclodextrin of 1:8; dissolve 8 parts of β-cyclodextrin in 40 parts of distilled water at 60±2℃ and stir until completely dissolved; dissolve 1 part of camphor leaf essential oil in 2 parts of anhydrous ethanol to obtain an essential oil-ethanol mixture; under magnetic stirring, add the essential oil-ethanol mixture dropwise to the cyclodextrin aqueous solution at a rate of 1 drop every 2-3 seconds, and stir continuously at 60℃ for 2 hours; after stirring, refrigerate at 4℃ for 24 hours to precipitate inclusion complex crystals; separate the crystals by filtration, wash twice with distilled water, and dry at 40℃ for 24 hours to obtain a white powdery β-cyclodextrin-camphor leaf essential oil inclusion complex, which is then sealed and stored for later use.

[0045] The preparation of the above-mentioned β-cyclodextrin-camphor leaf essential oil inclusion complex is a pretreatment step for this component in the various embodiments of the present invention.

[0046] Example 1

[0047] This embodiment provides a multi-stage sustained-release mosquito repellent gel, which is composed of the following raw materials in parts by weight: 2 parts sodium alginate, 1.5 parts chitosan, 0.5 parts β-cyclodextrin, 0.5 parts camphor leaf essential oil, 0.5 parts quaternary compound essential oil, and 0.1 parts isopropyl myristate (IPM).

[0048] The preparation method of this multi-stage sustained-release mosquito repellent gel includes the following steps:

[0049] Step S1: Preparation of β-cyclodextrin-camphor leaf essential oil inclusion complex: The inclusion complex powder was prepared using the above-mentioned general inclusion process.

[0050] Step S2: Preparation of inner layer calcium alginate sustained-release microspheres: Take 2 parts of sodium alginate and add 100 parts of deionized water, stir in a 40°C water bath until completely dissolved; add 0.5 parts of β-cyclodextrin inclusion complex powder and 0.05 parts of IPM to the sodium alginate aqueous solution, and continue stirring until the system is uniform; add the mixture dropwise to a 2% (w / w) calcium chloride aqueous solution for crosslinking for 5 min, rinse with water to remove free calcium ions on the surface, and obtain the inner layer sustained-release microspheres.

[0051] Step S3: Preparation of outer chitosan gel solution: Take 1.5 parts of chitosan and dissolve it in 100 parts of 1% acetic acid aqueous solution, and stir magnetically until completely dissolved; add 0.5 parts of quaternary compound essential oil nanoemulsion and the remaining 0.05 parts of IPM, stir evenly to obtain outer gel solution.

[0052] Step S4: Double-layer cross-linking molding: All inner layer calcium alginate microspheres are uniformly mixed into the outer layer chitosan gel solution; the mixture is added dropwise to sodium tripolyphosphate (TPP) cross-linking solution and cross-linked for 15 minutes; after curing, the mixture is washed multiple times with water and dried at low temperature to obtain the multi-stage sustained-release mosquito repellent gel of this invention (e.g., Figure 1 (As shown in Figure D).

[0053] The performance test results are as follows: The release rate test showed that after continuous monitoring for 7 days using the weighing method in a 35℃ constant temperature chamber, the overall release rate of the essential oil was reduced by 35% compared to the single-layer control gel; the repellency rate was 76.2% on the 3rd day after a single waterless application, and it still had an effective repellency effect after 7 days.

[0054] Human real-world mosquito repellent tests showed that, in outdoor normal temperature conditions, no mosquito bites occurred 12 hours after applying the gel of this embodiment; mosquito bites occurred within 1 hour in the blank control group, 3.4 hours in the monolayer cyclodextrin control group (see Comparative Example 2), and 4.0 hours in the double-layer non-encapsulated control group (see Comparative Example 3).

[0055] Stability and safety results show that after 90 days of sealed storage at room temperature, the gel does not separate or release essential oils, and the texture is uniform. All raw materials are biodegradable, and soil culture tests showed no ecotoxicity to earthworms and springtails. Short-term contact with sensitive skin and infants' skin did not cause redness, swelling, itching, or other irritation.

[0056] Example 2

[0057] This embodiment provides a low-dose, multi-stage sustained-release mosquito repellent gel composed of the following raw materials in parts by weight: 1.5 parts sodium alginate, 1.0 part chitosan, 0.4 parts β-cyclodextrin, 0.4 parts camphor leaf essential oil, 0.4 parts quaternary compound essential oil, and 0.05 parts isopropyl myristate (IPM).

[0058] The preparation method of this low-dose, multi-stage sustained-release mosquito repellent gel includes the following steps:

[0059] Step S1: Preparation of β-cyclodextrin-camphor leaf essential oil inclusion complex: According to the above general inclusion process, camphor leaf essential oil and β-cyclodextrin are included in a mass ratio of 1:8 to prepare β-cyclodextrin-camphor leaf essential oil inclusion complex powder.

[0060] Step S2: Preparation of inner layer calcium alginate sustained-release microspheres: Take 1.5 parts of sodium alginate and add 100 parts of deionized water, stir in a 40°C water bath until completely dissolved; add 0.4 parts of the β-cyclodextrin inclusion complex powder prepared above and 0.025 parts of IPM to the sodium alginate aqueous solution, and continue stirring until the system is uniform; add the mixture dropwise to a 2% (w / w) calcium chloride aqueous solution for crosslinking for 5 min, rinse with water to remove free calcium ions on the surface, and obtain the inner layer sustained-release microspheres.

[0061] Step S3: Preparation of outer chitosan gel solution: Take 1.0 part of chitosan and dissolve it in 100 parts of 1% acetic acid aqueous solution, and stir magnetically until completely dissolved; add 0.4 parts of quaternary compound essential oil nanoemulsion and the remaining 0.025 parts of IPM, stir evenly to obtain outer gel solution.

[0062] Step S4: Double-layer cross-linking molding: All inner layer calcium alginate microspheres are uniformly mixed into the outer layer chitosan gel liquid; the mixture is added dropwise to sodium tripolyphosphate (TPP) cross-linking solution and cross-linked for 15 minutes; after curing, it is washed with water several times and dried at low temperature to obtain a low-dose multi-stage sustained-release mosquito repellent gel.

[0063] The performance test results are as follows: The release rate test showed that the overall release rate of the essential oil was 31% lower than that of the single-layer control gel; the repellency rate was 71.5% on the 3rd day after a single waterless application, and it still had an effective repellency effect after 5 days.

[0064] Human real-world mosquito repellent tests showed that no mosquito bites occurred 10 hours after applying the gel of this embodiment; bites appeared in the monolayer cyclodextrin control group after 3.5 hours.

[0065] Stability and safety indicators show that after 60 days of sealed storage at room temperature, the gel does not separate into layers or release essential oils, and the texture remains uniform.

[0066] Example 3

[0067] This embodiment provides a high-dose, multi-stage sustained-release mosquito repellent gel composed of the following raw materials in parts by weight: 2.5 parts sodium alginate, 2.0 parts chitosan, 0.6 parts β-cyclodextrin, 0.6 parts camphor leaf essential oil, 0.6 parts quaternary compound essential oil, and 0.15 parts isopropyl myristate (IPM).

[0068] The preparation method of this high-dose, multi-stage sustained-release mosquito repellent gel includes the following steps:

[0069] Step S1: Preparation of β-cyclodextrin-camphor leaf essential oil inclusion complex: According to the above general inclusion process, camphor leaf essential oil and β-cyclodextrin are included in a mass ratio of 1:8 to prepare β-cyclodextrin-camphor leaf essential oil inclusion complex powder.

[0070] Step S2: Preparation of inner layer calcium alginate sustained-release microspheres: Take 2.5 parts of sodium alginate and add 100 parts of deionized water, stir in a 40°C water bath until completely dissolved; add 0.6 parts of the β-cyclodextrin inclusion complex powder prepared above and 0.075 parts of IPM to the sodium alginate aqueous solution, and continue stirring until the system is uniform; add the mixture dropwise to a 2% (w / w) calcium chloride aqueous solution for crosslinking for 5 min, rinse with water to remove free calcium ions on the surface, and obtain the inner layer sustained-release microspheres.

[0071] Step S3: Preparation of outer chitosan gel solution: Take 2.0 parts of chitosan and dissolve it in 100 parts of 1% acetic acid aqueous solution, and stir magnetically until completely dissolved; add 0.6 parts of quaternary compound essential oil nanoemulsion and the remaining 0.075 parts of IPM, stir evenly to obtain outer gel solution.

[0072] Step S4: Double-layer cross-linking molding: All inner layer calcium alginate microspheres are uniformly mixed into the outer layer chitosan gel liquid; the mixture is added dropwise to sodium tripolyphosphate (TPP) cross-linking solution and cross-linked for 15 minutes; after curing, it is washed with water several times and dried at low temperature to obtain a high-dose multi-stage sustained-release mosquito repellent gel.

[0073] The performance test results are as follows:

[0074] Release rate tests showed that the overall release rate of the essential oil was 37% lower than that of the single-layer control gel; the repellency rate was 78.9% on the 3rd day after a single waterless application, and it still had an effective repellency effect after 7 days.

[0075] Human real-world mosquito repellent tests showed that no mosquito bites occurred 13 hours after applying the gel of this embodiment; bites appeared in the monolayer cyclodextrin control group after 3.3 hours.

[0076] Stability and safety indicators show that after 90 days of sealed storage at room temperature, the gel does not separate into layers or release essential oils, and the texture remains uniform.

[0077] To verify the effectiveness of the "multi-stage sustained-release technology" of this invention, the following comparative examples were set up; the preparation process and physical morphology of the comparative gels are described in [reference needed]. Figure 1 Groups A, B, and C.

[0078] Comparative Example 1: Monolayer chitosan gel (corresponding to) Figure 1 Group A)

[0079] The components (parts by weight) for this comparative example include: 1.5 parts chitosan, 0.5 parts quaternary compound essential oil, 0.02 parts Tween 80, and 100 parts 1% acetic acid aqueous solution.

[0080] The preparation method is as follows: 1.5 parts of chitosan are dissolved in 100 parts of 1% acetic acid aqueous solution and magnetically stirred until completely dissolved; 0.5 parts of quaternary compound essential oil and 0.02 parts of Tween 80 are added and stirred evenly; the mixture is added dropwise to 0.5% sodium tripolyphosphate (TPP) aqueous solution for cross-linking and curing for 15 min; after curing, it is washed with water several times and dried at 40℃ to obtain a single-layer chitosan gel.

[0081] The difference in this comparative example is that: no β-cyclodextrin inclusion complex was added, no inner layer calcium alginate microspheres were prepared, and no IPM additive was added.

[0082] Performance test results: The essential oil evaporates quickly, with a sustained-release effect lasting only 1-3 days; the repellency rate drops to 39.6% on the 3rd day after a single anhydrous application; mosquito bites appear 1 hour after application. Oil-water separation occurs after 7 days of storage.

[0083] Comparative Example 2: Monolayer gel plus cyclodextrin mixture (corresponding) Figure 1 Group B)

[0084] The comparative sample components (parts by weight) include: 1.5 parts chitosan, 0.4 parts β-cyclodextrin, 0.05 parts camphor leaf essential oil, 0.5 parts quaternary compound essential oil, and 100 parts 1% acetic acid aqueous solution.

[0085] The preparation method is as follows: 0.05 parts of camphor leaf essential oil and 0.4 parts of β-cyclodextrin are first simply physically ground and mixed (without forming inclusion complex crystals); 1.5 parts of chitosan are dissolved in 100 parts of 1% acetic acid aqueous solution and magnetically stirred until completely dissolved; the above premixed β-cyclodextrin and camphor leaf essential oil mixture and 0.5 parts of quaternary compound essential oil are added, stirred, and then added dropwise to 0.5% TPP aqueous solution for cross-linking and curing for 15 min; after curing, the mixture is washed with water several times and dried at 40℃ to obtain a monolayer gel.

[0086] The difference in this comparative example is that no inclusion complex crystals were formed, no inner layer microspheres were prepared, no nanoemulsion was used, and no IPM was added.

[0087] Performance test results: It can only slightly slow down the initial burst release, and the sustained release period is only 1-2 days; the repellency rate is 45.1% on the 3rd day after a single waterless application; mosquito bites appeared 3.4 hours after application. Slight essential oil precipitation occurred after 30 days of storage.

[0088] Comparative Example 3: Bilayer gel but without cyclodextrin inclusion structure (corresponding to) Figure 1 Group C)

[0089] The components for this comparative example (parts by weight) are: 2.0 parts sodium alginate, 1.5 parts chitosan, 0.5 parts quaternary compound essential oil, 100 parts deionized water, 100 parts 1% acetic acid aqueous solution, appropriate amount of 2% calcium chloride aqueous solution, and appropriate amount of 0.5% TPP aqueous solution.

[0090] Its preparation methods include:

[0091] Preparation of inner layer microspheres: Dissolve 2.0 parts of sodium alginate in 100 parts of deionized water without adding β-cyclodextrin inclusion complex, and crosslink with 2% calcium chloride solution for 5 min to obtain pure calcium alginate microspheres.

[0092] Preparation of outer gel: Dissolve 1.5 parts of chitosan in 100 parts of 1% acetic acid aqueous solution, add 0.5 parts of quaternary compound essential oil that has not been treated with nanoemulsion, and stir evenly.

[0093] Molding: Mix the inner layer microspheres into the outer layer gel liquid, drop them into 0.5% TPP aqueous solution for cross-linking and curing for 15 minutes, then clean and dry.

[0094] The difference in proportions lies in the fact that the inner layer has no inclusion complex, the outer layer of essential oil is not nano-emulsified, and there is no IPM additive.

[0095] Performance test results: The dual-layer structure can extend the sustained release to 1-4 days, but the initial release of essential oil is insufficient and the mosquito repellent effect is slow; the repellency rate is 58.3% on the 3rd day after a single waterless application; mosquito bites appeared 4.0 hours after application, and the uniformity of essential oil dispersion is slightly worse after long-term storage.

[0096] Comparative Example 4: Commercially available ordinary natural essential oil mosquito repellent gel

[0097] The components of this comparative example (parts by weight) are as follows: 1 part lemongrass essential oil, 0.5 part carbomer, 1 part glycerin, 97.5 parts water, 0.1 part fragrance, and 0.1 part preservative.

[0098] The preparation method is as follows: Carbomer is dispersed in water, the pH is neutralized and adjusted to 6.5~7.0, citronella essential oil, glycerin, fragrance and preservative are added, and the mixture is stirred and mixed evenly to obtain a gel matrix.

[0099] The difference in this comparative example is that it has no sustained-release structure, no biodegradable polymer materials, and contains a synthetic polymer carrier.

[0100] Performance test results: The essential oil completely evaporates within 0.5 to 1 hour at room temperature, with no sustained-release effect; mosquitoes bite within 1 hour after application; the carrier material is non-biodegradable and poses an ecotoxicity risk.

[0101] Application Examples

[0102] This embodiment aims to verify the immediate protective effect and durability of the multi-stage slow-release mosquito repellent gel prepared by the present invention in actual use.

[0103] Experimental subjects and methods: Healthy adults were selected as subjects, and the inner side of their forearms was used as the test area.

[0104] Test group: Apply an appropriate amount of the multi-stage sustained-release mosquito repellent gel prepared in Example 1 evenly to the left forearm.

[0105] Control group: The right forearm was left untreated and without any product applied.

[0106] Exposure environment: Subjects entered outdoor natural environments with high mosquito density (such as park grass or the edge of woods) and sat with their skin exposed for 4 hours.

[0107] Test Results and Analysis: After the experiment, the skin condition of the subjects' arms was photographed, recorded, and statistically analyzed. The results are as follows: Figure 2 As shown.

[0108] Visual effect comparison: such as Figure 2 As shown in the left photo, the "gel-applied" area, where the gel of this invention has been applied, has a smooth and even skin surface, with no redness, swelling, or inflammatory reaction caused by mosquito bites; Figure 2As shown in the photo on the right, multiple obvious red papules and scratches are visible on the skin in the area where "no gel was applied," which are typical symptoms of mosquito bites.

[0109] Data statistics: During the 4-hour exposure period, the mosquito bite incidence rate in the test group (with gel applied) was 0%; the mosquito bite incidence rate in the control group (without gel applied) was 100%, with an average of 3-5 effective bite points in each test area.

[0110] Conclusion: The above results show that the multi-stage slow-release mosquito repellent gel prepared in the embodiments of the present invention has excellent immediate repellency and protection effects, can effectively prevent mosquito bites, and has a long-lasting effect, which is significantly better than the untreated state.

[0111] It should be noted that, in this document, relational terms such as "first" and "second" are used only to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitations, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes said element.

[0112] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A multi-stage sustained-release mosquito repellent gel based on a compound of plant essential oils, characterized in that: It includes an inner sustained-release unit and an outer gel coating layer; The inner layer sustained-release unit is composed of sodium alginate matrix, β-cyclodextrin inclusion complex and isopropyl myristate; The outer gel coating layer is composed of chitosan matrix, quaternary compound plant essential oil nanoemulsion and isopropyl myristate; The β-cyclodextrin inclusion complex contains camphor leaf essential oil and β-cyclodextrin; The quaternary compound plant essential oil is composed of orange peel essential oil, sesame essential oil, turmeric essential oil and camphor leaf essential oil.

2. The multi-stage sustained-release mosquito repellent gel based on plant essential oil compound according to claim 1, characterized in that: In the quaternary compound plant essential oil, the volume ratio of orange peel essential oil, sesame essential oil, turmeric essential oil and camphor leaf essential oil is 1:1:0.5:0.

5.

3. The multi-stage sustained-release mosquito repellent gel based on plant essential oil compound according to claim 1, characterized in that: In the β-cyclodextrin inclusion complex, the mass ratio of camphor leaf essential oil to β-cyclodextrin is 1:

8.

4. The multi-stage sustained-release mosquito repellent gel based on plant essential oil compound according to claim 1, characterized in that: The preparation method of the quaternary compound plant essential oil nanoemulsion includes: mixing and emulsifying the quaternary compound plant essential oil with Tween 80; wherein the volume ratio of the quaternary compound plant essential oil to Tween 80 is 1:

2.

5. The multi-stage sustained-release mosquito repellent gel based on plant essential oil compound according to claim 1, characterized in that: The mass fractions of each component in the gel are as follows: sodium alginate 1.5-2.5 parts, chitosan 1.0-2.0 parts, β-cyclodextrin 0.4-0.6 parts, camphor leaf essential oil 0.4-0.6 parts, quaternary compound essential oil 0.4-0.6 parts, and isopropyl myristate 0.05-0.15 parts.

6. The multi-stage sustained-release mosquito repellent gel based on plant essential oil compound according to claim 1, characterized in that: The preparation process of the orange peel essential oil includes: scraping off the white pith from the inside of the orange peel, cutting it into strips, and then steam distilling it. The preparation process of camphor tree leaf essential oil includes: collecting old camphor tree leaves, cutting them into small pieces, and then steam distilling them.

7. A method for preparing a multi-stage sustained-release mosquito repellent gel based on a compound of plant essential oils, wherein the multi-stage sustained-release mosquito repellent gel based on a compound of plant essential oils as described in any one of claims 1-6 is characterized in that: Includes the following steps: Step S1: Preparation of β-cyclodextrin inclusion complex: Dissolve camphor leaf essential oil in an organic solvent, slowly add it dropwise to an aqueous solution of β-cyclodextrin while stirring, stir at a constant temperature, refrigerate to crystallize, filter and dry to obtain inclusion complex powder; Step S2: Preparation of inner layer microspheres: Sodium alginate is dissolved in water, and the inclusion complex powder obtained in step S1 and isopropyl myristate are added. After stirring evenly, the mixture is dropped into a calcium salt solution for cross-linking and curing to form inner layer microspheres. Step S3: Preparation of outer gel solution: Dissolve chitosan in acidic aqueous solution, add quaternary compound plant essential oil nanoemulsion and isopropyl myristate, and stir evenly; Step S4: Assembly: Mix the inner layer microspheres obtained in step S2 into the outer layer gel liquid obtained in step S3, drop them into the crosslinking agent solution for crosslinking and curing, and then clean and dry to obtain the final product.

8. The preparation method of a multi-stage sustained-release mosquito repellent gel based on plant essential oil compound according to claim 7, characterized in that: In step S1, the temperature of the constant temperature stirring is controlled at 60±2℃, and the stirring time is 2 hours; the refrigeration temperature is 4℃, and the time is 24 hours. In step S2, the calcium salt solution is a 2% (w / w) calcium chloride solution, and the crosslinking time is 5 minutes; In step S4, the crosslinking agent is sodium tripolyphosphate (TPP) solution, and the crosslinking time is 15 minutes.

9. The application of a multi-stage slow-release mosquito repellent gel based on plant essential oil compound as described in any one of claims 1-7 in the preparation of mosquito repellent and mosquito prevention products.

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