Hydrogel loaded with menthol and preparation method thereof

Abstract

The invention discloses menthol-loaded hydrogel and a preparation method thereof, belongs to the technical field of menthol hydrogel, and aims to solve the technical problems of poor antibacterial property, poor moisturizing effect and poor cooling time of menthol-loaded hydrogel in the prior art. The preservative is specifically prepared from the following components in parts by weight: 80-100 parts of polyvinyl alcohol, 20-30 parts of sodium alginate, 3-5 parts of boric acid, 5-8 parts of calcium chloride, 10-15 parts of glycerol, 15-20 parts of a menthol compound, 5-10 parts of a chitosan compound, 1-2 parts of vitamin E and 350-400 parts of purified water. The menthol-loaded hydrogel is enhanced and modified through the menthol compound, the modified quaternary ammonium salt, the modified xylitol and the chitosan compound, so that the antibacterial rate and the moisturizing effect of the menthol hydrogel are effectively improved, the slow-release effect of the menthol hydrogel is improved, and the cooling time is prolonged.

Description

Technical Field

[0001] The present invention relates to the technical field of menthol hydrogels, and in particular to a menthol-loaded hydrogel and a preparation method thereof. Background Art

[0002] Menthol is a natural organic compound with multiple biological activities such as cooling, analgesia, and antibacterial properties. It is widely used in pharmaceuticals, food, and cosmetics. Hydrogel has good moisturizing effects, which can help keep the skin moisturized and promote wound healing. As a drug delivery system, it can slowly release drugs and provide sustained therapeutic effects. Therefore, menthol hydrogel is widely used in the biomedical field and daily chemical and personal care fields. The former uses its sustained-release analgesia to achieve targeted treatment, and the latter uses its cooling, moisturizing and soothing effects to provide post-sun relief and repair.

[0003] However, traditional menthol hydrogels only use pure menthol for loading. Because menthol is easily volatile, it causes a burst of menthol release during the release process, which cannot meet the long-term effect of the drug and greatly shortens the cooling time of the drug. Secondly, quaternary ammonium salts can largely make the hydrogel antibacterial, but quaternary ammonium salt molecules can reduce the skin's ability to lock in water and easily cause dryness. Therefore, they need to be modified to enhance their moisturizing and nourishing effects while maintaining their antibacterial properties.

[0004] In addition, ordinary chitosan lacks charge modification and cannot inhibit oxygen penetration through the charge barrier, accelerating the oxidation and rancidity of oils and greatly shortening the cooling time. By introducing chitosan complexes, the film-forming property of chitosan can not only significantly increase the cooling time, but also slow down volatilization, giving it a better moisturizing effect. Summary of the Invention

[0005] The present invention aims to provide a menthol-loaded hydrogel and a preparation method thereof, so as to solve the technical problem in the prior art that the antibacterial performance, moisturizing effect and cooling time of menthol-loaded hydrogels need to be further improved.

[0006] The object of the present invention can be achieved by the following technical solution: a menthol-loaded hydrogel, comprising the following components in parts by weight: 80-100 parts of polyvinyl alcohol, 20-30 parts of sodium alginate, 3-5 parts of boric acid, 5-8 parts of calcium chloride, 10-15 parts of glycerol, 15-20 parts of menthol complex, 5-10 parts of chitosan complex, 1-2 parts of vitamin E and 350-400 parts of purified water;

[0007] The chitosan complex consists of modified xylitol and chitosan in a volume ratio of 1:5.

[0008] Furthermore, the preparation method of the menthol complex is as follows: menthol, β-cyclodextrin and purified water are added into a reactor at a dosage ratio of 1g:2g:50mL, stirred at 50-60°C for 2h, and post-treated to obtain the menthol complex.

[0009] The synthetic mechanism of menthol complex is:

[0010] During the reaction process, β-cyclodextrin is composed of 7 glucose units connected by α-1,4-glycosidic bonds, and is hollow and truncated. It is hydrophilic on the outside and hydrophobic on the inside. Menthol is volatile and hydrophobic. When stirred in a 50-60°C aqueous solution, menthol diffuses into the hydrophobic cavity of β-cyclodextrin due to molecular movement and enters the cavity with the help of stirring. The two form an inclusion complex through weak interactions such as van der Waals forces and hydrogen bonds. Subsequently, freeze-drying is performed to freeze the water in the system into ice first, and then sublimation at low temperature and low pressure is removed to finally obtain a stable menthol complex.

[0011] Furthermore, the chitosan complex is prepared by dissolving chitosan in acetic acid solution, stirring at 25° C. until the solution becomes transparent, then mixing modified xylitol with the solution, adding sodium tripolyphosphate dropwise for cross-linking for 30 minutes, and freeze-drying to obtain the chitosan complex.

[0012] The synthesis mechanism of chitosan complex is:

[0013] During the reaction process, chitosan is first dissolved in acetic acid solution and stirred at 25°C until the solution becomes transparent to form a uniform chitosan solution. Modified xylitol is then added to the solution. The hydrophilic groups in xylitol and the amino groups in the chitosan molecules enhance the compatibility and stability of the two through hydrogen bonds and electrostatic interactions. Subsequently, sodium tripolyphosphate is added dropwise. The phosphate groups in the sodium tripolyphosphate interact electrostatically with the amino groups of the chitosan, promoting cross-linking between chitosan molecules to form a stable three-dimensional network structure. Finally, the solvent is removed through freeze-drying to obtain a chitosan complex with good stability and structure.

[0014] Furthermore, the amount ratio of chitosan, acetic acid solution, modified xylitol and sodium tripolyphosphate is 2g:20mL:10g:0.1g, the concentration of acetic acid solution is 2wt%, and the concentration of sodium tripolyphosphate is 1wt%.

[0015] Furthermore, the modified xylitol is prepared by the following steps:

[0016] A1. After dissolving the quaternary ammonium salt in purified water, the mixture was slowly added dropwise to a reactor containing aloe extract, followed by addition of carboxymethyl chitosan and sodium dodecylbenzene sulfonate, and ultrasonic treatment was performed for 30 min. The modified quaternary ammonium salt was obtained by post-treatment.

[0017] The synthesis mechanism of modified quaternary ammonium salt is:

[0018] During the reaction process, the polysaccharides in the aloe vera extract form hydrogen bonds or hydrophobic interaction complexes with the quaternary ammonium salt, wrapping its molecules to reduce irritation and achieve sustained release. Subsequently, carboxymethyl chitosan combines with the quaternary ammonium cations of the quaternary ammonium salt through electrostatic attraction to form a polyelectrolyte complex. Sodium dodecylbenzenesulfonate is further compounded with it to form mixed micelles. Finally, the ultrasonic cavitation effect promotes the uniform dispersion of each component and the intermolecular bonding to form a homogeneous and stable modified quaternary ammonium salt.

[0019] A2. Dissolve polyvinyl alcohol in purified water, stir at 90°C for 30 minutes, cool to 50°C, add xylitol and modified quaternary ammonium salt, emulsify for 15 minutes, add boric acid solution, let stand at 25°C for 2 hours, and post-treat to obtain modified xylitol.

[0020] The synthesis mechanism of modified xylitol is:

[0021] During the reaction process, polyvinyl alcohol is first dissolved at high temperature to form a flexible hydroxyl network matrix, and the active sites are exposed after cooling. Subsequently, xylitol enhances the network density and exerts a plasticizing effect through hydrogen bonding between polyhydroxyl groups and polyvinyl alcohol. At the same time, the modified quaternary ammonium salt is synergistically compounded with polyvinyl alcohol and xylitol through cationic electrostatic attraction and hydrophobic interaction, and a homogeneous microphase structure is formed after emulsification and dispersion. Finally, boric acid solution is introduced, which forms a dynamically reversible borate ester bond cross-linked network with the polyvinyl alcohol hydroxyl group, fixing the xylitol and quaternary ammonium salt molecules, and finally obtaining modified xylitol.

[0022] Furthermore, in step A1, the preparation method of the aloe extract is: mixing the aloe mesophyll with purified water, homogenizing and crushing for 10 minutes, filtering to obtain a primary extract, adding anhydrous ethanol to the primary extract, standing at 4°C for 12 hours, and post-processing to obtain an aloe extract with a solid content of 15-20%, wherein the usage ratio of aloe mesophyll, purified water and anhydrous ethanol is 2g:4mL:1mL.

[0023] Furthermore, in step A1, the amount ratio of the quaternary ammonium salt, purified water, aloe extract, carboxymethyl chitosan and sodium dodecylbenzenesulfonate is 10g:20mL:60g:2g:1g; in step A2, the amount ratio of polyvinyl alcohol, purified water, xylitol, modified quaternary ammonium salt and boric acid solution is 5g:100mL:40g:10g:0.3g, and the concentration of the boric acid solution is 0.3wt%.

[0024] The present invention also provides a method for preparing a menthol-loaded hydrogel, comprising the following steps:

[0025] S1. After uniformly mixing the polyvinyl alcohol solution and the sodium alginate solution, boric acid solution, calcium chloride solution, glycerol, and vitamin E were added in sequence, and magnetic stirring was performed for 30 minutes to obtain a hydrogel;

[0026] S2. Adding the menthol complex and the chitosan complex into the hydrogel and stirring for 15 minutes to obtain the menthol hydrogel.

[0027] Furthermore, in step S1, the polyvinyl alcohol solution is a 3-5wt% polyvinyl alcohol aqueous solution; the sodium alginate solution is a 0.5-1wt% sodium alginate aqueous solution; the boric acid solution is a 0.3-0.5wt% boric acid aqueous solution; and the calcium chloride solution is a 0.5-1wt% calcium chloride aqueous solution.

[0028] The present invention has the following beneficial effects:

[0029] 1. In the present invention, first, the hydrophilic outer cavity of β-cyclodextrin embeds fat-soluble menthol molecules into its cavity through hydrophobic interactions, significantly improving the solubility and dispersion uniformity of menthol in the hydrogel system, thereby enhancing the drug loading capacity. Second, the supramolecular structure formed by inclusion can effectively isolate menthol from the external environment, reducing its degradation or loss due to light, oxidation, or volatilization, and prolonging the storage stability of the active ingredient. Finally, the inclusion of menthol avoids burst release during the release process, and through continuous and controllable sustained release behavior, the cooling time of the hydrogel is extended, while also reducing the risk of irritation or toxicity that may be caused by high concentrations of free drugs.

[0030] 2. In the present invention, first, the active ingredients in aloe vera work synergistically with quaternary ammonium salts to significantly enhance the antibacterial properties, while exerting their natural anti-inflammatory effects to alleviate the potential irritation of menthol and quaternary ammonium salts. Secondly, xylitol, as a natural moisturizing factor, significantly improves the water-holding capacity of the hydrogel through a hydrogen bond network, alleviates the skin dryness problem caused by quaternary ammonium salts, and greatly increases the moisturizing effect of the hydrogel. At the same time, combined with the biocompatibility of aloe vera, the risk of material cytotoxicity is jointly reduced. In addition, the dynamic cross-linked network constructed by aloe polysaccharides and quaternary ammonium salts achieves the targeted release of menthol, and the swelling behavior regulated by xylitol can prolong the antibacterial properties, forming an intelligent multi-responsive drug delivery system.

[0031] 3. In the present invention, the hydrogen bond cross-linking between the molecular chains of xylitol and chitosan optimizes the mechanical properties of the hydrogel, making it both film-forming and ductile, while the microphase separation of the quaternary ammonium salt hydrophobic segments and the hydrophilic groups further enhances the stability and loading capacity of the hydrogel. In addition, thanks to the porous network structure and hydrophobic interaction, the hydrogel can efficiently load menthol and achieve long-lasting sustained release, extending the cooling time. At the same time, the hygroscopicity of xylitol and the film-forming property of chitosan synergistically maintain the moisturizing effect of the hydrogel, provide a moist environment for the wound surface, and promote cell regeneration. DETAILED DESCRIPTION

[0032] The technical solutions of the present invention will be clearly and completely described below in conjunction with the embodiments. Obviously, the embodiments described are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0033] In the present invention, polyvinyl alcohol is selected from Hubei Qibajiu Chemical Co., Ltd., with CAS number 9002-89-5, brand 1799, and active ingredient content of 99%;

[0034] In the present invention, sodium alginate is selected from Anhui Xinsheng Biotechnology Co., Ltd., with a CAS number of 9005-38-3 and an active ingredient content of 99%;

[0035] In the present invention, glycerol is selected from Shandong Xinbaiwei Chemical Co., Ltd., with a CAS number of 56-81-5 and a density of 1.25 g / cm 3 , the active ingredient content is 99%;

[0036] In the present invention, menthol is selected from Shandong Pingju Biotechnology Co., Ltd., with a CAS number of 1490-04-6, an EINECS number of 216-074-4, and an active ingredient content of 99%;

[0037] In the present invention, chitosan is selected from Shaanxi Changji Fu Biotechnology Co., Ltd., with a CAS number of 9012-76-4 and an active ingredient content of 99%;

[0038] In the present invention, β-cyclodextrin is selected from Shandong Tongwang Biotechnology Co., Ltd., with a CAS number of 128446-35-5 and an active ingredient content of 99.5%;

[0039] In the present invention, the quaternary ammonium salt is selected from Hubei Langbowan Biopharmaceutical Co., Ltd., with a CAS number of 68424-85-1 and an active ingredient content of 99%;

[0040] In the present invention, carboxymethyl chitosan is selected from Shanghai Zhongfeng Biotechnology Co., Ltd., with a CAS number of 83512-85-0 and a carboxylation degree of 80%;

[0041] In the present invention, sodium dodecylbenzenesulfonate is selected from Jinan Jiayang Chemical Co., Ltd., with a CAS number of 25155-30-0 and an active ingredient content of 99%;

[0042] In the present invention, sodium tripolyphosphate is selected from Shandong Pingju Biotechnology Co., Ltd., with a CAS number of 7758-29-4, an EINECS number of 231-838-7, and an active ingredient content of 99%.

[0043] Example 1

[0044] This embodiment provides a method for preparing a menthol-loaded hydrogel, comprising the following steps:

[0045] S1. Preparation of menthol complex

[0046] Weigh 4 g of menthol, 8 g of β-cyclodextrin and 200 mL of purified water, add them into a reactor, stir at 50° C. for 2 h, and freeze-dry to obtain a menthol complex.

[0047] S2. Preparation of Aloe Vera Extract

[0048] Weigh: 10g of aloe vera leaf pulp and 20mL of purified water, mix them, homogenize and crush them for 10 minutes, filter to obtain the primary extract, add 5mL of anhydrous ethanol to the primary extract, let it stand at 4°C for 12 hours, and concentrate it by centrifugation to obtain an aloe vera extract with a solid content of 15%.

[0049] S3. Preparation of modified quaternary ammonium salt

[0050] Weigh: 10 g of quaternary ammonium salt was dissolved in 20 mL of purified water and slowly added dropwise to a reactor containing 60 g of aloe extract. Subsequently, 2 g of carboxymethyl chitosan and 1 g of sodium dodecylbenzenesulfonate were added, and ultrasonic treatment was performed for 30 minutes to obtain a modified quaternary ammonium salt.

[0051] S4. Preparation of modified xylitol

[0052] Weigh: 5 g of polyvinyl alcohol was dissolved in 100 mL of purified water, stirred at 90° C. for 30 min, cooled to 50° C., added with 40 g of xylitol and 10 g of modified quaternary ammonium salt, emulsified for 15 min, and then added with 0.3 g of 0.3 wt% boric acid aqueous solution. The mixture was allowed to stand at 25° C. for 2 h to obtain modified xylitol.

[0053] S5. Preparation of Chitosan Composite

[0054] Weigh: 4g chitosan is dissolved in 40mL 2wt% acetic acid solution, stirred at 25°C until the solution is transparent, then mixed with 20g modified xylitol, and then dropwise added with 0.1g 1wt% sodium tripolyphosphate for cross-linking for 30min, and freeze-dried to obtain a chitosan complex.

[0055] S6. Preparation of hydrogel

[0056] Weigh 80 parts of a 3 wt % polyvinyl alcohol aqueous solution and 20 parts of a 0.5 wt % sodium alginate aqueous solution, mix them evenly, then add 3 parts of a 0.3 wt % boric acid aqueous solution, 5 parts of a 0.5 wt % calcium chloride aqueous solution, 10 parts of glycerol, and 1 part of vitamin E in sequence, and stir magnetically for 30 minutes to obtain a hydrogel.

[0057] S7. Preparation of Menthol Hydrogel

[0058] 15 parts of menthol complex and 5 parts of chitosan complex were weighed in parts by weight and added into the hydrogel, and stirred for 15 minutes to obtain menthol hydrogel.

[0059] Example 2

[0060] This embodiment provides a method for preparing a menthol-loaded hydrogel, comprising the following steps:

[0061] S1. Preparation of menthol complex

[0062] Weigh 4 g of menthol, 8 g of β-cyclodextrin and 200 mL of purified water, add them into a reactor, stir at 55° C. for 2 h, and freeze-dry to obtain a menthol complex.

[0063] S2. Preparation of Aloe Vera Extract

[0064] Weigh: 10g of aloe vera leaf pulp and 20mL of purified water, mix them, homogenize and crush them for 10 minutes, filter to obtain the primary extract, add 5mL of anhydrous ethanol to the primary extract, let it stand at 4°C for 12 hours, and concentrate it by centrifugation to obtain an aloe vera extract with a solid content of 18%.

[0065] S3. Preparation of modified quaternary ammonium salt

[0066] Weigh: 10 g of quaternary ammonium salt was dissolved in 20 mL of purified water and slowly added dropwise to a reactor containing 60 g of aloe extract. Subsequently, 2 g of carboxymethyl chitosan and 1 g of sodium dodecylbenzenesulfonate were added, and ultrasonic treatment was performed for 30 minutes to obtain a modified quaternary ammonium salt.

[0067] S4. Preparation of modified xylitol

[0068] Weigh: 5 g of polyvinyl alcohol was dissolved in 100 mL of purified water, stirred at 90° C. for 30 min, cooled to 50° C., added with 40 g of xylitol and 10 g of modified quaternary ammonium salt, emulsified for 15 min, and then added with 0.3 g of 0.3 wt% boric acid aqueous solution. The mixture was allowed to stand at 25° C. for 2 h to obtain modified xylitol.

[0069] S5. Preparation of Chitosan Composite

[0070] Weigh: 4g chitosan is dissolved in 40mL 2wt% acetic acid solution, stirred at 25°C until the solution is transparent, then mixed with 20g modified xylitol, and then dropwise added with 0.1g 1wt% sodium tripolyphosphate for cross-linking for 30min, and freeze-dried to obtain a chitosan complex.

[0071] S6. Preparation of hydrogel

[0072] Weigh by weight: 90 parts of a 4 wt% polyvinyl alcohol aqueous solution and 25 parts of a 0.8 wt% sodium alginate aqueous solution were mixed evenly, and then 4 parts of a 0.4 wt% boric acid aqueous solution, 6 parts of a 0.8 wt% calcium chloride aqueous solution, 12 parts of glycerol, and 1.5 parts of vitamin E were added in sequence. The mixture was magnetically stirred for 30 minutes to obtain a hydrogel.

[0073] S7. Preparation of Menthol Hydrogel

[0074] 18 parts of menthol complex and 8 parts of chitosan complex were weighed in parts by weight and added into the hydrogel, and stirred for 15 minutes to obtain menthol hydrogel.

[0075] Example 3

[0076] This embodiment provides a method for preparing a menthol-loaded hydrogel, comprising the following steps:

[0077] S1. Preparation of menthol complex

[0078] Weigh 4 g of menthol, 8 g of β-cyclodextrin and 200 mL of purified water, add them into a reactor, stir at 60° C. for 2 h, and freeze-dry to obtain a menthol complex.

[0079] S2. Preparation of Aloe Vera Extract

[0080] Weigh: 10g of aloe vera leaf pulp and 20mL of purified water, mix them, homogenize and crush them for 10 minutes, filter to obtain the primary extract, add 5mL of anhydrous ethanol to the primary extract, let it stand at 4°C for 12 hours, and concentrate it by centrifugation to obtain an aloe vera extract with a solid content of 20%.

[0081] S3. Preparation of modified quaternary ammonium salt

[0082] Weigh: 10 g of quaternary ammonium salt was dissolved in 20 mL of purified water and slowly added dropwise to a reactor containing 60 g of aloe extract. Subsequently, 2 g of carboxymethyl chitosan and 1 g of sodium dodecylbenzenesulfonate were added, and ultrasonic treatment was performed for 30 minutes to obtain a modified quaternary ammonium salt.

[0083] S4. Preparation of modified xylitol

[0084] Weigh: 5 g of polyvinyl alcohol was dissolved in 100 mL of purified water, stirred at 90° C. for 30 min, cooled to 50° C., added with 40 g of xylitol and 10 g of modified quaternary ammonium salt, emulsified for 15 min, and then added with 0.3 g of 0.3 wt% boric acid aqueous solution. The mixture was allowed to stand at 25° C. for 2 h to obtain modified xylitol.

[0085] S5. Preparation of Chitosan Composite

[0086] Weigh: 4g chitosan is dissolved in 40mL 2wt% acetic acid solution, stirred at 25°C until the solution is transparent, then mixed with 20g modified xylitol, and then dropwise added with 0.1g 1wt% sodium tripolyphosphate for cross-linking for 30min, and freeze-dried to obtain a chitosan complex.

[0087] S6. Preparation of hydrogel

[0088] Weigh by weight: 100 parts of a 5wt% polyvinyl alcohol aqueous solution and 30 parts of a 1wt% sodium alginate aqueous solution were mixed evenly, and then 5 parts of a 0.5wt% boric acid aqueous solution, 8 parts of a 1wt% calcium chloride aqueous solution, 15 parts of glycerol and 2 parts of vitamin E were added in sequence. The mixture was magnetically stirred for 30 minutes to obtain a hydrogel.

[0089] S7. Preparation of Menthol Hydrogel

[0090] Weigh 20 parts of menthol complex and 10 parts of chitosan complex in parts by weight, add them into the hydrogel, and stir for 15 minutes to obtain menthol hydrogel.

[0091] Comparative Example 1

[0092] The difference between this comparative example and Example 3 is that step S1 is omitted, and the menthol in step S1 is substituted for the menthol complex in step S7.

[0093] Comparative Example 2

[0094] The difference between this comparative example and Example 3 is that step S3 is eliminated, and the modified quaternary ammonium salt in step S4 is replaced by the quaternary ammonium salt in step S3.

[0095] Comparative Example 3

[0096] The difference between this comparative example and Example 3 is that step S4 is omitted, and the xylitol in step S4 is substituted for the modified xylitol in step S5.

[0097] Comparative Example 4

[0098] The difference between this comparative example and Example 3 is that step S5 is eliminated, and the chitosan complex in step S7 is replaced by the chitosan in step S5.

[0099] Performance testing:

[0100] Referring to the standard GB / T 26369-2020 "Hygiene Requirements for Quaternary Ammonium Disinfectants", the killing logarithm of the menthol-loaded hydrogels prepared in Examples 1-3 and Comparative Examples 1-4 was measured, and the units were converted to obtain the antibacterial rate of the menthol-loaded hydrogel;

[0101] The capacitance of the skin was measured after the menthol-loaded hydrogels prepared in Examples 1-3 and Comparative Examples 1-4 were applied to the skin surface in accordance with the standard QB / T 4256-2011 "Guidelines for the Evaluation of Moisturizing Efficacy of Cosmetics," thereby demonstrating the moisturizing effect of the menthol-loaded hydrogels.

[0102] 1 g of each of the menthol hydrogels prepared in Examples 1-3 and Comparative Examples 1-4 was evenly applied to a 4 cm x 4 cm area of ​​skin. The cooling effect of the menthol hydrogel was recorded every half minute. This provided the cooling time of the hydrogel, and thus its sustained release rate. The specific test results are shown in Table 1 below:

[0103] Table 1-Performance test data of the sample

[0104]

[0105]

[0106] Data Analysis:

[0107] Comparative analysis of the data in Table 1 above shows that the menthol-loaded hydrogel prepared by the present invention has an antibacterial rate of 98.1%, a capacitance of 25 μF, and a cooling time of 35 minutes;

[0108] Compared with Example 3, Comparative Example 1 showed little improvement in the antibacterial rate and moisturizing effect of the menthol-loaded hydrogel. However, the menthol encapsulated by β-cyclodextrin had a certain stability, which prevented the sudden release phenomenon during the release process. Therefore, the sustained release rate of menthol was greatly improved, and the cooling time of the menthol hydrogel was greatly prolonged.

[0109] Compared with Example 3, in Comparative Example 2, the antibacterial rate of the menthol-loaded hydrogel is improved due to the synergistic effect of the active ingredients in aloe vera and the quaternary ammonium salt. The dynamic cross-linked network constructed by aloe polysaccharides and quaternary ammonium salts achieves the targeted release of menthol, thereby greatly improving the moisturizing effect and cooling time of the menthol hydrogel.

[0110] Comparative Example 3 Compared with Example 3, xylitol, as a natural moisturizing factor, significantly improves the water holding capacity of the hydrogel through the hydrogen bond network, while the active ingredients in aloe vera and the quaternary ammonium salt synergistically enhance the antibacterial properties. The three synergistically improve the antibacterial rate of the menthol-loaded hydrogel while also maximizing the moisturizing effect of the menthol hydrogel.

[0111] Compared with Example 3, in Comparative Example 4, the hygroscopicity of xylitol and the film-forming property of chitosan synergistically improve the cooling time of the menthol-loaded hydrogel, while also significantly improving the antibacterial rate and moisturizing effect of the menthol hydrogel.

[0112] The above contents are merely examples and explanations of the structure of the present invention. Those skilled in the art may make various modifications or additions to the described specific embodiments or replace them in a similar manner. As long as they do not deviate from the structure of the invention or exceed the scope defined by the claims, they shall fall within the scope of protection of the present invention.

[0113] Throughout this specification, references to terms such as "one embodiment," "example," or "specific example" indicate that the specific features, structures, materials, or characteristics described in conjunction with that embodiment or example are included in at least one embodiment or example of the present invention. In this specification, schematic representations of these terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in any one or more embodiments or examples.

[0114] The preferred embodiments of the present invention disclosed above are intended only to help illustrate the present invention. These preferred embodiments do not exhaustively describe all details, nor do they limit the present invention to specific embodiments. Obviously, many modifications and variations are possible based on the contents of this specification. These embodiments are selected and described in detail in this specification to better explain the principles and practical applications of the present invention, thereby enabling those skilled in the art to better understand and utilize the present invention. The present invention is limited only by the claims and their full scope and equivalents.

Claims

1. A menthol-loaded hydrogel, characterized in that: The invention comprises the following components in parts by weight: 80-100 parts of polyvinyl alcohol, 20-30 parts of sodium alginate, 3-5 parts of boric acid, 5-8 parts of calcium chloride, 10-15 parts of glycerol, 15-20 parts of menthol complex, 5-10 parts of chitosan complex, 1-2 parts of vitamin E and 350-400 parts of purified water; The chitosan complex consists of modified xylitol and chitosan in a volume ratio of 1:

5.

2. The menthol-loaded hydrogel according to claim 1, characterized in that: The preparation method of the menthol complex comprises the following steps: adding menthol, β-cyclodextrin and purified water into a reaction kettle at a dosage ratio of 1 g:2 g:50 mL, stirring at 50-60° C. for 2 hours, and performing post-treatment to obtain the menthol complex.

3. The menthol-loaded hydrogel according to claim 1, characterized in that: The preparation method of the chitosan complex comprises: dissolving chitosan in acetic acid solution, stirring at 25° C. until the solution becomes transparent, mixing the chitosan with modified xylitol, adding sodium tripolyphosphate dropwise for cross-linking for 30 minutes, and freeze-drying to obtain the chitosan complex.

4. The menthol-loaded hydrogel according to claim 3, characterized in that: The usage ratio of the chitosan, acetic acid solution, modified xylitol and sodium tripolyphosphate is 2g:20mL:10g:0.1g, the concentration of the acetic acid solution is 2wt%, and the concentration of the sodium tripolyphosphate is 1wt%.

5. The menthol-loaded hydrogel according to claim 3, characterized in that: Modified xylitol is prepared by the following steps: A1. After dissolving the quaternary ammonium salt in purified water, the mixture was slowly added dropwise to a reactor containing aloe extract, followed by addition of carboxymethyl chitosan and sodium dodecylbenzene sulfonate, and ultrasonic treatment was performed for 30 min. The modified quaternary ammonium salt was obtained by post-treatment. A2. Dissolve polyvinyl alcohol in purified water, stir at 90°C for 30 minutes, cool to 50°C, add xylitol and modified quaternary ammonium salt, emulsify for 15 minutes, add boric acid solution, let stand at 25°C for 2 hours, and post-treat to obtain modified xylitol.

6. The menthol-loaded hydrogel according to claim 5, characterized in that: In step A1, the preparation method of the aloe extract is: mixing aloe mesophyll with purified water, homogenizing and crushing for 10 minutes, filtering to obtain a primary extract, adding anhydrous ethanol to the primary extract, standing at 4°C for 12 hours, and post-processing to obtain an aloe extract with a solid content of 15-20%, wherein the amount ratio of aloe mesophyll, purified water and anhydrous ethanol is 2g:4mL:1mL.

7. The menthol-loaded hydrogel according to claim 5, characterized in that: In step A1, the amount ratio of the quaternary ammonium salt, purified water, aloe extract, carboxymethyl chitosan and sodium dodecylbenzenesulfonate is 10g:20mL:60g:2g:1g; in step A2, the amount ratio of polyvinyl alcohol, purified water, xylitol, modified quaternary ammonium salt and boric acid solution is 5g:100mL:40g:10g:0.3g, and the concentration of the boric acid solution is 0.3wt%.

8. The method for preparing a menthol-loaded hydrogel according to any one of claims 1 to 7, characterized in that: The following steps are involved: S1. After uniformly mixing the polyvinyl alcohol solution and the sodium alginate solution, boric acid solution, calcium chloride solution, glycerol, and vitamin E were added in sequence, and magnetic stirring was performed for 30 minutes to obtain a hydrogel; S2. Adding the menthol complex and the chitosan complex into the hydrogel and stirring for 15 minutes to obtain the menthol hydrogel.

9. The method for preparing a menthol-loaded hydrogel according to claim 8, characterized in that: In step S1, the polyvinyl alcohol solution is a 3-5wt% polyvinyl alcohol aqueous solution; the sodium alginate solution is a 0.5-1wt% sodium alginate aqueous solution; the boric acid solution is a 0.3-0.5wt% boric acid aqueous solution; and the calcium chloride solution is a 0.5-1wt% calcium chloride aqueous solution.

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