Tea polyphenol-loaded modified carboxymethyl chitosan gel as well as preparation method and application thereof

Abstract

The invention belongs to the technical field of chitosan, and particularly relates to tea polyphenol-loaded modified carboxymethyl chitosan gel as well as a preparation method and application thereof. Hydroxypropyl-beta-cyclodextrin is adopted to modify carboxymethyl chitosan, the modified carboxymethyl chitosan gel is prepared through the multi-carboxyl cross-linking agent and polyvinyl alcohol, and the gel prepared from the modified carboxymethyl chitosan is good in mechanical property and excellent in water retention capacity. Carboxymethyl chitosan is subjected to crosslinking modification through cyclic molecules with hydroxypropyl, and polyvinyl alcohol is used as a long straight-chain polymer and can be effectively connected with carboxymethyl chitosan and hydroxypropyl-beta-cyclodextrin through hydrogen bonds. Meanwhile, through an impregnation process, on the basis of hydrogen bond crosslinking of the tea polyphenol, the cross-linked porous structure of the carboxymethyl chitosan-based hydrogel and the encapsulation effect of hydroxypropyl-beta-cyclodextrin are fully played, the tea polyphenol can be effectively encapsulated, the activity of the tea polyphenol can be ensured, and the moisturizing and antibacterial capabilities of the hydrogel are improved.

Description

Technical Field

[0001] The invention belongs to the technical field of chitosan, and in particular relates to modified carboxymethyl chitosan gel carrying tea polyphenols, and a preparation method and application thereof. Background Art

[0002] Although chitosan has excellent properties such as good antibacterial activity, non-toxicity, biodegradability, and biocompatibility, its development and application are greatly restricted due to its poor water solubility. Chitosan contains two active groups, hydroxyl and amine, so some of its properties can be improved by modifying chitosan. For example, carboxymethyl chitosan prepared by carboxymethylation of chitosan can significantly improve its water solubility. Compared with chitosan, carboxymethyl chitosan is a water-soluble polysaccharide. The main reason is that carboxymethyl chitosan is a sodium carboxylate salt substance, and the hydrogen bond structure in the molecule is destroyed during the introduction of carboxymethyl groups into chitosan, thereby reducing its crystallinity and increasing its water solubility. In addition, chitosan after carboxymethylation has stronger biological activity, pH sensitivity, biocompatibility, moisturizing ability and antibacterial activity. Carboxymethyl chitosan promotes the formation of granulation tissue and the regeneration of epidermal cells, so it is also of great help to the late healing of wounds. Due to these excellent properties, carboxymethyl chitosan has been widely used in drug delivery, biosensors, wound healing biomaterials, food preservation and other fields.

[0003] Hydrogel is a flexible material composed of a hydrophilic polymer network. The cross-linked network allows the polymer chains to swell in water without dissolving, so the hydrogel can absorb and retain a large amount of water. Hydrogels made of carboxymethyl chitosan have excellent biocompatibility, can avoid inducing inflammation or immune response, and are degradable, so they have significant advantages in biomedical applications. Because carboxymethyl chitosan hydrogel has a variety of unique properties in mechanics, interfacial dynamics and biology, it has a wide range of application value in tissue engineering, flexible electronics, wound dressings, drug delivery, 3D printing, personal care, sewage treatment, biochemical catalysis and other fields.

[0004] However, the adhesion strength of traditional carboxymethyl chitosan hydrogels is usually weak, the water retention capacity is poor, and the antibacterial ability is low. In addition, water molecules interact with the adhesion groups in the hydrogel through hydrogen bonds, which significantly reduces the interfacial reaction between the carboxymethyl chitosan hydrogel and the solid material, which is not conducive to the attachment of antibacterial materials; especially for high-strength hydrogels, their rigid network is even more unfavorable for surface adhesion. Therefore, the research on highly moisturizing and antibacterial carboxymethyl chitosan hydrogels is still a major challenge in the current hydrogel field.

[0005] With the in-depth study of carboxymethyl chitosan hydrogel adhesive materials, carboxymethyl chitosan hydrogels directly used on the skin with the advantages of keeping the skin moist, heat insulation, breathability and antibacterial have been reported one after another. However, the carboxymethyl chitosan hydrogels prepared by the prior art generally have the disadvantages of poor moisture retention, low stability and weak antibacterial ability. Therefore, it is urgent to modify carboxymethyl chitosan to develop a carboxymethyl chitosan hydrogel with high water absorption, moisture retention and antibacterial ability. Summary of the invention

[0006] In view of the shortcomings of the prior art, the purpose of the present invention is to provide a modified carboxymethyl chitosan gel loaded with tea polyphenols, and a preparation method and application thereof. The gel material has a wide source of raw materials, a simple preparation process, and has excellent moisturizing, antibacterial and mechanical properties. It can meet the use requirements of skin wound dressings in the cosmetics and medical fields and has good application prospects.

[0007] The purpose of the present invention is achieved through the following technical solutions.

[0008] The preparation method of modified carboxymethyl chitosan gel loaded with tea polyphenols comprises the following steps:

[0009] (1) adding 2 parts by weight of carboxymethyl chitosan and 0.5-1 parts by weight of hydroxypropyl-β-cyclodextrin into deionized water to dissolve to obtain a premix;

[0010] (2) adding 1-4 parts by weight of a polycarboxyl crosslinking agent to the premix, stirring; and adjusting the pH with an alkali solution to obtain a mixed solution;

[0011] (3) Add a condensing agent to the mixed solution, and stir the reaction at 60-80°C for 1-6 hours to obtain a primary reaction mixture; the initial reaction can construct a preliminary structure of the hydrogel, at which point the molecular chain grows to a certain extent, which is conducive to forming an interactive structure with the linear polyvinyl alcohol. Further, the reaction time is 2-4 hours, at which point the molecular chain length is appropriate, with both a certain length and a certain mobility, which is conducive to forming an intertwined structure with the polyvinyl alcohol.

[0012] (4) adding 0.3-0.6 parts by weight of polyvinyl alcohol to the primary reaction mixture, and continuing to stir and react at 60-80° C. for 10-20 hours to obtain a primary gel solution;

[0013] (5) Dissolve tea polyphenols in deionized water, and add the solution dropwise to the primary gel solution under stirring. After the addition is complete, a primary gel mixed solution is obtained. Continue stirring to obtain a modified carboxymethyl chitosan gel loaded with tea polyphenols.

[0014] Carboxymethyl chitosan is a derivative of chitosan with excellent water solubility. Carboxymethyl chitosan includes O-carboxymethyl chitosan, N-carboxymethyl chitosan, N,O-carboxymethyl chitosan and N,N-carboxymethyl chitosan. The moisturizing property of carboxymethyl chitosan is related to the structure-effect relationship between its molecular structure. The carboxymethyl substitution on the 6-hydroxyl group has the strongest moisturizing ability. Increasing the molecular weight or cross-linking is conducive to enhancing the moisturizing effect.

[0015] The cross-linking methods of carboxymethyl chitosan-based hydrogels mainly include Schiff base reaction and the formation of insoluble substances by combining carboxyl groups and metal ions. Among them, the Schiff base reaction mainly utilizes aldehyde groups and amino groups in carboxymethyl chitosan for cross-linking reaction, but the commonly used glutaraldehyde has cytotoxicity, which limits its application. And the metal ion combination also affects its biocompatibility due to the introduction of metal heteroatoms. In order to overcome the above problems, the present invention adopts small molecule polycarboxyl compounds as cross-linking agents to prepare modified carboxymethyl chitosan-based cross-linked hydrogels, and the internal structure of the hydrogel is stable and uniform, and has a certain ability to resist deformation.

[0016] However, the mechanical properties of pure carboxymethyl chitosan-based cross-linked hydrogels are insufficient and their water retention capacity is limited. Hydroxypropyl-β-cyclodextrin is a cyclodextrin derivative modified from β-cyclodextrin. The introduction of hydroxypropyl into cyclodextrin increases its water solubility. Hydroxypropyl-β-cyclodextrin presents a hollow cylindrical conical structure, which is hydrophilic on the outside and hydrophobic on the inside. Tea polyphenols can enter the cavity of hydroxypropyl-β-cyclodextrin to form an encapsulated cage structure, thereby improving the loading efficiency of tea polyphenols. The presence of hydroxypropyl side chains and cyclic structures increases the degree of interaction between them and the carboxymethyl chitosan molecular chain. By cross-linking the cyclic molecules with hydroxypropyl groups with carboxymethyl chitosan, the mechanical properties and water retention capacity of the hydrogel are greatly increased. At the same time, polyvinyl alcohol, as a long linear polymer, is added to the reaction system after the initial polymerization reaction, and can effectively connect carboxymethyl chitosan and hydroxypropyl-β-cyclodextrin through hydrogen bonds, thereby increasing the degree of cross-linking of the hydrogel and thereby improving its water retention capacity.

[0017] Tea polyphenols have multiple phenolic hydroxyl groups, which can provide tea polyphenols with strong antioxidant activity and have certain antibacterial activity against fungi and bacteria. Due to the poor stability of tea polyphenols, its application is limited to a certain extent. The present invention uses a simple impregnation process to give full play to the cross-linked porous structure of the carboxymethyl chitosan-based hydrogel and the encapsulation effect of hydroxypropyl-β-cyclodextrin on the basis of hydrogen bond cross-linking of tea polyphenols, so as to effectively encapsulate tea polyphenols and ensure their activity, thereby improving the antibacterial ability of the hydrogel.

[0018] Furthermore, in step (1), the amount of deionized water is 100-150 parts by weight; in step (2), the amount of the polycarboxyl crosslinking agent is 1.5-3 parts by weight. By adjusting the amount of the crosslinking agent, the properties of the hydrogel can be regulated. However, when the amount of the polycarboxyl crosslinking agent is too small, the degree of crosslinking is insufficient, and the ability to retain water and encapsulate tea polyphenols is limited; when the amount is too large, the degree of crosslinking is too large, which is not conducive to the infiltration of water and the entry of tea polyphenols into the cavity of hydroxypropyl-β-cyclodextrin.

[0019] Furthermore, in step (2), the polycarboxyl crosslinking agent is one or more of iminodiacetic acid, nitrilotriacetic acid, ethylenediaminetetraacetic acid, and diethylenetriaminepentaacetic acid.

[0020] Furthermore, in step (2), the stirring rate is 600-700 rpm, and the stirring time is 20-30 min.

[0021] Furthermore, in step (2), the alkali solution is a sodium hydroxide solution or a potassium hydroxide solution.

[0022] Furthermore, in step (2), the pH is 5-6.

[0023] Furthermore, in step (3), the condensing agent is one or more of dicyclohexylcarbodiimide / N-hydroxysuccinimide, dicyclohexylcarbodiimide / 4-dimethylaminopyridine, 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride / N-hydroxysuccinimide; and the condensing agent is 5-15 parts by weight.

[0024] Furthermore, in step (5), the amount of tea polyphenols added is such that its concentration in the primary gel mixed solution is 50-100 μg / mL; and the stirring time is continued for 1-2 hours.

[0025] The invention also provides a tea polyphenol-loaded modified carboxymethyl chitosan gel and application of the gel in preparing an antibacterial and moisturizing material.

[0026] Technical effect:

[0027] The present invention uses carboxymethyl chitosan as a matrix material and uses hydroxypropyl-β-cyclodextrin to modify it. The gel prepared by the modified carboxymethyl chitosan has good mechanical properties and excellent water retention performance. A small molecule polycarboxyl compound is used as a cross-linking agent to prepare a modified carboxymethyl chitosan-based cross-linked hydrogel, and the internal structure of the hydrogel is stable and uniform, and has a certain ability to resist deformation. The presence of hydroxypropyl side chains and cyclic structures improves the degree of interaction between them and the carboxymethyl chitosan molecular chain. By cross-linking the cyclic molecules with hydroxypropyl groups with carboxymethyl chitosan, the mechanical properties and water retention capacity of the hydrogel are greatly increased. At the same time, polyvinyl alcohol, as a long straight-chain polymer, is added to the reaction system after the preliminary polymerization reaction, and can effectively connect carboxymethyl chitosan and hydroxypropyl-β-cyclodextrin through hydrogen bonds, thereby improving the cross-linking degree of the hydrogel and further improving its water retention capacity. Through a simple impregnation process, on the basis of hydrogen bond cross-linking of tea polyphenols, the cross-linked porous structure of the carboxymethyl chitosan-based hydrogel and the encapsulation effect of hydroxypropyl-β-cyclodextrin of the present invention are fully utilized, tea polyphenols can be effectively encapsulated and its activity can be guaranteed, and the antibacterial ability of the hydrogel can be improved. DETAILED DESCRIPTION

[0028] The specific embodiments of the present invention are described in detail below, but it should be pointed out that the protection scope of the present invention is not limited to these specific embodiments.

[0029] Unless otherwise defined, all technical and scientific terms used in this specification have the meanings commonly understood by those skilled in the art. In the event of conflict, the definitions in this specification shall prevail. The carboxymethyl chitosan used in the examples and comparative examples is O-carboxymethyl chitosan substituted with C6-OH carboxymethyl, with a deacetylation degree of 44.5% and a substitution degree of 0.64. The degree of substitution of hydroxypropyl-β-cyclodextrin is 4.

[0030] Example 1: A method for preparing a modified carboxymethyl chitosan gel loaded with tea polyphenols, comprising the following steps:

[0031] (1) adding 2 parts by weight of carboxymethyl chitosan and 0.5 parts by weight of hydroxypropyl-β-cyclodextrin to 100 parts by weight of deionized water and dissolving them to obtain a premix;

[0032] (2) adding 1.5 parts by weight of a polycarboxyl crosslinking agent, ethylenediaminetetraacetic acid, to the premix, stirring; and adjusting the pH to 5 with a sodium hydroxide solution to obtain a mixed solution; the stirring rate was 600 rpm, and the stirring time was 30 min;

[0033] (3) adding a condensing agent, dicyclohexylcarbodiimide / 4-dimethylaminopyridine, to the mixed solution, and stirring the mixture at 60° C. for 4 h to obtain a primary reaction mixture; the condensing agent is 5 parts by weight, and the mass ratio of dicyclohexylcarbodiimide to 4-dimethylaminopyridine is 5:1;

[0034] (4) adding 0.3 parts by weight of polyvinyl alcohol to the primary reaction mixture, and continuing to stir and react at 80° C. for 10 hours to obtain a primary gel solution;

[0035] (5) Dissolve tea polyphenols in deionized water, and add the solution dropwise to the primary gel solution under stirring. After the addition is complete, a primary gel mixed solution is obtained. Continue stirring to obtain a modified carboxymethyl chitosan gel loaded with tea polyphenols. The amount of tea polyphenol added is such that its concentration in the primary gel mixed solution is 50 μg / mL. Continue stirring for 1 hour.

[0036] Example 2: A method for preparing a modified carboxymethyl chitosan gel loaded with tea polyphenols, comprising the following steps:

[0037] (1) adding 2 parts by weight of carboxymethyl chitosan and 1 part by weight of hydroxypropyl-β-cyclodextrin to 150 parts by weight of deionized water to dissolve to obtain a premix;

[0038] (2) adding 3 parts by weight of a polycarboxyl crosslinking agent, diethylenetriamine pentaacetic acid, to the premix and stirring; and adjusting the pH to 6 with a sodium hydroxide solution to obtain a mixed solution; the stirring rate was 700 rpm, and the stirring time was 20 min;

[0039] (3) adding a condensing agent, dicyclohexylcarbodiimide / 4-dimethylaminopyridine, to the mixed solution, and stirring the mixture at 80° C. for 2 h to obtain a primary reaction mixture; the condensing agent is 15 parts by weight, and the mass ratio of dicyclohexylcarbodiimide to 4-dimethylaminopyridine is 10:1;

[0040] (4) adding 0.6 parts by weight of polyvinyl alcohol to the primary reaction mixture, and continuing to stir and react at 60° C. for 20 hours to obtain a primary gel solution;

[0041] (5) Dissolve tea polyphenols in deionized water, and add the solution dropwise to the primary gel solution under stirring. After the addition is complete, a primary gel mixed solution is obtained. Continue stirring to obtain a modified carboxymethyl chitosan gel loaded with tea polyphenols. The amount of tea polyphenol added is such that its concentration in the primary gel mixed solution is 100 μg / mL. Continue stirring for 2 h.

[0042] Example 3: A method for preparing a modified carboxymethyl chitosan gel loaded with tea polyphenols, comprising the following steps:

[0043] (1) adding 2 parts by weight of carboxymethyl chitosan and 0.6 parts by weight of hydroxypropyl-β-cyclodextrin to 120 parts by weight of deionized water to dissolve to obtain a premix;

[0044] (2) adding 1.8 parts by weight of a polycarboxyl crosslinking agent, ethylenediaminetetraacetic acid, to the premix and stirring; and adjusting the pH to 6 with a sodium hydroxide solution to obtain a mixed solution; the stirring rate was 660 rpm, and the stirring time was 24 min;

[0045] (3) adding a condensing agent, dicyclohexylcarbodiimide / 4-dimethylaminopyridine, to the mixed solution, and stirring the mixture at 65° C. for 2.5 h to obtain a primary reaction mixture; the condensing agent is 13 parts by weight, and the mass ratio of dicyclohexylcarbodiimide to 4-dimethylaminopyridine is 8:1;

[0046] (4) adding 0.4 parts by weight of polyvinyl alcohol to the primary reaction mixture, and continuing to stir and react at 67° C. for 18 hours to obtain a primary gel solution;

[0047] (5) Dissolve tea polyphenols in deionized water, and add the solution dropwise to the primary gel solution under stirring. After the addition is complete, a primary gel mixed solution is obtained. Continue stirring to obtain a modified carboxymethyl chitosan gel loaded with tea polyphenols. The amount of tea polyphenol added is such that its concentration in the primary gel mixed solution is 60 μg / mL. Continue stirring for 1.2 h.

[0048] Example 4: A method for preparing a modified carboxymethyl chitosan gel loaded with tea polyphenols, comprising the following steps:

[0049] (1) adding 2 parts by weight of carboxymethyl chitosan and 0.9 parts by weight of hydroxypropyl-β-cyclodextrin to 130 parts by weight of deionized water to dissolve to obtain a premix;

[0050] (2) adding 2.8 parts by weight of a polycarboxyl crosslinking agent, diethylenetriamine pentaacetic acid, to the premix and stirring; and adjusting the pH to 5 with a sodium hydroxide solution to obtain a mixed solution; the stirring rate was 670 rpm, and the stirring time was 22 min;

[0051] (3) adding a condensing agent, dicyclohexylcarbodiimide / 4-dimethylaminopyridine, to the mixed solution, and stirring the mixture at 74° C. for 3.6 hours to obtain a primary reaction mixture; the condensing agent is 14 parts by weight, and the mass ratio of dicyclohexylcarbodiimide to 4-dimethylaminopyridine is 10:1;

[0052] (4) adding 0.5 parts by weight of polyvinyl alcohol to the primary reaction mixture, and continuing to stir and react at 76° C. for 13 hours to obtain a primary gel solution;

[0053] (5) Dissolve tea polyphenols in deionized water and add the solution dropwise to the primary gel solution under stirring. After the addition is complete, a primary gel mixed solution is obtained. Continue stirring to obtain a modified carboxymethyl chitosan gel loaded with tea polyphenols. The amount of tea polyphenol added is such that its concentration in the primary gel mixed solution is 90 μg / mL. Continue stirring for 1.8 h.

[0054] Example 5: A method for preparing a modified carboxymethyl chitosan gel loaded with tea polyphenols, comprising the following steps:

[0055] (1) adding 2 parts by weight of carboxymethyl chitosan and 0.8 parts by weight of hydroxypropyl-β-cyclodextrin to 110 parts by weight of deionized water to dissolve to obtain a premix;

[0056] (2) adding 2.2 parts by weight of a polycarboxyl crosslinking agent, ethylenediaminetetraacetic acid, to the premix and stirring; and adjusting the pH to 6 with a sodium hydroxide solution to obtain a mixed solution; the stirring rate was 620 rpm, and the stirring time was 23 min;

[0057] (3) adding a condensing agent, dicyclohexylcarbodiimide / 4-dimethylaminopyridine, to the mixed solution, and stirring the mixture at 67° C. for 3.1 h to obtain a primary reaction mixture; the condensing agent is 10 parts by weight, and the mass ratio of dicyclohexylcarbodiimide to 4-dimethylaminopyridine is 13:1;

[0058] (4) adding 0.4 parts by weight of polyvinyl alcohol to the primary reaction mixture, and continuing to stir and react at 77° C. for 15 hours to obtain a primary gel solution;

[0059] (5) Dissolve tea polyphenols in deionized water, and add the solution dropwise to the primary gel solution under stirring. After the addition is complete, a primary gel mixed solution is obtained. Continue stirring to obtain a modified carboxymethyl chitosan gel loaded with tea polyphenols. The amount of tea polyphenol added is such that its concentration in the primary gel mixed solution is 70 μg / mL. Continue stirring for 1.3 h.

[0060] Example 6: A method for preparing a modified carboxymethyl chitosan gel loaded with tea polyphenols, comprising the following steps:

[0061] (1) adding 2 parts by weight of carboxymethyl chitosan and 0.7 parts by weight of hydroxypropyl-β-cyclodextrin to 130 parts by weight of deionized water to dissolve to obtain a premix;

[0062] (2) adding 2.2 parts by weight of a polycarboxyl crosslinking agent, ethylenediaminetetraacetic acid, to the premix, stirring; and adjusting the pH to 5 with a sodium hydroxide solution to obtain a mixed solution; stirring at a rate of 650 rpm for 25 min;

[0063] (3) adding a condensing agent, dicyclohexylcarbodiimide / 4-dimethylaminopyridine, to the mixed solution, and stirring the mixture at 70° C. for 3 h to obtain a primary reaction mixture; the condensing agent is 10 parts by weight, and the mass ratio of dicyclohexylcarbodiimide to 4-dimethylaminopyridine is 12:1;

[0064] (4) adding 0.5 parts by weight of polyvinyl alcohol to the primary reaction mixture, and continuing to stir and react at 70° C. for 16 hours to obtain a primary gel solution;

[0065] (5) Dissolve tea polyphenols in deionized water, and add the solution dropwise to the primary gel solution under stirring. After the addition is complete, a primary gel mixed solution is obtained. Continue stirring to obtain a modified carboxymethyl chitosan gel loaded with tea polyphenols. The amount of tea polyphenol added is such that its concentration in the primary gel mixed solution is 70 μg / mL. Continue stirring for 1.5 h.

[0066] Example 7: A method for preparing a modified carboxymethyl chitosan gel loaded with tea polyphenols, comprising the following steps:

[0067] (1) adding 2 parts by weight of carboxymethyl chitosan and 0.7 parts by weight of hydroxypropyl-β-cyclodextrin to 130 parts by weight of deionized water to dissolve to obtain a premix;

[0068] (2) adding 1 part by weight of a polycarboxyl crosslinking agent, ethylenediaminetetraacetic acid, to the premix, stirring; and adjusting the pH to 5 with a sodium hydroxide solution to obtain a mixed solution; the stirring rate was 650 rpm, and the stirring time was 25 min;

[0069] (3) adding a condensing agent, dicyclohexylcarbodiimide / 4-dimethylaminopyridine, to the mixed solution, and stirring the mixture at 70° C. for 3 h to obtain a primary reaction mixture; the condensing agent is 10 parts by weight, and the mass ratio of dicyclohexylcarbodiimide to 4-dimethylaminopyridine is 12:1;

[0070] (4) adding 0.5 parts by weight of polyvinyl alcohol to the primary reaction mixture, and continuing to stir and react at 70° C. for 16 hours to obtain a primary gel solution;

[0071] (5) Dissolve tea polyphenols in deionized water, and add the solution dropwise to the primary gel solution under stirring. After the addition is complete, a primary gel mixed solution is obtained. Continue stirring to obtain a modified carboxymethyl chitosan gel loaded with tea polyphenols. The amount of tea polyphenol added is such that its concentration in the primary gel mixed solution is 70 μg / mL. Continue stirring for 1.5 h.

[0072] Example 8: A method for preparing a modified carboxymethyl chitosan gel loaded with tea polyphenols, comprising the following steps:

[0073] (1) adding 2 parts by weight of carboxymethyl chitosan and 0.7 parts by weight of hydroxypropyl-β-cyclodextrin to 130 parts by weight of deionized water to dissolve to obtain a premix;

[0074] (2) adding 4 parts by weight of a polycarboxyl crosslinking agent, ethylenediaminetetraacetic acid, to the premix and stirring; and adjusting the pH to 5 with a sodium hydroxide solution to obtain a mixed solution; the stirring rate was 650 rpm, and the stirring time was 25 min;

[0075] (3) adding a condensing agent, dicyclohexylcarbodiimide / 4-dimethylaminopyridine, to the mixed solution, and stirring the mixture at 70° C. for 3 h to obtain a primary reaction mixture; the condensing agent is 10 parts by weight, and the mass ratio of dicyclohexylcarbodiimide to 4-dimethylaminopyridine is 12:1;

[0076] (4) adding 0.5 parts by weight of polyvinyl alcohol to the primary reaction mixture, and continuing to stir and react at 70° C. for 16 hours to obtain a primary gel solution;

[0077] (5) Dissolve tea polyphenols in deionized water, and add the solution dropwise to the primary gel solution under stirring. After the addition is complete, a primary gel mixed solution is obtained. Continue stirring to obtain a modified carboxymethyl chitosan gel loaded with tea polyphenols. The amount of tea polyphenol added is such that its concentration in the primary gel mixed solution is 70 μg / mL. Continue stirring for 1.5 h.

[0078] Example 9: A method for preparing a modified carboxymethyl chitosan gel loaded with tea polyphenols, comprising the following steps:

[0079] (1) adding 2 parts by weight of carboxymethyl chitosan and 0.7 parts by weight of hydroxypropyl-β-cyclodextrin to 130 parts by weight of deionized water to dissolve to obtain a premix;

[0080] (2) adding 2.2 parts by weight of a polycarboxyl crosslinking agent, ethylenediaminetetraacetic acid, to the premix, stirring; and adjusting the pH to 5 with a sodium hydroxide solution to obtain a mixed solution; stirring at a rate of 650 rpm for 25 min;

[0081] (3) adding a condensing agent, dicyclohexylcarbodiimide / 4-dimethylaminopyridine, to the mixed solution, and stirring the mixture at 70° C. for 1 h to obtain a primary reaction mixture; the condensing agent is 10 parts by weight, and the mass ratio of dicyclohexylcarbodiimide to 4-dimethylaminopyridine is 12:1;

[0082] (4) adding 0.5 parts by weight of polyvinyl alcohol to the primary reaction mixture, and continuing to stir and react at 70° C. for 16 hours to obtain a primary gel solution;

[0083] (5) Dissolve tea polyphenols in deionized water, and add the solution dropwise to the primary gel solution under stirring. After the addition is complete, a primary gel mixed solution is obtained. Continue stirring to obtain a modified carboxymethyl chitosan gel loaded with tea polyphenols. The amount of tea polyphenol added is such that its concentration in the primary gel mixed solution is 70 μg / mL. Continue stirring for 1.5 h.

[0084] Embodiment 10: The preparation method of modified carboxymethyl chitosan gel loaded with tea polyphenols comprises the following steps:

[0085] (1) adding 2 parts by weight of carboxymethyl chitosan and 0.7 parts by weight of hydroxypropyl-β-cyclodextrin to 130 parts by weight of deionized water to dissolve to obtain a premix;

[0086] (2) adding 2.2 parts by weight of a polycarboxyl crosslinking agent, ethylenediaminetetraacetic acid, to the premix, stirring; and adjusting the pH to 5 with a sodium hydroxide solution to obtain a mixed solution; stirring at a rate of 650 rpm for 25 min;

[0087] (3) adding a condensing agent, dicyclohexylcarbodiimide / 4-dimethylaminopyridine, to the mixed solution, and stirring the mixture at 70° C. for 6 h to obtain a primary reaction mixture; the condensing agent is 10 parts by weight, and the mass ratio of dicyclohexylcarbodiimide to 4-dimethylaminopyridine is 12:1;

[0088] (4) adding 0.5 parts by weight of polyvinyl alcohol to the primary reaction mixture, and continuing to stir and react at 70° C. for 16 hours to obtain a primary gel solution;

[0089] (5) Dissolve tea polyphenols in deionized water, and add the solution dropwise to the primary gel solution under stirring. After the addition is complete, a primary gel mixed solution is obtained. Continue stirring to obtain a modified carboxymethyl chitosan gel loaded with tea polyphenols. The amount of tea polyphenol added is such that its concentration in the primary gel mixed solution is 70 μg / mL. Continue stirring for 1.5 h.

[0090] Comparative Example 1: A method for preparing a modified carboxymethyl chitosan gel loaded with tea polyphenols, comprising the following steps:

[0091] (1) adding 2 parts by weight of carboxymethyl chitosan and 0.2 parts by weight of hydroxypropyl-β-cyclodextrin to 130 parts by weight of deionized water to dissolve to obtain a premix;

[0092] (2) adding 2.2 parts by weight of a polycarboxyl crosslinking agent, ethylenediaminetetraacetic acid, to the premix, stirring; and adjusting the pH to 5 with a sodium hydroxide solution to obtain a mixed solution; stirring at a rate of 650 rpm for 25 min;

[0093] (3) adding a condensing agent, dicyclohexylcarbodiimide / 4-dimethylaminopyridine, to the mixed solution, and stirring the mixture at 70° C. for 3 h to obtain a primary reaction mixture; the condensing agent is 10 parts by weight, and the mass ratio of dicyclohexylcarbodiimide to 4-dimethylaminopyridine is 12:1;

[0094] (4) adding 0.5 parts by weight of polyvinyl alcohol to the primary reaction mixture, and continuing to stir and react at 70° C. for 16 hours to obtain a primary gel solution;

[0095] (5) Dissolve tea polyphenols in deionized water, and add the solution dropwise to the primary gel solution under stirring. After the addition is complete, a primary gel mixed solution is obtained. Continue stirring to obtain a modified carboxymethyl chitosan gel loaded with tea polyphenols. The amount of tea polyphenol added is such that its concentration in the primary gel mixed solution is 70 μg / mL. Continue stirring for 1.5 h.

[0096] Comparative Example 2: A method for preparing a modified carboxymethyl chitosan gel loaded with tea polyphenols, comprising the following steps:

[0097] (1) adding 2 parts by weight of carboxymethyl chitosan and 2 parts by weight of hydroxypropyl-β-cyclodextrin to 130 parts by weight of deionized water to dissolve to obtain a premix;

[0098] (2) adding 2.2 parts by weight of a polycarboxyl crosslinking agent, ethylenediaminetetraacetic acid, to the premix, stirring; and adjusting the pH to 5 with a sodium hydroxide solution to obtain a mixed solution; stirring at a rate of 650 rpm for 25 min;

[0099] (3) adding a condensing agent, dicyclohexylcarbodiimide / 4-dimethylaminopyridine, to the mixed solution, and stirring the mixture at 70° C. for 3 h to obtain a primary reaction mixture; the condensing agent is 10 parts by weight, and the mass ratio of dicyclohexylcarbodiimide to 4-dimethylaminopyridine is 12:1;

[0100] (4) adding 0.5 parts by weight of polyvinyl alcohol to the primary reaction mixture, and continuing to stir and react at 70° C. for 16 hours to obtain a primary gel solution;

[0101] (5) Dissolve tea polyphenols in deionized water, and add the solution dropwise to the primary gel solution under stirring. After the addition is complete, a primary gel mixed solution is obtained. Continue stirring to obtain a modified carboxymethyl chitosan gel loaded with tea polyphenols. The amount of tea polyphenol added is such that its concentration in the primary gel mixed solution is 70 μg / mL. Continue stirring for 1.5 h.

[0102] Comparative Example 3: A method for preparing a modified carboxymethyl chitosan gel loaded with tea polyphenols, comprising the following steps:

[0103] (1) adding 2 parts by weight of carboxymethyl chitosan and 0.7 parts by weight of hydroxypropyl-β-cyclodextrin to 130 parts by weight of deionized water to dissolve to obtain a premix;

[0104] (2) adding 2.2 parts by weight of a polycarboxyl crosslinking agent, ethylenediaminetetraacetic acid, to the premix, stirring; and adjusting the pH to 5 with a sodium hydroxide solution to obtain a mixed solution; stirring at a rate of 650 rpm for 25 min;

[0105] (3) adding a condensing agent, dicyclohexylcarbodiimide / 4-dimethylaminopyridine and 0.5 parts by weight of polyvinyl alcohol to the mixed solution, and stirring the mixture at 70° C. for 19 hours to obtain a primary gel solution; the condensing agent is 10 parts by weight, and the mass ratio of dicyclohexylcarbodiimide to 4-dimethylaminopyridine is 12:1;

[0106] (4) Dissolve tea polyphenols in deionized water and add the solution dropwise to the primary gel solution under stirring. After the addition is complete, a primary gel mixed solution is obtained. Continue stirring to obtain a modified carboxymethyl chitosan gel loaded with tea polyphenols. The amount of tea polyphenol added is such that its concentration in the primary gel mixed solution is 70 μg / mL. Continue stirring for 1.5 h.

[0107] Comparative Example 4: A method for preparing a modified carboxymethyl chitosan gel loaded with tea polyphenols, comprising the following steps:

[0108] (1) adding 2 parts by weight of carboxymethyl chitosan and 0.7 parts by weight of hydroxypropyl-β-cyclodextrin to 130 parts by weight of deionized water to dissolve to obtain a premix;

[0109] (2) adding 2.2 parts by weight of a polycarboxyl crosslinking agent, ethylenediaminetetraacetic acid, to the premix, stirring; and adjusting the pH to 5 with a sodium hydroxide solution to obtain a mixed solution; stirring at a rate of 650 rpm for 25 min;

[0110] (3) adding a condensing agent, dicyclohexylcarbodiimide / 4-dimethylaminopyridine, to the mixed solution, and stirring the mixture at 70° C. for 3 h to obtain a primary reaction mixture; the condensing agent is 10 parts by weight, and the mass ratio of dicyclohexylcarbodiimide to 4-dimethylaminopyridine is 12:1;

[0111] (4) adding 0.1 parts by weight of polyvinyl alcohol to the primary reaction mixture, and continuing to stir and react at 70° C. for 16 hours to obtain a primary gel solution;

[0112] (5) Dissolve tea polyphenols in deionized water, and add the solution dropwise to the primary gel solution under stirring. After the addition is complete, a primary gel mixed solution is obtained. Continue stirring to obtain a modified carboxymethyl chitosan gel loaded with tea polyphenols. The amount of tea polyphenol added is such that its concentration in the primary gel mixed solution is 70 μg / mL. Continue stirring for 1.5 h.

[0113] Comparative Example 5: A method for preparing a modified carboxymethyl chitosan gel loaded with tea polyphenols, comprising the following steps:

[0114] (1) adding 2 parts by weight of carboxymethyl chitosan and 0.7 parts by weight of hydroxypropyl-β-cyclodextrin to 130 parts by weight of deionized water to dissolve to obtain a premix;

[0115] (2) adding 2.2 parts by weight of a polycarboxyl crosslinking agent, ethylenediaminetetraacetic acid, to the premix, stirring; and adjusting the pH to 5 with a sodium hydroxide solution to obtain a mixed solution; stirring at a rate of 650 rpm for 25 min;

[0116] (3) adding a condensing agent, dicyclohexylcarbodiimide / 4-dimethylaminopyridine, to the mixed solution, and stirring the mixture at 70° C. for 3 h to obtain a primary reaction mixture; the condensing agent is 10 parts by weight, and the mass ratio of dicyclohexylcarbodiimide to 4-dimethylaminopyridine is 12:1;

[0117] (4) adding 1 part by weight of polyvinyl alcohol to the primary reaction mixture, and continuing to stir and react at 70° C. for 16 hours to obtain a primary gel solution;

[0118] (5) Dissolve tea polyphenols in deionized water, and add the solution dropwise to the primary gel solution under stirring. After the addition is complete, a primary gel mixed solution is obtained. Continue stirring to obtain a modified carboxymethyl chitosan gel loaded with tea polyphenols. The amount of tea polyphenol added is such that its concentration in the primary gel mixed solution is 70 μg / mL. Continue stirring for 1.5 h.

[0119] Performance test: Under the same test standard, the compressive strength (kPa), water retention rate (%, mass of hydrogel after drying at 35°C for 48 hours / initial mass of hydrogel), and antibacterial rate of Staphylococcus aureus (%) of the gels prepared in Examples 1-10 and Comparative Examples 1-5 were tested respectively. The results are shown in Tables 1-2.

[0120] Table 1: Modified carboxymethyl chitosan gel loaded with tea polyphenols prepared in Examples 1 to 10

[0121]

[0122] Table 2: Modified carboxymethyl chitosan gels loaded with tea polyphenols prepared in Comparative Examples 1 to 5

[0123]

[0124] It can be seen from Table 1-Table 2 that the present invention uses hydroxypropyl-β-cyclodextrin to modify carboxymethyl chitosan, and prepares modified carboxymethyl chitosan gel by multi-carboxyl crosslinking agent and polyvinyl alcohol. By crosslinking carboxymethyl chitosan with cyclic molecules having hydroxypropyl, polyvinyl alcohol, as a long straight-chain polymer, can effectively connect carboxymethyl chitosan and hydroxypropyl-β-cyclodextrin through hydrogen bonds, greatly increasing the mechanical properties and water retention capacity of the hydrogel. At the same time, through a simple impregnation process, on the basis of hydrogen bond crosslinking of tea polyphenols, the crosslinked porous structure of carboxymethyl chitosan-based hydrogel and the encapsulation effect of hydroxypropyl-β-cyclodextrin are fully utilized, tea polyphenols can be effectively encapsulated and its activity is guaranteed, and the moisturizing and antibacterial ability of the hydrogel is improved. It can be seen from Example 6-Example 10 that the crosslinking agent and the degree of primary reaction have a greater impact on the performance of the hydrogel. By adjusting the amount of the crosslinking agent and the primary reaction time, the performance of the hydrogel can be regulated. When the amount of polycarboxyl crosslinking agent is too small, the degree of crosslinking is insufficient; when the amount is too large, the degree of crosslinking is too large, which is not conducive to the infiltration of water and the entry of tea polyphenols into the cavity of hydroxypropyl-β-cyclodextrin. By controlling the reaction time, the length of the molecular chain is appropriate, which has both a certain length and a certain mobility, which is conducive to forming a entangled structure with polyvinyl alcohol.

[0125] Comparative Examples 1-2 show that the cyclic molecules with hydroxypropyl groups are cross-linked with carboxymethyl chitosan, which greatly increases the mechanical properties and water-retaining and antibacterial ability of the hydrogel; too little dosage cannot be fully cross-linked with carboxymethyl chitosan, and too much dosage, due to the hydrophobic structure of its internal cavity, may not only affect the water-retaining performance, but also be unfavorable for the improvement of its mechanical properties. Comparative Examples 3-5 show that polyvinyl alcohol is added to the reaction system after the preliminary polymerization reaction, and can effectively connect carboxymethyl chitosan and hydroxypropyl-β-cyclodextrin through hydrogen bonds, thereby improving the cross-linking degree of the hydrogel, and then improving its water-retaining and mechanical properties. At the same time, since the hydrophilicity of polyvinyl alcohol is poorer than that of chitosan, when the dosage is too much, it is not conducive to the mutual entanglement between the components, and is not conducive to the improvement of water-retaining and mechanical properties, and affects the loading effect of tea polyphenols.

[0126] Finally, it should be noted that the above preferred embodiments are only used to illustrate the technical solutions of the present invention rather than to limit it. Although the present invention has been described in detail through the above preferred embodiments, those skilled in the art should understand that various changes can be made in form and details without departing from the scope defined by the claims of the present invention.

Claims

1. A method for preparing a modified carboxymethyl chitosan gel loaded with tea polyphenols, characterized in that: The following steps are involved: (1) adding 2 parts by weight of carboxymethyl chitosan and 0.5-1 parts by weight of hydroxypropyl-β-cyclodextrin into deionized water to dissolve to obtain a premix; (2) adding 1-4 parts by weight of a polycarboxyl crosslinking agent to the premix, stirring, and adjusting the pH with an alkali solution to obtain a mixed solution; (3) adding a condensing agent to the mixed solution, and stirring the mixture at 60-80° C. for 1-6 h to obtain a primary reaction mixture; (4) adding 0.3-0.6 parts by weight of polyvinyl alcohol to the primary reaction mixture, and continuing to stir and react at 60-80° C. for 10-20 hours to obtain a primary gel solution; (5) Dissolve tea polyphenols in deionized water, and add the solution dropwise to the primary gel solution under stirring. After the addition is complete, a primary gel mixed solution is obtained. Continue stirring to obtain a modified carboxymethyl chitosan gel loaded with tea polyphenols.

2. The method for preparing the modified carboxymethyl chitosan gel loaded with tea polyphenols as claimed in claim 1, characterized in that: In step (1), the amount of deionized water is 100-150 parts by weight; and in step (2), the amount of the polycarboxyl crosslinking agent is 1.5-3 parts by weight.

3. The method for preparing the modified carboxymethyl chitosan gel loaded with tea polyphenols as claimed in claim 1, characterized in that: In step (2), the polycarboxyl crosslinking agent is one or more of iminodiacetic acid, nitrilotriacetic acid, ethylenediaminetetraacetic acid, and diethylenetriaminepentaacetic acid.

4. The method for preparing the modified carboxymethyl chitosan gel loaded with tea polyphenols as claimed in claim 1, characterized in that: In step (2), the stirring rate is 600-700 rpm and the stirring time is 20-30 min.

5. The method for preparing the modified carboxymethyl chitosan gel loaded with tea polyphenols as claimed in claim 1, characterized in that: In step (2), the alkali solution is a sodium hydroxide solution or a potassium hydroxide solution.

6. The method for preparing the modified carboxymethyl chitosan gel loaded with tea polyphenols as claimed in claim 1, characterized in that: In step (2), the pH is 5-6.

7. The method for preparing the modified carboxymethyl chitosan gel loaded with tea polyphenols as claimed in claim 1, characterized in that: In step (3), the condensing agent is one or more of dicyclohexylcarbodiimide / N-hydroxysuccinimide, dicyclohexylcarbodiimide / 4-dimethylaminopyridine, 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride / N-hydroxysuccinimide; the condensing agent is 5-15 parts by weight.

8. The method for preparing the modified carboxymethyl chitosan gel loaded with tea polyphenols as claimed in claim 1, characterized in that: In step (5), the amount of tea polyphenols added is such that its concentration in the primary gel mixed solution is 50-100 μg / mL; the stirring time is continued for 1-2 hours.

9. A modified carboxymethyl chitosan gel loaded with tea polyphenols, characterized in that: The tea polyphenol-loaded modified carboxymethyl chitosan gel is prepared by the preparation method of any one of claims 1 to 8.

10. Use of the modified carboxymethyl chitosan gel loaded with tea polyphenols as claimed in claim 9 in the preparation of antibacterial and moisturizing materials.

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