Procyanidine enhanced boric acid ester cross-linked hydrogel as well as preparation method and application thereof

Abstract

The invention relates to a procyanidine enhanced boric acid ester cross-linked hydrogel as well as a preparation method and application thereof, and belongs to the technical field of biomedical polymer materials. The cross-linked hydrogel is prepared from the following raw materials: phenylboronic acid functionalized hyaluronic acid, sodium alginate, quaternized chitosan, procyanidine and water. In the cross-linked hydrogel, the mass percent of the phenylboronic acid functionalized hyaluronic acid is 60-65%; the mass percentage of the sodium alginate is 10-15%; the mass percent of the quaternized chitosan is 10 to 15 percent; the mass percentage of the procyanidine is 10-15%. The preparation method comprises the following steps: mixing procyanidine, quaternized chitosan, phenylboronic acid functionalized hyaluronic acid and sodium alginate in water, the preparation process is rapid, the reaction condition is mild, and the obtained cross-linked hydrogel has good biocompatibility.

Description

Technical Field

[0001] The present invention belongs to the technical field of biomedical polymer materials, and particularly relates to proanthocyanidin-enhanced borate-crosslinked hydrogels and their preparation methods and applications. Background Art

[0002] Oral ulcers are a common oral mucosal disease, usually manifested as persistent burning sensation and pain, and are prone to recurrent attacks, seriously affecting the quality of life of patients. Due to the extremely complex etiology of oral ulcers, including fatigue, oral flora imbalance, psychological stress, diabetic complications, and chemotherapy side effects, there is currently no standardized treatment method to effectively cure oral ulcers. In addition, the progression of oral mucosal inflammation is often related to elevated levels of oxidative stress and concurrent bacterial infections, resulting in limited therapeutic effects of single drugs.

[0003] Topical administration is the preferred route of drug delivery for clinical treatment of oral ulcers, including administration of antibiotics, glucocorticoids, and anesthetics to relieve symptoms. However, due to the frequent recurrence of oral ulcers, long-term use of corticosteroids and antibiotics can respectively bring risks of serious side effects and bacterial drug resistance. In addition, due to the humid oral environment, filled with saliva and various foods, and frequent actions such as speaking and chewing, these drugs will be rapidly diluted or cleared in the oral cavity. Hydrogel dressings based on natural macromolecules are an ideal choice to improve the efficiency of oral mucosal drug delivery. These hydrogels can degrade in the gastrointestinal tract after completing their tasks without producing any toxic effects. Currently, the viscosity of oral hydrogel dressings on the market is low, resulting in a short residence time at the oral ulcer wound, affecting the exertion of their drug efficacy, and often requiring multiple applications of the hydrogel dressing to achieve ulcer wound healing.

[0004] Therefore, there is an urgent need to develop multifunctional materials with wet adhesion, anti-inflammatory, antioxidant, and antibacterial capabilities to promote the healing of oral ulcers. Summary of the Invention

[0005] In view of the above problems, the present invention provides proanthocyanidin-enhanced borate-crosslinked hydrogels and their preparation methods and applications.

[0006] The first object of the present invention is to provide a proanthocyanidin-enhanced borate-crosslinked hydrogel, and the raw materials for preparation include: phenylboronic acid-functionalized hyaluronic acid, sodium alginate, quaternized chitosan, proanthocyanidin, and water.

[0007] Furthermore, in the crosslinked hydrogel, the mass percentage of phenylboronic acid-functionalized hyaluronic acid is 60-65%; the mass percentage of sodium alginate is 10-15%; the mass percentage of quaternized chitosan is 10-15%; the mass percentage of proanthocyanidin is 10-15%.

[0008] Further, in the crosslinked hydrogel, the water is water with a pH value of 7 - 8.5.

[0009] Further, the water with a pH value of 7 - 8.5 is a buffered aqueous solution containing PBS.

[0010] Further, the strength of the crosslinked hydrogel is 100 - 20000 Pa, preferably 2000 - 3000 Pa.

[0011] Further, the molecular structural formula of the phenylboronic acid - functionalized hyaluronic acid is shown in Formula I:

[0012]

[0013] In Formula I, n is the degree of polymerization of hyaluronic acid and n is a positive integer, 3000 ≤ n ≤ 8000; m is the number of structural units functionalized with phenylboronic acid in hyaluronic acid, m / n = x, 50% ≤ x ≤ 90%.

[0014] Preferably, the n is 3000, 3500, 4000, 4500, 5000, 5500, 6000, 5500, 7000, 7500 or 8000.

[0015] Preferably, the x is 50%, 55%, 60%, 65%, 70%, 75%, 80%, 85% or 90%.

[0016] Further, the proanthocyanidin is one of proanthocyanidin C1 and proanthocyanidin B1 or a mixture in any ratio.

[0017] The molecular structural formulas of proanthocyanidin C1 and proanthocyanidin B1 are shown as follows.

[0018]

[0019] The second object of the present invention is to provide a preparation method of a proanthocyanidin - enhanced borate - crosslinked hydrogel, including:

[0020] Mix proanthocyanidin with water evenly to obtain a proanthocyanidin solution;

[0021] Mix the proanthocyanidin solution, quaternized chitosan, sodium alginate and phenylboronic acid - functionalized hyaluronic acid evenly and let stand to obtain a pre - gel solution.

[0022] Further, when mixing proanthocyanidin with water, the mixing temperature is 25 - 37 °C.

[0023] Further, the pH value of the proanthocyanidin solution is 7 - 8.5, preferably, the pH value of the proanthocyanidin solution is 7.4.

[0024] Furthermore, the quaternized chitosan is prepared by reacting chitosan with a quaternizing reagent in an aqueous phase containing acetic acid.

[0025] Furthermore, the reaction temperature for the reaction of chitosan with the quaternizing reagent in the aqueous phase containing acetic acid is 20 - 80 °C, and the reaction time is 1 - 24 h.

[0026] Preferably, in the aqueous phase containing acetic acid, the volume ratio of acetic acid to water is 0.2 - 2:1.

[0027] Furthermore, the molar ratio of the quaternizing reagent to the chitosan structural unit is 0.5 - 2.5:1. Preferably, the molar ratio of the quaternizing reagent to the chitosan structural unit is 1.2:1.

[0028] Preferably, the quaternizing reagent is 2,3-epoxypropyltrimethylammonium chloride.

[0029] Furthermore, the phenylboronic acid-functionalized hyaluronic acid is prepared by condensing hyaluronic acid with 3-aminophenylboronic acid in water.

[0030] Furthermore, an activator is involved in the condensation reaction.

[0031] Preferably, the activator is a mixture of N-hydroxysuccinimide and 1-ethyl-(3-dimethylaminopropyl)carbodiimide hydrochloride.

[0032] Furthermore, the reaction temperature of the condensation reaction is 20 - 90 °C, and the reaction time is 1 - 72 h.

[0033] Furthermore, the molar ratio of 3-aminophenylboronic acid to the hyaluronic acid structural unit is 1 - 3:1. Preferably, the molar ratio of 3-aminophenylboronic acid to the hyaluronic acid structural unit is 2:1.

[0034] The third object of the present invention is to provide the application of the above-mentioned proanthocyanidin-enhanced borate cross-linked hydrogel in the preparation of drugs for treating oral ulcers.

[0035] The beneficial effects of the present invention:

[0036] The proanthocyanidin-enhanced borate cross-linked hydrogel of the present invention, its preparation method and application are prepared by mixing proanthocyanidin, quaternized chitosan, phenylboronic acid-functionalized hyaluronic acid and sodium alginate in water; the preparation process is rapid, the reaction conditions are mild, and the obtained cross-linked hydrogel has good biocompatibility. In addition, the present invention also has the following advantages:

[0037] Utilizing the borate cross-linked network of proanthocyanidin to enhance the hydrogel not only enhances the mechanical properties of the hydrogel, but also improves its antibacterial, antioxidant and anti-inflammatory biological activities;

[0038] Compared with traditional oral ulcer treatment drugs such as antibiotics and glucocorticoids, the hydrogel provided by the present invention has good wet adhesiveness. The corresponding strength of the cross-linked hydrogel can be guaranteed to be between 100 - 20000 Pa, mainly concentrated in 2000 - 3000 Pa, which can extend the drug retention time. On the premise of ensuring good adhesiveness of the hydrogel, it can prevent the excessive strength of the hydrogel from causing poor self-adaptability of the hydrogel to the ulcer surface;

[0039] The combined action of quaternized chitosan and procyanidins achieves antibacterial effect by destroying the cell membrane structure of bacteria and is not likely to cause drug resistance;

[0040] Procyanidins exist in many natural herbs, have good antioxidant and anti-inflammatory treatment effects and are not likely to cause toxic side effects.

[0041] Other features and advantages of the present invention will be described in the subsequent description, and in part, will become obvious from the description, or can be understood by implementing the present invention. The objectives and other advantages of the present invention can be achieved and obtained through the structures pointed out in the description, claims and drawings. Description of the Drawings

[0042] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required for use in the description of the embodiments or the prior art. Obviously, the following drawings are some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained based on these drawings.

[0043] Figure 1 Shows the molecular structure diagram of phenylboronic acid-functionalized hyaluronic acid prepared in Example 2 of the present invention and its corresponding nuclear magnetic resonance hydrogen spectrum;

[0044] Figure 2 Shows the molecular structure diagram of quaternized chitosan prepared in Example 3 of the present invention and its corresponding nuclear magnetic resonance hydrogen spectrum;

[0045] Figure 3 Is the mechanical strength test result of the procyanidin-enhanced borate cross-linked hydrogel prepared in Example 4 of the present invention;

[0046] Figure 4 Is the test result diagram of the self-healing performance of the procyanidin-enhanced borate cross-linked hydrogel prepared in Example 4 of the present invention;

[0047] Figure 5 Is the scanning electron microscope image of the procyanidin-enhanced borate cross-linked hydrogel prepared in Example 4 of the present invention;

[0048] Figure 6 Toxicity test results of hydrogel materials prepared in Example 4 of the present invention with different concentrations on L929 cells;

[0049] Figure 7 Measurement of the content of MDA in cells after treatment with the proanthocyanidin-enhanced borate cross-linked hydrogel prepared in Example 4 of the present invention and each control group;

[0050] Figure 8 Antibacterial activity test of the proanthocyanidin-enhanced borate cross-linked hydrogel prepared in Example 4 of the present invention and each control group;

[0051] Figure 9 Morphological observation diagrams of the local lesions after 7 days of using PBS, commercial gel, proanthocyanidin-enhanced borate cross-linked hydrogel prepared in Example 4, and blank hydrogel for treating oral ulcers respectively.

[0052] Figure 10 H&E staining diagrams of the lesion tissues after treating oral ulcers with PBS, commercial gel, proanthocyanidin-enhanced borate cross-linked hydrogel prepared in Example 4, and blank hydrogel respectively;

[0053] Figure 11 Masson staining diagrams of the lesion tissues after treating oral ulcers with PBS, commercial gel, proanthocyanidin-enhanced borate cross-linked hydrogel prepared in Example 4 of the present invention, and blank hydrogel respectively. Detailed implementation manners

[0054] To make the objectives, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, rather than all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

[0055] In the following examples, proanthocyanidin, 3-aminophenylboronic acid, sodium alginate, 2,3-epoxypropyltrimethylammonium chloride, acetic acid, hyaluronic acid and chitosan were all purchased from Shanghai Aladdin Reagent Co., Ltd.; among them, the molecular weight of hyaluronic acid was 1.5-2.5 million. The viscosity of chitosan was 100-200 mPa·s, and the viscosity of sodium alginate was 200±20 mPa·s.

[0056] Example 1

[0057] Preparation method of proanthocyanidin (PA) solution:

[0058] Dissolve 0 mg, 1 mg, and 2 mg of PA in 0.5 mL of PBS with a pH of 7.4, sonicate for 1 min, and control the temperature at 50 - 60 °C until completely dissolved to obtain proanthocyanidin solutions with different concentrations, denoted as PA-0, PA-1, and PA-2, respectively.

[0059] Example 2

[0060] Preparation method of phenylboronic acid-functionalized hyaluronic acid (HA-PBA):

[0061] Dissolve 1.0 g of hyaluronic acid (HA) in 150 mL of deionized water and adjust the pH to 6 with hydrochloric acid. Subsequently, add N-hydroxysuccinimide (0.57 g) (Mw = 217.13), 1-ethyl-(3-dimethylaminopropyl)carbodiimide hydrochloride (1.57 g) (Mw = 191.7), and 3-aminophenylboronic acid (0.67 g) (Mw = 136.95) to the HA solution, and then adjust the pH to 6. After stirring at 25 °C for 48 hours, stop the reaction, and purify by dialysis with deionized water and freeze-drying to obtain the HA-PBA polymer.

[0062] Perform nuclear magnetic resonance analysis on the obtained phenylboronic acid-functionalized hyaluronic acid. Figure 1 1H NMR spectrum of the phenylboronic acid-functionalized hyaluronic acid prepared in Example 2 of the present invention.

[0063] Example 3

[0064] Preparation method of quaternized chitosan:

[0065] Weigh 2.00 g of chitosan (CS, in terms of the molar amount of structural units: 12.4 mmol), disperse it in 80 mL of distilled water, and add 400 μL of acetic acid and stir for 30 min until completely dissolved. Then, divide 0.94 g of 2,3-epoxypropyltrimethylammonium chloride (GTMAC, 15.10 mmol) into three equal portions and add them to the above chitosan solution at intervals of 2 h for reaction. Stir and heat to 60 °C. After adding the last portion of GTMAC, seal the reaction for 18 hours. After the reaction is completed, centrifuge the reaction solution (4000 rpm, 10 min), filter by suction, and retain the filtrate. Transfer the filtrate to a dialysis bag and dialyze it in distilled water for three days, and then freeze-dry for 2 days to obtain quaternized chitosan (QCS).

[0066] Perform nuclear magnetic resonance hydrogen spectrum analysis on the obtained quaternized chitosan. Figure 2 1H NMR spectrum of the quaternized chitosan prepared in Example 3 of the present invention.

[0067] Example 4

[0068] Preparation of proanthocyanidin-enhanced borate crosslinked hydrogel (AHQP):

[0069] The procyanidin solution PA-2 prepared in Example 1, the phenylboronic acid-functionalized hyaluronic acid HA-PBA (10 mg) prepared in Example 2, the quaternized chitosan QCS (2 mg) prepared in Example 3, and the sodium alginate Alg (2 mg) powder were thoroughly mixed to obtain a pre-gelatinized solution, which was allowed to gel at room temperature. Observation by the inversion method showed that the gelation time was 5 min.

[0070] Example 5

[0071] Preparation of procyanidin-enhanced borate crosslinked hydrogel (AHQP 1 )

[0072] The procyanidin solution PA-1 prepared in Example 1, the phenylboronic acid-functionalized hyaluronic acid HA-PBA (10 mg) prepared in Example 2, the quaternized chitosan QCS (2 mg) prepared in Example 3, and the sodium alginate Alg (2 mg) powder were thoroughly mixed to obtain a pre-gelatinized solution, which was allowed to gel at room temperature. Observation by the inversion method showed that the gelation time was 5 min.

[0073] Example 6

[0074] Preparation of enhanced borate crosslinked hydrogel (AHQ)

[0075] The procyanidin solution PA-0 prepared in Example 1, the phenylboronic acid-functionalized hyaluronic acid HA-PBA (10 mg) prepared in Example 2, the quaternized chitosan QCS (2 mg) prepared in Example 3, and the sodium alginate Alg (2 mg) powder were thoroughly mixed to obtain a pre-gelatinized solution, which was allowed to gel at room temperature. Observation by the inversion method showed that the gelation time was 5 min.

[0076] Testing

[0077] The hydrogel prepared in Example 4 was subjected to performance testing, and the results were as follows:

[0078] After the hydrogel was formed, it was transferred to a rotational rheometer to observe the changes in its storage modulus and loss modulus over time. As Figure 3 shown, the storage modulus was higher than the loss modulus, indicating that the network structure of the hydrogel had been formed and was stable;

[0079] From Figure 3It can be seen that the strength of the hydrogel in the embodiments of the present invention is mainly concentrated in the range of 2000 - 3000 Pa. Moreover, during the experiment, the inventors found that when the strength of the hydrogel is lower than 10 Pa, it is difficult to fix the hydrogel on the ulcer surface; while when the strength is greater than 8000 Pa, the self - adaptability of the hydrogel to the ulcer surface becomes poor and the adhesion is not good. Therefore, the rheological properties of the hydrogel in the embodiments of the present invention meet the actual application requirements of oral wet - adhesive dressings and can be used as hydrogel dressings for treating oral ulcers.

[0080] Subsequently, the hydrogel was transferred to a rotational rheometer, and the changes of its storage modulus and loss modulus with time were alternately evaluated under 1% and 500% strain, as Figure 4 shown. Under 1% strain, the storage modulus of the hydrogel was always higher than the loss modulus, indicating that the polymer network of the hydrogel belongs to the gel high - elastic state. While under 500% strain, the loss modulus was greater than the storage modulus, proving that the gel changed from the high - elastic state to the viscous flow state and the cross - linked network had been damaged. It can be seen that after multiple strain cycles, the hydrogel can still maintain high - elastic deformation, indicating its good self - repair ability.

[0081] The gel material obtained in Example 4 was placed in a freeze - dryer for freeze - drying, the hydrogel was sputter - coated with gold, and the microscopic morphology was observed by a scanning electron microscope. The results are shown in Figure 5 that the gel presented a regular three - dimensional network structure.

[0082] The hydrogels prepared in Example 4 were co - incubated with L929 cells at gradient concentrations for 24 hours, as shown in Figure 6 . By testing the cell viability through the CCK - 8 method, it can be seen that the gel did not produce obvious toxicity to the cells.

[0083] The hydrogel prepared in Example 4 (AHQP, with a final concentration containing 50 μg / mL of PA), the corresponding amount of PA (a solution containing only 50 μg / mL of PA), the blank hydrogel (AHQ) prepared in Example 6, and PBS buffer solution were respectively added to the cells and incubated for 24 h. Subsequently, 10 μg / mL of LPS was added for stimulation, and incubation was continued at 37 °C for 12 hours. Then the supernatant was collected, and the content of MDA in each group was measured according to the detection instructions of the malondialdehyde (MDA) kit (Beijing Solarbio Science & Technology Co., Ltd.). The results are shown in Figure 7 .

[0084] From Figure 7 it can be seen that the antioxidant property of the hydrogel in the AHQP group is stronger than that of the hydrogel in the AHQ group, the PA group, and the PBS group, indicating that other components (gel skeleton and / or quaternary ammonium salt chitosan) in the hydrogel of the present invention contribute to the exertion of the antioxidant property of procyanidins.

[0085] The hydrogel (AHQP) prepared in Example 4, the corresponding amount of PA, and the blank hydrogel (AHQ) were incubated with Staphylococcus aureus in LB medium overnight. Subsequently, an appropriate amount of the bacterial suspension was taken, diluted, and evenly spread on the surface of the agarose gel. After overnight incubation, the growth of colonies was observed. As Figure 8 shown, the hydrogel in the AHQP group almost completely killed Staphylococcus aureus 6 hours after contact with the bacteria.

[0086] Example 7

[0087] In vivo pharmacodynamic evaluation of proanthocyanidin-enhanced borate-crosslinked hydrogel in the treatment of oral ulcers in rats:

[0088] In this example, the proanthocyanidin-enhanced borate-crosslinked hydrogel (AHQP) prepared in Example 4 was used as an external dressing. An oral ulcer model was established in male SD rats to investigate the therapeutic effect of the hydrogel prepared in this invention. A commercially available external gel of a growth factor (recombinant bovine basic fibroblast growth factor gel) was selected as the positive control group.

[0089] Experimental materials and methods

[0090] Experimental reagents: A commercially available external gel of a growth factor; proanthocyanidin (Beijing Solarbio Co., Ltd.).

[0091] Experimental animals: Rats (SD, female, 180 - 200 g, Animal Experiment Center of Anhui University of Chinese Medicine)

[0092] Establishment of the rat oral ulcer model: Male SD rats weighing 180 - 200 g were selected to establish the oral ulcer model. The rats were anesthetized by intraperitoneal injection of 2% sodium pentobarbital (0.2 mL / 100 g body weight). A round dental drill with a diameter of 2 mm was used to punch holes in the buccal mucosa of the rats. Subsequently, 10 μL of Staphylococcus aureus at a concentration of 108 CFU / mL was inoculated onto the wound surface to construct the oral ulcer model.

[0093] Experimental grouping and drug administration: PBS group, AHQP hydrogel group, and a commercially available external gel of a growth factor group. After successful model establishment, drug administration was performed once, and the experiment ended on the 7th day after treatment.

[0094] PBS group: 50 μL of PBS solution was dropped at the lesion site.

[0095] AHQP hydrogel group (the proanthocyanidin-enhanced borate-crosslinked hydrogel prepared in Example 4): The time points and operation methods for establishing the model on the buccal mucosa of rats were the same as those in the PBS group, and 50 μL of the hydrogel was applied at the lesion site.

[0096] A commercial growth factor topical gel group (hereinafter referred to as the commercial gel group): The time points and operation methods for establishing the model on the buccal mucosa of rats were the same as those in the model group, and 50 μL of the commercial gel was applied to the lesion site.

[0097] Evaluation methods

[0098] 1. Morphological observation of the wound size of the buccal mucosa of rats.

[0099] 2. H&E staining and Masson staining of the tissue of the buccal mucosa wound of rats.

[0100] Experimental results

[0101] Figure 9 Figures showing the local morphological observations of the lesions of oral ulcers in rats treated with the PBS group, the AHQP hydrogel group, and the commercial gel group;

[0102] Figure 10 H&E staining of the lesion tissues of oral ulcers in rats treated with the PBS group, the AHQP hydrogel group, and the commercial gel group;

[0103] Figure 11 Masson staining of the lesion tissues of oral ulcers in rats treated with the PBS group, the AHQP hydrogel group, and the commercial gel group;

[0104] From Figures 9 - 11 it can be seen that the proanthocyanidin-enhanced borate cross-linked hydrogel provided in Example 4 of the present invention, as a dressing for oral ulcers, only needs to be applied to the lesion site once, and satisfactory therapeutic effects can be obtained after 7 days, and it has better therapeutic effects compared with the positive drug commercial gel.

[0105] Although the present invention has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that: they can still modify the technical solutions described in the foregoing embodiments, or perform equivalent replacements on some of the technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A proanthocyanidin-enhanced borate cross-linked hydrogel, characterized in that: The preparation raw materials include: phenylboronic acid functionalized hyaluronic acid, sodium alginate, quaternized chitosan, proanthocyanidin and water.

2. The proanthocyanidin-enhanced borate cross-linked hydrogel according to claim 1, characterized in that: In the cross-linked hydrogel, the mass percentage of phenylboronic acid functionalized hyaluronic acid is 60-65%; the mass percentage of sodium alginate is 10-15%; the mass percentage of quaternized chitosan is 10-15%; and the mass percentage of proanthocyanidins is 10-15%.

3. The proanthocyanidin-enhanced borate cross-linked hydrogel according to claim 1, characterized in that: The strength of the cross-linked hydrogel is 100-20000Pa.

4. The proanthocyanidin-enhanced borate cross-linked hydrogel according to claim 1, characterized in that: The molecular structure of the phenylboronic acid functionalized hyaluronic acid is shown in Formula I: In formula I, n is the degree of polymerization of hyaluronic acid and n is a positive integer, 3000≤n≤8000; m is the number of structural units functionalized with phenylboronic acid in hyaluronic acid, m / n=x, 50%≤x≤90%.

5. A proanthocyanidin-enhanced borate cross-linked hydrogel according to any one of claims 1 to 4, characterized in that: The proanthocyanidin is one of proanthocyanidin C1 and proanthocyanidin B1, or a mixture of any ratio.

6. The method for preparing a proanthocyanidin-enhanced borate cross-linked hydrogel according to any one of claims 1 to 5, characterized in that: include: Mixing proanthocyanidin and water evenly to obtain a proanthocyanidin solution; The proanthocyanidin solution, quaternized chitosan, sodium alginate and phenylboronic acid functionalized hyaluronic acid are mixed evenly and allowed to stand to obtain a pre-gel solution.

7. The method for preparing a proanthocyanidin-enhanced borate cross-linked hydrogel according to claim 6, characterized in that: When the proanthocyanidins are mixed with water, the mixing temperature is 25-37° C.; the pH value of the proanthocyanidins solution is 7-8.

5.

8. The method for preparing a proanthocyanidin-enhanced borate cross-linked hydrogel according to claim 6, characterized in that: The quaternized chitosan is prepared by reacting chitosan with a quaternary ammonium agent in an aqueous phase containing acetic acid.

9. The method for preparing a proanthocyanidin-enhanced borate cross-linked hydrogel according to claim 8, characterized in that: The reaction temperature of the chitosan and the quaternary ammonium agent in the aqueous phase containing acetic acid is 20-80° C., and the reaction time is 1-24 hours; the molar ratio of the quaternary ammonium agent to the chitosan structural unit is 0.5-2.5:

1.

10. The method for preparing a proanthocyanidin-enhanced borate cross-linked hydrogel according to claim 6, characterized in that: The phenylboronic acid functionalized hyaluronic acid is prepared by condensing hyaluronic acid and 3-aminophenylboronic acid in water.

11. The method for preparing a proanthocyanidin-enhanced borate cross-linked hydrogel according to claim 10, characterized in that: The molar ratio of the 3-aminophenylboronic acid to the hyaluronic acid structural unit is 1-3:

1.

12. Use of a proanthocyanidin-enhanced borate cross-linked hydrogel according to any one of claims 1 to 5 in the preparation of a drug for treating oral ulcers.

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