Method for preparing hyaluronic acid with different molecular weights based on catalysis of bimetal organic framework material

Abstract

The invention discloses a method for preparing hyaluronic acid with different molecular weights based on catalysis of a bimetal organic framework material. Comprising the following steps: dissolving hyaluronic acid with deionized water, and sealing, freezing and storing the dissolved hyaluronic acid for later use; synthesizing a bimetal organic framework material, and performing vacuum drying for later use; the bimetallic organic framework material is used for catalytically degrading hyaluronic acid; performing reduced-pressure filtration on the low-molecular-weight hyaluronic acid to remove the metal organic framework material; and freeze-drying the low-molecular-weight hyaluronic acid to obtain a low-molecular-weight hyaluronic acid solid. The method provided by the invention is simple to operate, the molecular weight of the product hyaluronic acid can be simply and effectively regulated, the chemical preparation environment is mild, the degradation efficiency is high, and the prepared small molecular hyaluronic acid is safe and reliable in quality, can be applied to the fields of medicines, foods, cosmetics and the like, and has a good application prospect.

Description

Technical Field

[0001] The present invention relates to the technical field of the application of bimetallic organic framework materials in the catalytic preparation of small molecular weight polymers, and specifically relates to a method for catalytically preparing hyaluronic acid with different molecular weights based on bimetallic organic framework materials. Background Art

[0002] Hyaluronic acid (HA), as a linear mucopolysaccharide widely distributed in tissue cells, has good biocompatibility and is widely used in health products, cosmetics, medicine, etc. It has been found that hyaluronic acid has molecular weight dependence. Compared with high relative molecular weight HA (molecular weight range > 1.0×10 6 Da), low molecular weight HA (1×10 4 Da < molecular weight range < 25×10 4 Da) and oligomeric hyaluronic acid (molecular weight range < 1×10 4 Da) have stronger permeability, can directly penetrate into the dermis, directly produce nutritional repair effects on the stratum corneum of the skin, can anti-tumor, promote bone and blood vessel formation, delay skin aging, etc. The smaller the molecular weight, the more easily it can penetrate to the skin basal layer, and the better the moisturizing effect.

[0003] Currently, low relative molecular weight HA is mainly obtained by degrading high relative molecular weight HA through physical, chemical, and biological enzyme methods. Among them, the chemical degradation method has a lower cost and is easy for large-scale production. However, the traditional homogeneous chemical degradation method has problems such as harsh pH conditions, chemical reagent residues in the product, difficult recovery of homogeneous catalysts, and complex product components.

[0004] CN202410256391.7 discloses a method for catalytically degrading hyaluronic acid based on metal-organic framework materials, but this method is prone to waste water when adjusting the acid-base environment with acetic acid, has high requirements for equipment, the catalyst is expensive, and the product has a single molecular weight and is not easy to control. Therefore, there is an urgent need to develop an efficient and economical hyaluronic acid degradation technology with controllable product molecular weight and suitable for industrial large-scale production.

[0005] Metal Organic Frameworks (MOFs) are porous materials composed of orderly assembly of metal ions / clusters and organic ligands. The special structure of metal organic frameworks gives them many advantages, such as large specific surface area, pores, adjustable composition and high porosity. These advantages make MOFs very promising in the field of heterogeneous catalysis. Bimetallic organic frameworks (Bimetallic MOFs) retain the organic framework structure of MOF due to the bimetallic synergistic effect. At the same time, they can adjust the reaction effect by adjusting the ratio of bimetals, improve the stability and catalytic activity of the catalyst, and realize the economical preparation of the catalyst. Summary of the invention

[0006] The purpose of the present invention is to overcome the defects of the above-mentioned prior art and to provide a method for preparing hyaluronic acid with different molecular weights based on the catalysis of bimetallic organic framework materials.

[0007] The technical solution of the present invention is:

[0008] A method for preparing hyaluronic acid with different molecular weights based on bimetallic organic framework material catalysis comprises the following steps:

[0009] S1. Dissolve hyaluronic acid in deionized water, seal and freeze for later use.

[0010] S2. Synthesize bimetallic organic framework materials and vacuum dry them at 70-110°C for 12 h for later use.

[0011] S3. Using the bimetallic organic framework obtained in step 2 to degrade the hyaluronic acid obtained in step 1.

[0012] S4. The low molecular weight hyaluronic acid obtained in step 3 is filtered under reduced pressure to remove the bimetallic organic framework catalyst.

[0013] S5. freeze-drying the low molecular weight hyaluronic acid obtained in step 4 to obtain a low molecular weight hyaluronic acid solid.

[0014] Furthermore, the molecular weight of the hyaluronic acid described in S1 is greater than 1000 kDa.

[0015] Furthermore, the metal organic framework material of S2 is one of MIL-101 (Fe, Cu), Zn / Co-ZIF or Zn / Cu-ZIF prepared with raw materials of different metal ratios. The molar ratio of the raw metals of iron salt and copper salt in MIL-101 (Fe, Cu) is 1:1 to 1:10; the molar ratio of the raw metals of zinc salt and cobalt salt in Zn / Co-ZIF is 10:1 to 1:5; the molar ratio of the raw metals of zinc salt and copper salt in Zn / Cu-ZIF is 5:1 to 1:1.

[0016] Furthermore, the reaction in S3 is carried out without adding acid-base regulators.

[0017] Furthermore, the hyaluronic acid degradation conditions in S3 are that the content of the bimetallic organic framework material is 0.00375 - 0.0225 g per gram of hyaluronic acid.

[0018] Furthermore, the concentration of hydrogen peroxide added in S3 is 2 - 20 mmol of hydrogen peroxide per gram of hyaluronic acid.

[0019] Furthermore, the reaction temperature controlled in S3 is 30 °C.

[0020] Furthermore, the reaction time controlled in S3 is 1 - 4 h.

[0021] Furthermore, the hyaluronic acid degradation process in S3 is as follows: First, measure a certain amount of hyaluronic acid solution, add hydrogen peroxide, and finally add the metal-organic framework material, control the solution temperature and start the reaction.

[0022] According to the above technical solution, in step S3, if the MIL-101(Fe,Cu) bimetallic organic framework material is used, controlling the molar ratio of the iron salt and copper salt raw materials in MIL-101(Fe,Cu) to be 1:5, the addition content of the metal-organic framework material is 0.015 g per gram of hyaluronic acid, and the addition range of hydrogen peroxide is more than 8 mmol of hydrogen peroxide per gram of hyaluronic acid, and the reaction duration is more than 2 h, hyaluronic acid with a molecular weight less than 5 kDa can be prepared.

[0023] According to the above technical solution, in step S3, if the MIL-101(Fe,Cu) bimetallic organic framework material is used, controlling the molar ratio of the iron salt and copper salt raw materials in MIL-101(Fe,Cu) to be 1:5, the addition content range of the metal-organic framework material is 0.00375 - 0.0225 g per gram of hyaluronic acid, the addition amount of hydrogen peroxide is 4 mmol of hydrogen peroxide per gram of hyaluronic acid, and the reaction duration is 4 h, hyaluronic acid with a molecular weight in the range of 5 - 10 kDa can be prepared.

[0024] According to the above technical solution, in step S3, if the Zn / Cu-ZIF bimetallic organic framework material is used, controlling the molar ratio of the zinc salt and copper salt raw materials in Zn / Cu-ZIF to be 5:1; the addition content range of the metal-organic framework material is 0.075 - 0.225 g per gram of hyaluronic acid; the addition content range of hydrogen peroxide is more than 10 mmol of hydrogen peroxide per gram of hyaluronic acid; when the reaction duration is 4 h, hyaluronic acid with a molecular weight less than 10 kDa can be prepared.

[0025] According to the above technical solution, in step S3, if the Zn / Co-ZIF bimetallic organic framework material is used, the molar ratio of the zinc salt and cobalt salt raw materials in Zn / Co-ZIF is controlled to be 10:1; the addition content range of the metal organic framework material is 0.015 g per gram of hyaluronic acid; the addition content range of hydrogen peroxide is 12 - 20 mmol of hydrogen peroxide per gram of hyaluronic acid; when the reaction duration is 4 h, hyaluronic acid with a molecular weight in the range of 10 - 50 kDa can be prepared.

[0026] According to the above technical solution, in step S3, if the Zn / Co-ZIF bimetallic organic framework material is used, the molar ratio of the zinc salt and cobalt salt raw materials in Zn / Co-ZIF is controlled to be 10:1; the addition content range of the metal organic framework material is 0.00375 - 0.0225 g per gram of hyaluronic acid; the addition content of hydrogen peroxide is 10 mmol of hydrogen peroxide per gram of hyaluronic acid; when the reaction duration is 4 h, hyaluronic acid with a molecular weight in the range of 50 - 100 kDa can be prepared.

[0027] According to the above technical solution, in step S3, if the Zn / Co-ZIF bimetallic organic framework material is used, the molar ratio of the zinc salt and cobalt salt raw materials in Zn / Co-ZIF is controlled to be 10:1; the addition content of the metal organic framework material is 0.015 g per gram of hyaluronic acid; the addition range of hydrogen peroxide is 2 - 4 mmol of hydrogen peroxide per gram of hyaluronic acid; when the reaction duration is 4 h, hyaluronic acid with a molecular weight in the range of 100 - 150 kDa can be prepared.

[0028] According to the above technical solution, in step S3, if the Zn / Co-ZIF bimetallic organic framework material is used, the molar ratio of the zinc salt and cobalt salt raw materials in Zn / Co-ZIF is controlled to be 1:5; the addition content range of the metal organic framework material is 0.00375 - 0.015 g per gram of hyaluronic acid; the addition range of hydrogen peroxide is 2 - 10 mmol of hydrogen peroxide per gram of hyaluronic acid; when the reaction duration is 4 h, hyaluronic acid with a molecular weight greater than 150 kDa can be prepared.

[0029] Compared with the prior art, the present invention has the following advantages and beneficial effects:

[0030] 1. The method for catalytically preparing hyaluronic acid with different molecular weights based on the bimetallic organic framework material provided by the present invention does not require adjusting the acid-base environment, and the reaction can be carried out at room temperature. The operation is simple, the equipment requirements are low, and the degradation efficiency is high.

[0031] 2. The degradation system of the present invention can effectively control the molecular weight range of the product hyaluronic acid by controlling some reaction conditions. There are few by-products and the product quality is high, and it can be applied to fields such as medicine, food, and cosmetics.

[0032] 3. The selected raw materials for the synthesis of the bimetallic organic framework material catalyst are inexpensive, enabling large-scale low-cost preparation. Moreover, it can be recycled for secondary catalytic degradation after the reaction, significantly reducing production costs. Description of the Drawings

[0033] Figure 1 For the preparation of HA with different molecular weight ranges by controlling different bimetallic ratios in the Zn / Co-ZIF system in Example 2;

[0034] Figure 2 For the effect of different catalyst contents on the molecular weight of the degradation product HA in the Zn / Co-ZIF system in Example 3;

[0035] Figure 3 For the preparation of HA with different molecular weight ranges by controlling different hydrogen peroxide concentrations in the Zn / Co-ZIF system in Example 4;

[0036] Figure 4 For the effect of different bimetallic ratios on the molecular weight of the degradation product HA in the Zn / Cu-ZIF system in Example 6;

[0037] Figure 5 For the effect of different catalyst contents on the molecular weight of the degradation product HA in the Zn / Cu-ZIF system in Example 7;

[0038] Figure 6 For the effect of different hydrogen peroxide concentrations on the molecular weight of the degradation product HA in the Zn / Cu-ZIF system in Example 8;

[0039] Figure 7 For the effect of different bimetallic ratios on the molecular weight of the degradation product HA in the MIL-101(Fe,Cu) system in Example 10;

[0040] Figure 8 For the effect of different catalyst contents on the molecular weight of the degradation product HA in the MIL-101(Fe,Cu) system in Example 11; Figure 9 For the effect of different hydrogen peroxide concentrations on the molecular weight of the degradation product HA in the MIL-101(Fe,Cu) system in Example 12;

[0041] Figure 10 For the effect of different reaction durations on the molecular weight of the degradation product HA in the MIL-101(Fe,Cu) system in Example 13. Detailed Embodiments

[0042] The present invention will be further described below with reference to the drawings and examples, but the scope of implementation and protection of the present invention is not limited thereto.

[0043] Example 1

[0044] This example provides a method for catalytic degradation of hyaluronic acid based on Zn / Co-ZIF bimetallic organic framework material, including the following steps:

[0045] (1) Prepare a 1% hyaluronic acid solution with a number average molecular weight of 1330 kDa, seal it, freeze it, and store it for later use.

[0046] (2) Dissolve 0.54 g of Zn(CH 3 COO) 2 ·2H 2 O (2.5 mmol) and 0.06 g of Co(CH 3 COO) 2 ·4H 2 O (0.25 mmol) in 10 mL of deionized water, and add the mixture to a 10 mL aqueous solution of deionized water containing 2.24 g of dimethylimidazole C 4 H 6 N 2 (27 mmol). Mix and stir evenly, let it stand for 24 h, and then obtain a purple paste by centrifugation; wash the purple paste three times with methanol to remove unreacted raw materials, and activate it by vacuum drying at 70 °C for 12 h to obtain Zn / Co-ZIF(10:1) with a bimetallic ratio of 10:1.

[0047] (3) Take 40 mL of a 1% hyaluronic acid solution with a number average molecular weight of about 1330 kDa, add 18 mmol of hydrogen peroxide and Zn / Co-ZIF(10:1) at 0.015 g / g of hyaluronic acid simultaneously. The reaction temperature is 30 °C and the reaction time is 4 h.

[0048] (4) Filter the reaction solution through a 0.22 μm aqueous filter membrane under reduced pressure to remove the catalyst Zn / Co-ZIF(10:1). The obtained hyaluronic acid solution is freeze-dried to obtain a low molecular weight hyaluronic acid solid. The molecular weight (Mn) is determined by high performance gel permeation chromatography. The mobile phase is phosphate buffer (0.2 M, pH = 7.0), and dextrans with different molecular weights are used as standards. Calculate that the molecular weight of hyaluronic acid drops from 1330 kDa to about 10 kDa after the reaction.

[0049] Example 2

[0050] HA with different molecular weight ranges is prepared by adjusting the bimetallic ratio in Zn / Co-ZIF

[0051] (1) The same as step (1) of Example 1;

[0052] (2) 0.54 g, 0.52 g, 0.50 g, 0.45 g, 0.30 g, 0.15 g, 0.10 g of Zn(CH3 COO) 2 ·2H 2 O was respectively mixed and dissolved with 0.06 g, 0.08 g, 0.11 g, 0.17 g, 0.34 g, 0.51 g, 0.56 g of Co(CH 3 COO) 2 ·4H 2 O. The other steps were the same as those in step (2) of Example 1 to prepare bimetallic organic frameworks Zn / Co-ZIF with zinc-cobalt preparation ratios of 10:1, 7:1, 5:1, 3:1, 1:1, 1:3, and 1:5 respectively;

[0053] (3) Seven catalysts prepared in step (2) were respectively added to the reaction system according to the mass of 0.015 g / g of hyaluronic acid, the addition amount of hydrogen peroxide was 10 mmol, and the other steps were the same as those in step (3) of Example 1;

[0054] (4) The same as step (4) of Example 1. After the reaction, the molecular weight of hyaluronic acid was as Figure 1 shown. It can be seen that: under this reaction condition, an increase in the Co content in the Zn / Co-ZIF bimetal has a counterproductive effect on the degradation degree. When n(Zn / Co) is less than 1:1, HA with a molecular weight range of 50 kDa to 100 kDa can be obtained. Among them, the degradation effect is the best when the zinc-cobalt preparation ratio is 10:1. This is because an increase in zinc content is beneficial to the stability of the catalyst, and the synergistic effect of zinc and cobalt reaches the optimal degradation effect at this ratio.

[0055] Example 3

[0056] Effect of Zn / Co-ZIF (10:1) content on the degradation of hyaluronic acid.

[0057] (1) The same as step (1) of Example 1;

[0058] (2) The same as step (2) of Example 2;

[0059] (3) Zn / Co-ZIF (10:1) of 0.0037, 0.0075, 0.011, 0.015, 0.018, 0.022 g / g of hyaluronic acid was respectively added to the reaction system, and the other steps were the same as those in step (3) of Example 1;

[0060] (4) The same as step (4) of Example 1. After the reaction, the molecular weight of hyaluronic acid was as Figure 2As shown, it can be seen that when 0.015 g / g of hyaluronic acid is added to the Zn / Co-ZIF (10:1) system, the molecular weight of the prepared HA is the smallest. If the catalyst dosage continues to increase, the molecular weight of the product does not decrease but increases instead. This may be because too much catalyst dosage causes aggregation and reduces the degradation effect. Therefore, in order to save materials and achieve the best degradation effect, Zn / Co-ZIF (10:1) with 0.015 g / g of hyaluronic acid added is selected.

[0061] Example 4

[0062] Preparation of HA with different molecular weight ranges by controlling the concentration of hydrogen peroxide under the Zn / Co-ZIF system

[0063] (1) The same as step (1) of Example 1;

[0064] (2) The same as step (2) of Example 1;

[0065] (3) Add 2, 4, 6, 8, 10, 12, 14, 16, 18, 20 mmol of hydrogen peroxide to the reaction system respectively, and the others are the same as step (3) of Example 1;

[0066] (4) The same as step (4) of Example 1. After the reaction, the molecular weight of hyaluronic acid is as Figure 3 shown. It can be seen that when the addition amount of H 2 O 2 is in the range of 12 - 20 mmol, the molecular weight of the prepared HA is in the range of 20 kDa - 40 kDa; when the addition amount of H 2 O 2 is in the range of 6 - 10 mmol, the molecular weight of the prepared HA is in the range of 50 kDa - 100 kDa; when the addition amount of H 2 O 2 is in the range of 2 - 4 mmol, the molecular weight of the prepared HA is in the range of 100 kDa - 150 kDa.

[0067] Example 5

[0068] This example provides a method for catalytic degradation of hyaluronic acid based on Zn / Cu-ZIF bimetallic organic framework material, including the following steps:

[0069] (1) The same as step (1) of Example 1;

[0070] (2) Dissolve 0.6 g of Zn(CH 3 COO) 2 ·2H 2 O (2.7 mmol) and 0.11 g of Cu(CH 3 COO) 2 ·H 2O (0.55 mmol) was mixed and dissolved, and added to 10 mL of deionized aqueous solution dissolving 2.24 g of dimethylimidazole C 4 H 6 N 2 (27 mmol). After mixing and stirring evenly, it was left standing for 24 h and then a sludge was obtained by centrifugation; the sludge was washed three times with methanol to remove unreacted raw materials, and activated by vacuum drying at 70 °C for 12 h to obtain Zn / Cu-ZIF (5:1) with a raw material bimetal ratio of 5:1.

[0071] (3) 40 mL of a hyaluronic acid solution with a concentration of 1% and a number average molecular weight of about 1330 kDa was taken, and 10 mmol of hydrogen peroxide and Zn / Cu-ZIF (5:1) at 0.015 g / g of hyaluronic acid were added simultaneously. The reaction temperature was 30 °C and the reaction time was 4 h.

[0072] (4) The reaction solution was filtered under reduced pressure through a 0.22 μm aqueous filter membrane to remove the catalyst Zn / Cu-ZIF (5:1). The obtained hyaluronic acid solution was freeze-dried to obtain an oligomeric hyaluronic acid solid. The molecular weight (Mn) was determined by high performance gel permeation chromatography. The mobile phase was phosphate buffer (0.2 M, pH = 7.0). Using dextrans with different molecular weights as standards, the number average molecular weight of hyaluronic acid after the reaction was calculated to decrease from 1330 kDa to about 5 kDa.

[0073] Example 6

[0074] Effect of Zn / Cu-ZIF Bimetal Ratio on the Molecular Weight of Degradation Product HA

[0075] (1) The same as step (1) of Example 1;

[0076] (2) 0.18, 0.3, 0.42, 0.6, 0.6, 0.6 g of Zn(CH 3 COO) 2 ·2H 2 O were respectively mixed and dissolved with 0.38, 0.27, 0.16, 0.11, 0.27, 0.54 g of Cu(CH 3 COO) 2 ·H 2 O. Others were the same as step (2) of Example 5 to prepare bimetal organic frameworks Zn / Cu-ZIF with zinc-cobalt preparation ratios of 3:7, 1:1, 7:3 respectively under the condition of constant total metal amount and zinc-copper content ratios of 5:1, 2:1, 1:1 by keeping the Zn content unchanged and adding Cu element additionally.

[0077] (3) Add the 6 catalysts prepared in step (2) to the reaction system at a mass of 0.0075 g / g of hyaluronic acid, and the other steps are the same as step (3) of Example 5;

[0078] (4) The same as step (4) of Example 1. After the reaction, the molecular weight of hyaluronic acid is as Figure 4 shown. It can be seen that the degradation effect of the system where Zn / Cu-ZIF (5:1) with a raw material bimetal ratio of 5:1 is the best. Therefore, the Zn / Cu-ZIF bimetallic MOF catalyst synthesized and prepared at this ratio is selected.

[0079] Example 7

[0080] Effect of catalyst content in Zn / Cu-ZIF bimetallic system on the molecular weight of product HA

[0081] (1) The same as step (1) of Example 1;

[0082] (2) The same as step (2) of Example 5;

[0083] (3) Add Zn / Cu-ZIF (5:1) with 0.00375, 0.0075, 0.01125, 0.015, 0.01875, and 0.0225 g / g of sodium hyaluronate to the reaction system respectively, and the other steps are the same as step (3) of Example 5;

[0084] (4) The same as step (4) of Example 5. After the reaction, the molecular weight of hyaluronic acid is as Figure 5 shown. It can be seen that when the content of Zn / Cu-ZIF (5:1) added to the system is greater than 0.015 g / g of hyaluronic acid, the change in the molecular weight of the prepared HA is not significant. Therefore, to balance the material consumption and degradation effect, Zn / Cu-ZIF (5:1) added with 0.015 g / g of hyaluronic acid is selected.

[0085] Example 8

[0086] Effect of hydrogen peroxide concentration in Zn / Cu-ZIF bimetallic system on the molecular weight of product HA

[0087] (1) The same as step (1) of Example 1;

[0088] (2) The same as step (2) of Example 5;

[0089] (3) Add 2, 4, 6, 8, 10, and 12 mmol of hydrogen peroxide to the reaction system respectively, and the other steps are the same as step (3) of Example 5;

[0090] (4) The same as step (4) of Example 5. After the reaction, the molecular weight of sodium hyaluronate is as Figure 6 shown. It can be seen that when H 2 O2 When the addition amount is greater than 10 mmol, the change range of the molecular weight of the product HA is very small, and the molecular weight of the product is around 5 kDa.

[0091] Example 9

[0092] This example provides a method for catalytic degradation of hyaluronic acid based on the MIL-101(Fe,Cu) bimetallic organic framework material, including the following steps:

[0093] (1) The same as step (1) of Example 1;

[0094] (2) Mix 0.11 g of FeCl 3 ·6H 2 O (0.42 mmol), 0.50 g (2.1 mmol) of Cu(NO 3 ) 2 ·3H 2 O and 1.23 g of phthalic acid (H 2 BDC) in 15 mL of dimethylformamide (DMF), stir evenly to dissolve, seal in a 20 mL glass sample bottle, heat at 110 °C for 20 h, and then obtain a sludge by centrifugation; wash the sludge three times with DMF and ethanol to remove unreacted raw materials, and activate it in a vacuum drying oven at 110 °C for 12 h to obtain MIL-101(Fe,Cu) (1:5).

[0095] (3) Take 40 mL of a hyaluronic acid solution with a concentration of 1% and a number average molecular weight of about 1330 kDa, and simultaneously add 10 mmol of hydrogen peroxide and 0.015 g / g of hyaluronic acid sodium of MIL-101(Fe,Cu) (1:5). The reaction temperature is 30 °C and the reaction time is 4 h.

[0096] (4) Filter the reaction solution through a 0.22 μm aqueous filter membrane under reduced pressure to remove the catalyst MIL-101(Fe,Cu). The obtained sodium hyaluronate solution is freeze-dried to obtain an oligomeric hyaluronic acid solid. The molecular weight (Mn) is determined by high performance gel permeation chromatography. The mobile phase is phosphate buffer solution (0.2 M, pH = 7.0), and dextrans with different molecular weights are used as standards. Calculate that the number average molecular weight of hyaluronic acid drops from 1330 kDa to about 4 kDa after the reaction ends.

[0097] Example 10

[0098] Effect of the bimetallic ratio of MIL-101(Fe,Cu) on the molecular weight of the degradation product HA

[0099] (1) The same as step (1) of Example 1;

[0100] (2) Add 0.33 g, 0.16 g, 0.11 g, and 0.06 g of FeCl 3 ·6H 2 O to 0.30 g, 0.45 g, 0.50 g, and 0.54 g of Cu(NO 3 ) 2 ·3H 2 O respectively, and add them to 15 mL of dimethylformamide (DMF) dissolved with 1.23 g of phthalic acid (H 2 BDC). The other steps are the same as step (2) of Example 9 to prepare MIL-101(Fe,Cu) with iron-copper preparation ratios of 1:1, 1:3, 1:5, and 1:10 respectively;

[0101] (3) Change the catalyst added to the system to the four kinds of MIL-101(Fe,Cu) synthesized in step (2) and add them according to the content of 0.015 g / g of hyaluronic acid. The other steps are the same as step (3) of Example 9;

[0102] (4) The same as step (4) of Example 9. After the reaction, the molecular weight of hyaluronic acid is as Figure 7 shown. It can be seen that when the bimetallic ratio of iron and copper raw materials is less than 1:3, the molecular weight change range is not large. Considering the material stability, MIL-101(Fe,Cu) with an iron-copper bimetallic ratio of 1:5 (1:5) is preferably selected.

[0103] Example 11

[0104] Effect of catalyst content in MIL-101(Fe,Cu) bimetallic system on the molecular weight of product HA

[0105] (1) The same as step (1) of Example 1;

[0106] (2) The same as step (2) of Example 9;

[0107] (3) Add MIL-101(Fe,Cu) (1:5) with 0.00375, 0.0075, 0.01125, 0.015, 0.01875, and 0.0225 g / g of sodium hyaluronate to the reaction system respectively. The other steps are the same as step (3) of Example 9;

[0108] (4) The same as step (4) of Example 9. After the reaction, the molecular weight of hyaluronic acid is as Figure 8 shown. It can be seen that when the content of MIL-101(Fe,Cu) (1:5) added to the system is greater than 0.015 g / g of hyaluronic acid, the molecular weight change of the prepared HA is not large. Therefore, in order to balance the material consumption and degradation effect, MIL-101(Fe,Cu) (1:5) added with 0.015 g / g of hyaluronic acid is selected.

[0109] Example 12

[0110] Effect of Hydrogen Peroxide Concentration on the Molecular Weight of Product HA in the MIL-101(Fe,Cu) Bimetallic System

[0111] (1) The same as step (1) of Example 9;

[0112] (2) The same as step (2) of Example 9;

[0113] (3) Add 2, 4, 6, 8, 10, 12 mmol of hydrogen peroxide to the reaction system respectively, and the other steps are the same as step (3) of Example 9;

[0114] (4) The same as step (4) of Example 9. After the reaction, the molecular weight of hyaluronic acid is as Figure 9 shown. It can be seen that when the addition amount of H 2 O 2 is greater than 10 mmol, the change range of the molecular weight of product HA is very small, and the molecular weight of the product is about 4 kDa. Therefore, the amount of H 2 O 2 is preferably 10 mmol.

[0115] Example 13

[0116] Effect of Reaction Duration on the Molecular Weight of Product HA in the MIL-101(Fe,Cu) Bimetallic System

[0117] (1) The same as step (1) of Example 9;

[0118] (2) The same as step (2) of Example 9;

[0119] (3) Adjust the reaction time to 1, 2, 3, 4 hours respectively, and the other steps are the same as step (3) of Example 9;

[0120] (4) The same as step (4) of Example 9. After the reaction, the molecular weight of sodium hyaluronate is as Figure 10 shown. It can be seen that when the reaction time is after 3 h, the change range of the molecular weight of product HA is very small. Therefore, considering the balance between the degradation effect and the time cost, the preferred reaction duration is 3 h.

[0121] The above embodiments are part of the implementation process of the present invention, but the implementation manner of the present invention is not limited by the above embodiments. Any other changes, substitutions, combinations, and simplifications made under the premise of violating the spirit and principle of the present invention shall be equivalent replacement methods and are all included in the protection scope of the present invention.

Claims

1. A method for preparing hyaluronic acid of different molecular weights based on bimetallic organic framework material catalysis, characterized in that: The steps include: S1. Dissolve hyaluronic acid with deionized water, seal and freeze for later use; S2. The two metal salts are uniformly mixed and dissolved in the corresponding solvent, and then the ligand solution is added and mixed and stirred. The MIL-101 series bimetallic organic framework is synthesized by hydrothermal method, and the ZIF series bimetallic organic framework is synthesized by self-assembly at room temperature. Finally, the bimetallic organic framework material is obtained, and then vacuum dried after centrifugation for standby use; the two metal salts are selected from two of zinc salts, cobalt salts, copper salts, and iron salts, and the ligand is one of terephthalic acid or 2-methylimidazole; S3. The bimetallic organic framework material obtained in S2 is used to degrade the hyaluronic acid obtained in S1 to obtain low molecular weight hyaluronic acid; the hyaluronic acid degradation process is: first measure the hyaluronic acid solution, add hydrogen peroxide, add the bimetallic organic framework material, control the solution temperature and start the reaction; S4. The low molecular weight hyaluronic acid obtained in S3 is filtered under reduced pressure to remove the metal organic framework material; S5. Freeze-dry the low molecular weight hyaluronic acid obtained in S4 to obtain a low molecular weight hyaluronic acid solid.

2. According to claim 1, a method for preparing hyaluronic acid of different molecular weights based on bimetallic organic framework material catalysis, characterized in that: In step S1, the hyaluronic acid is a high molecular weight hyaluronic acid with a molecular weight of more than 1000 kDa.

3. According to claim 1, a method for preparing hyaluronic acid of different molecular weights based on bimetallic organic framework material catalysis, characterized in that: In step S2, the vacuum drying is carried out at a temperature of 70-110°C and for a time of 12 hours.

4. According to claim 1, a method for preparing hyaluronic acid with different molecular weights based on bimetallic organic framework material catalysis, characterized in that: In step S3, the bimetallic organic framework material is one of MIL-101 (Fe, Cu), Zn / Co-ZIF or Zn / Cu-ZIF prepared from metal salt raw materials in different molar ratios.

5. The method for preparing hyaluronic acid of different molecular weights based on bimetallic organic framework catalysis according to claim 1, characterized in that: In step S3, the bimetallic molar ratio of the raw materials used to synthesize the bimetallic organic framework material is 10:1 to 1:

5.

6. A method for preparing hyaluronic acid of different molecular weights based on bimetallic organic framework catalysis according to claim 1, characterized in that: In step S3, the content of the bimetallic organic framework material is 0.00375 to 0.0225 g per gram of hyaluronic acid.

7. A method for preparing hyaluronic acid of different molecular weights based on bimetallic organic framework catalysis according to claim 1, characterized in that: In step S3, the concentration of hydrogen peroxide added is 2-20 mmol per gram of hyaluronic acid.

8. The method for preparing hyaluronic acid with different molecular weights based on bimetallic organic framework catalysis according to claim 1, characterized in that: In step S3, the reaction temperature is 30°C.

9. A method for preparing hyaluronic acid of different molecular weights based on bimetallic organic framework catalysis according to claim 1, characterized in that: In step S3, no reagent needs to be added to adjust the pH of the system.

10. The method for preparing hyaluronic acid with different molecular weights based on bimetallic organic framework catalysis according to claim 1, characterized in that: In step S3, the reaction time is 1 to 4 hours.

Images