CN118546395A - Preparation method of polysaccharide sodium hyaluronate composite gel - Google Patents

Abstract

The present invention relates to a method for preparing a polysaccharide sodium hyaluronate composite gel, and belongs to the technical field of polymer material preparation. The preparation method of the present invention prepares a polysaccharide sodium hyaluronate composite gel by first cross-linking under low temperature conditions and then cross-linking under high temperature conditions. The method provided by the present invention can obtain a gel product with good elasticity and easy injection with the simplest operation and the fastest time, has good reproducibility, is suitable for the preparation of different types of polysaccharide sodium hyaluronate composite gels, and is more conducive to industrial production.

Description

A preparation method of polysaccharide sodium hyaluronate composite gel

Technical Field

The invention belongs to the technical field of polymer material preparation, and particularly relates to a method for preparing a polysaccharide sodium hyaluronate composite gel.

Background Art

Hyaluronic acid is a straight-chain high-molecular polysaccharide composed of glucuronic acid and glucosamine as disaccharide units. It exists in many connective tissues such as skin, vitreous body, cartilage, synovial fluid, etc., and plays physiological roles in moisturizing, nourishing, repairing and preventing damage. Hyaluronic acid is generally in the form of its sodium salt, sodium hyaluronate (hereinafter referred to as HA), which is soluble in water but insoluble in organic solvents.

Chondroitin sulfate (hereinafter referred to as "CS") is widely present in various animal tissues, especially in cartilage and connective tissue.

CN100582146C discloses a method for preparing a biocompatible cross-linked gel, wherein a polymer is first added to react and then another or the same polymer is added to react to obtain a high polymer. The degree of reaction must be continuously monitored during the reaction, and another or the same polymer is added only when a specific degree of polymerization is reached. The operation is cumbersome and not conducive to industrial production.

The invention provides a polysaccharide sodium hyaluronate composite gel and a preparation method thereof. The operation is simple and a gel product with higher gel strength and better fluidity can be obtained without other additives.

Therefore, the preparation method of the polysaccharide sodium hyaluronate composite gel provided by the present invention is suitable for industrial production and has greater market value and far-reaching practical significance.

Summary of the invention

In view of the above technical background, the present invention provides a method for preparing a polysaccharide sodium hyaluronate composite gel, which is a new method suitable for industrial production.

The present invention provides a method for preparing a polysaccharide sodium hyaluronate composite gel, which comprises the following steps:

Step 1: Dissolve sodium hyaluronate in sodium hydroxide aqueous solution, add low molecular weight polysaccharide and cross-linking agent, first react at temperature A, then cross-link at temperature B to prepare polysaccharide sodium hyaluronate composite gel.

In the step 1, the reaction can be carried out at temperature A for 24 hours to 72 hours, preferably 36 hours to 60 hours, and more preferably 48 hours to 72 hours.

In the step 1, the reaction can be carried out at temperature B for 1 h to 6 h, preferably 2 h to 5 h.

According to the present invention, the temperature A in step 1 may be 0°C to 20°C, preferably 5°C to 15°C or 8°C to 12°C.

According to the present invention, the temperature B in step 1 may be 25°C to 50°C, preferably 25°C to 45°C, and more preferably 30°C to 40°C.

According to the present invention, the low molecular weight polysaccharide is selected from one or more of sodium hyaluronate (HA), chondroitin sulfate (CS), chondroitin (C), heparin, and cellulose, preferably one or more of sodium hyaluronate, chondroitin sulfate, and chondroitin.

In step 1, the mass ratio of sodium hyaluronate to low molecular weight polysaccharide can be (1-9):1, preferably (1-6):1.

In step 1, the molecular weight of the sodium hyaluronate may be in the range of 1×10 ⁶ to 3×10 ⁶ Da, preferably 2×10 ⁶ to 3×10 ⁶ Da.

In step 1, the molecular weight of the low molecular weight polysaccharide may be 1×10 ⁴ to 6×10 ⁵ Da, preferably 2×10 ⁴ to 4×10 ⁵ Da.

The mass concentration of the sodium hydroxide aqueous solution can be 0.5wt% to 3wt%, preferably 0.5wt% to 2wt%;

The mass concentration of the sodium hyaluronate in the sodium hydroxide aqueous solution may be 10 wt % to 30 wt %, preferably 12 wt % to 25 wt %.

The crosslinking agent is one of 1,4-butanediol diglycidyl ether (BDDE), 1-(2,3-epoxypropyl)-2,3-epoxycyclohexane and 1,2-ethylene glycol diglycidyl ether.

In step 1, the mass ratio of the cross-linking agent to the sum of sodium hyaluronate and low molecular weight polysaccharide can be 1:(5-50), preferably 1:(5-40).

In certain embodiments, the preparation method further comprises: cutting the obtained gel into small pieces, soaking them in PBS buffer solution, repeatedly replacing the PBS buffer solution until the gel becomes colorless; then sieving the gel into small gel particles through a 160-mesh sieve, and then mechanically homogenizing to prepare a polysaccharide sodium hyaluronate composite gel.

In certain embodiments, the preparation method further comprises: cutting the obtained gel into small pieces, soaking them in a PBS buffer solution containing hydrochloric acid, repeatedly replacing the PBS buffer solution until the gel pieces are colorless; then sieving the gel into small gel particles through a 160-mesh sieve, and then mechanically homogenizing to prepare a polysaccharide sodium hyaluronate composite gel.

The PBS buffer solution can be prepared from sodium chloride, disodium hydrogen phosphate, sodium dihydrogen phosphate, hydrochloric acid and water.

The pH of the PBS buffer solution may be 6.5 to 7.5. In certain embodiments, the pH of the PBS buffer solution is 6.5 to 6.8.

In certain embodiments, the PBS buffer solution is prepared from sodium chloride, disodium hydrogen phosphate, sodium dihydrogen phosphate, hydrochloric acid and water, and has a pH of 6.5-7.0.

In certain embodiments, the PBS buffer solution is prepared from sodium chloride, disodium hydrogen phosphate, sodium dihydrogen phosphate and water, and has a pH of 7.0 to 7.5.

According to the present invention, as a preferred embodiment, the PBS buffer solution is repeatedly replaced 4 to 8 times.

According to the present invention, the total concentration of polysaccharide and sodium hyaluronate in the gel may be 20 mg/mL to 30 mg/mL. In certain embodiments, the total concentration of polysaccharide and sodium hyaluronate in the gel is 20 mg/mL to 25 mg/mL.

According to the present invention, the polysaccharide sodium hyaluronate composite gel can be injected for use. The polysaccharide sodium hyaluronate composite gel can be suitably used for separating, replacing or filling biological tissues, or increasing the volume of the tissues, or for the medical and aesthetic purposes of filling wrinkles, concealing scars, or increasing the volume of lips.

The advantages of the preparation method provided by the present invention are mainly:

1. The present invention provides a new and industrially applicable method for preparing polysaccharide sodium hyaluronate composite gel; the present invention adjusts factors such as alkali concentration, crosslinking agent dosage, system pH, temperature, time, etc., especially the multi-level crosslinking process conditions combining cold crosslinking and hot crosslinking, so that the obtained gel has a tighter structure, a high degree of crosslinking, better viscoelasticity, and stronger resistance to enzymolysis while maintaining excellent biocompatibility.

2. The present invention solves the problems that long-term high-temperature cross-linking reaction easily leads to degradation of raw materials, the final product is mainly composed of cross-linked polymer short chains, the gel strength is greatly reduced, and the reaction speed of low-temperature cross-linking reaction is slow, the overall strength of the obtained product is low, and the degree of cross-linking is even lower.

The inventors found through a large number of experiments that the method of the present invention increases the strength of the gel by 0.4 to 3.8 times compared with simple low-temperature cross-linking, and increases the strength of the gel by 2 to 17 times compared with simple high-temperature cross-linking, which has significant advantages over conventional methods.

3. The present invention uses a multi-level crosslinking method that combines low-temperature crosslinking with high-temperature crosslinking. First, low-temperature crosslinking (0°C to 20°C) is used to prepare a dense gel with good elasticity and low hardness; due to the low temperature, the gelation time is long, and the material distribution in the polymerization system is uniform, so that the topological structure of the gel is complete, thereby having better elasticity; low-temperature crosslinking can achieve crosslinking while reducing the degradation of the raw materials, so that the crosslinked network can better resist high-temperature degradation and achieve further crosslinking simultaneously; then the temperature rises, the rate of binding between the raw materials and the crosslinking agent is accelerated, so that the degree of crosslinking increases and the hardness of the gel increases. Therefore, by combining low-temperature and high-temperature crosslinking, a composite gel with good viscoelasticity can be obtained, the crosslinking degree and structural stability of the gel are improved, and the viscoelasticity of the gel and the supporting force after injection are increased (the preparation of crosslinked gel by high temperature and then low temperature process will destroy the chain length of the HA macromolecular chain, making it lose the advantage of high molecular weight, and affecting the stability and durability of the product during use.) The composite gel prepared by the method of the present invention is 31.3% to 114% higher than the gel prepared by the method of first hot crosslinking and then cold crosslinking, and an unexpected technical effect is achieved.

4. The inventors found that the longer the low-temperature cross-linking reaction time, the less likely the raw material is to degrade, and the longer the contact time with the cross-linking agent, the higher the degree of reaction. The high temperature further promotes the cross-linking reaction, and a gel with high strength but reduced pushing force is obtained, which is conducive to the injection of the gel. At the same time, the reaction conditions with mild conditions, low degree of raw material degradation and high product strength were determined through experiments, making the preparation method suitable for further industrial production implementation.

5. The method provided by the present invention has good reproducibility and is suitable for the preparation of different types of polysaccharide sodium hyaluronate composite gels. The present invention explores the relationship between the reaction temperature range and reaction time and the strength of the polysaccharide sodium hyaluronate composite gel, and can obtain a gel product with good elasticity and easy injection with the simplest operation and the fastest time.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG1 is a graph showing the molecular weight change of a 20 wt% HA raw material in Example 5 after being allowed to stand at 10° C. and 40° C. for 48 h and 3 h, respectively;

FIG2 is a graph showing the molecular weight change of 20 wt% HA raw materials in Example 5 after being allowed to stand at 40° C. for 27 h;

FIG3 is a graph showing the molecular weight change of a 5 wt% CS raw material in Example 5 after standing at 40° C. for 22 h;

In the drawings, WDa stands for ten thousand Daltons.

DETAILED DESCRIPTION

The present invention will be further described below in conjunction with specific examples. It should be understood that these examples are only used to illustrate the present invention and are not intended to limit the scope of the present invention. The experimental methods in the following examples where specific conditions are not specified are usually carried out under normal conditions.

Unless otherwise specified, the raw materials and reagents used in the examples are commercially available.

The room temperature described in the examples is 20° C. to 30° C. Unless otherwise specified, the reagents were used directly without purification. All solvents were purchased from commercial suppliers, such as Aldrich, and were used without treatment.

Example 1: Effects of low temperature, high temperature and reaction time on the viscoelasticity of HA/CS composite gel

Sodium hyaluronate (HA) (molecular weight 2.3×10 ⁶ Da, 4.0 g) powder was slowly added to 1wt% NaOH aqueous solution (20 mL) under stirring. After being uniformly dissolved, chondroitin sulfate (CS) (6.5×10 ⁴ Da, 1.0 g) was slowly added and stirred evenly until it became light yellow and transparent. 1,4-Butanediol diglycidyl ether (BDDE) (0.36 g) was added to the above solution, stirred for 30 min, and then transferred to a Y ₁ ℃ water bath for reaction for X ₁ h. After the low-temperature reaction was completed, it was transferred to a Y ₂ ℃ water bath for continued cross-linking for X ₂ h to obtain a light yellow block gel.

The obtained block gel was cut into small pieces of about ¹ cm3, and the gel was soaked in a PBS buffer solution (pH 6.8) containing hydrochloric acid to neutralize the sodium hydroxide therein. The PBS buffer solution (pH 6.5-7.5) was then continuously replaced until the final gel pieces were colorless. The swollen gel was sieved into small gel particles through a 160-mesh sieve, and then mechanically homogenized to obtain a HA/CS composite cross-linked gel product. The total HA/CS concentration and cross-linking degree are shown in Table 1.

The prepared HA/CS cross-linked gel was extruded through a 30G needle to test the average pushing force; the experimental gel was degraded and tested for ¹ H NMR, and the degree of cross-linking (R = BDDE molar number/(total molar number of HA/CS disaccharide units) was calculated by the characteristic peaks of BDDE and HA/CS disaccharide units; the experimental gel was placed on a rotational rheometer, in the plate mode, with a fixed strain of 0.01%, and a frequency sweep (0.01 Hz to 100 Hz) was selected to test the viscoelasticity of the gel at 0.1 Hz. The test results are shown in Table 1.

Table 1 Process conditions and gel properties of Example 1

From the results in Table 1, it can be seen that the gel strength of Examples 1-5, 1-8 to 1-12 is improved by 24.8% to 305% compared with other examples, and the average pushing force is reduced by 11.4% to 43.4%; the longer the low-temperature reaction time, the less likely the raw material is to degrade, and the longer the contact time with the cross-linking agent, the higher the degree of reaction, and the high temperature further promotes the cross-linking reaction, so that the gel strength is higher and the pushing force is also reduced; under the same low-temperature reaction time, the reaction conditions of 30°C and 5h are milder, the degree of degradation of the raw material is low, and a gel sample with higher strength can be prepared under a longer reaction time.

Example 2: Effects of the type and molecular weight of low molecular weight polysaccharides on the properties of HA composite gel

Sodium hyaluronate (molecular weight 2.3×10 ⁶ Da, 4.0g) powder was added to 1wt% NaOH solution (20mL). After the sodium hyaluronate was evenly dissolved, 1g of low molecular weight polysaccharide was slowly added, stirred evenly until it was light yellow and transparent, BDDE (0.36g) was added, stirred for 30min, first reacted at 10°C for 48h, and then reacted at 40°C for 3h to obtain a light yellow block gel. The obtained block gel was cut into small pieces of about 1cm ³ , and the gel was soaked in a PBS buffer solution (pH 6.8) containing hydrochloric acid to neutralize the sodium hydroxide therein. After that, the PBS buffer solution (pH 6.5-7.5) was continuously replaced until the final gel block was colorless. The swollen gel was sieved into small gel particles through a 160-mesh sieve, and then mechanically homogenized to obtain a high molecular weight HA/low molecular weight polysaccharide composite cross-linked gel product. The total concentration of high molecular weight HA/low molecular weight polysaccharide is shown in Table 2.

The high molecular weight HA/low molecular weight polysaccharide cross-linked gel prepared in Example 2 was extruded through a 30G needle to test the average pushing force; the experimental gel was degraded and tested for ¹ H NMR, and the degree of cross-linking (R = BDDE molar number/(total molar number of HA/low molecular weight polysaccharide disaccharide units) was calculated through the characteristic peaks of BDDE and HA/low molecular weight polysaccharide disaccharide units; the experimental gel was placed on a rotational rheometer, and in the flat plate mode, frequency scanning (0.01 Hz to 100 Hz) was selected to test the viscoelasticity of the gel at 0.1 Hz. The test results are shown in Table 2.

Table 2 Process conditions and gel properties of Example 2

From the results in Table 2, it can be seen that compared with Examples 1-5, under the same conditions, the introduction of low molecular weight HA reduces the strength of the composite cross-linked gel and increases the pushing force; while the contribution of chondroitin and chondroitin sulfate to the performance of the composite cross-linked gel is relatively small. Overall, as the molecular weight of the low molecular weight polysaccharide increases, the gel strength increases and the pushing force increases; for the types of low molecular weight polysaccharides, compared with low molecular weight HA, the addition of C and CS slightly reduces the pushing force of the composite cross-linked gel.

Example 3: Effect of Sodium Hyaluronate Concentration on the Properties of HA Composite Gel

Sodium hyaluronate (molecular weight 2.3×10 ⁶ Da, 2.4g) or sodium hyaluronate (molecular weight 2.3×10 ⁶ Da, 3.2g) powder was added to 1wt% NaOH solution (20mL). After sodium hyaluronate was evenly dissolved, low molecular weight polysaccharide, such as L-HA (molecular weight 4.6×10 ⁴ Da, 0.6g) or chondroitin sulfate (molecular weight 6.5×10 ⁴ Da, 0.8g) was slowly added, stirred evenly until transparent, BDDE (0.22g or 0.29g) was added accordingly, stirred for 30min, reacted at 10℃ for 48h, and then reacted at 40℃ for 3h to obtain a light yellow block gel. The obtained block gel was cut into small pieces of about 1cm ³ , and the gel was soaked in a PBS buffer solution (pH 6.5) containing hydrochloric acid to neutralize the sodium hydroxide therein. After that, the PBS buffer solution (pH 6.5-7.5) was continuously replaced until the final gel pieces were colorless. The swollen gel was sieved into gel particles through a 160-mesh sieve, and then mechanically homogenized to obtain a high molecular weight HA/low molecular weight polysaccharide composite cross-linked gel product. The total concentration and cross-linking degree of high molecular weight HA/low molecular weight polysaccharide are shown in Table 3.

The high molecular weight HA/low molecular weight polysaccharide cross-linked gel prepared in Example 3 was extruded through a 30G needle to test the average pushing force; the experimental gel was degraded and tested for ¹ H NMR, and the degree of cross-linking (R = BDDE molar number/(total molar number of HA/low molecular weight polysaccharide disaccharide units) was calculated through the characteristic peaks of BDDE and HA/low molecular weight polysaccharide disaccharide units; the experimental gel was placed on a rotational rheometer, and in the flat plate mode, frequency scanning (0.01 Hz to 100 Hz) was selected to test the viscoelasticity of the gel at 0.1 Hz. The test results are shown in Table 3.

Table 3 Process conditions and gel properties of Example 3

From the results in Table 3, it can be seen that with the increase of high molecular weight HA concentration, the gel strength increases; at lower HA concentrations, compared with L-HA, CS has a more obvious reduction in the pushing force of the composite cross-linked gel, making it easier to push during product use.

Example 4: Effect of the ratio of HA to CS on the viscoelasticity of HA/CS composite gel

Under stirring, sodium hyaluronate (4.0 g, 2.3 × 10 ⁶ Da) powder was slowly added to 1wt% NaOH solution (20 mL). After being uniformly dissolved, chondroitin sulfate (CS, 6.5 × 10 ⁴ Da) was slowly added and stirred evenly until it was light yellow and transparent. Then BDDE was added to the above solution and stirred evenly for 30 minutes. Then, light yellow block gel was obtained at 10℃/24h+30℃/5h and 10℃/48h+40℃/3h, respectively. The obtained block gel was cut into small pieces of about 1 cm ³ , and the gel was soaked in PBS buffer solution (pH 6.5) containing hydrochloric acid to neutralize the sodium hydroxide therein. After that, the PBS buffer solution (pH 6.5-7.5) was continuously replaced until the final gel block was colorless. The swollen gel was sieved into small gel particles through a 160-mesh sieve, and then mechanically homogenized to obtain a HA/CS composite cross-linked gel product. The total concentration of HA/CS is shown in Table 4.

The HA/CS cross-linked gel prepared in Example 4 was extruded through a 30G needle to test the average pushing force; the experimental gel was degraded and tested for ¹ HNMR, and the degree of cross-linking (R = BDDE molar number/(total HA/CS disaccharide unit molar number) was calculated by the characteristic peaks of BDDE and HA/CS disaccharide units; the experimental gel was placed on a rotational rheometer, and in the flat plate mode, a frequency scan (0.01-100 Hz) was selected to test the viscoelasticity of the gel at 0.1 Hz. The test results are shown in Table 4.

Table 4 Process conditions and gel properties of Example 4

From the results in Table 4, it can be seen that with the increase of the proportion of chondroitin sulfate, the gel strength gradually increases and the pushing force gradually decreases, indicating that when preparing HA composite cross-linked gel, CS has the effect of simultaneously improving strength and promoting pushing.

Example 5: Changes in molecular weight (unit: ten thousand Daltons) of HA raw materials under different crosslinking temperature conditions

Table 5 Molecular weight changes of 20wt% HA raw materials after standing at 10℃ and 40℃ for 48h and 3h respectively

Table 6 Molecular weight change of 20wt% HA raw material at 40℃ for 27h

Table 7 Molecular weight change of 5wt% CS raw material at 40℃ for 22h

As shown in Table 5, the molecular weight of HA raw materials decreased less within 20h to 48h of low-temperature standing, from 2.09 million Daltons to 1.66 million Daltons and 1.46 million Daltons respectively. In particular, after HA was placed at low temperature for 48h and then transferred to high-temperature standing, after 3h, the molecular weight of HA decreased even less, only to 910,000 Daltons (38%, relative to the molecular weight after low-temperature standing). The above results show that the longer the low-temperature time, the more physical entanglements the raw materials will undergo during the standing process, and the stronger the ability to resist degradation in the subsequent high-temperature cross-linking process.

As shown in Table 6, after the HA raw material was left at high temperature for 3 hours, the molecular weight directly decreased to 820,000 Daltons (61%). If it is left at low temperature again, the molecular weight will only continue to decrease slowly, which is more degraded than the case where it was left at low temperature first and then at high temperature. After being left at high temperature for 27 hours, the molecular weight of HA has dropped to 150,000 Daltons, losing its advantage of high molecular weight.

In summary, compared with the raw materials that were first placed at low temperature and then at high temperature, the molecular weight of the HA raw materials after high temperature placement was reduced to 800,000 Daltons to 900,000 Daltons, but the raw materials that were first placed at low temperature would undergo varying degrees of physical entanglement during this process, and have a certain resistance to high temperature, and the high temperature would not directly destroy the macromolecular chain into short chains. When a chemical crosslinking agent is added, it is easier to obtain physically and chemically co-crosslinked long-chain molecules and prepare HA/CS crosslinked gels with higher stability and durability.

Comparative Example 1: Effect of low temperature cross-linking process conditions on the viscoelasticity of the inventive gel

The operation was carried out according to Example 1, wherein X ₁ , Y ₁ , X ₂ , and Y ₂ are shown in Table 8.

Comparative Example 2: Effect of high temperature cross-linking process conditions on the viscoelasticity of the inventive gel

The operation was carried out according to Example 1, wherein X ₁ , Y ₁ , X ₂ , and Y ₂ are shown in Table 8.

Table 8 Process conditions and gel properties of Comparative Examples 1 to 2

Combining Table 1 and Table 2, it can be seen that the gel strength of Examples 1-5 and 1-8 to 1-12 is increased by 44.1% to 376.5% relative to that of Comparative Examples 1-1 to 1-4, and the gel strength of Examples 1-5 and 1-8 to 1-12 is increased by 210.3% to 1718% relative to that of Comparative Examples 2-1 to 2-4; from the results in Table 2, it can be seen that the gels prepared in Comparative Examples 1-1 to 1-4 have improved gel strength as the reaction time increases, and compared with Example 1, the overall strength is low and the degree of crosslinking is also lower; the gels prepared in Comparative Examples 2-1 to 2-4 have increased crosslinking degrees and are yellow-brown in color, but the gel strength is reduced more than that in Example 1.

Comparative Example 3: Preparation of HA/CS cross-linked gel by high temperature followed by low temperature process

This comparative example investigates the changes in the viscoelasticity of the gel under the same sodium hyaluronate concentration, molecular weight, ratio of sodium hyaluronate to chondroitin sulfate, amount of cross-linking agent and alkaline conditions as in Example 1, with reference to the gel preparation process of patent CN112812330B, and investigates the changes in the viscoelasticity of the gel after the sample is first reacted at a cross-linking reaction temperature of 40°C for 3h and then the gel is transferred to 10°C for reaction for 24h/48h.

Table 9 Process conditions and gel properties of comparative example 3

The preparation of HA/CS cross-linked gel by high temperature first and then low temperature process can improve gel strength and cross-linking degree, but the raw material degradation data shows that high temperature first will destroy the chain length of HA macromolecular chain and break it into shorter chains. The elastic modulus of the gel prepared by this method has no advantage over the elastic modulus of the gel prepared by low temperature for 24h/48h and then high temperature cross-linking for 3h, but it loses the advantage of high molecular weight of the molecule, which will affect the stability and durability of the product during use.

Claims (10)

1. A method for preparing a polysaccharide sodium hyaluronate composite gel, characterized in that it comprises the following steps: dissolving sodium hyaluronate in a sodium hydroxide aqueous solution, adding a low molecular weight polysaccharide, and then adding a cross-linking agent, first reacting at temperature A for 24h to 72h, and then cross-linking reacting at temperature B for 1h to 6h to prepare a polysaccharide sodium hyaluronate composite gel; wherein the low molecular weight polysaccharide is one or more of sodium hyaluronate, chondroitin sulfate, chondroitin, heparin and cellulose; the temperature A is 0°C to 20°C; the temperature B is 25°C to 50°C. 2. The preparation method according to claim 1, characterized in that: the temperature A is 5°C to 15°C; and/or the temperature B is 25°C to 45°C. 3. The preparation method according to claim 1 is characterized in that the reaction is carried out at temperature A for 36 hours to 60 hours, and/or the cross-linking reaction is carried out at temperature B for 2 hours to 5 hours. 4. The preparation method according to claim 1, characterized in that the low molecular weight polysaccharide is one or more of sodium hyaluronate, chondroitin sulfate and chondroitin. 5. The preparation method according to claim 1, characterized in that the cross-linking agent is one of 1,4-butanediol diglycidyl ether, 1-(2,3-epoxypropyl)-2,3-epoxycyclohexane and 1,2-ethylene glycol diglycidyl ether. 6. The preparation method according to claim 1, characterized in that it comprises at least one of the following conditions: The mass ratio of sodium hyaluronate to low molecular weight polysaccharide is (1-9):1; The molecular weight of the sodium hyaluronate is 1×10 ⁶ to 3×10 ⁶ Da; The molecular weight of the low molecular weight polysaccharide is 1×10 ⁴ to 6×10 ⁵ Da; The mass concentration of the sodium hydroxide aqueous solution is 0.5wt% to 3wt%; The mass concentration of the sodium hyaluronate in the sodium hydroxide aqueous solution is 10wt% to 30wt%; The mass ratio of the cross-linking agent to the total amount of sodium hyaluronate and low-molecular polysaccharide is 1:(5-50). 7. The preparation method according to claim 1, characterized in that it comprises at least one of the following conditions: The mass ratio of sodium hyaluronate to low molecular weight polysaccharide is (1-6):1; The molecular weight of the sodium hyaluronate is 2×10 ⁶ to 3×10 ⁶ Da; The molecular weight of the low molecular weight polysaccharide is 2×10 ⁴ to 4×10 ⁵ Da; The mass concentration of the sodium hydroxide aqueous solution is 0.5wt% to 2wt%; The mass concentration of the sodium hyaluronate in the sodium hydroxide aqueous solution is 12wt% to 25wt%; The mass ratio of the cross-linking agent to the total amount of sodium hyaluronate and low-molecular polysaccharide is 1:(5-40). 8. The preparation method according to any one of claims 1 to 7, characterized in that it also includes: cutting the obtained gel into small pieces, soaking them in a PBS buffer solution containing hydrochloric acid to neutralize the sodium hydroxide therein; then repeatedly replacing the PBS buffer solution until the gel pieces are colorless; then sieving the gel through a 160-mesh sieve, and then mechanically homogenizing to prepare a polysaccharide sodium hyaluronate composite gel product; in the gel product, the total concentration of polysaccharide and sodium hyaluronate is 20 mg/mL to 30 mg/mL; the PBS buffer solution is prepared from sodium chloride, disodium hydrogen phosphate, sodium dihydrogen phosphate, hydrochloric acid and water, and has a pH of 6.5 to 7.5. 9. The preparation method according to any one of claims 1 to 5, characterized in that it comprises: Sodium hyaluronate is dissolved in a 0.5wt%-2wt% sodium hydroxide aqueous solution, chondroitin sulfate is added, and then a cross-linking agent 1,4-butanediol diglycidyl ether is added, and the mixture is first reacted at 5°C to 15°C for 48h to 72h, and then cross-linked at 25°C to 45°C for 2h to 5h to obtain a gel; wherein the mass concentration of the sodium hyaluronate in the sodium hydroxide aqueous solution is 12wt% to 20wt%; the mass ratio of the sodium hyaluronate to the chondroitin sulfate is (1 to 4):1; the mass ratio of the cross-linking agent to the sum of the sodium hyaluronate and the low molecular weight polysaccharide is 1:(10 to 25); the molecular weight of the sodium hyaluronate is 2×10 ⁶ Da to 2.5×10 ⁶ Da; the molecular weight of the chondroitin sulfate is 3×10 ⁴ Da to 1×10 ⁵ Da; The obtained gel is cut into small pieces, and soaked in PBS buffer solution to neutralize the sodium hydroxide therein; then the PBS buffer solution is repeatedly replaced until the gel pieces are colorless; then the gel is sieved into small gel particles through a 160-mesh sieve, and then mechanically homogenized to prepare a polysaccharide sodium hyaluronate composite gel product; in the gel product, the total concentration of polysaccharide and sodium hyaluronate is 20 mg/mL to 30 mg/mL; the PBS buffer solution is prepared from sodium chloride, disodium hydrogen phosphate, sodium dihydrogen phosphate, hydrochloric acid and water, and has a pH of 6.5 to 7.5. 10. The preparation method according to any one of claims 1 to 5, characterized in that it comprises: Sodium hyaluronate is dissolved in a 1wt% sodium hydroxide aqueous solution, chondroitin sulfate is added, and then a cross-linking agent 1,4-butanediol diglycidyl ether is added, and the mixture is first reacted at 8°C to 12°C for 48h to 72h, and then cross-linked at 30°C to 40°C for 2h to 5h to obtain a gel; wherein the mass concentration of the sodium hyaluronate in the sodium hydroxide aqueous solution is 16wt% to 20wt%; the mass ratio of the sodium hyaluronate to the chondroitin sulfate is 4:1; the mass ratio of the cross-linking agent to the sum of the sodium hyaluronate and the low molecular weight polysaccharide is 1:(10-15); the molecular weight of the sodium hyaluronate is (2-2.5)×10 ⁶ Da; the molecular weight of the chondroitin sulfate is (3-7)×10 ⁴ Da; The obtained gel is cut into small pieces, and soaked in a PBS buffer solution with a pH of 6.5 to 7.0 containing hydrochloric acid to neutralize the sodium hydroxide therein; then the PBS buffer solution is repeatedly replaced until the gel pieces are colorless; then the gel is sieved into small gel particles through a 160-mesh sieve, and then mechanically homogenized to prepare a polysaccharide sodium hyaluronate composite gel product; in the gel product, the total concentration of polysaccharide and sodium hyaluronate is 20 mg/mL to 25 mg/mL; the PBS buffer solution is prepared from sodium chloride, disodium hydrogen phosphate, sodium dihydrogen phosphate, hydrochloric acid and water; the pH of the replacement PBS buffer solution is 6.5 to 7.5.