A cross-linking method of sodium hyaluronate gel for injection

Abstract

The application provides a cross-linking method of a hyaluronic acid sodium gel for injection, and comprises the following steps: S1, uniformly dispersing two kinds of dry hyaluronic acid sodium powders with different molecular weights in an alkaline solution to obtain an alkaline hyaluronic acid sodium solution; S2, adding a cross-linking agent and a phase transfer catalyst to the alkaline hyaluronic acid sodium solution in the step S1, uniformly mixing and stirring for 15-30 min, and performing incubation reaction at 40-45 DEG C for 2-3 h to obtain a mixture; S3, adding a secondary cross-linking agent to the mixture in the step S2, adding dilute acid to adjust pH, and performing reaction at 20-25 DEG C for 2-3 d, then performing filtration, washing and drying to obtain a powdery solid, and collecting the powdery solid after sieving; S4, adding water for injection, swelling under high pressure, collecting the particles after swelling, and obtaining the hyaluronic acid sodium gel for injection; and the cross-linking system formed by polypropylene glycol diglycidyl ether or polyethylene glycol diacrylate and EDC is selected, so that a more stable cross-linking structure is formed between hyaluronic acid sodium molecules, and the stability and biocompatibility are improved.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of medical cosmetic materials, and particularly relates to a cross-linking method of sodium hyaluronate gel for injection. BACKGROUND

[0002] The domestic medical cosmetic industry has experienced the stages of infancy, exploration, growth and maturity, and is currently in the stage of gradual standardization development with the help of the Internet era. Among them, the gel used for medical cosmetic surgery is a relatively common medical cosmetic material. The commonly used gels at present include various materials, such as silicone rubber, polytetrafluoroethylene and other implant filling materials, and collagen and hyaluronic acid and other injectable filling materials.

[0003] The linear molecular chain of sodium hyaluronate contains multiple hydroxyl groups and multiple carboxyl groups, and can be cross-linked by selecting a suitable cross-linking agent such as glutaraldehyde, epoxy ether, carbodiimide, etc. When the amount of cross-linking agent used is small, the cross-linking density is not enough, and the prepared cross-linked sodium hyaluronate gel has a short existence period in the body. When the amount of cross-linking agent used is large, although the three-dimensional network structure formed is very tight, the in-vivo degradation time is prolonged, but the prepared cross-linked sodium hyaluronate gel has a hard texture and poor swelling capacity, which reduces its injectability. At the same time, after the cross-linking of sodium hyaluronate is completed, part of the unreacted (including single-end un-bonded and both-end un-bonded) cross-linking agent may be covered in the three-dimensional network structure, affecting its biocompatibility and causing rejection reaction in the human body.

[0004] The commonly used cross-linking agent at present is 1,4-butanediol diglycidyl ether (BDDE), which can better cross-link with sodium hyaluronate. However, the design specification of BDDE in the finished product cannot be regenerated, and the presence of free BDDE may cause potential harm, especially for gel materials for injection. Any BDDE molecule that is not cross-linked with sodium hyaluronate or water in the reaction may have a toxic risk. At the same time, the addition amount of BDDE also has a certain influence on double cross-linking.

[0005] Therefore, the related technology about the cross-linking method of sodium hyaluronate gel in the prior art still needs to be further improved. SUMMARY

[0006] Therefore, the present application provides a cross-linking method of sodium hyaluronate gel for injection, which solves the technical problems of poor cross-linking stability, low biocompatibility, poor injection effect and short maintenance time in the prior art.

[0007] The technical scheme of the present application is as follows:

[0008] On the one hand, the present application provides a cross-linking method of sodium hyaluronate gel for injection, comprising the following steps:

[0009] S1, uniformly dispersing two different molecular weight sodium hyaluronate dry powders in an alkaline solution to obtain a sodium hyaluronate alkaline solution;

[0010] S2, adding a crosslinking agent and a phase transfer catalyst to the sodium hyaluronate alkaline solution in step S1, uniformly mixing and stirring for 15-30 min, and incubating at 40-45℃ for 2-3h to obtain a mixture;

[0011] S3, adding a secondary crosslinking agent to the mixture in step S2, and then adding dilute acid to adjust pH, and reacting at 20-25℃ for 2-3d, and then filtering, washing, and drying to obtain a powder solid, and collecting the sieved powder;

[0012] S4, adding water for injection, swelling under high pressure, and collecting the swelled particles to obtain the sodium hyaluronate gel for injection.

[0013] On the basis of this technical solution, further preferably, the crosslinking agent in step S2 is polypropylene glycol diglycidyl ether or polyethylene glycol diacrylate.

[0014] On the basis of this technical solution, further preferably, the phase transfer catalyst in step S2 includes one of benzyltrimethylammonium hydroxide, benzyltriethylammonium chloride, tetrabutylammonium bromide, tetrabutylammonium chloride, tetrabutylammonium hydrogen sulfate, trioctylmethylammonium chloride, dodecyltrimethylammonium chloride, and tetradecyltrimethylammonium chloride.

[0015] On the basis of this technical solution, further preferably, the mass ratio of the sodium hyaluronate dry powder, the crosslinking agent, and the phase transfer catalyst is 1:(4.2-6):(1-3).

[0016] On the basis of this technical solution, further preferably, the molecular weight of the sodium hyaluronate dry powder is 200000-900000Da and 1000000-3000000Da, respectively.

[0017] On the basis of this technical solution, further preferably, the pH of the alkaline solution is 10-14, and the alkaline solution is prepared from 0.4-0.5M sodium hydroxide solution and acetone, and the volume ratio of the sodium hydroxide solution to acetone is 3 / 7-2 / 3.

[0018] On the basis of this technical solution, further preferably, the secondary crosslinking agent in step S3 is 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide (EDC).

[0019] On the basis of this technical solution, further preferably, the mass ratio of the secondary crosslinking agent to the mixture is (0.4-1.7):1.

[0020] Further preferably, the dilute acid in step S3 comprises dilute hydrochloric acid, acetic acid or citric acid, and the pH is adjusted to 2-4.5.

[0021] Further preferably, the high pressure in step S4 is 300-303 kPa.

[0022] Compared with the prior art, the cross-linking method for the hyaluronic acid sodium gel for injection provided by the application has the following beneficial effects:

[0023] The conventional hyaluronic acid sodium filler has unstable cross-linking degree, which may result in inconsistent filling effect and short maintenance time; and when the existing BDDE is used as a cross-linking agent, the dosage needs to be strictly controlled, and the residual BDDE molecules may be harmful to the human body; therefore, the application selects polypropylene glycol diglycidyl ether or polyethylene glycol diacrylate to replace BDDE, and forms a cross-linking system together with EDC, so as to accurately control the amount of the cross-linking agent and the strict cross-linking reaction conditions, and to form a more stable cross-linking structure between the hyaluronic acid sodium molecules, thereby improving the stability of the filler in the dermis layer and ensuring that the filling effect is long-lasting and uniform.

[0024] In addition, a double cross-linking process is also adopted, that is, the primary cross-linking is performed under alkaline conditions, and the secondary cross-linking is performed under acidic conditions. The double cross-linking process can significantly improve the cross-linking degree of the hyaluronic acid sodium, and enhance the mechanical strength, stability and biocompatibility thereof; the alkaline cross-linking with the pH controlled to 10-14 can form a relatively close cross-linking network, and improve the strength and stability of the gel; and the acidic cross-linking with the pH controlled to 2-4.5 can further modify the cross-linking structure, and increase the biological activity and adaptability thereof.

[0025] Finally, the method also comprises post-treatment to remove impurities, improve the purity and safety of the product, and ensure that the product meets the standards of medical cosmetology; and by accurately controlling the reaction conditions and parameters, products with different properties can be produced to meet the individual needs. BRIEF DESCRIPTION OF DRAWINGS

[0026] In order to more clearly illustrate the technical solutions in the embodiments of the application or the prior art, the following will briefly introduce the drawings needed to be used in the embodiments or the prior art description. Obviously, the drawings in the following description are only some embodiments of the application, and other drawings can also be obtained by those skilled in the art without any creative effort on the basis of these drawings.

[0027] Figure 1 The particle size distribution diagram of the hyaluronic acid sodium gel for injection prepared in Embodiment 1 of the application;

[0028] Figure 2A particle distribution diagram of the sodium hyaluronate gel for injection prepared in Embodiment 2 of the present application under a microscope;

[0029] Figure 3 A test diagram of injection pushing force of the sodium hyaluronate gel for injection prepared in Embodiment 1 of the present application. DETAILED DESCRIPTION

[0030] The technical solutions in the embodiments of the present application will be clearly and completely described in combination with the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments of the present application, all other embodiments obtained by those skilled in the art without creative labor fall within the scope of protection of the present application.

[0031] The present application provides a cross-linking method of a sodium hyaluronate gel for injection, which adopts a specific proportion of sodium hydroxide solution, acetone and sodium hyaluronate dry powder to form a sodium hyaluronate acetone alkaline solution. This unique mixed solution provides a suitable chemical environment for the subsequent cross-linking reaction, helps to promote the progress of the cross-linking reaction, and also improves the selectivity and efficiency of the reaction; compared with the traditional single solvent system, the mixed solution can better disperse sodium hyaluronate, so that it fully contacts with the cross-linking agent and catalyst, thereby improving the cross-linking effect.

[0032] Embodiment 1

[0033] A cross-linking method of a sodium hyaluronate gel for injection, comprising the following steps:

[0034] S1, uniformly dispersing 0.2g of sodium hyaluronate dry powder with a molecular weight of 900000Da and 0.5g of sodium hyaluronate dry powder with a molecular weight of 3000000Da in an alkaline solution to obtain a sodium hyaluronate alkaline solution;

[0035] Specifically, the pH of the alkaline solution is 13, which is prepared from 90mL of 0.5M sodium hydroxide solution and 210mL of acetone.

[0036] S2, adding polypropylene glycol diglycidyl ether and a phase transfer catalyst to the sodium hyaluronate alkaline solution in step S1, uniformly mixing and stirring for 15min, and incubating at 45℃ for 2h to obtain a mixture;

[0037] Specifically, the phase transfer catalyst in step S2 is benzyltrimethylammonium hydroxide; and the mass ratio of the sodium hyaluronate dry powder, the cross-linking agent and the phase transfer catalyst is 1:4.2:1.

[0038] Polypropylene glycol diglycidyl ether and EDC were chosen as cross-linking agents, which have high cross-linking ability and can react with sodium hyaluronate molecules under relatively mild conditions to form stable cross-linked structures.

[0039] In addition, a quaternary ammonium salt phase transfer catalyst is introduced, which can promote the transfer of the cross-linking agent between different phases, improve the reaction rate and cross-linking uniformity. Compared with traditional catalysts, it has higher catalytic activity and selectivity, can effectively reduce the reaction temperature and time, and improve the production efficiency.

[0040] S3, add a secondary cross-linking agent to the mixture in step S2, and add dilute acid to adjust the pH, react at 25°C for 2d, filter, wash and dry to obtain a powdery solid, and collect the sieved particles;

[0041] Specifically, the secondary cross-linking agent in step S3 is EDC, and the mass ratio of the secondary cross-linking agent EDC to the mixture is 0.4:1. The dilute acid in step S3 is dilute hydrochloric acid, and the pH is adjusted to 2. At this time, the acidic environment and the acidic cross-linking can further modify the cross-linked structure, which can significantly improve the cross-linking degree of sodium hyaluronate, and enhance the mechanical strength, stability and biocompatibility.

[0042] S4, add water for injection, swell under high pressure of 303kPa, collect the swollen particles to obtain the sodium hyaluronate gel for injection.

[0043] Results: Figure 1 The particle size distribution diagram of the sodium hyaluronate gel for injection prepared in Example 1 shows that the hydrogel after double cross-linking with polypropylene glycol diglycidyl ether and EDC has a uniform three-dimensional structure, the pore size is close, and the compatibility is good.

[0044] Example 2

[0045] A cross-linking method of a sodium hyaluronate gel for injection, comprising the following steps:

[0046] S1, uniformly disperse 0.5g of sodium hyaluronate dry powder with a molecular weight of 200000Da and 0.8g of sodium hyaluronate dry powder with a molecular weight of 3000000Da in an alkaline solution to obtain an alkaline sodium hyaluronate solution;

[0047] Specifically, the pH of the alkaline solution is 13, which is prepared from 120mL of 0.4M sodium hydroxide solution and 180mL of acetone.

[0048] S2, add polypropylene glycol diglycidyl ether and a phase transfer catalyst to the sodium hyaluronate alkaline solution in step S1, mix and stir for 30min, and react at 40°C for 3h to obtain a mixture;

[0049] Specifically, the phase transfer catalyst in step S2 is benzyltriethylammonium chloride; the mass ratio of the sodium hyaluronate dry powder, the crosslinking agent and the phase transfer catalyst is 1:6:3;

[0050] Polypropylene glycol diglycidyl ether and EDC are selected as the crosslinking agent, which has high crosslinking capacity and can react with sodium hyaluronate molecules under relatively mild conditions to form a stable crosslinking structure.

[0051] In addition, a quaternary ammonium salt phase transfer catalyst is introduced, which can promote the transfer of the crosslinking agent between different phases, improve the reaction rate and crosslinking uniformity. Compared with traditional catalysts, it has higher catalytic activity and selectivity, can effectively reduce the reaction temperature and time, and improve the production efficiency.

[0052] S3, adding a secondary crosslinking agent to the mixture in step S2, and then adding dilute acid to adjust the pH, reacting at 20℃ for 3d, filtering, washing and drying to obtain a powdery solid, and collecting the sieved particles;

[0053] Specifically, the secondary crosslinking agent in step S3 is EDC, and the mass ratio of the secondary crosslinking agent EDC to the mixture is 1.7:1. The dilute acid in step S3 is dilute hydrochloric acid, and the pH is adjusted to 4.5. At this time, the acidic environment can further modify the crosslinking structure, which can significantly improve the crosslinking degree of sodium hyaluronate, and enhance the mechanical strength, stability and biocompatibility.

[0054] S4, adding water for injection, swelling under high pressure of 303kPa, collecting the swollen particles to obtain the sodium hyaluronate gel for injection.

[0055] Results: Figure 2 The particle distribution diagram of the sodium hyaluronate gel for injection prepared in Example 2 under a microscope shows that the particle size distribution of the sodium hyaluronate gel is relatively narrow.

[0056] Example 3

[0057] A crosslinking method of a sodium hyaluronate gel for injection, comprising the following steps:

[0058] S1, uniformly dispersing 0.3g of sodium hyaluronate dry powder with a molecular weight of 900000Da and 0.7g of sodium hyaluronate dry powder with a molecular weight of 3000000Da in an alkaline solution to obtain an alkaline sodium hyaluronate solution;

[0059] Specifically, the pH of the alkaline solution is 13, which is prepared from 120mL of 0.4M sodium hydroxide solution and 180mL of acetone.

[0060] S2, the sodium hyaluronate alkaline solution in step S1 is added with polypropylene glycol diglycidyl ether and a phase transfer catalyst, uniformly stirred for 20 min, and reacted at 42℃ for 2.5 h to obtain a mixture;

[0061] Specifically, the phase transfer catalyst in step S2 is tetrabutylammonium chloride; the mass ratio of the sodium hyaluronate dry powder, the crosslinking agent and the phase transfer catalyst is 1:4.5:2;

[0062] Polypropylene glycol diglycidyl ether and EDC are selected as the crosslinking agent, which has high crosslinking capacity and can react with sodium hyaluronate molecules under relatively mild conditions to form a stable crosslinked structure.

[0063] In addition, a quaternary ammonium salt phase transfer catalyst is introduced, which can promote the transfer of the crosslinking agent between different phases, improve the reaction rate and crosslinking uniformity. Compared with traditional catalysts, it has higher catalytic activity and selectivity, can effectively reduce the reaction temperature and time, and improve the production efficiency.

[0064] S3, the mixture in step S2 is added with a secondary crosslinking agent, and then a dilute acid is added to adjust the pH, and reacted at 22℃ for 2d, filtered, washed and dried to obtain a powdery solid, which is collected by sieving;

[0065] Specifically, the secondary crosslinking agent in step S3 is EDC, and the mass ratio of the secondary crosslinking agent to the mixture is 0.8:1. The dilute acid in step S3 is citric acid, and the pH is adjusted to 4. At this time, the acidic environment can further modify the crosslinked structure, which can significantly improve the crosslinking degree of sodium hyaluronate, and enhance its mechanical strength, stability and biocompatibility.

[0066] S4, injectable water is added, and the mixture is swelled under high pressure of 302kPa, and the swelled particles are collected to obtain the injectable sodium hyaluronate gel.

[0067] Example 4

[0068] A crosslinking method of an injectable sodium hyaluronate gel, comprising the following steps:

[0069] S1, 0.2g of sodium hyaluronate dry powder with a molecular weight of 900000Da and 0.8g of sodium hyaluronate dry powder with a molecular weight of 3000000Da are uniformly dispersed in an alkaline solution to obtain a sodium hyaluronate alkaline solution;

[0070] Specifically, the pH of the alkaline solution is 13, which is prepared from 90mL of 0.5M sodium hydroxide solution and 210mL of acetone.

[0071] S2, the sodium hyaluronate alkaline solution in step S1 is added with polyethylene glycol diacrylate and a phase transfer catalyst, mixed and stirred for 20 min, and reacted at 45°C for 2 h to obtain a mixture;

[0072] Specifically, the phase transfer catalyst in step S2 is benzyltrimethylammonium hydroxide; the mass ratio of the sodium hyaluronate dry powder, the crosslinking agent and the phase transfer catalyst is 1:4.4:1.5;

[0073] Polyethylene glycol diacrylate and EDC are selected as the crosslinking agent, which has high crosslinking ability and can react with sodium hyaluronate molecules under relatively mild conditions to form a stable crosslinked structure.

[0074] In addition, a quaternary ammonium salt phase transfer catalyst is introduced, which can promote the transfer of the crosslinking agent between different phases, improve the reaction rate and crosslinking uniformity. Compared with traditional catalysts, it has higher catalytic activity and selectivity, can effectively reduce the reaction temperature and time, and improve the production efficiency.

[0075] S3, the mixture in step S2 is added with a secondary crosslinking agent, and dilute acid is added to adjust the pH, and reacted at 25°C for 2 d, and then filtered, washed and dried to obtain a powdery solid, which is collected by sieving;

[0076] Specifically, the secondary crosslinking agent in step S3 is EDC, and the mass ratio of the secondary crosslinking agent to the mixture is 0.5:1. The dilute acid in step S3 is citric acid, and the pH is adjusted to 3. At this time, the acidic environment can further modify the crosslinked structure, which can significantly improve the crosslinking degree of sodium hyaluronate, and enhance its mechanical strength, stability and biocompatibility.

[0077] S4, injectable water is added, and the mixture is swelled under high pressure of 303 kPa, and then the swelled particles are collected to obtain the injectable sodium hyaluronate gel.

[0078] Comparative Example 1

[0079] A crosslinking method of an injectable sodium hyaluronate gel, which is different from Example 1 in that the crosslinking agent is BDDE.

[0080] Comparative Example 2

[0081] A crosslinking method of an injectable sodium hyaluronate gel, which is different from Example 1 in that the crosslinking agent is 1,4-butanediol diglycidyl ether.

[0082] Comparative Example 3

[0083] A crosslinking method of an injectable sodium hyaluronate gel, which is different from Example 1 in that no secondary crosslinking agent is added.

[0084] Comparative Example 4

[0085] A cross-linking method of a sodium hyaluronate gel for injection, which is different from Example 1 in that the pH of the basic solution in step S1 is 9 and the pH in step S3 is 5.

[0086] Comparative Example 5

[0087] A cross-linking method of a sodium hyaluronate gel for injection, which is different from Example 1 in that the mass ratio of the sodium hyaluronate dry powder, the cross-linking agent and the phase transfer catalyst is 1:0.8:1.

[0088] Quality test

[0089] The sodium hyaluronate gels obtained in each example and comparative example were tested for maintenance effect, adverse reaction and biocompatibility.

[0090] Maintenance effect and adverse reaction: 1 g of the sodium hyaluronate gel prepared in the present application was diluted to 100 mL of stock solution, and 9 adult healthy mice were selected as test objects, with a body weight of about 3 kg. After anesthesia, 1 mL of the stock solution was injected into the abdomen, and the mice were normally fed. The condition of the mice and the condition of the injection site within 72 h after injection were tested.

[0091] Table 1 Medical aesthetic material characterization test

[0092] Item Effect maintenance time / month Mouse condition Example 1 13 No adverse reaction Example 2 13 No adverse reaction Example 3 12 No adverse reaction Example 4 12 No adverse reaction Comparative Example 1 11 No adverse reaction Comparative Example 2 10 Slight swelling Comparative Example 3 10 Swelling Comparative Example 4 10 Swelling Comparative Example 5 11 Slight swelling

[0093] As can be seen from Table 1, the results of Example 1 and Comparative Examples 1-5 show that different cross-linking systems of cross-linking agents BDDE and EDC, or no secondary cross-linking, the pH environment during cross-linking, and the excess ratio of sodium hyaluronate dry powder and cross-linking agent all have different degrees of influence on the maintenance effect and adverse reaction of the finally prepared sodium hyaluronate gel. The reason may be that there is no suitable acidic environment to modify the cross-linked structure for secondary cross-linking. The cross-linking degree, mechanical strength, stability and biocompatibility of sodium hyaluronate are all decreased to different degrees. While polypropylene glycol diglycidyl ether and EDC as cross-linking agents have high cross-linking ability and can react with sodium hyaluronate molecules under relatively mild conditions to form stable cross-linked structures. Compared with existing BDDE, there may be free BDDE molecules reacting with water, which can produce certain toxicity to the test mice and cause adverse reactions.

[0094] Injection flow test, including the following steps:

[0095] I. Sample installation

[0096] Fix the syringe on the clamp, make sure the plunger head of the syringe is tightly connected with the push device, and the needle seat part of the syringe is closed (a suitable plug can be used) to prevent leakage. Connect the pressure sensor to the appropriate position of the push device so that the sensor can accurately measure the pressure during the push.

[0097] II. Set the push parameters

[0098] Set the push speed through the control interface of the push device. You can refer to the actual clinical injection scene, for example, set it to the commonly used injection speed, such as 30 mm / min. At the same time, make sure that the data acquisition system starts recording data and sets a suitable data recording interval, such as recording pressure values every 0.1 s.

[0099] III. Perform the push test

[0100] Start the push device and start pushing at the set speed. During the push, the data acquisition system will record the pressure changes measured by the pressure sensor in real time. Continue pushing until most of the sample in the syringe is pushed out, or the preset push volume is reached, while observing and recording the pressure change curve.

[0101] IV. Repeat the test

[0102] In order to ensure the accuracy and reliability of the data, multiple (for example, 3-5) repeated tests are performed on the same batch of samples. Before each test, make sure that the syringe is refilled and the system returns to the initial state. After each test, check whether the equipment and samples are normal. If there are abnormal conditions (such as sample leakage, equipment failure, etc.), the test data is invalid and needs to be retested.

[0103] Results: Figure 3 For the push force test of the sodium hyaluronate gel prepared in Example 1 of the present application, the push force is small and the injection is uniform, indicating that the gel prepared by the double crosslinking process has good compatibility.

[0104] In summary, the crosslinking method of the sodium hyaluronate gel for injection provided by the present application uses polypropylene glycol diglycidyl ether or polyethylene glycol diacrylate instead of BDDE to form a crosslinking system with EDC, and then combines a double crosslinking process to first crosslink under alkaline conditions and then crosslink again under acidic conditions. This double crosslinking process can significantly improve the crosslinking degree of sodium hyaluronate, enhance its mechanical strength, stability and biocompatibility, and solve the technical problems of poor crosslinking stability, low biocompatibility, poor injection effect and short maintenance time in the prior art.

[0105] The above merely provides the preferred embodiment of the present application, and is not used to limit the present application. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application shall be included in the protection scope of the present application.

Claims

1. A method for cross-linking of a sodium hyaluronate gel for injection, characterized in that, The method comprises the following steps: S1, uniformly dispersing two kinds of sodium hyaluronate dry powder with different molecular weights in an alkaline solution with pH of 10-14 to obtain an alkaline sodium hyaluronate solution; S2, adding a crosslinking agent and a phase transfer catalyst to the alkaline sodium hyaluronate solution in step S1, uniformly mixing and stirring for 15-30 min, and incubating at 40-45℃ for 2-3 h to obtain a mixture; S3, adding a secondary crosslinking agent to the mixture in step S2, and adding dilute acid to adjust the pH to 2-4.5, and reacting at 20-25℃ for 2-3 d under acidic conditions, and filtering, washing, and drying to obtain a powder solid, and collecting the sieved product; S4, adding water for injection, swelling under high pressure, and collecting the swelled particles to obtain the sodium hyaluronate gel for injection; The crosslinking agent in step S2 is polypropylene glycol diglycidyl ether or polyethylene glycol diacrylate; The phase transfer catalyst in step S2 is one of benzyltrimethylammonium hydroxide, benzyltriethylammonium chloride, tetrabutylammonium bromide, tetrabutylammonium chloride, tetrabutylammonium bisulfate, trioctylmethylammonium chloride, dodecyltrimethylammonium chloride, and tetradecyltrimethylammonium chloride; The mass ratio of the sodium hyaluronate dry powder, the crosslinking agent, and the phase transfer catalyst is 1:(4.2-6):(1-3); the secondary crosslinking agent in step S3 is 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide; The mass ratio of the secondary crosslinking agent to the mixture is (0.4-1.7):

1.

2. The cross-linking method of the sodium hyaluronate gel for injection according to claim 1, wherein The molecular weights of the sodium hyaluronate dry powder are 200000-900000 Da and 1000000-3000000 Da, respectively; The alkaline solution is prepared from 0.4-0.5 M sodium hydroxide solution and acetone, and the volume ratio of the sodium hydroxide solution to acetone is 3 / 7-2 / 3; The dilute acid in step S3 is one of dilute hydrochloric acid, acetic acid, and citric acid.

3. The cross-linking method of the sodium hyaluronate gel for injection according to claim 1, wherein The high pressure in step S4 is 300-303 kPa.

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