Hyaluronic acid-polylactic acid copolymer cross-linked gel, and preparation method therefor and use thereof

Abstract

The present disclosure relates to a hyaluronic acid-polylactic acid copolymer cross-linked gel, and a preparation method therefor and the use thereof. The method comprises the following steps: S1, changing the ions of hyaluronic acid by means of an ion exchange resin, adjusting the pH of a solution to 7.0 by using an alkaline reagent, and conducting freeze-drying, so as to obtain amphiphilic hyaluronic acid; S2, activating the carboxyl of polylactic acid by using a catalyst, so as to obtain carboxyl-activated polylactic acid; S3, subjecting the carboxyl-activated polylactic acid and the amphiphilic hyaluronic acid to an esterification reaction, and performing dialyzing and freeze-drying, so as to obtain a hyaluronic acid-polylactic acid copolymer; and S4, placing the hyaluronic acid-polylactic acid copolymer in an alkaline solvent, subjecting same to a cross-linking reaction under the action of a cross-linking agent, and performing swelling with a PBS buffer solution, so as to obtain a hyaluronic acid-polylactic acid copolymer cross-linked gel. Compared with a single hyaluronic acid gel and polylactic acid, by grafting polylactic acid onto a molecular chain of hyaluronic acid, not only is the degradation time of the cross-linked gel prolonged, but the hydrophilic performance of the polylactic acid is also improved.

Description

Hyaluronic acid-polylactic acid copolymer cross-linked gel, preparation method and application thereof TECHNICAL FIELD

[0001] The present disclosure relates to the technical field of biomaterials, in particular to a hyaluronic acid-polylactic acid copolymer cross-linked gel, a preparation method and application thereof. BACKGROUND

[0002] Facial aging (such as the appearance of wrinkles, dry skin, and dark pigmentation, etc.) is a complex process, not only affected by internal conditions such as the rupture of tissue fibers such as collagen and elastin, the loss of hyaluronic acid and moisture, etc., but also by external environmental factors such as air environment, living habits and bacterial diseases, etc.

[0003] Hyaluronic acid (HA) is a natural biological macromolecule composed of D-glucuronic acid and N-acetyl amino-D-glucose, and widely exists in various parts of the human body such as skin, joints, blood, etc., has excellent functions such as maintaining moisture, improving skin elasticity and signal transmission, and is widely used in skin anti-aging products.

[0004] Filling type hyaluronic acid is one of the main types of hyaluronic acid products, by injecting hyaluronic acid gel into the dermis of the skin, it can enhance skin elasticity, supplement moisture, and thus achieve the purpose of improving skin condition. Filling type hyaluronic acid has short operation time and significant effect, and is the mainstream product in the field of medical beauty filling at present. However, the traditional filling type hyaluronic acid gel still has the shortcomings of weak supporting performance, fast degradation speed, short maintenance time, etc.

[0005] Polylactic acid (PLA) is a biodegradable polymer material approved by the U.S. Food and Drug Administration (FDA) for use in the human body, which is polymerized from lactic acid. Polylactic acid is first decomposed into oligomeric lactic acid in the human body, and further decomposed into lactic acid, which is involved in human metabolism, and is degraded into carbon dioxide and water and excreted outside the body. As an injection material filled into the dermis of the human body, polylactic acid can stimulate fibroblasts to produce collagen, thereby improving facial volume and achieving the purpose of regenerative filling. However, polylactic acid has strong hydrophobic properties and is difficult to dissolve in water, and direct injection into the human body can cause immune reactions, causing redness, inflammation and other adverse phenomena.

[0006] Many existing technologies combine hyaluronic acid and polylactic acid to obtain anti-aging filling products with better effects.

[0007] CN117085178A discloses a kind of injection type cosmetic plastic face filling agent composition and its preparation method, which adds left-handed polylactic acid and right-handed polylactic acid to hyaluronic acid solution respectively, forms gel by self-crosslinking using the physical action between left-handed polylactic acid and right-handed polylactic acid.This method although prolongs the degradation time of hyaluronic acid, but the gel formed by self-crosslinking has poor stability, weak mechanical properties and fast degradation rate.

[0008] CN110964215A discloses a preparation method of injection left-handed polylactic acid and crosslinked hyaluronic acid composite gel, which obtains lyophilized material by adding polylactic acid to hyaluronic acid solution, and prepares composite gel by secondary crosslinking, but it is difficult to disperse uniformly in aqueous solution and easy to agglomerate due to the poor hydrophilic property of polylactic acid, which may cause needle blockage.

[0009] CN117024770A discloses a preparation method of modified polylactic acid microspheres and sodium hyaluronate mixed gel, which first modifies polylactic acid microspheres with nicotinamide, and then mixes the modified polylactic acid microspheres with hyaluronic acid solution to obtain gel, which increases the hydrophilicity of polylactic acid to some extent, but injecting nicotinamide into the body may cause skin irritation, redness, itching and other phenomena, and the degradation rate of hyaluronic acid solution in the body is fast, without obvious filling and shaping effect. SUMMARY

[0010] The purpose of the present disclosure is to provide a stable and biologically safe skin anti-aging filler.

[0011] To achieve the above purpose, the present disclosure provides a preparation method of hyaluronic acid-polylactic acid copolymer crosslinked gel, comprising the following steps:

[0012] S1. Change the ion of hyaluronic acid by ion exchange resin, adjust the pH of the solution to 7.0 with alkaline reagent, and freeze-dry to obtain amphiphilic hyaluronic acid with the following structure

[0013] S2. Use a catalyst to activate the carboxyl group of polylactic acid to obtain carboxyl-activated polylactic acid;

[0014] S3. The carboxyl-activated polylactic acid and the amphiphilic hyaluronic acid undergo esterification reaction, and after dialysis and freeze-drying, hyaluronic acid-polylactic acid copolymer with the following structure is obtained

[0015] S4. The hyaluronic acid-polylactic acid copolymer is placed in an alkaline solvent and undergoes crosslinking reaction under the action of a crosslinking agent, and after swelling with PBS buffer solution, a hyaluronic acid-polylactic acid copolymer crosslinked gel is obtained.

[0016] Preferably, the molecular weight of the polylactic acid is 5,000-200,000 Da;

[0017] The polylactic acid is selected from one of poly-L-lactic acid, poly-D-lactic acid, racemic polylactic acid or polyethylene glycol modified polylactic acid.

[0018] Preferably, in the reaction system of step S2, the catalyst comprises at least one of N-(3-dimethylaminopropyl)-ethyl carbodiimide, dicyclohexyl carbodiimide, 4-dimethylamino pyridine and N-hydroxy succinimide, and the solvent used comprises dichloromethane or trichloromethane.

[0019] More preferably, the catalyst is N-hydroxy succinimide and N-(3-dimethylaminopropyl)-ethyl carbodiimide;

[0020] The mass ratio of the polylactic acid, the N-hydroxy succinimide and the N-(3-dimethylaminopropyl)-ethyl carbodiimide is 1:0.01:0.01 to 1:5:5, the reaction temperature is 25-50℃, and the reaction time is 8-48h.

[0021] Preferably, in the reaction system of step S3, the solvent used comprises dimethyl sulfoxide, the mass ratio of the carboxyl-activated polylactic acid to the amphiphilic hyaluronic acid is 1:0.01 to 1:5, the reaction temperature is 40-60℃, the reaction time is 8-24h, and the dialysis time is 2-5 days.

[0022] Preferably, in step S1, the molecular weight of the hyaluronic acid is 20,000-2,000,000 Da, the ion exchange resin is a cation exchange resin, the treatment time is 18-36h, and the basic reagent comprises a tetrabutylammonium hydroxide solution.

[0023] Preferably, the basic reagent comprises a 1% sodium hydroxide solution by mass fraction, and the composition of the PBS buffer solution comprises sodium chloride, disodium hydrogen phosphate and sodium dihydrogen phosphate monohydrate;

[0024] The mass ratio of the hyaluronic acid-polylactic acid copolymer to the crosslinking agent is 1:0.01 to 1:0.5, the crosslinking temperature is 25-50℃, the crosslinking time is 12-48h, and the swelling time is 12-72h.

[0025] The crosslinking agent comprises 1,4-butanediol diglycidyl ether, divinyl sulfone, ethylene glycol diglycidyl ether, 1,6-hexanediol diglycidyl ether or diethylene glycol diglycidyl ether.

[0026] To achieve the above-mentioned purposes, the present disclosure further provides a hyaluronic acid-polylactic acid copolymer crosslinked gel obtained according to any one of the above-mentioned preparation methods.

[0027] Preferably, the cross-linked gel comprises the following chemical structure:

[0028] To achieve the above object, the present disclosure further provides an application of the cross-linked gel according to any one of the preceding embodiments, which is applied in a facial filler.

[0029] The technical solution claimed in the present disclosure has the following beneficial effects:

[0030] The hyaluronic acid-polylactic acid copolymer cross-linked gel in the present disclosure prolongs the degradation time of the cross-linked gel by extending the molecular chain through grafting polylactic acid onto the molecular chain of hyaluronic acid, and compared with a single hyaluronic acid gel, the hyaluronic acid grafted with polylactic acid has a stronger effect of stimulating the regeneration of human collagen. Moreover, hyaluronic acid is a natural macromolecule and has no immune response. The polylactic acid is connected to the hyaluronic acid through covalent action, which reduces the hydrophobic property of the polylactic acid, and the polylactic acid can be degraded into carbon dioxide and water in the body, and has high biological safety. BRIEF DESCRIPTION OF DRAWINGS

[0031] In order to more clearly illustrate the technical solutions in the embodiments of the present disclosure, the drawings needed in the embodiment description will be briefly introduced as follows.

[0032] FIG. 1 is an infrared spectrum result of HA, PLLA and HA-g-PLLA.

[0033] FIG. 2 is a morphology diagram of the cross-linked gel prepared from HA-g-PLLA. DETAILED DESCRIPTION

[0034] In order to make the object, technical solutions and beneficial effects of the embodiments in the present disclosure more clear, the technical solutions in the embodiments of the present disclosure will be clearly and completely described below in combination with the drawings in the embodiments of the present disclosure. Obviously, the described embodiments are part of the embodiments of the present disclosure, rather than all the embodiments. Based on the embodiments in the present disclosure, all other embodiments obtained by those skilled in the art without creative labor are within the protection scope of the present disclosure.

[0035] Embodiment 1

[0036] The present embodiment provides a preparation method of a hyaluronic acid-polylactic acid copolymer cross-linked gel, comprising the following steps:

[0037] S1. Preparation of amphiphilic hyaluronic acid: the ion of sodium hyaluronate is changed by using ion exchange resin, and the pH is adjusted to neutral by using an alkaline reagent, and then the amphiphilic hyaluronic acid (HA-TBA) is obtained after freeze-drying, and the chemical structural formula is as follows:

[0038] In this step, the molecular weight of sodium hyaluronate is preferably 20,000-2,000,000 Da, the ion exchange resin is a cation exchange resin, the treatment time is 18-36 h, and the basic reagent is a tetrabutylammonium hydroxide solution.

[0039] S2. Activation of carboxyl group of polylactic acid: polylactic acid is dissolved in an organic solvent, and a catalyst is added to activate the carboxyl group, and the reaction chemical equation is as follows:

[0040] In this step, the polylactic acid is poly-L-lactic acid (PLLA), poly-D-lactic acid (PDLA), racemic polylactic acid (PDLLA), polyethylene glycol (PEG)-modified polylactic acid (PLA), including polyethylene glycol-modified L-lactic acid (PLLA-PEG), polyethylene glycol-modified D-lactic acid (PDLA-PEG), and polyethylene glycol-modified racemic polylactic acid (PDLLA-PEG). The molecular weight of polylactic acid is preferably 5,000-200,000 Da, the organic solvent is dichloromethane or trichloromethane, preferably dichloromethane;

[0041] The catalyst used in this step is N-(3-dimethylaminopropyl)-ethyl carbodiimide (EDC), dicyclohexyl carbodiimide (DCC), 4-dimethylaminopyridine (DMAP), or N-hydroxysuccinimide (NHS), preferably N-(3-dimethylaminopropyl)-ethyl carbodiimide (EDC) and N-hydroxysuccinimide (NHS). Among them, the mass ratio of polylactic acid, EDC and NHS is 1:0.01:0.01 to 1:5:5, the reaction temperature is 25-50°C, and the reaction time is 8-48 h.

[0042] S3. Preparation of hyaluronic acid-polylactic acid copolymer: the substances obtained in steps S1 and S2 are blended to prepare a copolymer, which is dialyzed and lyophilized to obtain a solid copolymer (HA-g-PLA), and the reaction process is as follows:

[0043] In this step, the mass ratio of hyaluronic acid to polylactic acid is 1:0.01 to 1:5, the blending solvent used is dimethyl sulfoxide (DMSO), the reaction temperature is 40-60°C, the catalyst is diethylamine, the time is 8-24 h, and the dialysis time required for the copolymer is 2-5 days.

[0044] S4. Preparation of hyaluronic acid-polylactic acid copolymer cross-linked gel: the solid copolymer in step S3 is dissolved in an alkaline solution, a cross-linking agent is added, and after uniform mixing, it is left to stand for 12-48 h, and then swelled in a PBS buffer solution to obtain a hyaluronic acid-polylactic acid copolymer cross-linked gel.

[0045] In this step, the basic solution is a 1% mass fraction sodium hydroxide solution, and the crosslinking agent is one of 1,4-butanediol diglycidyl ether (BDDE), divinyl sulfone, ethylene glycol diglycidyl ether, 1,6-hexanediol diglycidyl ether, and diethylene glycol diglycidyl ether, preferably 1,4-butanediol diglycidyl ether;

[0046] In a preferred embodiment, the mass ratio of hyaluronic acid-polylactic acid copolymer to crosslinking agent is 1:0.01 to 1:0.5, the crosslinking temperature is preferably 25-50°C, and the reaction time is preferably 18-36h. The composition of the PBS buffer solution is sodium chloride, disodium hydrogen phosphate, and sodium dihydrogen phosphate monohydrate, and the swelling time is 72h.

[0047] The scheme in Example 1 is further described in detail below in combination with a specific application example.

[0048] Application Example 1

[0049] The application example provides a preparation method of an injectable hyaluronic acid-polylactic acid copolymer crosslinked gel, comprising the following steps:

[0050] S1. Preparation of amphiphilic hyaluronic acid: 2g of sodium hyaluronate with a molecular weight of 1,600,000 Da is weighed to prepare a 2% hyaluronic acid solution. The sodium hyaluronate solution is soaked in a cation exchange resin for 24h, the pH of the HA solution is adjusted to 7.0 with a tetrabutylammonium hydroxide solution, and after freeze-drying, an amphiphilic hyaluronic acid solid (HA-TBA) is obtained;

[0051] S2. Activation of polylactic acid carboxyl group: 5g of poly-L-lactic acid with a molecular weight of 10,000 Da is dissolved in dichloromethane with 191.70mg of EDC and 115.09mg of NHS, 25°C, reaction for 24h, and vacuum drying to obtain carboxyl-activated polylactic acid (PLLA-NHS);

[0052] S3. Preparation of hyaluronic acid-polylactic acid copolymer: 600mg of HA-TBA in S1 and 21.6mg of PLLA-NHS in S2 are dissolved in dimethyl sulfoxide, a catalyst diethylamine is added, and the reaction is carried out at 40°C for 24h to obtain a copolymer solution. After dialysis of the copolymer solution for 48h, freeze-drying is performed to obtain a hyaluronic acid-polylactic acid copolymer freeze-dried sample (HA-g-PLLA);

[0053] S4. Preparation of hyaluronic acid-poly-lactic acid copolymer cross-linked gel: 500 mg of HA-g-PLLA in S3 was dissolved in 9.5 mL of 1% sodium hydroxide solution, 40 μL of 1,4-butanediol diglycidyl ether (BDDE) was added, and after cross-linking at 25°C for 24 h, 20 mL of PBS buffer was added for swelling for 72 h to obtain the cross-linked gel.

[0054] Application Example 2

[0055] The application example provides a preparation method of an injectable hyaluronic acid-poly-lactic acid copolymer cross-linked gel, comprising the following steps:

[0056] S1. Preparation of amphiphilic hyaluronic acid: 5 g of sodium hyaluronate with a molecular weight of 1,000,00 Da was dissolved in water to prepare a 5% hyaluronic acid solution. After soaking the sodium hyaluronate solution in an ion exchange resin for 24 h, the pH was adjusted to 7.0 with a tetrabutylammonium hydroxide solution, and the solution was freeze-dried to obtain amphiphilic hyaluronic acid (HA-TBA);

[0057] S2. Activation of poly-lactic acid carboxyl group: 5 g of poly-dextral lactic acid with a molecular weight of 10,000 Da was dissolved in dichloromethane with 383.40 mg of EDC and 230.18 mg of NHS, and reacted at 25°C for 24 h. After vacuum drying, carboxyl-activated poly-dextral lactic acid (PDLA-NHS) was obtained;

[0058] S3. Preparation of hyaluronic acid-poly-lactic acid copolymer: 600 mg of HA-TBA in S1 and 84 mg of PDLA-NHS in S2 were dissolved in dimethyl sulfoxide, and a catalyst diethylamine was added, and the reaction was carried out at 50°C for 24 h to obtain a copolymer solution. After dialysis of the copolymer solution for 72 h, the copolymer was freeze-dried to obtain a hyaluronic acid-poly-lactic acid copolymer;

[0059] S4. Preparation of hyaluronic acid-poly-lactic acid copolymer cross-linked gel: 500 mg of HA-g-PLLA in S3 was dissolved in 9.5 mL of 1% sodium hydroxide solution, 40 μL of 1,4-butanediol diglycidyl ether (BDDE) was added, and after cross-linking at 25°C for 24 h, 20 mL of PBS buffer was added for swelling for 72 h to obtain the cross-linked gel.

[0060] Application Example 3

[0061] The application example provides a preparation method of an injectable hyaluronic acid-poly-lactic acid copolymer cross-linked gel, comprising the following steps:

[0062] S1. Preparation of amphiphilic hyaluronic acid: 5 g of sodium hyaluronate with a molecular weight of 1,600,000 Da was dissolved in water to prepare a 5% hyaluronic acid solution. After soaking the sodium hyaluronate solution in ion exchange resin for 24 h, the pH was adjusted to 7.0 with tetrabutylammonium hydroxide solution, and the solution was freeze-dried to obtain amphiphilic hyaluronic acid (HA-TBA);

[0063] S2. Activation of polylactic acid carboxyl group: 5 g of poly-L-lactic acid with a molecular weight of 15,000 Da was dissolved in dichloromethane with 191.70 mg of EDC and 115.09 mg of NHS, and reacted at 25°C for 24 h. After vacuum drying, carboxyl-activated polylactic acid (PLLA-NHS) was obtained;

[0064] S3. Preparation of hyaluronic acid-polylactic acid copolymer: 1200 mg of HA-TBA in S1 and 102 mg of PLLA-NHS in S2 were dissolved in dimethyl sulfoxide and reacted at 50°C for 24 h. After dialysis of the solution for 72 h, the freeze-dried sample of hyaluronic acid-polylactic acid copolymer (HA-g-PLLA) was obtained.

[0065] S4. Preparation of hyaluronic acid-polylactic acid copolymer crosslinked gel: 500 mg of HA-g-PLLA in S3 was dissolved in 4.5 mL of 1% sodium hydroxide solution, and 100 μL of 1,4-butanediol diglycidyl ether (BDDE) was added. After crosslinking at 25°C for 24 h, 20 mL of PBS buffer was added for swelling for 72 h to obtain a crosslinked gel.

[0066] Comparative Example 1

[0067] 500 mg of sodium hyaluronate with a molecular weight of 1,600,000 Da was dissolved in 9.5 mL of 1% sodium hydroxide solution, and 80 μL of 1,4-butanediol diglycidyl ether (BDDE) was added. After crosslinking at 25°C for 24 h, 20 mL of PBS buffer was added for swelling to obtain a crosslinked gel.

[0068] Comparative Example 2

[0069] 500 mg of sodium hyaluronate with a molecular weight of 300,000 Da was dissolved in 9.5 mL of 1% sodium hydroxide solution, and 40 μL of 1,4-butanediol diglycidyl ether (BDDE) was added. After crosslinking at 25°C for 24 h, 20 mL of PBS buffer was added for swelling to obtain a crosslinked gel.

[0070] Performance comparison

[0071] The Fourier infrared spectrometer was used to determine the molecular weight of the copolymer at a wavelength of 4000-400 cm -1The infrared scanning of HA, PLLA and HA-g-PLLA in application example 1 was carried out in the range of 4000-650cm-1. Referring to Fig. 1, the results show that the copolymer (HA-g-PLLA) exhibits characteristic peaks of hyaluronic acid (HA) at 3389cm-1 -1 (-OH), 1610cm -1 (-COOH), 1378cm -1 (-CH2), 1150cm -1 (C-O-C), 1078cm- 1 (-C=O) and etc. In comparison with pure HA, the copolymer (HA-g-PLLA) forms new characteristic peaks at 1756cm -1 , 1456cm -1 , which is mainly due to the existence of ester bond (C=O) and methyl (-CH3) of PLLA, thus confirming the successful modification of HA by PLLA. Fig. 2 shows the morphology of the cross-linked gel prepared from the copolymer (HA-g-PLLA), indicating that the copolymer has the ability to form gel.

[0072] The rheological properties of the cross-linked gels in application examples 1-3 and comparative examples 1-2 were determined by using a rheometer. The results are shown in Table 1. At the amplitude frequency of 10Hz, the cross-linked gels have certain filling plastic effect, and the rheological properties of application examples 1-3 are higher than those of comparative examples.

[0073] Table 1 Rheological properties of application examples 1-3 and comparative examples 1-2

[0074] The cross-linked gels of application examples 1-3 and comparative examples 1-2 were degraded in vitro by using hyaluronidase. The degradation rates are shown in Table 2. The degradation rates of application examples 1-3 are lower than those of comparative examples 1-2, indicating that the polylactic acid groups increase the chain length of the hyaluronic acid molecular chain, so as to achieve the purpose of delaying the degradation of the material.

[0075] Table 2 Degradation rates of the cross-linked gels of application examples 1-3 and comparative examples 1-2

[0076] The above performance test results show that, compared with the pure hyaluronic acid cross-linked gel, the hyaluronic acid cross-linked gel grafted with polylactic acid of the present disclosure has enhanced mechanical properties and slowed down the degradation rate, and can enhance the shaping effect and shaping time when used as a skin anti-aging filler.

[0077] The present disclosure first changes hyaluronic acid into amphiphilic HA-TBA with ion exchange resin, and catalyzes carboxyl of polylactic acid by amidation reaction to obtain PLA-NHS, and then grafts the activated polylactic acid (PLA-NHS) with hyaluronic acid (HA-TBA) by esterification reaction to form copolymer (HA-g-PLA), and then the copolymer is prepared into gel under certain conditions with crosslinking agent. The gel greatly improves the shortcomings of poor mechanical property and short maintenance time in skin of hyaluronic acid through covalent action of polylactic acid and hyaluronic acid. At the same time, grafting polylactic acid onto hyaluronic acid increases the hydrophilicity of polylactic acid, which can reduce the immune rejection reaction. The crosslinked gel prepared by the method can play the effects of moisturizing, filling and plasticity, and can stimulate the regeneration of collagen cells in the skin, reduce the generation of wrinkles, and restore the elasticity of the skin.

[0078] The above-mentioned examples and application examples are only exemplary descriptions of the present disclosure, and do not limit the scope of the present disclosure. Without departing from the design spirit of the present disclosure, various modifications and improvements of the technical solutions of the present disclosure made by those skilled in the art shall fall within the protection scope of the present disclosure.

Claims

1. A method for preparing a hyaluronic acid-polylactic acid copolymer crosslinked gel, characterized by, The method comprises the following steps: S1. Changing the ion of hyaluronic acid by ion exchange resin, adjusting the pH of the solution to 7.0 with an alkaline reagent, lyophilizing to obtain an amphiphilic hyaluronic acid having the following formula S2. Activating carboxyl groups of polylactic acid using a catalyst to obtain carboxyl-activated polylactic acid; S3. The carboxyl-activated polylactic acid and the amphiphilic hyaluronic acid are subjected to esterification reaction, and after dialysis and lyophilization, a hyaluronic acid-polylactic acid copolymer comprising the following formula is obtained S4. Placing the hyaluronic acid-polylactic acid copolymer in an alkaline solvent to undergo crosslinking reaction under the action of a crosslinking agent, and obtaining a hyaluronic acid-polylactic acid copolymer crosslinked gel after swelling in a PBS buffer solution.

2. The production method according to claim 1, characterized by, The polylactic acid has a molecular weight of 5,000-200,000 Da; The polylactic acid is selected from one of polylactic acid, poly-D-lactic acid, poly-D-lactic acid, or polyethylene glycol modified polylactic acid.

3. The production method according to claim 1 or 2, characterized by, In the reaction system of step S2, the catalyst comprises at least one of N-(3-dimethylaminopropyl)-ethyl carbodiimide, dicyclohexyl carbodiimide, 4-dimethylamino pyridine, and N-hydroxy succinimide, and the solvent used comprises dichloromethane or trichloromethane.

4. The production method according to claim 3, characterized by, The catalyst is N-hydroxy succinimide and N-(3-dimethylaminopropyl)-ethyl carbodiimide; The mass ratio of the polylactic acid, the N-hydroxy succinimide, and the N-(3-dimethylaminopropyl)-ethyl carbodiimide is 1:0.01:0.01 to 1:5:5, the reaction temperature is 25-50℃, and the reaction time is 8-48h.

5. The production method according to claim 1 or 2, characterized by, In the reaction system of step S3, the solvent used comprises dimethyl sulfoxide, the mass ratio of the carboxyl-activated polylactic acid to the amphiphilic hyaluronic acid is 1:0.01 to 1:5, the reaction temperature is 40-60℃, the reaction time is 8-24h, and the dialysis time is 2-5 days.

6. The method of claim 1, wherein, In step S1, the hyaluronic acid has a molecular weight of 20,000-2,000,000 Da, the ion exchange resin is a cation exchange resin, the treatment time is 18-36h, and the alkaline reagent comprises a tetrabutylammonium hydroxide solution.

7. The production method according to claim 1 or 2, characterized by, In step S4, the alkaline reagent comprises a 1% sodium hydroxide solution by mass fraction, and the PBS buffer solution comprises the following components: sodium chloride, disodium hydrogen phosphate, and sodium dihydrogen phosphate monohydrate; The mass ratio of the hyaluronic acid-polylactic acid copolymer to the crosslinking agent is 1:0.01 to 1:0.5, the crosslinking temperature is 25-50℃, the crosslinking time is 12-48h, and the swelling time is 12-72h; The crosslinking agent comprises 1,4-butanediol diglycidyl ether, divinyl sulfone, ethylene glycol diglycidyl ether, 1,6-hexanediol diglycidyl ether, or diethylene glycol diglycidyl ether.

8. A hyaluronic acid-poly-lactic acid copolymer cross-linked gel, characterized in that, The crosslinked gel is obtained according to the preparation method of any one of claims 1-7.

9. The crosslinked gel of claim 8, wherein, The crosslinked gel comprises a chemical structure of the formula:

10. Use of a crosslinked gel according to claim 8 or 9, characterized in that, The crosslinked gel is applied in a facial filler.

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