Chitosan-based periodontal local drug delivery hydrogel and application thereof

Abstract

The application relates to the technical field of slow-release hydrogels, and discloses a periodontal local drug slow-release hydrogel based on chitosan and application thereof, which is prepared from the following components: triple modified chitosan, functional filler, therapeutic drug, crosslinking agent and deionized water; the triple modified chitosan is carboxymethylization-mussel biomimetic polyphenol-poly-beta-hydroxybutyrate triple modified chitosan, and the functional filler is a composite powder of hydroxyapatite and carboxylated graphene oxide loaded with nano-silver; the technical scheme of the application solves the technical problems of poor water solubility, insufficient wet adhesion, short slow-release period and single function of the existing chitosan hydrogel, the prepared hydrogel is suitable for the physiological environment of periodontal local, has excellent biocompatibility, structural stability, long-acting slow-release property and multifunctional synergy, provides a brand-new effective carrier for long-acting local treatment of periodontitis, and has extremely high practical value and popularization prospect in the field of oral clinical treatment.

Description

Technical Field

[0001] This invention relates to the field of sustained-release hydrogel technology, and more particularly to a chitosan-based sustained-release hydrogel for periodontal topical medications and its applications. Background Technology

[0002] Periodontitis is a prevalent chronic oral infectious disease worldwide. Its core pathogenesis is a series of inflammatory reactions caused by the continuous accumulation of bacterial biofilm in periodontal pockets. This reaction gradually leads to gingival recession, loss of periodontal attachment, and alveolar bone resorption and destruction. In severe cases, it can cause teeth to loosen or even fall out. It not only seriously damages human oral physiological health, but also has a significant negative impact on daily functions such as chewing and speech, as well as quality of life.

[0003] Currently, the mainstream treatment for periodontitis in clinical practice is mechanical debridement combined with topical drug therapy. Compared to systemic medication, topical drug delivery systems can directly target the periodontal lesions, effectively increasing local drug concentration while significantly reducing systemic adverse reactions, making them a key research focus and hot topic in the treatment of periodontitis. Hydrogels, as a type of hydrophilic polymer material with a three-dimensional interpenetrating network structure, can absorb and retain a large amount of water. Their structure is highly similar to the microenvironment of the human extracellular matrix, exhibiting good biocompatibility and tissue compatibility. They can also efficiently load various antibacterial and anti-inflammatory drugs and achieve slow drug release, making them ideal drug delivery carriers adapted to the local physiological environment of the periodontium.

[0004] Chitosan is a rare cationic basic polysaccharide found in nature, synthesized from the deacetylation of chitin. It is widely present in the exoskeletons of crustaceans and the cell walls of fungi, and its excellent biocompatibility has led to its application in the food and pharmaceutical fields. This material possesses good biocompatibility and biodegradability, and can exert natural antibacterial effects by inhibiting the growth of periodontal pathogens such as *Porphyromonas gingivalis* and *Actinomyces actinomycetes*. Simultaneously, it can promote local cell adhesion and tissue repair in the periodontal region, demonstrating promising application potential in oral biomedicine and periodontal disease treatment. It has also become a commonly used substrate for preparing sustained-release hydrogels for local periodontal drug delivery.

[0005] However, existing chitosan-based periodontal drug-releasing hydrogels still have many technical defects, making it difficult to meet the actual needs of long-term and efficient treatment of periodontitis in clinical practice, and their clinical application is greatly limited. First, natural chitosan has poor water solubility and can only dissolve in acidic environments, while the periodontal pocket has a weakly alkaline physiological microenvironment of pH 7.2-7.4. This results in poor swelling and dispersion performance of chitosan hydrogels in the periodontal area, making it impossible to form a stable three-dimensional gel network, and thus difficult to construct a reliable drug-releasing system. Second, the cross-linked network structure of existing chitosan hydrogels is not stable enough. The periodontal pocket has a dynamic liquid environment with continuous secretion of gingival crevicular fluid and saliva wetting and rinsing. In this environment, the hydrogel is prone to rapid degradation, shedding, or loss, resulting in a short retention time of the drug in the periodontal area. The sustained-release period is mostly no more than 7 days, which cannot meet the long-term treatment needs of chronic periodontitis. It is also prone to drug burst release, making it difficult to maintain a stable effective drug concentration in the periodontal area.

[0006] Therefore, how to fully utilize the inherent characteristics of chitosan's molecular structure containing free amino and hydroxyl groups and its strong modifiability, combined with its own advantages such as antibacterial and biocompatibility, and through targeted modification, to develop a chitosan-based periodontal local drug sustained-release hydrogel with excellent water solubility, strong wet adhesion, stable cross-linked structure, long drug sustained-release period, and multifunctional synergistic effects of antibacterial, anti-inflammatory, and periodontal tissue regeneration promotion, has become a key technical problem that urgently needs to be solved in the field of oral biomedicine. Summary of the Invention

[0007] To address the problems in the prior art, the present invention provides a chitosan-based periodontal topical drug sustained-release hydrogel.

[0008] The technical solution adopted by the present invention to solve its technical problem is: a chitosan-based periodontal topical drug sustained-release hydrogel, comprising the following mass fractions: 12-18 parts of triple-modified chitosan, 4-6 parts of functional filler, 0.8-1.5 parts of therapeutic drug, 1.2-2.5 parts of crosslinking agent, and 70-80 parts of deionized water; The triple-modified chitosan is a carboxymethylated mussel biomimetic polyphenol-polyβ-hydroxybutyrate triple-modified chitosan. The functional filler is a composite powder of hydroxyapatite and carboxylated graphene oxide loaded with nano-silver. The therapeutic drug is an antibacterial or anti-inflammatory drug for the treatment of periodontitis.

[0009] As a further technical solution, the preparation method of the triple-modified chitosan is as follows: (1) Preparation of carboxymethylated chitosan: Take natural chitosan with a degree of deacetylation ≥92% and a molecular weight of 60-90 kDa, add it to isopropanol, and stir and disperse it at 350-450 r / min for 40-50 min to prepare a chitosan dispersion with a mass concentration of 6%-8%; add a chloroacetic acid-sodium hydroxide mixed solution to the dispersion, wherein the molar ratio of chloroacetic acid to sodium hydroxide is 1:1.3-1.4, and the mass ratio of natural chitosan to chloroacetic acid is 1:1.8-2.2; control The reaction temperature was set at 58-62℃, the stirring rate at 350-450 r / min, and the reaction was carried out for 4.5-5.5 h. After the reaction was completed, the pH of the system was adjusted to 6.6-6.9 with 1 mol / L hydrochloric acid, and the mixture was centrifuged at 8000-10000 r / min for 12-15 min. The precipitate was washed 4 times with anhydrous ethanol, with 5 times the mass of the precipitate added for each wash. After soaking for 10 min, the mixture was centrifuged and dried under vacuum at 60℃ to constant weight to obtain carboxymethyl chitosan. (2) Preparation of intermediate product: The carboxymethylated chitosan obtained in step (1) is dissolved in dimethyl sulfoxide, with a mass ratio of carboxymethylated chitosan to dimethyl sulfoxide of 1:10. Poly(β-hydroxybutyrate) and coupling agent N,N'-dicyclohexylcarbodiimide are added. The mass ratio of carboxymethylated chitosan to poly(β-hydroxybutyrate) is 1:0.25-0.35, the molecular weight of poly(β-hydroxybutyrate) is 25-45 kDa, and the amount of coupling agent added is 6%-9% of the total mass of carboxymethylated chitosan and poly(β-hydroxybutyrate). The reaction temperature is controlled at 48-52℃, the stirring rate is 300-400 r / min, and the reaction is stirred for 6.5-7.5 h. Anhydrous ethanol is added in 3 times the volume of the reaction system to precipitate the product. After filtration, the product is washed 2-3 times with anhydrous ethanol. Each time, 4 times the mass of the filter residue is added to the product. The product is dried under vacuum at 50℃ to constant weight to obtain the intermediate product: carboxymethylated-poly(β-hydroxybutyrate) modified chitosan. (3) Preparation of triple-modified chitosan: Dissolve the intermediate product obtained in step (2) in deionized water to prepare an aqueous solution with a mass concentration of 3%-4%; add dopamine hydrochloride, wherein the mass ratio of the intermediate product to dopamine hydrochloride is 1:0.35-0.55, stir to dissolve, and adjust the pH of the system to 8.1-8.4 with 0.1mol / L Tris-HCl buffer; purge with nitrogen gas, control the reaction temperature at 32-38℃ and the stirring rate at 300-400r / min, and stir for 9-12h; dialyze the reaction solution with a dialysis bag for 3-4 days, changing the deionized water 2-3 times a day, and the amount of deionized water changed each time is 5 times the volume of the reaction solution in the dialysis bag, and then freeze-dry to constant weight under conditions of -45℃ to -40℃ and vacuum degree of 12-18Pa to obtain triple-modified chitosan.

[0010] As a further technical solution, the dialysis bag has a molecular weight cutoff of 8000-10000 Da.

[0011] As a further technical solution, the therapeutic drug is selected from one of minocycline hydrochloride, metronidazole, amoxicillin, ibuprofen, and dexamethasone.

[0012] As a further technical solution, the crosslinking agent is genipin.

[0013] As a further technical solution, the preparation method of the sustained-release hydrogel includes the following steps: S1: Prepare carboxymethylated mussel biomimetic polyphenol-polyβ-hydroxybutyrate triple-modified chitosan according to the method described above; S2: Preparation of functional composite fillers: Nano-sized hydroxyapatite was added to a 55%-65% (w / w) ethanol aqueous solution, with a hydroxyapatite to ethanol aqueous solution mass ratio of 1:10-15. A silane coupling agent, KH-550, was added. The mixture was stirred at 62-68℃ and 300-400 r / min for 2.0-2.8 h, centrifuged at 8000 r / min for 10 min, and vacuum dried at 50℃ to constant weight to obtain modified hydroxyapatite. Carboxymethylated graphene oxide was dispersed in deionized water, with a carboxymethylated graphene oxide to deionized water mass ratio of 1:20-30. Silver nitrate solution and reducing agent sodium citrate were added. The mass ratio of carboxymethylated graphene oxide was 1:5-8, the molar ratio of sodium citrate to silver nitrate was 1-1.2:1, the reaction was carried out at 65-75℃ and 300-400 r / min for 1.2-1.8 h, centrifuged at 8000 r / min for 10 min, and vacuum dried at 50℃ to constant weight to obtain carboxymethylated graphene oxide loaded with nano-silver; the modified hydroxyapatite and the carboxymethylated graphene oxide loaded with nano-silver were mixed at a mass ratio of 3.5-4.5:1, five times the mass of deionized water was added, the mixture was dispersed with an ultrasonic device with a power of 220-280W for 18-25 min, and freeze-dried to constant weight to obtain a functional composite filler; S3: Preparation of drug dispersion: Disperse the drug in 6-10 times the weight of deionized water using an ultrasonic device with a power of 160-200W for 12-18 minutes to obtain the drug dispersion. S4: Preparation of the mixed system: Add the triple-modified chitosan obtained in step S1 to deionized water, with a mass ratio of triple-modified chitosan to deionized water of 1:4-6. Dissolve the chitosan in a water bath at 60-68℃ and stir at 350-450 r / min until completely transparent and free of precipitate. Add the functional composite filler obtained in step S2 and the drug dispersion obtained in step S3. Disperse the mixture using an ultrasonic device with a power of 200-280W for 25-35 min, and then stir at 350-450 r / min for 10 min to obtain a homogeneous mixed system. S5: Cross-linking molding: Add genipin to the mixture obtained in step S4, stir at 350-450 r / min for 10 min until completely dissolved, adjust the pH to 7.0-7.1 with 0.1 mol / L Tris-HCl buffer; pour the system into a mold, place it in a constant temperature environment of 37℃ for static cross-linking for 2.5-3.5 h, cool to 25±2℃, demold, and vacuum dry at 50℃ for 2-3 h to constant weight to obtain the hydrogel product; S6: Sterilization treatment: The hydrogel product obtained in step S5 is sterilized by gamma rays. After sterilization, a periodontal local drug sustained-release hydrogel is obtained.

[0014] As a further technical solution, the carboxylated graphene oxide described in S2 has a carboxyl substitution degree of 12%-18%.

[0015] As a further technical solution, the γ-ray sterilization described in S6 has a sterilization dose of 22-25 kGy.

[0016] Application of chitosan-based sustained-release hydrogels for periodontal local drug delivery in the preparation of drug delivery carriers for local treatment of periodontitis, wherein the hydrogel can be formulated as a gel, film or injection.

[0017] As a further technical solution, the application method is intraperitoneal injection, local application, or plastering.

[0018] The beneficial effects of this invention are: This invention constructs a hydrogel-based system adapted to the local physiological environment of the periodontium through the combination of triple-modified chitosan, functional fillers, therapeutic drugs, cross-linking agents, and deionized water. This effectively solves the problems of poor gel stability and uncontrolled drug loading and release caused by unreasonable formulation design in existing chitosan hydrogels. By using triple-modified chitosan as the hydrogel substrate, its water solubility and biocompatibility are significantly improved after carboxymethylation, mussel biomimetic polyphenols, and poly-β-hydroxybutyrate modification. It can fully swell in the weakly alkaline environment of the periodontal pocket and form a stable three-dimensional network, providing a reliable carrier for sustained drug release. The addition of functional fillers can form physical cross-links and hydrogen bonds with the triple-modified chitosan, further densifying the gel network structure and endowing the hydrogel with additional functions such as antibacterial and tissue regeneration promotion. The formulation of therapeutic drugs ensures an effective drug concentration in the periodontal area while avoiding burst release and toxic side effects caused by drug overdose. The combination of cross-linking agents and deionized water can regulate the degree of cross-linking and swelling rate of the gel, making it suitable for the dynamic liquid environment of the periodontal pocket. The mass ratio of each component was screened through extensive experiments, and preliminary functional synergy was formed among them. At the formulation level, a balance was achieved between the water solubility, structural stability and drug loading performance of the hydrogel. This solved the basic performance defects of chitosan hydrogels caused by unreasonable formulation in the existing technology, and laid the core foundation for the subsequent realization of long-acting sustained release and multifunctional synergy.

[0019] In this invention, the process characteristics of each component and preparation step complement each other and progress step by step, ultimately forming a significant synergistic effect and achieving a comprehensive improvement in the overall performance of the hydrogel. The triple-modified chitosan preparation process solves the problem of poor water solubility of natural chitosan through carboxymethylation modification; polyβ-hydroxybutyrate grafting modification enhances the flexibility of the molecular chain and the mechanical stability of the gel network; and mussel-inspired polyphenol modification endows chitosan with excellent wet adhesion and natural antibacterial and anti-inflammatory properties. This three-step modification achieves multiple optimizations of the physicochemical and biological properties of chitosan at the molecular level. The functional filler preparation process significantly improves the compatibility of hydroxyapatite with the gel substrate by modifying it with a silane coupling agent. Hydroxyapatite can adapt to the physiological characteristics of periodontal hard tissue and promote bone regeneration. Carboxylated graphene oxide loaded with nano-silver... The highly efficient antibacterial properties of nano-silver and the physical barrier effect of its layered structure achieve a dual effect of enhanced antibacterial performance and densified gel network. Furthermore, the precise control of the preparation parameters of the functional filler ensures its dispersibility and functional activity, allowing it to be uniformly dispersed in the gel network and fully exert its function. Genipin, a natural crosslinking agent, is selected, which undergoes a mild Schiff base reaction with the amino groups of triple-modified chitosan, forming highly stable crosslinks that can construct a three-dimensional gel network with uniform pore size. This avoids the biocompatibility degradation problems caused by chemical crosslinking agents. Simultaneously, precise control of process parameters such as sterilization and crosslinking molding further guarantees the moldability and biosafety of the hydrogel. The process characteristics of each preparation step are adjusted to regulate the structure and function of each component, allowing the microscopic functions of each component to be fully utilized. The physical crosslinking, hydrogen bonding, and electrostatic interactions formed by the components in the gel system allow the microscopic effects of individual components to synergistically interact, ultimately achieving a comprehensive improvement in the hydrogel's water solubility, wet adhesion, structural stability, drug sustained release, and biofunctionality.

[0020] The technical solution of this invention fundamentally solves the technical problems of existing chitosan hydrogels, such as poor water solubility, insufficient wet adhesion, short sustained-release period, and single function. The prepared hydrogel is adapted to the local physiological environment of the periodontium and has excellent biocompatibility, structural stability, long-term sustained release and multifunctional synergy. It provides a new and effective carrier for local long-term treatment of periodontitis and has extremely high practical value and promotion prospects in the field of oral clinical treatment. Attached Figure Description

[0021] Figure 1 This is a comparison of the cumulative drug release rate in simulated periodontal fluid between a chitosan-based periodontal local drug sustained-release hydrogel example and a comparative hydrogel sample. Detailed Implementation

[0022] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0023] This invention provides a chitosan-based periodontal topical drug sustained-release hydrogel, which is prepared by mixing triple-modified chitosan, functional fillers, therapeutic drugs, crosslinking agents, and deionized water in a specific mass ratio. The invention also discloses the preparation method and application of this sustained-release hydrogel. This hydrogel possesses excellent drug sustained-release properties, antibacterial and anti-inflammatory effects, and biocompatibility, and is adapted to the local physiological environment of the periodontal region, effectively achieving local targeted treatment of periodontitis.

[0024] The chitosan-based periodontal topical drug sustained-release hydrogel of the present invention is preferably composed of the following parts by weight: 12-18 parts of triple-modified chitosan, 4-6 parts of functional filler, 0.8-1.5 parts of therapeutic drug, 1.2-2.5 parts of crosslinking agent, and 70-80 parts of deionized water. More preferably, it is composed of the following parts by weight: 15 parts of triple-modified chitosan, 5 parts of functional filler, 1.2 parts of therapeutic drug, 1.8 parts of crosslinking agent, and 75 parts of deionized water.

[0025] In this invention, the triple-modified chitosan is a carboxymethylated-mussel biomimetic polyphenol-polyβ-hydroxybutyrate triple-modified chitosan, and its preparation method preferably includes the following steps: (1) Preparation of carboxymethylated chitosan: Take natural chitosan with a degree of deacetylation ≥92% and a molecular weight of 60-90 kDa, add it to isopropanol, and stir and disperse it at 350-450 r / min for 40-50 min to prepare a chitosan dispersion with a mass concentration of 6%-8%; add a chloroacetic acid-sodium hydroxide mixed solution to the dispersion, wherein the molar ratio of chloroacetic acid to sodium hydroxide is 1:1.3-1.4, and the mass ratio of natural chitosan to chloroacetic acid is 1:1.8-2.2; control The reaction temperature was set at 58-62℃, the stirring rate at 350-450 r / min, and the reaction was carried out for 4.5-5.5 h. After the reaction was completed, the pH of the system was adjusted to 6.6-6.9 with 1 mol / L hydrochloric acid, and the mixture was centrifuged at 8000-10000 r / min for 12-15 min. The precipitate was washed 4 times with anhydrous ethanol, with 5 times the mass of the precipitate added for each wash. After soaking for 10 min, the mixture was centrifuged and dried under vacuum at 60℃ to constant weight to obtain carboxymethyl chitosan.

[0026] (2) Preparation of intermediate product: The carboxymethylated chitosan obtained in step (1) is dissolved in dimethyl sulfoxide, with a mass ratio of carboxymethylated chitosan to dimethyl sulfoxide of 1:10. Poly(β-hydroxybutyrate) and coupling agent N,N'-dicyclohexylcarbodiimide are added. The mass ratio of carboxymethylated chitosan to poly(β-hydroxybutyrate) is 1:0.25-0.35, the molecular weight of poly(β-hydroxybutyrate) is 25-45 kDa, and the amount of coupling agent added is 6%-9% of the total mass of carboxymethylated chitosan and poly(β-hydroxybutyrate). The reaction temperature is controlled at 48-52℃, the stirring rate is 300-400 r / min, and the reaction is stirred for 6.5-7.5 h. Anhydrous ethanol with a volume of 3 times that of the reaction system is added to precipitate the product. After filtration, the product is washed with anhydrous ethanol 2-3 times. Anhydrous ethanol with a mass of 4 times that of the filter residue is added each time. The product is dried under vacuum at 50℃ to constant weight to obtain the intermediate product, namely carboxymethylated-poly(β-hydroxybutyrate) modified chitosan.

[0027] (3) Preparation of triple-modified chitosan: Dissolve the intermediate product obtained in step (2) in deionized water to prepare an aqueous solution with a mass concentration of 3%-4%; add dopamine hydrochloride, wherein the mass ratio of the intermediate product to dopamine hydrochloride is 1:0.35-0.55, stir to dissolve, and adjust the pH of the system to 8.1-8.4 with 0.1mol / L Tris-HCl buffer; purge with nitrogen gas, control the reaction temperature at 32-38℃ and the stirring rate at 300-400r / min, and stir for 9-12h; dialyze the reaction solution with a dialysis bag for 3-4 days, preferably with a molecular weight cutoff of 8000-10000Da, change the deionized water 2-3 times a day, and the amount of deionized water changed each time is 5 times the volume of the reaction solution in the dialysis bag, and then freeze-dry to constant weight under conditions of -45℃ to -40℃ and vacuum degree of 12-18Pa to obtain triple-modified chitosan.

[0028] In this invention, the functional filler is a composite powder of hydroxyapatite and carboxylated graphene oxide loaded with nano-silver, and the degree of carboxyl substitution of the carboxylated graphene oxide is preferably 12%-18%.

[0029] In this invention, the therapeutic drug is an antibacterial or anti-inflammatory drug for the treatment of periodontitis, preferably selected from one of minocycline hydrochloride, metronidazole, amoxicillin, ibuprofen, and dexamethasone. This invention does not have any special restrictions on the source of the therapeutic drug, and conventional commercially available qualified products in the field can be used.

[0030] In this invention, the crosslinking agent is preferably genipin. This invention does not have any special restrictions on the source of genipin, and any commercially available qualified product in the art can be used.

[0031] The method for preparing the chitosan-based periodontal topical drug sustained-release hydrogel of the present invention preferably includes the following steps: S1: Prepare carboxymethylated mussel biomimetic polyphenol-polyβ-hydroxybutyrate triple-modified chitosan according to the above method; S2: Preparation of functional composite fillers: Nano-sized hydroxyapatite was added to a 55%-65% (w / w) ethanol aqueous solution, with a hydroxyapatite to ethanol aqueous solution mass ratio of 1:10-15. A silane coupling agent, KH-550, was added. The mixture was stirred at 62-68℃ and 300-400 r / min for 2.0-2.8 h, centrifuged at 8000 r / min for 10 min, and vacuum dried at 50℃ to constant weight to obtain modified hydroxyapatite. Carboxymethylated graphene oxide was dispersed in deionized water, with a carboxymethylated graphene oxide to deionized water mass ratio of 1:20-30. Silver nitrate solution and reducing agent sodium citrate were added. The mass ratio of carboxymethylated graphene oxide was 1:5-8, the molar ratio of sodium citrate to silver nitrate was 1-1.2:1, the reaction was carried out at 65-75℃ and 300-400 r / min for 1.2-1.8 h, centrifuged at 8000 r / min for 10 min, and vacuum dried at 50℃ to constant weight to obtain carboxymethylated graphene oxide loaded with nano-silver; the modified hydroxyapatite and the carboxymethylated graphene oxide loaded with nano-silver were mixed at a mass ratio of 3.5-4.5:1, five times the mass of deionized water was added, the mixture was dispersed with an ultrasonic device with a power of 220-280W for 18-25 min, and freeze-dried to constant weight to obtain a functional composite filler; S3: Preparation of drug dispersion: Take the therapeutic drug and add 6-10 times its mass of deionized water, disperse it for 12-18 minutes using an ultrasonic device with a power of 160-200W to obtain the drug dispersion; S4: Preparation of the mixed system: Add the triple-modified chitosan obtained in step S1 to deionized water, with a mass ratio of triple-modified chitosan to deionized water of 1:4-6. Dissolve the chitosan in a water bath at 60-68℃ and stir at 350-450 r / min until completely transparent and free of precipitate. Add the functional composite filler obtained in step S2 and the drug dispersion obtained in step S3. Disperse the mixture using an ultrasonic device with a power of 200-280W for 25-35 min, and then stir at 350-450 r / min for 10 min to obtain a homogeneous mixed system. S5: Cross-linking molding: Add genipin to the mixture obtained in step S4, stir at 350-450 r / min for 10 min until completely dissolved, adjust the pH to 7.0-7.1 with 0.1 mol / L Tris-HCl buffer; pour the system into a mold, place it in a constant temperature environment of 37℃ for static cross-linking for 2.5-3.5 h, cool to 25±2℃, demold, and vacuum dry at 50℃ for 2-3 h to constant weight to obtain the hydrogel product; S6: Sterilization treatment: The hydrogel product obtained in step S5 is sterilized by gamma rays. The preferred sterilization dose is 22-25 kGy. After sterilization, a periodontal local drug sustained-release hydrogel is obtained.

[0032] This invention also provides the application of the chitosan-based periodontal local drug sustained-release hydrogel in the preparation of a drug delivery carrier for local treatment of periodontitis. The hydrogel can be made into a gel, film or injection, and can be applied by intraperitoneal injection, local application or patch. As a drug delivery carrier, the hydrogel can realize the slow release of therapeutic drugs in the periodontal area, prolong the drug action time and improve the treatment effect of periodontitis.

[0033] This invention provides a chitosan-based periodontal topical drug-release hydrogel. Using triple-modified chitosan as the base material, combined with functional composite fillers and a dedicated cross-linking system, it achieves a synergistic improvement in the biocompatibility, mechanical properties, and drug release performance of the base material. The hydroxyapatite in the functional filler is adapted to the physiological characteristics of periodontal hard tissues, while carboxylated graphene oxide loaded with silver nanoparticles endows the hydrogel with excellent antibacterial properties, synergistically achieving antibacterial and anti-inflammatory effects with therapeutic drugs. Simultaneously, genipin, as a natural cross-linking agent, has lower cytotoxicity compared to traditional chemical cross-linking agents, further enhancing the biocompatibility of the hydrogel. The preparation method of this invention features controllable process parameters, is easily scalable for industrial production, and produces a hydrogel with good moldability, adaptability to the local physiological environment of the periodontal region, and a long drug release period. It effectively solves the problems of rapid drug loss, short duration of action, and poor therapeutic effect associated with traditional topical periodontal medications. Furthermore, the raw material formulation is reasonable, and the production cost is controllable, demonstrating promising clinical application prospects.

[0034] To further illustrate the present invention, detailed descriptions are provided below through the following embodiments. In the following embodiments of the present invention, the degree of deacetylation of the natural chitosan used is ≥92%, the degree of carboxyl substitution of the carboxylated graphene oxide used is 12%-18%, the therapeutic drug used is minocycline hydrochloride, and the silane coupling agent KH-550, coupling agent N,N'-dicyclohexylcarbodiimide, dopamine hydrochloride, and genistein used are all commercially available analytical grade products, and the molecular weight cutoff of the dialysis bag used is 8000-10000 Da.

[0035] Example 1: This embodiment prepares a chitosan-based periodontal topical drug sustained-release hydrogel, and the specific steps are as follows: Preparation of triple-modified chitosan: (1) Preparation of carboxymethylated chitosan: Take natural chitosan with a molecular weight of 60 kDa, add it to isopropanol, stir and disperse at 350 r / min for 40 min to prepare a chitosan dispersion with a mass concentration of 6%; add chloroacetic acid-sodium hydroxide mixed solution to the dispersion, the molar ratio of chloroacetic acid to sodium hydroxide is 1:1.3, and the mass ratio of natural chitosan to chloroacetic acid is 1:1.8; control the reaction temperature at 58℃ and the stirring rate at 350 r / min, and stir for 4.5 h; after the reaction, adjust the pH of the system to 6.6 with 1 mol / L hydrochloric acid, centrifuge at 8000 r / min for 12 min, take the precipitate and wash it 4 times with anhydrous ethanol, add 5 times the mass of anhydrous ethanol to each wash, soak for 10 min and then centrifuge, and vacuum dry at 60℃ to constant weight to obtain carboxymethylated chitosan.

[0036] (2) Preparation of intermediate products: The carboxymethylated chitosan obtained in step (1) was dissolved in dimethyl sulfoxide. The mass ratio of carboxymethylated chitosan to dimethyl sulfoxide was 1:10. Poly(β-hydroxybutyrate) and coupling agent N,N'-dicyclohexylcarbodiimide were added. The mass ratio of carboxymethylated chitosan to poly(β-hydroxybutyrate) was 1:0.25. The molecular weight of poly(β-hydroxybutyrate) was 25 kDa. The amount of coupling agent added was 6% of the total mass of carboxymethylated chitosan and poly(β-hydroxybutyrate). The reaction temperature was controlled at 48℃ and the stirring rate was 300 r / min. The reaction was stirred for 6.5 h. Anhydrous ethanol was added in 3 times the volume of the reaction system to precipitate the product. After filtration, the product was washed twice with anhydrous ethanol. Each time, 4 times the mass of the filter residue was added to the product. The product was dried under vacuum at 50℃ to constant weight to obtain carboxymethylated-poly(β-hydroxybutyrate) modified chitosan.

[0037] (3) Preparation of triple-modified chitosan: The intermediate product obtained in step (2) was dissolved in deionized water to prepare an aqueous solution with a mass concentration of 3%; dopamine hydrochloride was added, and the mass ratio of the intermediate product to dopamine hydrochloride was 1:0.35. After stirring and dissolving, the pH of the system was adjusted to 8.1 with 0.1 mol / L Tris-HCl buffer; nitrogen gas was introduced for protection, and the reaction temperature was controlled at 32℃ and the stirring rate was 300 r / min. The reaction was stirred for 9 h; the reaction solution was dialyzed with a dialysis bag for 3 days, and the deionized water was replaced twice a day. The amount of deionized water replaced each time was 5 times the volume of the reaction solution in the dialysis bag. Then, the solution was freeze-dried at -45℃ and vacuum degree 12 Pa to constant weight to obtain triple-modified chitosan.

[0038] Preparation of functional composite fillers: Nano-sized hydroxyapatite was added to a 55% (w / w) aqueous ethanol solution (hydroxyapatite to ethanol solution mass ratio 1:10), silane coupling agent KH-550 was added, and the mixture was stirred at 62℃ and 300 r / min for 2.0 h, centrifuged at 8000 r / min for 10 min, and vacuum dried at 50℃ to constant weight to obtain modified hydroxyapatite; Carboxylated graphene oxide was dispersed in deionized water (carboxylated graphene oxide to deionized water mass ratio 1:20), and silver nitrate solution and reducing agent sodium citrate were added. The mass ratio of sodium citrate to carboxymethylated graphene oxide was 1:5, and the molar ratio of sodium citrate to silver nitrate was 1:1. The mixture was stirred at 65℃ and 300 r / min for 1.2 h, centrifuged at 8000 r / min for 10 min, and vacuum dried at 50℃ to constant weight to obtain carboxymethylated graphene oxide loaded with nano-silver. Modified hydroxyapatite and carboxymethylated graphene oxide loaded with nano-silver were mixed at a mass ratio of 3.5:1, and five times the mass of deionized water was added. The mixture was dispersed using an ultrasonic device with a power of 220W for 18 min and freeze-dried to constant weight to obtain a functional composite filler.

[0039] Preparation of drug dispersion: Minocycline hydrochloride was added to 6 times its mass of deionized water and dispersed for 12 minutes using an ultrasonic device with a power of 160W to obtain the drug dispersion.

[0040] Preparation of sustained-release hydrogel: Take 12 parts by weight of triple-modified chitosan, 4 parts by weight of functional filler, 0.8 parts by weight of minocycline hydrochloride, 1.2 parts by weight of genipin, and 70 parts by weight of deionized water. Add the triple-modified chitosan to the corresponding amount of deionized water, with a mass ratio of triple-modified chitosan to deionized water of 1:4. Dissolve the mixture in a 60℃ water bath at 350 rpm until completely transparent and free of precipitate. Add the functional composite filler and drug dispersion, disperse using a 200W ultrasonic device for 25 min, and then stir at 350 rpm. After 10 min, a homogeneous mixture was obtained. Genipin was added to the mixture, and the mixture was stirred at 350 r / min for 10 min until completely dissolved. The pH was adjusted to 7.0 with 0.1 mol / L Tris-HCl buffer. The mixture was poured into a mold and statically crosslinked at 37℃ for 2.5 h. After cooling to 25±2℃, the mixture was demolded and vacuum dried at 50℃ for 2 h until constant weight was obtained to obtain the hydrogel product. The hydrogel product was sterilized by γ-ray with a sterilization dose of 22 kGy to obtain a periodontal local drug sustained-release hydrogel.

[0041] Example 2: This embodiment prepares a chitosan-based periodontal topical drug sustained-release hydrogel, and the specific steps are as follows: Preparation of triple-modified chitosan: (1) Preparation of carboxymethylated chitosan: Take natural chitosan with a molecular weight of 90 kDa, add it to isopropanol, stir and disperse at 450 r / min for 50 min to prepare a chitosan dispersion with a mass concentration of 8%; add chloroacetic acid-sodium hydroxide mixed solution to the dispersion, the molar ratio of chloroacetic acid to sodium hydroxide is 1:1.4, and the mass ratio of natural chitosan to chloroacetic acid is 1:2.2; control the reaction temperature at 62℃ and the stirring rate at 450 r / min, and stir for 5.5 h; after the reaction, adjust the pH of the system to 6.9 with 1 mol / L hydrochloric acid, centrifuge at 10000 r / min for 15 min, take the precipitate and wash it 4 times with anhydrous ethanol, add 5 times the mass of anhydrous ethanol to each wash, soak for 10 min and then centrifuge, and vacuum dry at 60℃ to constant weight to obtain carboxymethylated chitosan.

[0042] (2) Preparation of intermediate products: The carboxymethylated chitosan obtained in step (1) was dissolved in dimethyl sulfoxide. The mass ratio of carboxymethylated chitosan to dimethyl sulfoxide was 1:10. Poly(β-hydroxybutyrate) and coupling agent N,N'-dicyclohexylcarbodiimide were added. The mass ratio of carboxymethylated chitosan to poly(β-hydroxybutyrate) was 1:0.35. The molecular weight of poly(β-hydroxybutyrate) was 45 kDa. The amount of coupling agent added was 9% of the total mass of carboxymethylated chitosan and poly(β-hydroxybutyrate). The reaction temperature was controlled at 52℃ and the stirring rate was 400 r / min. The reaction was stirred for 7.5 h. Anhydrous ethanol was added in 3 times the volume of the reaction system to precipitate the product. After filtration, the product was washed 3 times with anhydrous ethanol. Each time, 4 times the mass of the filter residue was added to the product. The product was dried under vacuum at 50℃ to constant weight to obtain carboxymethylated-poly(β-hydroxybutyrate) modified chitosan.

[0043] (3) Preparation of triple-modified chitosan: The intermediate product obtained in step (2) was dissolved in deionized water to prepare an aqueous solution with a mass concentration of 4%; dopamine hydrochloride was added, and the mass ratio of the intermediate product to dopamine hydrochloride was 1:0.55. After stirring and dissolving, the pH of the system was adjusted to 8.4 with 0.1 mol / L Tris-HCl buffer; nitrogen gas was introduced for protection, and the reaction temperature was controlled at 38℃ and the stirring rate was 400 r / min. The reaction was stirred for 12 h; the reaction solution was dialyzed with a dialysis bag for 4 days, and the deionized water was replaced 3 times a day. The amount of deionized water replaced each time was 5 times the volume of the reaction solution in the dialysis bag. Then, the solution was freeze-dried at -40℃ and vacuum degree 18 Pa to constant weight to obtain triple-modified chitosan.

[0044] Preparation of functional composite fillers: Nano-sized hydroxyapatite was added to a 65% (w / w) aqueous ethanol solution at a mass ratio of 1:15. A silane coupling agent, KH-550, was added, and the mixture was stirred at 68°C and 400 rpm for 2.8 h. After centrifugation at 8000 rpm for 10 min, the mixture was vacuum dried at 50°C to constant weight to obtain modified hydroxyapatite. Carboxylated graphene oxide was dispersed in deionized water at a mass ratio of 1:30. Silver nitrate solution and a reducing agent, sodium citrate, were added. The mass ratio of carboxymethylated graphene oxide was 1:8, and the molar ratio of sodium citrate to silver nitrate was 1.2:1. The mixture was stirred at 75℃ and 400 r / min for 1.8 h, centrifuged at 8000 r / min for 10 min, and vacuum dried at 50℃ to constant weight to obtain carboxymethylated graphene oxide loaded with nano-silver. Modified hydroxyapatite and carboxymethylated graphene oxide loaded with nano-silver were mixed at a mass ratio of 4.5:1, and five times the mass of deionized water was added. The mixture was dispersed using an ultrasonic device with a power of 280W for 25 min and freeze-dried to constant weight to obtain a functional composite filler.

[0045] Preparation of drug dispersion: Minocycline hydrochloride was added to 10 times its mass of deionized water and dispersed for 18 minutes using an ultrasonic device with a power of 200W to obtain the drug dispersion.

[0046] Preparation of sustained-release hydrogel: Take 18 parts by weight of triple-modified chitosan, 6 parts by weight of functional filler, 1.5 parts by weight of minocycline hydrochloride, 2.5 parts by weight of genipin, and 80 parts by weight of deionized water. Add the triple-modified chitosan to the corresponding amount of deionized water, with a mass ratio of triple-modified chitosan to deionized water of 1:6. Dissolve the mixture in a 68℃ water bath at 450 rpm until completely transparent and free of precipitate. Add the functional composite filler and drug dispersion, disperse using a 280W ultrasonic device for 35 min, and then stir at 450 rpm. After 10 min, a homogeneous mixture was obtained. Genipin was added to the mixture, and the mixture was stirred at 450 r / min for 10 min until completely dissolved. The pH was adjusted to 7.1 with 0.1 mol / L Tris-HCl buffer. The mixture was poured into a mold and statically crosslinked at 37℃ for 3.5 h. After cooling to 25±2℃, the mixture was demolded and vacuum dried at 50℃ for 3 h until constant weight was obtained to obtain the hydrogel product. The hydrogel product was sterilized by γ-ray with a sterilization dose of 25 kGy to obtain a periodontal local drug sustained-release hydrogel.

[0047] Example 3: This embodiment prepares a chitosan-based periodontal topical drug sustained-release hydrogel, and the specific steps are as follows: Preparation of triple-modified chitosan: (1) Preparation of carboxymethylated chitosan: Take natural chitosan with a molecular weight of 75 kDa, add it to isopropanol, stir and disperse at 400 r / min for 45 min to prepare a chitosan dispersion with a mass concentration of 7%; add chloroacetic acid-sodium hydroxide mixed solution to the dispersion, the molar ratio of chloroacetic acid to sodium hydroxide is 1:1.35, and the mass ratio of natural chitosan to chloroacetic acid is 1:2.0; control the reaction temperature at 60℃ and the stirring rate at 400 r / min, and stir for 5.0 h; after the reaction, adjust the pH of the system to 6.75 with 1 mol / L hydrochloric acid, centrifuge at 9000 r / min for 13 min, take the precipitate and wash it 4 times with anhydrous ethanol, add 5 times the mass of anhydrous ethanol to each wash, soak for 10 min and then centrifuge, and vacuum dry at 60℃ to constant weight to obtain carboxymethylated chitosan.

[0048] (2) Preparation of intermediate products: The carboxymethylated chitosan obtained in step (1) was dissolved in dimethyl sulfoxide. The mass ratio of carboxymethylated chitosan to dimethyl sulfoxide was 1:10. Poly(β-hydroxybutyrate) and coupling agent N,N'-dicyclohexylcarbodiimide were added. The mass ratio of carboxymethylated chitosan to poly(β-hydroxybutyrate) was 1:0.30. The molecular weight of poly(β-hydroxybutyrate) was 35 kDa. The amount of coupling agent added was 7.5% of the total mass of carboxymethylated chitosan and poly(β-hydroxybutyrate). The reaction temperature was controlled at 50℃ and the stirring rate was 350 r / min. The reaction was stirred for 7.0 h. Anhydrous ethanol was added in 3 times the volume of the reaction system to precipitate the product. After filtration, the product was washed twice with anhydrous ethanol. Each time, anhydrous ethanol was added in 4 times the mass of the filter residue. The product was dried under vacuum at 50℃ to constant weight to obtain carboxymethylated-poly(β-hydroxybutyrate) modified chitosan.

[0049] (3) Preparation of triple-modified chitosan: The intermediate product obtained in step (2) was dissolved in deionized water to prepare an aqueous solution with a mass concentration of 3.5%; dopamine hydrochloride was added, and the mass ratio of the intermediate product to dopamine hydrochloride was 1:0.45. After stirring and dissolving, the pH of the system was adjusted to 8.25 with 0.1 mol / L Tris-HCl buffer; nitrogen gas was introduced for protection, and the reaction temperature was controlled at 35℃ and the stirring rate was 350 r / min. The reaction was stirred for 10.5 h; the reaction solution was dialyzed with a dialysis bag for 3 days, and the deionized water was replaced twice a day. The amount of deionized water replaced each time was 5 times the volume of the reaction solution in the dialysis bag. Then, the solution was freeze-dried at -42℃ and vacuum degree 15 Pa to constant weight to obtain triple-modified chitosan.

[0050] Preparation of functional composite fillers: Nano-sized hydroxyapatite was added to a 60% (w / w) aqueous ethanol solution at a mass ratio of 1:12. A silane coupling agent, KH-550, was added, and the mixture was stirred at 65°C and 350 rpm for 2.4 h. After centrifugation at 8000 rpm for 10 min, the mixture was vacuum dried at 50°C to constant weight to obtain modified hydroxyapatite. Carboxylated graphene oxide was dispersed in deionized water at a mass ratio of 1:25. Silver nitrate solution and sodium citrate reducing agent were added. The silver nitrate and carboxylated graphene oxide... The mass ratio of methylated graphene oxide was 1:6.5, and the molar ratio of sodium citrate to silver nitrate was 1.1:1. The reaction was carried out at 70℃ and 350 r / min for 1.5 h with stirring, followed by centrifugation at 8000 r / min for 10 min, and vacuum drying at 50℃ to constant weight to obtain carboxylated graphene oxide loaded with nano-silver. Modified hydroxyapatite and carboxylated graphene oxide loaded with nano-silver were mixed at a mass ratio of 4.0:1, and five times the mass of deionized water was added. The mixture was dispersed using an ultrasonic device with a power of 250W for 22 min and freeze-dried to constant weight to obtain a functional composite filler.

[0051] Preparation of drug dispersion: Minocycline hydrochloride was added to 8 times its mass of deionized water and dispersed for 15 minutes using an ultrasonic device with a power of 180W to obtain the drug dispersion.

[0052] Preparation of sustained-release hydrogel: Take 15 parts by weight of triple-modified chitosan, 5 parts by weight of functional filler, 1.2 parts by weight of minocycline hydrochloride, 1.8 parts by weight of genipin, and 75 parts by weight of deionized water. Add the triple-modified chitosan to the corresponding amount of deionized water, with a mass ratio of triple-modified chitosan to deionized water of 1:5. Dissolve the mixture in a 64℃ water bath at 400 rpm until completely transparent and free of precipitate. Add the functional composite filler and drug dispersion, disperse using a 250W ultrasonic device for 30 min, and then stir at 400 rpm for 10 min. A homogeneous mixture was obtained by stirring at 400 rpm for 10 minutes until completely dissolved. The pH was adjusted to 7.05 using 0.1 mol / L Tris-HCl buffer. The mixture was poured into a mold and statically crosslinked at 37°C for 3.0 hours. After cooling to 25±2°C, the mixture was demolded and vacuum dried at 50°C for 2.5 hours until constant weight, yielding the hydrogel product. The hydrogel product was sterilized using γ-rays at a sterilization dose of 23.5 kGy to obtain a sustained-release hydrogel for periodontal local drug delivery.

[0053] Comparative Example 1: This comparative example uses the preparation method of Example 3, with the only difference being that: the chitosan was not triple-modified, and natural chitosan was used directly as the hydrogel substrate; the other raw material ratios and preparation process parameters were the same as in Example 3.

[0054] Comparative Example 2: This comparative example uses the preparation method of Example 3, with the only difference being that no functional filler was added, while the other raw material ratios and preparation process parameters are the same as in Example 3.

[0055] Comparative Example 3: This comparative example uses the preparation method of Example 3, with the only difference being that the crosslinking agent genipin is replaced with glutaraldehyde, while the other raw material ratios and preparation process parameters are the same as in Example 3.

[0056] Comparative Example 4: This comparative example uses the preparation method of Example 3, with the only difference being that only hydroxyapatite is used as the functional filler, and no carboxylated graphene oxide loaded with nano-silver is added. The other raw material ratios and preparation process parameters are the same as those in Example 3.

[0057] Experiment 1: In vitro sustained-release performance test of the drug: 1.1 Experimental Objective: The cumulative drug release rate of the hydrogels in Examples 1-3 and Comparative Examples 1-4 was tested in a simulated periodontal fluid environment to verify the influence of the innovative technical features such as triple-modified chitosan, functional fillers, and special crosslinking agents on the drug sustained-release performance of the hydrogel. The cumulative drug release rate is the core performance indicator of periodontal local drug sustained-release hydrogels, which directly reflects the drug sustained-release effect and duration of action of the hydrogel.

[0058] 1.2 Experimental Principle: The release medium was prepared to simulate the physiological environment of periodontal fluid. The drug-loaded hydrogel sample was placed in the release medium and the drug concentration in the release medium was measured at regular intervals under constant temperature oscillation at 37℃. The cumulative drug release rate at different time points was calculated and the drug release curve was plotted to intuitively reflect the in vitro sustained-release performance of the hydrogel.

[0059] 1.3 Experimental Instruments and Reagents: Experimental instruments: intelligent dissolution tester, high performance liquid chromatograph, electronic balance (accuracy 0.0001g), constant temperature shaking incubator, centrifuge, volumetric flask, pipette; Experimental reagents: hydrogel samples of Examples 1-3 and Comparative Examples 1-4, minocycline hydrochloride standard, potassium dihydrogen phosphate, disodium hydrogen phosphate, sodium chloride, potassium chloride, all of which were analytical grade and deionized water.

[0060] 1.4 Test Methods: Preparation of simulated periodontal solution: Weigh 0.24g potassium dihydrogen phosphate, 1.42g disodium hydrogen phosphate, 8.00g sodium chloride, and 0.20g potassium chloride, add deionized water to make up to 1000mL, adjust the pH to 7.4, and obtain the simulated periodontal solution release medium; Sample preparation: Cut the hydrogel samples of Examples 1-3 and Comparative Examples 1-4 into round pieces with a diameter of 10 mm and a thickness of 2 mm. Weigh 0.1000 g of each sample accurately and place them in a dissolution cup. Slow-release test: Add 500 mL of simulated periodontal fluid to the dissolution cup, set the temperature of the intelligent dissolution tester to 37℃ and the oscillation rate to 50 r / min, and take 5 mL samples at 1 h, 4 h, 8 h, 12 h, 24 h, 48 h, 72 h, 96 h and 120 h respectively, and replenish with an equal volume of fresh simulated periodontal fluid at the same temperature. Concentration determination: After filtering the sample solution through a 0.22 μm filter membrane, the concentration of minocycline hydrochloride was determined by high performance liquid chromatography. Chromatographic conditions: C18 column, mobile phase: methanol-0.01 mol / L phosphate buffer (volume ratio 40:60), detection wavelength: 348 nm, column temperature: 30 ℃, flow rate: 1.0 mL / min. Calculate the cumulative release rate: Based on the measured drug concentration, calculate the cumulative release rate of the drug at each time point. Each sample is tested in parallel 3 times, and the average value is taken as the final result.

[0061] 1.5 Experimental Data: Table 1. Cumulative drug release rate (%) of hydrogel samples in simulated periodontal fluid As can be seen from the data of Experiment 1, the hydrogel samples of Examples 1-3 all exhibited excellent in vitro drug release performance. In the simulated periodontal fluid environment, the drug release rate was slow, and the cumulative drug release rate was above 90% after 120 hours.

[0062] Comparing Example 3 with Comparative Example 1, it can be seen that Comparative Example 1, which did not use triple-modified chitosan and directly used natural chitosan as the substrate, showed a significant increase in the initial drug release rate, with a cumulative release rate of 25.6% after 1 hour, 70.2% after 12 hours, and near-complete release after 48 hours, resulting in a sharp decline in sustained-release performance. This is because the triple-modified chitosan, after carboxymethylation, polyβ-hydroxybutyrate grafting, and mussel-inspired polyphenol modification, exhibits significantly improved hydrophilicity, gelling properties, and network structure stability of its molecular chains. The resulting three-dimensional hydrogel network has suitable pore size and cross-linking degree, enabling slow diffusion and release of the drug. In contrast, natural chitosan has poor gelling properties, resulting in a loose gel network structure where the drug easily dissolves rapidly, failing to achieve a sustained-release effect.

[0063] Comparing Example 3 and Comparative Example 2, it can be seen that Comparative Example 2, without the addition of functional fillers, had a higher overall cumulative drug release rate than Example 3, but the sustained-release effect was somewhat reduced. This is because the hydroxyapatite and carboxylated graphene oxide loaded with silver nanoparticles in the functional filler can form hydrogen bonds and physical cross-links with the molecular chains of triple-modified chitosan, further densifying the three-dimensional network structure of the hydrogel and slowing down the drug diffusion rate. Simultaneously, the micro-nano structure of the functional filler can physically adsorb drug molecules, further enhancing the sustained-release effect. Without this component, the density of the gel network decreases, the drug adsorption disappears, and the release rate accelerates.

[0064] Comparing Example 3 and Comparative Example 3, it can be seen that replacing the crosslinking agent genipin with glutaraldehyde in Comparative Example 3 significantly reduced the sustained-release performance of the hydrogel. The reason is that genipin undergoes a Schiff base reaction with the amino groups of chitosan, resulting in a mild crosslinking reaction and stable crosslinking bonds, which can construct a three-dimensional gel network with uniform pore size. In contrast, glutaraldehyde has a rapid crosslinking reaction rate, easily causing uneven crosslinking and resulting in a gel network with large pore size differences. Some drug molecules can easily dissolve rapidly from the larger pores. Furthermore, the crosslinking bonds of glutaraldehyde are less stable under physiological conditions and are prone to hydrolysis, leading to the destruction of the gel network structure and an accelerated drug release rate.

[0065] Comparing Example 3 and Comparative Example 4, it can be seen that Comparative Example 4, which uses only hydroxyapatite as the functional filler without adding carboxylated graphene oxide loaded with silver nanoparticles, exhibits a slightly higher drug release rate than Example 3, but a reduced sustained-release effect. This is because the carboxylated graphene oxide loaded with silver nanoparticles has a layered structure that can be uniformly dispersed in the gel network, forming a physical barrier layer that slows drug diffusion. Simultaneously, its surface carboxyl groups can form electrostatic interactions with the triple-modified chitosan, further stabilizing the gel network. When only hydroxyapatite is used, the physical barrier and electrostatic interaction effects are weakened, resulting in a slightly increased drug release rate.

[0066] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

[0067] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and variations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A chitosan-based periodontal topical drug sustained-release hydrogel, characterized in that, It is composed of the following components by weight: 12-18 parts of triple-modified chitosan, 4-6 parts of functional filler, 0.8-1.5 parts of therapeutic agent, 1.2-2.5 parts of crosslinking agent, and 70-80 parts of deionized water; The triple-modified chitosan is a carboxymethylated mussel biomimetic polyphenol-polyβ-hydroxybutyrate triple-modified chitosan. The functional filler is a composite powder of hydroxyapatite and carboxylated graphene oxide loaded with nano-silver. The therapeutic drug is an antibacterial or anti-inflammatory drug for the treatment of periodontitis.

2. The chitosan-based periodontal topical drug sustained-release hydrogel according to claim 1, characterized in that, The preparation method of the triple-modified chitosan is as follows: (1) Preparation of carboxymethylated chitosan: Take natural chitosan with a degree of deacetylation ≥92% and a molecular weight of 60-90 kDa, add it to isopropanol, and stir and disperse it at 350-450 r / min for 40-50 min to prepare a chitosan dispersion with a mass concentration of 6%-8%; add a chloroacetic acid-sodium hydroxide mixed solution to the dispersion, wherein the molar ratio of chloroacetic acid to sodium hydroxide is 1:1.3-1.4, and the mass ratio of natural chitosan to chloroacetic acid is 1:1.8-2.2; control The reaction temperature was set at 58-62℃, the stirring rate at 350-450 r / min, and the reaction was carried out for 4.5-5.5 h. After the reaction was completed, the pH of the system was adjusted to 6.6-6.9 with 1 mol / L hydrochloric acid, and the mixture was centrifuged at 8000-10000 r / min for 12-15 min. The precipitate was washed 4 times with anhydrous ethanol, with 5 times the mass of the precipitate added for each wash. After soaking for 10 min, the mixture was centrifuged and dried under vacuum at 60℃ to constant weight to obtain carboxymethyl chitosan. (2) Preparation of intermediate product: The carboxymethylated chitosan obtained in step (1) is dissolved in dimethyl sulfoxide, with a mass ratio of carboxymethylated chitosan to dimethyl sulfoxide of 1:

10. Poly(β-hydroxybutyrate) and coupling agent N,N'-dicyclohexylcarbodiimide are added. The mass ratio of carboxymethylated chitosan to poly(β-hydroxybutyrate) is 1:0.25-0.35, the molecular weight of poly(β-hydroxybutyrate) is 25-45 kDa, and the amount of coupling agent added is 6%-9% of the total mass of carboxymethylated chitosan and poly(β-hydroxybutyrate). The reaction temperature is controlled at 48-52℃, the stirring rate is 300-400 r / min, and the reaction is stirred for 6.5-7.5 h. Anhydrous ethanol is added in 3 times the volume of the reaction system to precipitate the product. After filtration, the product is washed 2-3 times with anhydrous ethanol. Each time, 4 times the mass of the filter residue is added to the product. The product is dried under vacuum at 50℃ to constant weight to obtain the intermediate product: carboxymethylated-poly(β-hydroxybutyrate) modified chitosan. (3) Preparation of triple-modified chitosan: Dissolve the intermediate product obtained in step (2) in deionized water to prepare an aqueous solution with a mass concentration of 3%-4%; add dopamine hydrochloride, wherein the mass ratio of the intermediate product to dopamine hydrochloride is 1:0.35-0.55, stir to dissolve, and then adjust the pH of the system to 8.1-8.4 with 0.1mol / L Tris-HCl buffer. Nitrogen gas was introduced for protection, and the reaction temperature was controlled at 32-38℃, the stirring rate at 300-400 r / min, and the reaction was carried out for 9-12 hours. The reaction solution was dialyzed through a dialysis bag for 3-4 days, with the deionized water replaced 2-3 times a day. Each time, the volume of deionized water replaced was 5 times the volume of the reaction solution in the dialysis bag. Then, the solution was freeze-dried to constant weight at -45℃ to -40℃ and a vacuum of 12-18 Pa to obtain triple-modified chitosan.

3. The chitosan-based periodontal topical drug sustained-release hydrogel according to claim 2, characterized in that, The dialysis bag has a molecular weight cutoff of 8000-10000 Da.

4. The chitosan-based periodontal topical drug sustained-release hydrogel according to claim 1, characterized in that, The therapeutic drug is selected from one of minocycline hydrochloride, metronidazole, amoxicillin, ibuprofen, and dexamethasone.

5. The chitosan-based periodontal topical drug sustained-release hydrogel according to claim 1, characterized in that, The crosslinking agent is genipin.

6. The chitosan-based periodontal topical drug sustained-release hydrogel according to any one of claims 1-5, characterized in that, Preparation method of sustained-release hydrogel, Includes the following steps: S1: Prepare carboxymethylated mussel biomimetic polyphenol-polyβ-hydroxybutyrate triple-modified chitosan according to the method described above; S2: Preparation of functional composite fillers: Nano-sized hydroxyapatite was added to a 55%-65% (w / w) ethanol aqueous solution, with a hydroxyapatite to ethanol aqueous solution mass ratio of 1:10-15. A silane coupling agent, KH-550, was added. The mixture was stirred at 62-68℃ and 300-400 r / min for 2.0-2.8 h, centrifuged at 8000 r / min for 10 min, and vacuum dried at 50℃ to constant weight to obtain modified hydroxyapatite. Carboxymethylated graphene oxide was dispersed in deionized water, with a carboxymethylated graphene oxide to deionized water mass ratio of 1:20-30. Silver nitrate solution and reducing agent sodium citrate were added. The mass ratio of carboxymethylated graphene oxide was 1:5-8, the molar ratio of sodium citrate to silver nitrate was 1-1.2:1, the reaction was carried out at 65-75℃ and 300-400 r / min for 1.2-1.8 h, centrifuged at 8000 r / min for 10 min, and vacuum dried at 50℃ to constant weight to obtain carboxymethylated graphene oxide loaded with nano-silver; the modified hydroxyapatite and the carboxymethylated graphene oxide loaded with nano-silver were mixed at a mass ratio of 3.5-4.5:1, five times the mass of deionized water was added, the mixture was dispersed with an ultrasonic device with a power of 220-280W for 18-25 min, and freeze-dried to constant weight to obtain a functional composite filler; S3: Preparation of drug dispersion: Disperse the drug in 6-10 times the weight of deionized water using an ultrasonic device with a power of 160-200W for 12-18 minutes to obtain the drug dispersion. S4: Preparation of the mixed system: Add the triple-modified chitosan obtained in step S1 to deionized water, with a mass ratio of triple-modified chitosan to deionized water of 1:4-6. Dissolve the chitosan in a water bath at 60-68℃ and stir at 350-450 r / min until completely transparent and free of precipitate. Add the functional composite filler obtained in step S2 and the drug dispersion obtained in step S3. Disperse the mixture using an ultrasonic device with a power of 200-280W for 25-35 min, and then stir at 350-450 r / min for 10 min to obtain a homogeneous mixed system. S5: Cross-linking molding: Add genipin to the mixture obtained in step S4, stir at 350-450 r / min for 10 min until completely dissolved, adjust the pH to 7.0-7.1 with 0.1 mol / L Tris-HCl buffer; pour the system into a mold, place it in a constant temperature environment of 37℃ for static cross-linking for 2.5-3.5 h, cool to 25±2℃, demold, and vacuum dry at 50℃ for 2-3 h to constant weight to obtain the hydrogel product; S6: Sterilization treatment: The hydrogel product obtained in step S5 is sterilized by gamma rays. After sterilization, a periodontal local drug sustained-release hydrogel is obtained.

7. The chitosan-based periodontal topical drug sustained-release hydrogel according to claim 6, characterized in that, The carboxylated graphene oxide described in S2 has a carboxyl substitution degree of 12%-18%.

8. The chitosan-based periodontal topical drug sustained-release hydrogel according to claim 6, characterized in that, The gamma ray sterilization described in S6 has a sterilization dose of 22-25 kGy.

9. The application of the chitosan-based periodontal topical drug sustained-release hydrogel as described in claim 1 in the preparation of a drug delivery carrier for the local treatment of periodontitis, characterized in that, The hydrogel can be formulated as a gel, film, or injection.

10. The application according to claim 9, characterized in that, The application methods are intraperitoneal injection, topical application, or plastering.

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