A temperature-sensitive modified chitin hydrogel-loaded local anesthetic sustained-release analgesic system, preparation method and application thereof

Abstract

The invention discloses a temperature-sensitive modified chitosan hydrogel-loaded local anesthetic sustained-release analgesic system, a preparation method and an application. A temperature-sensitive chitosan derivative is dissolved in water at low temperature, a local anesthetic analgesic aqueous solution or a degradable polymer microsphere loaded with a local anesthetic analgesic is added in a liquid state and mixed evenly at low temperature, and the system is injected into a part requiring local anesthesia and analgesia to quickly form a gel at body temperature and release the drug slowly. The main features of the local anesthetic sustained-release analgesic composite hydrogel system are simple preparation, no organic solvent is used, and the local anesthetic analgesic can be slowly released, which solves the problem of the existing local anesthetics such as bupivacaine hydrochloride, ropivacaine and lidocaine being released too quickly and having a short action time; it can completely fill irregular wounds, has good biocompatibility and biodegradability, and is conducive to long-term local anesthesia, analgesia, anti-inflammatory and antipruritic effects and promotes wound healing.

Description

Technical Field

[0001] The present invention belongs to the field of pharmaceutical preparations, and relates to a drug sustained-release system, a preparation method and an application thereof, and more specifically to a chitin hydrogel-loaded local anesthetic sustained-release analgesic system, a preparation method and an application thereof. Background Art

[0002] Pain is an unpleasant feeling and emotional sensation, accompanied by actual or potential tissue damage. It is a subjective feeling and is considered to be the fifth vital sign of the human body after breathing, pulse, body temperature, and blood pressure. It is one of the most common symptoms in clinical practice. It can be acute or chronic. Acute pain occurs after trauma or surgery and is self-limiting. It will be relieved when tissue damage recovers. If it is not relieved, it can develop into chronic pain. Chronic pain refers to pain that lasts longer than the normal recovery time of acute injury or disease and recurs over a long period of time. Some long-term severe pain, such as neuralgia, cancer pain, arthritis pain, low back pain, etc., is not only an unbearable torture for patients, but also causes physiological dysfunction. Therefore, analgesia is one of the important tasks and difficulties in clinical treatment, and it is also an important topic in medical research.

[0003] At present, postoperative analgesia mainly includes systemic analgesia and local analgesia. The former mainly refers to oral or intravenous analgesics, such as opioids and nonsteroidal anti-inflammatory drugs. Since the drugs have effects on multiple systems, they have more side effects, such as constipation, nausea, vomiting, etc., and more serious ones can cause respiratory depression or even death. In addition, long-term use of opioids can cause tolerance, drug abuse and addiction problems. Local analgesia mainly uses local anesthetics (local anesthetics). Local anesthetics can block the transmission of pain signals to the central nervous system by blocking sodium and other ion channels on the nerve cell membrane, resulting in the blocking of electrical signals of all nerve downstream structures, thereby achieving the effect of postoperative analgesia. Local anesthetics have strong targeted effects, reduce systemic side effects, and are safer. At the same time, local analgesia is simple to operate and can be completed in outpatient clinics. It is low-cost and reduces the burden on patients. At present, local anesthetics have been used for postoperative analgesia in surgical operations such as thoracotomy, laparotomy, cesarean section, breast cancer surgery, cosmetic breast surgery, limb amputation, etc., and have played an important role in the control and relief of acute and chronic pain after various major operations.

[0004] However, the existing local anesthetic analgesics have a short duration of action, generally not exceeding a few hours, while the analgesic time required clinically is generally 24 hours, a few days to more than ten days, which requires increasing the dosage, repeated administration, catheter implantation or self-controlled analgesia pumps to prolong the analgesic effect. However, although the incidence of these anesthetics' cardiocerebral side effects is low, once they occur, they are a great threat to the patient's life safety. Catheter implantation or self-controlled analgesia pumps not only require expensive equipment and continuous monitoring, but also need to be removed after use, and are prone to cause problems such as catheter blockage, breakage, and infection complications. Sustained-release local anesthetics can not only improve the analgesic effect of local anesthetics, but also reduce the frequency of medication and reduce the adverse reactions of high-dose use, so they have received more and more attention. At present, the long-acting sustained-release drug delivery systems for local anesthetics mainly include microspheres, liposomes, implants, injectable in situ gels, etc. Microspheres are spherical or quasi-spherical tiny spherical entities, and the particle size range of microspheres is generally 1-500 microns, with a small size of a few nanometers and a large size of up to 800 microns. Microspheres have better fluidity than irregular powder particles. In 1994, French scholars Corre et al. reported on the study of microspheres as local anesthetic carriers. They used polylactic acid (PLA) with different molecular weights to prepare bupivacaine sustained-release microspheres, which could release bupivacaine in vitro for up to 24 hours. They also found that increasing the amount of low molecular weight PLA would increase the initial burst release ratio of the drug [Preparation and characterization of bupivacaine-loaded polylactide and polylactide-co-glycolide microspheres, International Journal of Pharmaceutics, 1994, 107N1, 41-49, DOI: 10.1016 / 0378-5173(94)90300-X]. Traditional methods for preparing drug-loaded microspheres mainly include emulsification dispersion-solvent evaporation method, spray drying method and coacervation method. Emulsion dispersion method often requires the use of organic solvents and surfactants. It is simple and easy to operate and is the most commonly used method in laboratory research. However, there are problems with the residual organic solvents and dispersants, and there are many factors affecting the scale-up production, and the process control requirements are high. The spray drying process is simple, low-cost, and easy to scale up and continuously produce. However, it is limited in laboratory research, the size of the microspheres is difficult to control, and the microspheres are prone to aggregation. The coagulation method refers to the influence of external physical and chemical factors in the mixed liquid of the material, such as the use of opposite charges, dehydration, solvent replacement and other measures to change the solubility of the material and precipitate it from the solution. The size distribution of microspheres produced by these commonly used ball-forming drug loading methods is relatively wide, and many drugs are deposited and crystallized on the surface of the microspheres, with obvious high burst release.Ma Guanghui's team used a new rapid membrane emulsification technology to prepare ropivacaine-loaded polylactic-co-glycolic acid (PLGA) microspheres with uniform particle size, high embedding rate, and low burst release [CN201810874175.3, Anesthetic analgesic sustained-release microspheres, preparation method thereof, and application thereof]. However, the microspheres have poor in-situ properties and may diffuse along the intermuscular space at the injection site after injection. In addition, the initial burst release of drug-loaded microspheres may affect the duration of blockade and even produce local or systemic toxicity.

[0005] There are many studies on liposomal local anesthetics, among which the liposomal local anesthetic Exparel has become the first sustained-release local anesthetic for clinical use. It was first approved by the US Food and Drug Administration (FDA) in 2011 for local infiltration anesthesia. It can achieve an analgesic effect of 72 hours in vivo. In 2018, it was further approved for brachial plexus block with interscalene access. However, one weakness of Exparel is the instability of liposomes. The drug is easy to leak. The storage temperature needs to be controlled at 2-8°C. Transportation must be through the cold chain. In addition, the carrier liposomes used may cause some granulomatous inflammation [The safety and tolerability evaluation of DepoFoam bupivacaine (bupivacaine extended-release liposome injection) administered by incision wound infiltration in rabbits and dogs, Expert Opin. Investig. Drugs 2011, 20N10, 1327-1341]. At present, only a few countries use Exparel clinically, and this type of liposomal local anesthetic has not been approved for marketing in China. Recently, scholars from the United States and Canada published a systematic review and meta-analysis article in the Journal of Anesthesiology, stating that the analgesic effect of liposomal bupivacaine for peripheral nerve block is not superior to nonliposomal bupivacaine [Perineural Liposomal BupivacaineIs Not Superior to Nonliposomal Bupivacaine for Peripheral Nerve BlockAnalgesia, Anesthesiology 2021, 134, 147-64].

[0006] There is limited research on implants for sustained-release local anesthetics. The Kohane research group at Harvard Medical School in the United States used electrospinning technology to load the local anesthetic bupivacaine into polylactic-co-glycolic acid (PLGA) surgical sutures for postoperative wound sutures, achieving a slow-release and sustained analgesic effect. However, the mechanical strength of local anesthetic-loaded surgical sutures is difficult to reach that of commercial sutures, so there is a risk of suture breakage in clinical applications [Electrospundrug-eluting sutures for local anesthesia, JOURNAL OF CONTROLLED RELEASE 161N3, 903-909, DOI: 10.1016 / j.jconrel.2012.05.021]. Ma Chao's research group used electrospun PLGA solution containing bupivacaine to prepare drug-loaded nonwoven fabrics, and then hot-pressed them into drug-loaded nanomembranes, which were implanted into subcutaneous incisions in rats and showed a long analgesic effect and in vivo safety [Electrospun PLGA nanomembrane: A novel formulation of extended-release bupivacaine delivery reducing postoperative pain, 2020-033AE-MATERIALS&DESIGN 193, 108768, DOI: 10.1016 / j.matdes.2020.108768]. However, the organic solvent hexafluoroisopropanol was used in these preparation processes, and the complete removal of organic solvents is a difficult point, and safety is difficult to guarantee. On August 28, 2020, the US FDA approved the sterile surgical implant XARACOLL for pain control after open inguinal hernia repair. XARACOLL is a unique, non-injectable drug-device combination in the form of a fully bioresorbable collagen implant that contains bupivacaine hydrochloride. XARACOLL is placed directly at the surgical site during surgery and releases bupivacaine immediately and over time, providing statistically significant analgesia over 24 hours compared to placebo [https: / / www.drugs.com / history / xaracoll.html].

[0007] Injectable in situ gels are administered in the form of fluid drug-containing solutions. At the injection site, due to the physiological environment in the body, a phase transition or an in situ cross-linking reaction occurs, and the liquid is transformed into a non-cross-linked semi-solid gel or a cross-linked gel. The cross-linking here can be physical cross-linking or chemical cross-linking. Physical cross-linking is mainly formed by intermolecular interactions (van der Waals forces, hydrophobic interactions, charge interactions, hydrogen bonds, etc.). Since this type of gel does not involve chemical reactions during its formation, it gels quickly, making it simpler and safer to use. In particular, thermosensitive injectable hydrogels mainly achieve solution-gel transition based on changes in external temperature, do not require the participation of chemical reagents, have good biocompatibility, and are widely studied for medical purposes. This type of thermosensitive gel remains a flowable liquid at low temperatures (4°C), can uniformly encapsulate cells / drugs, and does not require surgical implantation, thereby improving patient compliance. After being injected into the body through a syringe, the polymer can quickly form a gel at body temperature (37°C) to avoid the loss of cells and bioactive drug molecules, etc., and can be used as an in situ drug delivery system to achieve local slow release of drugs. Because temperature response is the easiest and most effective response to achieve, this type of smart hydrogel drug sustained-release carrier has an attractive development prospect. At present, a variety of thermosensitive gels have been used in the long-acting analgesia research of local anesthetics. Fu Xudong et al. disclosed a thermosensitive PLGA-PEG-PLGA copolymer gel for long-acting injection of ropivacaine and its preparation method. The pharmacodynamic study showed that the thermosensitive gel group of ropivacaine can significantly prolong the duration of drug efficacy and can continuously exert analgesic effect for 48 hours [CN201510028754.2, Thermosensitive gel for long-acting injection of ropivacaine and its preparation method]. The Lim group in South Korea used thermosensitive poloxamer F-127 and hyaluronic acid to prepare an injectable gel containing 0.75% ropivacaine [Preclinical studies of ropivacaine extended-release from a temperatureresponsive hydrogel for prolonged relief of pain at the surgical wound, 2019-041HG-INT J PHARM 558, 225-230, DOI: 10.1016 / j.ijpharm.2019.01.011]. The peak concentration and average concentration of ropivacaine at the subcutaneous gel injection site in rats were twice that of ordinary drug solution injection, while the blood drug concentration of the injected gel was much lower than the drug concentration of the solution injection. These indicate that the thermosensitive gel has a local sustained release effect, although the gel release in vitro also has a burst release phenomenon.Zhang Wenjing et al. prepared a hydrogel / microsphere composite drug delivery system (Gel-MS) consisting of an in situ thermosensitive PLGA-PEG-PLGA hydrogel and PLGA microspheres loaded with bupivacaine. This drug delivery system can achieve in situ sustained and slow release of bupivacaine without obvious initial burst release. The rat sciatic nerve block model showed that the analgesic effect of the Gel-MS system was much stronger than that of simple microspheres and gel preparations [Precision guided long-acting analgesia by Gel-immobilized bupivacaine-loaded microsphere, Theranostics2018; 8(12): 3331-3347. doi:10.7150 / thno.25276]. Durect, a US company, has developed a sustained-release bupivacaine hydrochloride in situ gel injection, Posimir, which uses N-methylpyrrolidone and sucrose acetate isobutyrate as excipients. It is a solution with good fluidity before injection. After being injected into the local medication site, it comes into contact with body fluids and turns into a gel state. The high viscosity allows bupivacaine to remain locally at a high concentration and diffuse slowly. On February 1, 2021, the US Food and Drug Administration (FDA) approved the use of Posimir (bupivacaine solution) for infiltration and penetration in adults. It is used to treat arthroscopic subacromial decompression and directly visualize under the arthroscope to achieve postoperative analgesia for up to 72 hours and reduce the use of opioids. However, the gel injection system is greatly affected by the environment, the bupivacaine concentration is high, and it is easy to cause drug leakage. In addition, the use of the organic solvent N-methylpyrrolidone also has some toxicity and possible carcinogenic risks. [https: / / www.drugs.com / history / posimir.html]. Since local anesthesia is administered around nerves, it places high demands on the tissue compatibility, biodegradability, and local irritation of the materials. Therefore, it is of great significance to develop a new sustained-release dosage form of long-acting local anesthetics that can prolong the duration of action, is easy to use, and has good biodegradability and compatibility.

[0008] Because chitosan and its derivatives have very good biocompatibility, biodegradability and multiple biological activities, they are suitable for drug sustained-release carriers and biomedical materials. Chitosan reacts with a carboxylation agent in a sodium hydroxide-urea system to produce carboxyl chitosan with pH sensitivity and temperature sensitivity [China Invention Patent Application Publication Specification CN201310641249.6], chitosan reacts with a hydroxypropylation agent in a sodium hydroxide-urea system to produce temperature-sensitive hydroxypropyl chitosan [China Invention Patent Application Publication Specification CN201410170871.8], Hou Chunlin et al. reported the preparation of temperature-sensitive hydroxybutyl chitosan [China Patent Application Publication Specification CN200810033699.6] and temperature-sensitive hydroxypentyl chitosan [China Patent Application Publication Specification CN201210220246.0]. However, the research on using these thermosensitive and degradable chitosan derivatives to prepare a long-acting local anesthetic sustained-release system is very limited. Therefore, the present invention combines thermosensitive modified chitosan microspheres and thermosensitive modified chitosan hydrogels to obtain an injectable and degradable local anesthetic analgesic sustained-release composite system, which is expected to be applied in long-acting local anesthetic analgesia. Summary of the invention

[0009] In view of the deficiencies in the prior art and based on the previous work, the present invention aims to provide a temperature-sensitive modified chitin hydrogel-loaded local anesthetic sustained-release analgesic system, a preparation method and an application thereof.

[0010] The present invention utilizes the fact that the temperature-sensitive modified chitin is a flowing liquid at low temperatures, and after adding a local anesthetic analgesic aqueous solution or a degradable polymer microsphere loaded with a local anesthetic analgesic and mixing evenly at low temperatures, the chitosan has good fluidity and can be injected, and is rapidly physically cross-linked to form a gel for sustained-release drugs under physiological conditions in vivo. The specific technical solutions adopted by the present invention are as follows:

[0011] The invention provides a temperature-sensitive modified chitosan hydrogel-loaded local anesthetic sustained-release analgesic system. The local anesthetic sustained-release analgesic system is an injectable mixed hydrogel prepared by mixing temperature-sensitive modified chitosan and a local anesthetic analgesic. The gel transition temperature of the temperature-sensitive chitosan is lower than body temperature. In terms of mass percentage, the concentration of the temperature-sensitive chitosan in the injectable mixed hydrogel is 0.5-5%, and the concentration of the local anesthetic analgesic is 0.1-5%.

[0012] Preferably, the temperature-sensitive chitosan is any one or a combination of temperature-sensitive hydroxypropyl chitosan, temperature-sensitive hydroxyethyl chitosan or temperature-sensitive hydroxybutyl chitosan.

[0013] Preferably, the local anesthetic sustained-release analgesic system further contains hyaluronic acid dispersed in the injectable mixed hydrogel as an auxiliary component.

[0014] Preferably, the mass fraction of hyaluronic acid in the local anesthetic sustained-release analgesic system is 0.1-1%.

[0015] Preferably, in the local anesthetic sustained-release analgesic system, by mass percentage, the temperature-sensitive hydroxypropyl chitosan is 1-3%, the hyaluronic acid is 0.2-0.8%, and the local anesthetic analgesic is 0.5-3% of ropivacaine hydrochloride.

[0016] Preferably, the local anesthetic analgesic is selected from any one of procaine, bupivacaine, levobupivacaine, tetracaine, ropivacaine, etidocaine, articaine, lidocaine, mepivacaine, prilocaine and hydroxyethylcaine, or a mixture of several thereof.

[0017] Preferably, the local anesthetic sustained-release analgesic system further comprises degradable polymer microspheres loaded with local anesthetic analgesics, and the degradable polymer microspheres loaded with local anesthetic analgesics are uniformly dispersed in the injectable mixed hydrogel.

[0018] Preferably, the degradable polymer microspheres are thermosensitive carboxymethyl chitosan porous microspheres, and the loaded local anesthetic analgesic is ropivacaine hydrochloride.

[0019] The present invention also provides a method for preparing a temperature-sensitive modified chitin hydrogel-loaded local anesthetic sustained-release analgesic system, comprising the following steps:

[0020] (1) Dissolving thermosensitive hydroxypropyl chitosan and hyaluronic acid in physiological saline or alkaline water at low temperature to obtain liquid A;

[0021] (2) dissolving the local anesthetic analgesic hydrochloride in normal saline or acidic water to obtain solution B;

[0022] (3) At the gel transition temperature, liquid A and liquid B are mixed to prepare a mixed hydrogel precursor solution, and the pH is adjusted to 5-6 to obtain a uniform injectable mixed hydrogel, which is a local anesthetic sustained-release analgesic system.

[0023] Preferably, the low temperature refers to 2-30°C, and further preferably 4-15°C. The gel transition temperature of the thermosensitive hydroxypropyl chitosan is lower than body temperature, and the injectable mixed hydrogel can form a hydrogel at body temperature to slowly release drugs.

[0024] The present invention also provides a method for preparing a temperature-sensitive modified chitin hydrogel / microsphere composite local anesthetic sustained-release analgesic system, which is characterized by comprising the following steps:

[0025] (1) Dissolving the thermosensitive modified chitosan in physiological saline or alkaline water at low temperature to obtain liquid A;

[0026] (2) Preparation of biodegradable polymer microspheres containing local anesthetic analgesics;

[0027] (3) At low temperature, the biodegradable polymer microspheres containing local anesthetic analgesics are uniformly mixed in A to prepare an injectable mixed hydrogel, i.e., a local anesthetic sustained-release analgesic system, wherein the low temperature is lower than the gel transition temperature of the thermosensitive chitin.

[0028] Preferably, hyaluronic acid is added during the preparation of liquid A in step (1).

[0029] Preferably, the low temperature refers to 2-30°C, and further preferably 4-15°C. The gel transition temperature of the thermosensitive chitin is lower than body temperature, and the injectable mixed hydrogel can become a hydrogel at body temperature to slowly release drugs.

[0030] Preferably, the method for preparing the degradable polymer microspheres in step (2) is as follows:

[0031] (2.1) preparing an alkaline carboxymethyl chitosan aqueous solution with thermosensitive carboxymethyl chitosan, dissolving polyethylene glycol in the alkaline solution to obtain a polyethylene glycol solution, and storing the solution at low temperature;

[0032] (2.2) stirring and mixing the carboxymethyl chitosan aqueous solution and the polyethylene glycol solution at low temperature, then heating them for physical cross-linking and neutralizing the reaction system with an acidic solution, then washing and purifying to obtain carboxymethyl chitosan microspheres, and freeze-drying to obtain carboxymethyl chitosan porous microspheres;

[0033] (2.3) The hydrochloride of the local anesthetic analgesic is dissolved in physiological saline or acidic water, and then carboxymethyl chitosan porous microspheres are added for immersion, and centrifugal drying is performed to obtain drug-loaded microspheres, i.e., biodegradable polymer microspheres containing the local anesthetic analgesic.

[0034] Preferably, the low temperature refers to 2-30°C, and further preferably 4-15°C. The gel transition temperature of the thermosensitive carboxymethyl chitosan is lower than body temperature, and the injectable mixed hydrogel can form a hydrogel at body temperature to slowly release drugs.

[0035] Preferably, the molecular weight of the polyethylene glycol is in the range of 4-30 kDa, and the concentration thereof is in the range of 20-50%.

[0036] Preferably, the acetylation degree of carboxymethyl chitosan is in the range of 0.72-0.92, the carboxymethyl substitution degree of carboxymethyl chitosan is in the range of 0.07-0.23, and the concentration of carboxymethyl chitosan is in the range of 0.5-10 wt %.

[0037] Preferably, the volume ratio of the carboxymethyl chitosan aqueous solution to the polyethylene glycol solution is 1:1-1:20.

[0038] The present invention also provides an injectable thermosensitive modified chitin hydrogel-loaded local anesthetic sustained-release analgesic system for application: in the preparation of drugs including but not limited to local anesthetic, analgesic, anti-inflammatory and antipruritic effects, the release time of the drug is prolonged to achieve the purpose and application of long-term effect. Preferably, it is applied to the loading and sustained release of drugs for peripheral nerve block or control of postoperative wound pain.

[0039] Compared with the prior art, this technology has the following beneficial effects:

[0040] (1) The present invention directly mixes the thermosensitive modified chitosan aqueous solution with the local anesthetic analgesic aqueous solution and injects it into the area where local anesthesia is needed to quickly form a gel at body temperature and release the drug slowly, thereby significantly prolonging the analgesic time of the local anesthetic in the animal body. The preparation process is simple and does not use organic solvents and chemical cross-linking agents.

[0041] (2) In particular, thermosensitive carboxymethyl chitosan is used to prepare microspheres and local anesthetic analgesic microspheres through a two-phase aqueous polymer solution (polyethylene glycol and carboxymethyl chitosan double aqueous phase) method, and finally a new thermosensitive injectable modified chitosan hydrogel and carboxymethyl chitosan microsphere composite local anesthetic analgesic sustained-release system is prepared. The drug release rate is slower than that of thermosensitive hydrogel or drug-loaded microspheres used alone, which solves the problem of short action time of existing local anesthetics. The preparation process does not use any chemical cross-linking agents and organic solvents. The drug-loaded microspheres and gels do not have the toxicity problem of residual cross-linking agents and organic solvents, and the cost is low and there is no pollution to the environment.

[0042] (3) The thermosensitive modified chitin material used in the present invention has good biocompatibility and biodegradability, can be injected and can completely fill irregular wounds, and is beneficial for long-term local anesthesia, analgesia, anti-inflammatory and itching, and promoting wound healing. BRIEF DESCRIPTION OF THE DRAWINGS

[0043] Figure 1 This is the cumulative drug release curve of the 2.0% R-HPCH-HA hydrogel sustained-release system represented by 2.0% ropivacaine hydrochloride in Example 2 of the present invention in PBS buffer solution, using pure drug (R) with the same drug content and only HPCH carrier (R-HPCH) as the control group.

[0044] Figure 2 The in vitro cytotoxicity of the R-HPCH-HA hydrogel sustained-release system loaded with different concentrations of ropivacaine hydrochloride (0.5-5 mM) and the pure drug (R) control group on the human neuroblastoma cell line (SH-SY5Y) in Example 2 of the present invention.

[0045] Figure 3The cumulative drug release curves of the three groups of carboxymethyl chitin microspheres CMCH-Ms loaded with ropivacaine hydrochloride (abbreviated as R or RPH) with a drug loading of 160 mg / g, drug-loaded hydrogel R-loaded HPCH, and microsphere hydrogel composite drug-loaded sustained-release system CMCH-Ms / HPCH in buffer solution in Example 4 are shown in FIG. Figure 3 (a) Cumulative drug release curve in pH 5.0 buffer solution. Figure 3 (b) is the cumulative drug release curve in pH 7.4 buffer solution.

[0046] Figure 4 In vivo anesthetic effect: Figure 4 (A) The maximum analgesic effect ratio (MPE) at different time points after different drug-loaded sustained-release systems were injected around the sciatic nerve of rats; Figure 4 (B) Motor blockade scores at different time points after injection of different drug-loaded sustained-release systems around the sciatic nerve of rats; Figure 4 (C) The sensory blockade time at different time points after different drug-loaded sustained-release systems were injected around the sciatic nerve of rats; Figure 4 (D) The motor blockade time at different time points after different drug-loaded sustained-release systems were injected around the sciatic nerve of rats. Data are expressed as mean ± standard deviation SD (n = 8; *P<0.05, **P<0.01). DETAILED DESCRIPTION

[0047] In order to make the present invention easier to understand, specific embodiments of the present invention will be further described below.

[0048] The present invention is further described below in conjunction with embodiments and drawings, the purpose of which is to help better understand the content of the present invention, but these specific embodiments do not limit the protection scope of the present invention in any way.

[0049] Example 1: Synthesis of thermosensitive injectable modified chitin

[0050] According to our previous research work [China Invention Patent Application Publication Specification CN201910768980.2], the homogeneous method was used to prepare low deacetylation degree temperature-sensitive chitin derivatives hydroxypropyl chitosan and carboxymethyl chitosan in a sodium hydroxide-urea system. The specific preparation method is: weigh 2 grams of purified chitosan and stir and disperse it in a pre-frozen 100 grams of aqueous solution containing 11wt% sodium hydroxide and 4wt% urea, freeze it at -30°C for 24 h, take it out and mechanically stir it at room temperature to thaw it to obtain a dissolved chitosan aqueous solution. 11.4 grams of propylene oxide were added to the obtained chitosan solution (100 grams, 2wt%), and the system was stirred at 2°C to mix the reactants evenly, then heated to 5°C for 24 h, and then heated to 15°C for 6 h. Finally, the system was cooled to 2°C, the pH value of the system was adjusted to 7 with 3M hydrochloric acid, dialyzed with deionized water, and freeze-dried to obtain white sponge-like hydroxypropyl chitosan (HPCH) with a yield of 87%. 1 The acetylation degree of the product was calculated to be 0.89 and the substitution degree was 0.84 by H NMR spectrum. Its viscosity average molecular weight was measured by Ubbelohde viscometer to be Mη=410 kDa. The homogeneously synthesized HPCH solution was temperature sensitive, and the rheological results showed a reversible sol-gel transition behavior, wherein the gel transition temperature of the 2wt% HPCH solution was 18°C.

[0051] Preparation of thermosensitive carboxymethyl chitosan: According to the inventor's previous research work [China Invention Patent Application Publication Specification CN201310641249.6], a homogeneous method was used to prepare low-deacetylation carboxymethyl chitosan in a sodium hydroxide-urea system. Weigh 2 grams of purified chitosan and stir and disperse it in a pre-frozen 100-gram aqueous solution containing 11wt% sodium hydroxide and 4wt% urea, freeze it at -20°C for 6 h, take it out and mechanically stir and thaw it at room temperature, and repeat freezing and thawing twice to obtain a dissolved chitosan aqueous solution. Slowly add 5.7 grams of sodium chloroacetate to the chitosan solution, maintain mechanical stirring so that the reactants can react evenly, and react at 5°C for 24 h. Then cool the system to 2°C, adjust the pH value of the system to 7 with 3M hydrochloric acid, and then add the obtained neutral solution dropwise to acetone to precipitate it. Wash the precipitate with 80% ethanol (V / V) to remove the salt and urea therein. After washing, the mixture was dried at 60°C to obtain white powdered carboxymethyl chitosan with a yield of 87%. 1The acetylation degree of the product was calculated to be 0.82 and the substitution degree was 0.13 from the H NMR spectrum. The homogeneously synthesized CMCH solution is temperature sensitive and pH sensitive. It can dissolve in alkaline water at low temperature and undergo gelation transformation under conditions of increased temperature and decreased alkalinity. By changing the amount of sodium chloroacetate and controlling the molar ratio of sodium chloroacetate to the sugar unit in the chitin structure, a series of CMCH products with different substitution degrees (0.07-0.23) were obtained. By changing the ratio and reaction conditions, a series of carboxymethyl chitins with different substitution degrees, temperature sensitivity and low deacetylation degree (0.72-0.92) can be obtained, with a molecular weight range of 5 kDa-1000 kDa.

[0052] Similarly, hydroxyethyl chitosan and hydroxybutyl chitosan with low deacetylation degree were prepared in a sodium hydroxide-urea system by a homogeneous method. The acetylation degree of these chitosan derivatives ranged from 0.7 to 0.92, and their molecular weights ranged from 5 kDa to 1000 kDa.

[0053] Example 2: Thermosensitive Hydroxypropyl Chitosan Hydrogel-Carried Local Anesthetic Ropivacaine Sustained Release System

[0054] Using the thermosensitive hydroxypropyl chitosan prepared in Example 1, 100 mg of hydroxypropyl chitosan (HPCH) and 25 mg of hyaluronic acid (HA) were weighed and added to 5 mL of normal saline, mixed and shaken evenly, and then placed in a refrigerator at 4°C overnight. After complete dissolution, a colorless, transparent, flowable viscous liquid (HPCH-HA) was obtained. Then, 37.5 mg of local anesthetic ropivacaine hydrochloride was added, mixed and shaken, and dissolved to obtain 0.75% R HCL -HPCH-HA injectable sustained-release hydrogel precursor solution, before injection, add a small amount of NaOH solution at low temperature to adjust the pH to between 5.5-6.0 to obtain a uniform milky white injectable suspension, which forms a local anesthetic ropivacaine hydrogel sustained-release system at 37 degrees or in vivo. Similarly, 1.0% R HCL -HPCH-HA, 1.5% R HCL -HPCH-HA, 2.0% R HCL -HPCH-HA, 2.25% R HCL -HPCH-HA injectable local anesthetic ropivacaine hydrogel sustained-release system, abbreviated as 0.75% R-HPCH-HA, 1.0% R-HPCH-HA, 1.5% R-HPCH-HA, 2.0% R-HPCH-HA, and 2.25% R-HPCH-HA respectively.

[0055] At 4°C, 1 mL of the above suspension was accurately extracted using a precision syringe and placed in a dialysis bag (molecular weight cutoff: 8000-14,000 Da). The dialysis bag was then placed in a centrifuge tube containing 30 mL of PBS solution and placed in a constant temperature water bath shaker at 37°C. The shaker was shaken at a speed of 100 rpm. Samples were taken at different times, and 2 mL of PBS solution was taken out as samples each time, and 2 mL of fresh PBS solution was added. The taken samples were detected using a UV spectrophotometer, with PBS solution as the blank control. The detection wavelength was 263 nm. Based on the standard curve of ropivacaine, the drug concentration of ropivacaine was calculated and the cumulative release curve was obtained. Three samples were repeated in each group. Figure 1 The in vitro cumulative release curve of the 2.0% R-HPCH-HA hydrogel sustained-release system represented by 2.0% ropivacaine hydrochloride was used as a comparison between a pure drug control group with the same drug content and a control group using only HPCH carrier (without hyaluronic acid, R-HPCH group). Figure 1 It can be seen that the pure drug ropivacaine was released quickly in normal saline, with a release rate of more than 80% within 6 hours, while about 61.2% and 38.9% of ropivacaine in the R-HPCH group and R-HPCH-HA group were released within the first 16 hours, both showing a significant drug sustained release effect. However, compared with the R-HPCH group, the R-HPCH-HA group had less drug burst release and slower sustained release.

[0056] The in vitro cytotoxicity test of the drug-loaded sustained-release system containing ropivacaine was conducted using human neuroblastoma cell line (SH-SY5Y). Ropivacaine hydrochloride was dissolved in PBS buffer to prepare a 10 mM ropivacaine solution, which was diluted with cell culture medium to prepare a cell culture medium with a ropivacaine concentration gradient of 0.5-5 mM; a cell culture medium solution containing HPCH2% and HA0.5% and a ropivacaine concentration of 10 mM was prepared at low temperature and gelled at 37°C, and then a cell culture medium with a ropivacaine concentration of 0.5-5 mM containing the corresponding gel sustained-release system was prepared. 4 / mL cell density, SH-SY5Y cells were seeded in a 96-well plate and cultured in a constant temperature incubator for 24 h, and then the cell culture medium containing the above-mentioned pure drug and drug-containing gel was added and cultured for 24 hours, and the relative viable cell value ( Figure 2 ), at low concentrations (0.5 mM, 1 mM, 2 mM), there was no significant difference between the two groups of SH-SY5Y cells, and the surface HPCH-HA carrier system did not increase the cytotoxic response. As the drug concentration increased, although the R-HPCH-HA group produced cytotoxic effects at 5 mM, the cytotoxic response of the R-HPCH-HA group was significantly reduced compared with the pure drug group alone (p < 0.05).

[0057] Example 3: Preparation of carboxymethyl chitosan porous microspheres and drug-loaded microspheres by a solvent-free green method

[0058] The powdered thermosensitive carboxymethyl chitosan CMCH synthesized in Example 1 was used to prepare 10 mL of a 2wt% sample solution with a 1 mol / L sodium hydroxide solution and stored at 2°C. PEG-10k (polyethylene glycol with a molecular weight of 10,000) was used to prepare 50 mL of a 30wt% polyethylene glycol solution with a 1 mol / L sodium hydroxide solution, placed in an ice-water bath, mechanical stirring was started, and 10 mL of the CMCH solution was slowly added dropwise and stirred for half an hour. The ice-water bath was then replaced with a 60°C oil bath, and the system was neutralized to neutrality with 1.0 M HCl. Neutralization and temperature physical crosslinking cured the microspheres for 20 min without using any chemical crosslinking agent. The carboxymethyl chitosan microspheres were then repeatedly washed with deionized water and freeze-dried to prepare carboxymethyl chitosan porous microspheres. Carboxymethyl chitosan porous microspheres can be prepared by changing the volume ratio of CMCH aqueous solution and polyethylene glycol solution (1:10-7:10). Changing the molecular weight of PEG (from 6k to 30k), changing the concentration of PEG (20-50%), changing the acetylation degree (0.72-0.92) and substitution degree (0.07-0.23) of CMCH and its concentration 0.5-10 wt %, and changing the volume ratio of CMCH solution to PEG solution (1:1-1:20) did not affect the above preparation.

[0059] Ropivacaine hydrochloride (R) powder was dissolved in 0.1 M HCl solution to prepare drug solutions of different concentrations (1-80 mg / mL). 0.1 g of freeze-dried carboxymethyl chitin porous microspheres were immersed in 0.5-5 mL of ropivacaine solutions of different concentrations for a certain period of time and then loaded with ropivacaine. If there was flowing liquid, the microspheres were centrifuged at 3000 rpm for 5 min and dried in an oven to obtain drug-loaded microspheres. If there was liquid obtained by centrifugation, the amount of drug not loaded into the microspheres was calculated by testing the volume of the clear liquid and the ultraviolet absorbance at 262 nm. sup ; If there is no flowing liquid, m sup Then it is 0.

[0060] The drug loading calculation formula is:

[0061] Among them, m add is the mass of R initially added, m c is the mass of the dried drug-loaded microspheres.

[0062] The drug loading of ropivacaine hydrochloride in carboxymethyl chitin porous microspheres increases with the increase of immersion time. When the immersion time reaches 24 h, the drug loading is basically saturated, and the drug loading increases with the increase of R concentration. For example, when the concentration of ropivacaine hydrochloride R is 8 mg / mL, the drug loading of microspheres prepared after immersion time of 24 h is 160 mg / g of ropivacaine hydrochloride carboxymethyl chitin microspheres (R-loaded CMCH-Ms). The preparation of other drug-loaded microspheres such as PLGA loaded with ropivacaine requires the use of organic solvents.

[0063] Example 4: Preparation of injectable microsphere hydrogel composite drug-loaded sustained-release system

[0064] 10 mg of dried R-loaded CMCH-Ms was added to 1 mL of 3% HPCH solution at 4°C and mixed evenly to obtain an injectable microsphere hydrogel composite drug delivery system precursor solution, which quickly formed a gel at 37°C or in vivo. At the same time, ropivacaine hydrochloride-loaded hydroxypropyl chitosan gel (R-loaded HPCH) was used as a control group. The same mass of R was directly added to 1 mL of 3% HPCH solution at 4°C and mixed evenly, forming a gel at 37°C.

[0065] In the in vitro drug release experiment, 10 mg of R-loaded CMCH-Ms, 1 mL of R-loaded HPCH gel, and 1 mL of R-loaded CMCH-Ms / HPCH gel were weighed and loaded into dialysis bags (molecular weight cutoff: 8-14 kDa), and then the dialysis bags were placed in centrifuge tubes containing 10 mL of pH 5.0 and pH 7.4 buffer solutions. The centrifuge tubes were placed in a 37°C water bath shaker and shaken at 70 rpm. At the predetermined time point, 2 mL of release medium was taken from the centrifuge tube and supplemented with 2 mL of fresh buffer solution. The concentration of ropivacaine hydrochloride R in the removed release medium was measured by UV-visible spectrometer at 262 nm absorbance. According to the standard curve of ropivacaine, the drug concentration of ropivacaine was calculated and the cumulative release curve was prepared. Each group of experiments was repeated three times in parallel, and the test results were the mean ± standard deviation (SD) values. Figure 3It can be seen that at pH 5.0, the initial drug release rate of the R-loadedCMCH-Ms / HPCH group at 1 h was 24.7±2.4%, the initial drug release rates of the R-loaded CMCH-Ms group and the R-loaded HPCH group at 1 h were 33.7±1.6% and 35.5±1.5%, respectively; at pH 7.4, the initial drug release rates of the R-loaded HPCH group and the R-loaded CMCH-Ms group at 1 h were 28.9±0.14% and 25.4±1.5%, respectively, while the microsphere hydrogel composite drug delivery system R-loaded CMCH-Ms / HPCH group was only 18.8±1.7%. Therefore, the microsphere hydrogel composite drug delivery system showed an obvious drug sustained release effect, with less burst release and slower release than using thermosensitive hydrogel or microspheres as carriers alone, and showed long-term sustainable release. Using other drug-loaded microspheres such as PLGA-loaded ropivacaine instead of carboxymethyl chitin-loaded microspheres can achieve a similar sustained-release effect.

[0066] Example 5: Evaluation of the long-acting sustained-release anesthetic analgesic effect and safety in animals

[0067] In order to evaluate the analgesic effect of the drug-loaded sustained-release system in vivo, an ultrasound-guided sciatic nerve block model was used. Various sustained-release injections containing ropivacaine were injected into the sciatic nerve of the right hind limb of SD rats under ultrasound guidance and the blocking effect was observed. The rats were anesthetized with 2% isoflurane and placed in a prone position. Under ultrasound guidance, the needle was inserted out of plane. After locating the sciatic nerve by ultrasound, a 23G needle was inserted vertically on the inner side of the femur to reach the two layers of fascia of the gluteus medius muscle. 0.5 mL or less of the drug was injected into the sciatic nerve. The hot plate method and the 4-point motor block method were then used to evaluate the sensory and motor block of the right hind limb of the rats. The experiment was divided into 6 groups: (1) 2.25% R-HPCH-HA, (2) 1.5% R-HPCH-HA, (3) 0.75% R-HPCH-HA, (4) 0.75% R, (5) HPCH-HA, and (6) NS (normal saline), with 6 rats in each group.

[0068] Hot plate method: The rat is placed on a preheated metal surface (55±0.5°C), surrounded by a circle of cylindrical glass (20 cm high and 28 cm in diameter) to restrict the rat's activities. The rat is placed in the timer immediately. When the researcher observes three reactions in the right hind limb of the rat, indicating the feeling of pain: licking the hind paw, shaking / trembling the hind paw or jumping, the timer is stopped immediately and the rat is taken out of the glass column. This time is counted as the rat's basal thermal latency (tested 2 days before the start of the experiment), which is generally about 3-5 s. Rats with too low or too high basal values ​​are eliminated. To prevent burns, if the rat still has no pain after 20 s, the rat is taken out and the time is recorded as 20 s. There is a 5-minute interval between each measurement to prevent sensitization. The evaluation starts 15 minutes after the injection of the drug, and then tests are performed every 2 hours. If the rat reaches the baseline level in 3 measurements, it is measured every 4 hours until all rats have completed the test. All observation tasks were completed by three independent observers, and the test data were converted into maximum pain relief effect ratio (MPE%). The MPE% calculation formula is as follows:

[0069] MPE%=(Lt-Bt) / (Ct-Bt)×100%

[0070] Among them, Bt is the basal thermal latency value of rats; Lt is the thermal latency value of rats at different time points; Ct is the maximum allowable thermal latency value of rats, that is, 20 s. The effective analgesic effect of the sustained-release preparation is defined as the time span required for the MPE value to recover from 100% to 50% after injection (sensory block time). Figure 4 As shown in AC, all rats reached the maximum thermal latency value (20 s) within 15 min after injection of the ropivacaine-containing preparation, indicating that the application of the HPCH-HA sustained-release system did not affect the onset time of the drug. The MPE value of the 0.75% R pure drug control group returned to the normal baseline within 6 hours, while the average MPE% value of the R-HPCH-HA group was prolonged in a dose-dependent manner. The 50% MPE analgesic duration of the 2.25% R-HPCH-HA group and the 1.5% R-HPCH-HA group was 16.2 h and 8.1 h, respectively, which was significantly longer than that of the R pure drug control group (P<0.01). The pure carrier itself did not have any nerve blocking effect. The motor block of rats was also tested at the same time as the sensory block, and the effect of producing motor disorders was scored using the 4-point motor block method (1 point means that the rat's movement is completely normal; 2 points means that the rat's foot dorsiflexion dysfunction occurs, and the rat cannot fully open its toes when the rat's tail is lifted; 3 points means that the rat's plantar flexion dysfunction occurs, and the rat cannot fully open its toes when the rat's tail is lifted; 4 points means that the rat completely loses the dorsiflexion and plantar flexion functions and has gait disorders). Figure 4As shown in BD, the motor blockade time in the 2.25% R-HPCH-HA group and the 1.5% R-HPCH-HA group was 6.8 h and 5.6 h, respectively, which was significantly longer than that in the 0.75% R pure drug control group (P<0.01). After 12 hours, the motor function scores of all rats returned to normal.

[0071] Tissue inflammation and neurotoxicity assessment: HPCH-HA residual gel injected into rats adhered to the tissue near the sciatic nerve. By the 14th day, the gel was almost unobservable, and it was basically completely degraded. HE-stained tissue sections showed that the 2.25% R-HPCH-HA implantation site had moderate inflammation on the 7th day, and other ropivacaine-containing preparation groups and vehicle groups only had mild inflammation. After 14 days, the inflammatory response of the ropivacaine-containing preparation group and the vehicle group was alleviated, indicating that the inflammatory response caused by HPCH-HA as a ropivacaine carrier is reversible to a certain extent. The inflammation in each group did not infiltrate the epineurium, indicating that HPCH-HA as a ropivacaine carrier did not cause inflammatory response to the sciatic nerve. The results of transmission electron microscopy (TEM), toluidine blue (TB) staining and TUNEL staining of sciatic nerve tissues on the 7th and 14th days after injection showed that the axon and myelin structure in each group showed neatly arranged fibers and uniform myelin structure. There was no significant difference in axon density and abnormal myelin percentage between the groups, and there was no significant difference in the TUNEL positive cell detection results, indicating that no obvious apoptotic changes occurred in any group. The above results show that the sustained-release system containing ropivacaine can be degraded in vivo, has a slight effect on the structure of nerve fibers, and has no obvious structural damage. After 7 and 14 days of injection of the preparation containing ropivacaine, there was no significant difference in the aspartate aminotransferase (AST), urea (BUN) and creatinine (Cr) of rats in each group, all of which were within the normal range. Therefore, it is shown that the HPCH-HA sustained-release system containing ropivacaine has no significant effect on the liver and kidney function of rats.

[0072] The concentration of thermosensitive hydroxypropyl chitosan is 0.5-5% instead of the above 2%, the concentration of local anesthetic is in the range of 0.1-5%, the concentration of hyaluronic acid is between 0.1-1%, and the local anesthetic analgesic is selected from procaine, bupivacaine, levobupivacaine, tetracaine, ropivacaine, etidocaine, articaine, lidocaine, mepivacaine, prilocaine or hydroxyethylcaine, one or a mixture of several of which replaces the ropivacaine in the above experiment, and similar long-acting sustained-release results can be obtained. The auxiliary component containing thermosensitive hydroxypropyl chitosan 1-3% and hyaluronic acid containing 0.2-0.8%, and the local anesthetic analgesic is selected from ropivacaine hydrochloride 0.5-3%, which has a better long-acting sustained-release effect.

[0073] Finally, it should be noted that the above embodiments are only used to illustrate the technical solution of the present invention rather than to limit the scope of protection of the present invention. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solution of the present invention can be modified or replaced by equivalents without departing from the essence and scope of the technical solution of the present invention.

Claims

1. A temperature-sensitive modified chitin hydrogel-loaded local anesthetic sustained-release analgesic system, characterized in that: An injectable mixed hydrogel is prepared by mixing thermosensitive modified chitosan, hyaluronic acid and local anesthetic analgesics, wherein the pH of the injectable mixed hydrogel is 5-6; the gel transition temperature of the thermosensitive modified chitosan is lower than body temperature, and the concentration of the thermosensitive modified chitosan in the injectable mixed hydrogel is 0.5-5% and the concentration of the local anesthetic analgesics is 0.1-5% by mass percentage; The temperature-sensitive modified chitosan is any one or a combination of temperature-sensitive hydroxypropyl chitosan, temperature-sensitive hydroxyethyl chitosan or temperature-sensitive hydroxybutyl chitosan; The local anesthetic analgesic is ropivacaine.

2. A thermosensitive modified chitin hydrogel / microsphere composite local anesthetic sustained-release analgesic system, characterized in that: The injectable hybrid hydrogel is prepared by mixing thermosensitive modified chitosan and degradable polymer microspheres loaded with local anesthetic analgesics, and the pH of the injectable hybrid hydrogel is 5-6; the gel transition temperature of the thermosensitive modified chitosan is lower than body temperature, and the concentration of the thermosensitive modified chitosan in the injectable hybrid hydrogel is 0.5-5% and the concentration of the local anesthetic analgesic is 0.1-5% by mass percentage; The temperature-sensitive modified chitosan is any one or a combination of temperature-sensitive hydroxypropyl chitosan, temperature-sensitive hydroxyethyl chitosan or temperature-sensitive hydroxybutyl chitosan; The local anesthetic analgesic is ropivacaine; The degradable polymer microspheres are temperature-sensitive carboxymethyl chitosan porous microspheres.

3. A method for preparing the temperature-sensitive modified chitin hydrogel-loaded local anesthetic sustained-release analgesic system according to claim 1, characterized in that: The following steps are involved: (1) Dissolving thermosensitive hydroxypropyl chitosan and hyaluronic acid in physiological saline or alkaline water at the gel transition temperature to obtain liquid A; (2) dissolving the local anesthetic analgesic hydrochloride in normal saline or acidic water to obtain solution B; (3) Mixing liquid A and liquid B at low temperature to prepare a mixed hydrogel precursor solution, adjusting the pH to 5-6, and obtaining a uniform injectable mixed hydrogel, which is a local anesthetic sustained-release analgesic system.

4. A method for preparing the thermosensitive modified chitin hydrogel / microsphere composite local anesthetic sustained-release analgesic system according to claim 2, characterized in that: The following steps are involved: (1) Dissolving the thermosensitive modified chitosan in physiological saline or alkaline water at low temperature to obtain liquid A; (2) Preparation of degradable polymer microspheres containing local anesthetic analgesics, the specific method is as follows: (2.1) preparing an alkaline carboxymethyl chitosan aqueous solution with thermosensitive carboxymethyl chitosan, dissolving polyethylene glycol in the alkaline solution to obtain a polyethylene glycol solution, and storing the solution at low temperature; (2.2) stirring and mixing the carboxymethyl chitosan aqueous solution and the polyethylene glycol solution at low temperature, then heating them for physical cross-linking and neutralizing the reaction system with an acidic solution, then washing and purifying to obtain carboxymethyl chitosan microspheres, and freeze-drying to obtain carboxymethyl chitosan porous microspheres; (2.3) dissolving the hydrochloride of the local anesthetic analgesic in physiological saline or acidic water, then adding carboxymethyl chitosan porous microspheres for immersion, and drying to obtain drug-loaded microspheres, i.e., degradable polymer microspheres containing the local anesthetic analgesic; (3) At low temperature, the biodegradable polymer microspheres containing local anesthetic analgesics are uniformly mixed in liquid A to prepare an injectable mixed hydrogel, i.e., a local anesthetic sustained-release analgesic system, wherein the low temperature is lower than the gel transition temperature of the thermosensitive modified chitin.

5. Use of the thermosensitive modified chitin hydrogel-loaded local anesthetic sustained-release analgesic system as claimed in claim 1 or the thermosensitive modified chitin hydrogel / microsphere composite-loaded local anesthetic sustained-release analgesic system as claimed in claim 2 in the preparation of a long-acting local anesthetic analgesic agent.

6. Use of the thermosensitive modified chitin hydrogel-loaded local anesthetic sustained-release analgesic system as claimed in claim 1 or the thermosensitive modified chitin hydrogel / microsphere composite-loaded local anesthetic sustained-release analgesic system as claimed in claim 2 in the preparation of a medicament for peripheral nerve blocking or controlling postoperative wound pain.

Images