A low-molecular-weight gel and liposome of a local anesthetic and a preparation method thereof

Abstract

The present invention discloses a low-molecular-weight local anesthetic gel, liposomes, and preparation methods thereof. The raw materials of the low-molecular-weight local anesthetic gel include: a local anesthetic, a bile salt, an aqueous solvent, or a buffer; the local anesthetic is selected from an amide local anesthetic; and the bile salt is selected from at least one of sodium cholate, sodium deoxycholate, sodium chenodeoxycholate, sodium lithocholic acid, sodium ursocholic acid, sodium ursodeoxycholate, sodium glycodeoxycholate, sodium taurolithocholic acid, sodium glycotaurocholate, sodium glycochenodeoxycholate, sodium phenylpropanecholate, sodium casocholic acid, sodium leukocholic acid, bile acid dimer, bile acid side chain amino acid conjugate, bile acid side chain PEG conjugate, and bile acid side chain glucose conjugate. The preparation process of the gel and liposome of the present invention is simple and controllable, and can achieve the purpose of postoperative pain management after a single administration.

Description

Technical Field

[0001] The invention belongs to the field of pharmaceutical preparations and relates to a local anesthetic low molecular weight gel, a liposome and a preparation method thereof. Background Art

[0002] Although unwelcome, pain is an unavoidable consequence of surgery. It's reported that up to 80% of surgical patients experience acute postoperative pain, and 30% experience severe pain after surgery. Pain is most severe within the first 48 hours after surgery. Studies have found that higher levels of acute postoperative pain nearly triple the risk of developing moderate chronic pain, increasing the risk of cardiac and pulmonary complications and hindering postoperative recovery. Furthermore, poorly controlled postoperative pain can lead to high medical costs and increased mortality due to prolonged hospital stays, unplanned readmissions, and subsequent chronic pain syndromes, making it an event with significant clinical, social, and economic impacts. A postoperative pain management market research report indicates that the postoperative pain management market was valued at US$31.5 billion in 2020 and is projected to reach US$48 billion by 2028, growing at a compound annual growth rate of 5.4% from 2021 to 2028.

[0003] Chronic pain is defined as any pain lasting longer than six months. Despite treatment recommendations from international pain guidelines, over 60% of patients with chronic pain experience no improvement or a poor response, and adverse effects are common. The mechanisms of chronic pain are complex, and identifying the underlying mechanisms can be challenging or impossible in clinical practice. Therefore, effective management of acute postoperative pain is one of the best means of preventing chronic pain. In fact, a single injection of a peripheral nerve block lasting less than one day can reduce persistent postoperative mastectomy pain at three and 12 months. Opioids have long been the gold standard for relieving acute postoperative pain, especially when pain is moderate or severe. However, they can easily lead to tolerance, dependence, and addiction, further causing significant adverse events, including but not limited to respiratory and central nervous system depression, constipation, nausea, and vomiting.

[0004] Opioid minimization strategies include the use of opioid-free anesthesia, regional anesthetic techniques, multimodal non-opioid analgesics, and nonpharmacological interventions (such as early physical therapy and acupuncture). Infiltration of the surgical site with local anesthetic (LA) is a key component of a multimodal analgesic regimen. Although LAs offer excellent analgesic efficacy (with significantly fewer systemic adverse reactions than opioids), their duration of action after a single injection is relatively short, reaching only 12 hours. Combination with various adjuvants (dexmedetomidine, clonidine, and particularly dexamethasone) can extend the duration of analgesia to 24 hours. This is attributed to adjuvants' effects on local vasoconstriction, direct effects on peripheral nerves, or initiation of systemic anti-inflammatory processes. However, most adjuvants only prolong analgesia by 0–12 hours, and at best (buprenorphine and dexamethasone), the duration is less than 24 hours. The likelihood of adverse reactions increases with the number of drugs administered, and many adjuvants may increase the incidence of side effects such as pruritus, nausea / vomiting, hypotension, bradycardia, and sedation. Continuous peripheral nerve block is an important clinical approach for prolonging the analgesic effect of local anesthetics. Compared with single-injection local anesthetic peripheral nerve block, its pain relief is comparable to that of epidural analgesia, but with improved hemodynamic stability. Although advances in ultrasound-guided technology have enabled accurate catheter insertion near nerves, exogenous catheters, once inserted into the human body, are inevitably subject to problems such as catheter-related mechanical nerve stimulation, kinking, migration, obstruction or shearing, fluid leakage or inflammation at the catheter insertion site, bacterial colonization, and infusion pump failure.

[0005] Therefore, sustained-release local anesthetic formulations that can achieve analgesic efficacy comparable to epidural analgesia and continuous infusion via nerve catheters with a single dose and minimize fluctuations in blood concentrations are currently a hot topic in the field of long-term postoperative analgesia. These formulations not only mitigate the side effects and poor patient compliance associated with invasive techniques such as catheters and epidural punctures, but also significantly reduce the risk of systemic toxicity by reducing the total dose and frequency of administration. They play a crucial role in controlling acute postoperative pain, preventing the brief but intense "burning" rebound pain after a single block, and preventing chronic pain that persists after surgery. Numerous studies have described long-acting local anesthetic formulations, including liposomes, suspensions, inclusion compounds, gels, injectable liquid polymers, and polymer microparticles. While some progress has been made in improving analgesic efficacy, several challenges remain, including severe microsphere burst release and high muscle toxicity; poor implant biocompatibility and insufficient mechanical strength; weak hydrogel encapsulation and slow degradation; and rapid dissolution of nanoparticles.

[0006] Currently approved long-acting local anesthetic formulations include Exparel, a multivesicular liposome containing bupivacaine for injection; Xaracoll, a collagen matrix containing bupivacaine for implantation; Zynrelef, a polymeric solution containing bupivacaine and meloxicam for instillation; and Posimir, a viscous solution containing bupivacaine and sucrose acetate isobutyrate for instillation. Exparel has been on the market for a decade, but recent studies have highlighted that it only partially demonstrates prolonged postoperative analgesia compared to a single dose of conventional bupivacaine. Furthermore, Exparel has a limited drug loading capacity, requires strict temperature control, and has a relatively short shelf life. Xaracoll, Zynrelef, and Posimir, which were launched in the past two years, have relatively few approved indications and no serious adverse reactions have been reported. However, their comprehensive efficacy and safety remain to be explored: Xaracoll implants have a strong foreign body sensation and degrade slowly; Posimir, which contains an extremely high dose of bupivacaine (660mg), has side effects such as nausea, vomiting, and bruising that cannot be underestimated, and the organic solvent benzyl alcohol used in it has low safety in nerve blocks and no significant analgesic effect; Zynrelef, a dual-action anesthetic, has the best efficacy among the four, but is relatively expensive, and the safety of the combined drug meloxicam directly instilled into the wound remains to be tested.

[0007] Liposomes, the most extensively researched drug delivery vehicle for sustained-release local anesthetics in recent years, offer significant advantages over non-lipid delivery vehicles, including biocompatibility, biodegradability, non-immunogenicity, and relatively low cost. Currently, two local anesthetic liposomes are in clinical trials in China: Luye Pharma's ropivacaine multivesicular liposome LY09606, currently in Phase I clinical trials, and ropivacaine liposomes for injection HR18034, planned for Phase II clinical trials.

[0008] However, in addition to the inherent limitations of liposomes, such as poor stability and burst drug release, the development of liposomes for encapsulating local anesthetics also faces the following challenges: First, local anesthetics have poor water solubility. While hydrochloride hydrates are commonly used clinically, these hydrochloride hydrates are difficult to load during liposome preparation. Second, single-chamber liposomes containing local anesthetics, obtained by direct active loading of lipid-soluble local anesthetics, often suffer from low drug loading and encapsulation efficiency. This not only hinders long-term analgesia, but also poses potential toxicity risks for unencapsulated drugs, and their removal increases costs. Conventional local anesthetic liposomes often struggle to achieve the high drug loading and desired sustained-release effects. A common characteristic of previously studied liposome formulations is that LA encapsulation is not as high as that achieved with other DDSs.

[0009] The production of EXPAREL, which is already on the market, relies on a complex two-step double emulsification process and requires neutral lipids, which is generally expensive. Chinese Patent 202110046374.7 discloses a "oil-lecithin-local anesthetic-pharmacological enhancer" ropivacaine reservoir composition. The phospholipids in the composition are stimulated by body fluids to complete the self-assembly of liposomes after local application, thereby obtaining high-drug-loaded local anesthetic liposomes, which can achieve two to three days of analgesia in rats. However, the initial diffusion and release of this preparation are large after administration, and the organic solvent benzyl alcohol therein is highly irritating after local application. Chinese Patent 202110964079.X discloses a near-infrared responsive liposome thermosensitive gel encapsulating a local anesthetic, which overcomes the shortcomings of insufficient sustained-release ability of simple liposomes, realizes the problems of responsiveness and adjustable release, and achieves a slow release of more than 3 days in vitro. The liposome is composed of DLPC, DSPC, EggPC and cholesterol, and has an encapsulation efficiency of ropivacaine of 94%. However, its small particle size (200nm) is not conducive to sustained release, and the low concentration of local anesthetic (ropivacaine 1mg / mL) is not conducive to long-term analgesia. Although the additional introduction of gel is beneficial for sustained release, there are many quality indicators that need to be examined in the process, which is not conducive to scale-up production. Ion gradient liposomes provide higher encapsulation efficiency than traditional liposomes. Patent US20150250724A1 discloses a local anesthetic ion gradient liposome in which the pH of the aqueous phase in the internal region of the liposome (pH 6.5 citric acid solution / ammonium sulfate solution) is lower than the pH of the external aqueous phase (pH 7.2 PBS). The average particle diameter of the liposome is not less than 1μm and has 10 or more membrane layers, and the analgesic time after administration is at least 3 days. However, the ion gradient liposome process is complex and difficult to industrialize. The low pH value of the internal aqueous phase also leads to stability that needs to be further enhanced.

[0010] Therefore, the field of long-acting local anesthetic preparations still needs to develop more preparations with good biocompatibility, controllable processes and stable long-acting anesthetic effects to meet patients' diverse postoperative analgesia needs. Summary of the Invention

[0011] The present invention provides a low-molecular-weight hydrogel and liposome containing an amide local anesthetic with a simple and controllable preparation process and a preparation method thereof, which can achieve the purpose of postoperative pain management after a single administration.

[0012] Local anesthetics (LA) are weak bases that exist in solution in charged and uncharged forms. The uncharged form of LA easily diffuses into neurons and then binds to the intracellular portion of voltage-gated sodium channels, thereby blocking the propagation of action potentials. However, due to injury, infection or surgery, tissue acidosis often occurs during inflammation and is maintained for a long time due to the presence of inflammatory factors. This reduces the penetration of fat-soluble LA into nerve cell membranes and does not maintain analgesic efficacy. The hydrochloride hydrate of local anesthetics commonly used in clinical practice has good water solubility, so it is easy to diffuse rapidly into the blood circulation after local injection and has a short half-life.

[0013] Exogenous toxicity from crosslinkers, additives, initiators, or byproducts, as well as low gelation efficiency due to the use of light and radiation to initiate crosslinking reactions, are unavoidable challenges in many polymer gel applications. However, low-molecular-weight natural substances, as promising alternatives to polymer biomaterials, offer considerable advantages in developing hydrogels for drug delivery systems. Low-molecular-weight gelators (LMWGs) are formed by small molecules through various non-covalent interactions. Compared to polymer gels, they offer significant advantages in terms of high biodegradability, high biocompatibility, and the absence of toxic impurities due to the simple gelation process. The amphiphilic small molecules that form LMWGs are readily accessible, have high purity, known chemical structures, biocompatible starting components, and are readily gelatinizable. The tunable and reversible nature of these non-covalent interactions imparts stimuli-responsiveness and self-healing properties to LMWGs. Various stimuli, such as pH, light, temperature, carbon dioxide, and redox reactions, can induce microstructural transformations and changes in macroscopic properties of hydrogels. The ease of chemical modification and reversible physical gelation make low molecular weight gels more easily decomposed or dissolved in body fluids than polymer gels, thus allowing the loaded drugs to be released in a desired manner.

[0014] Natural bile acids (BAs) and bile salts (BSs), along with their derivatives, are highly biocompatible and safe, exhibiting valuable gel-forming properties. Sodium salts of bile acids and their side-chain derivatives possess a unique bowl-shaped structure with one hydrophobic side and the other hydrophilic side. Under appropriate conditions, they can form nanofibers, nanoribbons, nanotubes, and micelles through hydrogen bonding and hydrophobic interactions, which can then crosslink to form gels and precipitates. BSs and their derivatives promote paracellular and transcellular drug absorption by expanding tight junctions between cells and facilitating the transport of lipid-soluble drugs in micellar form. They are widely used as absorption enhancers and to increase drug encapsulation.

[0015] The inventors discovered that using a bile salt gel system to deliver local anesthetics offers unexpected advantages: first, bile salts are typical surfactants. Earlier studies by the inventors revealed that applying high concentrations of surfactant to hydrophobic LA at relatively high concentrations significantly enhanced LA solubility through hydrophobic interactions and the formation of aggregates such as micelles. This is consistent with widely reported studies that surfactants promote wetting of hydrophobic substances by reducing the surface tension at the interface of dissolved drug particles. However, when the inventors controlled the concentration of a specific surfactant to below the critical micelle concentration (CMC), the addition of surfactant to the hydrophobic drug actually led to a further decrease in drug solubility. Specifically, adding a small amount of surfactant to a pharmaceutical salt solution of LA resulted in the precipitation of tiny crystals, forming a suspension. This sparked the inventors' interest. The inventors believe that below the CMC, the surfactant and the hydrophobic drug with amino groups form a more hydrophobic complex based on non-covalent interactions such as electrostatic interactions, hydrophobic interactions, van der Waals forces, and π-π interactions. The formation of this hydrophobic complex increases the lipophilicity of LA, significantly improving the ability of LA to penetrate lipophilic membranes. This is beneficial for local anesthetics whose lipid solubility is reduced due to protonation in the acidic environment of the surgical site. This will promote their penetration into nerve cells and help maintain analgesic efficacy.

[0016] Therefore, when bile salts are combined with drugs and gradually gelled due to intermolecular hydrogen bonding and hydrophobic interactions, the hydrophobic domains of the local anesthetic also participate in the construction of the gel system, creating a surfactant-LA complex between the gel backbone and the drug. Furthermore, free gelling molecules form a surfactant-LA complex with the local anesthetic, increasing its hydrophobicity and anchoring it to the gel backbone. The resulting local anesthetic bile salt gel possesses a very strong drug-gel interaction, resulting in exceptional stability and sustained release.

[0017] In summary, in response to the shortcomings in the art, the present invention combines local anesthetics with bile salts, and simultaneously triggers bile salts to form a low molecular weight hydrogel. Through a simple preparation process, a low molecular weight hydrogel of local anesthetics with a sustained release mechanism of gel skeleton drug release combined with complex dissolution is obtained.

[0018] The technical solutions of the present invention are as follows:

[0019] A local anesthetic low molecular weight hydrogel, the raw materials of which include: local anesthetic, bile salt, aqueous solvent or buffer;

[0020] The local anesthetic is selected from amide local anesthetics;

[0021] The bile salt is selected from at least one of sodium cholate, sodium deoxycholate, sodium chenodeoxycholate, sodium lithocholate, sodium ursocholic acid, sodium ursodeoxycholate, sodium glycodeoxycholate, sodium taurolithocholic acid, sodium glycotaurocholate, sodium glycochenodeoxycholate, sodium phenylpropanecholate, sodium casocholic acid, sodium leukocholic acid, bile acid dimer, bile acid side chain amino acid conjugate, bile acid side chain PEG conjugate and bile acid side chain glucose conjugate.

[0022] The local anesthetic used in the present invention can be a commercially available pure product, or can be prepared from a pharmaceutically acceptable salt of the local anesthetic: the pH of the pharmaceutically acceptable saline solution of the local anesthetic is adjusted to alkaline to precipitate the local anesthetic base, which is then directly used in subsequent preparations or centrifuged and freeze-dried to obtain a sample for subsequent preparations.

[0023] Preferably, the local anesthetic is selected from at least one of ropivacaine, bupivacaine, lidocaine, levobupivacaine, mepivacaine, cinchocaine, pyrocaine, etidocaine, prilocaine and pharmaceutically acceptable salts thereof.

[0024] More preferably, the local anesthetic is ropivacaine or a pharmaceutically acceptable salt thereof.

[0025] The preferred local anesthetic is ropivacaine or a pharmaceutically acceptable salt thereof. Bupivacaine and ropivacaine are the most widely used local anesthetics in clinical practice. Compared to bupivacaine, ropivacaine is less lipid-soluble, resulting in lower potency, but also offers a higher safety margin. In actual clinical practice, equivalent doses of ropivacaine demonstrate nearly identical analgesic efficacy to bupivacaine, while producing less motor block and exhibiting a clear sensory / motor block separation. Therefore, ropivacaine is becoming increasingly preferred for clinical local analgesia.

[0026] Preferably, the bile salt is sodium deoxycholate. The gelation process of sodium deoxycholate is simple and controllable, and can be initiated by an acidic environment. The resulting gel is composed of hydrophobic interaction and hydrogen bonding, and has good drug release properties.

[0027] The aqueous solvent or buffer is selected from at least one of water, hydrochloric acid with a pH of 6.5, an acid aqueous solution with a pH of 6.5, a histidine buffer with a pH of 6.5, a PBS buffer, a Tris-HCl buffer with a pH of 6.5, physiological saline, a 1wt% sodium carboxymethylcellulose solution, and a 1wt% sodium hyaluronate solution.

[0028] The acid aqueous solution refers to adjusting the pH of water with an organic acid such as formic acid, acetic acid, tartaric acid, succinic acid, etc., or adjusting the pH of water with an amino acid such as glycine, alanine, aspartic acid, glutamic acid, etc.

[0029] In addition to the role of building the gel, bile salts also need to form a hydrophobic complex with the local anesthetic. Preferably, the molar ratio of bile salts to local anesthetics is 1.2-4.5:1; preferably 2-2.5:1; and most preferably 2:1.

[0030] Preferably, the low molecular weight local anesthetic gel further contains a gel modifier; the gel modifier is at least one of mannitol, sodium chloride, calcium chloride, glycine, alanine, aspartic acid, glutamic acid, alanine, graphene, graphene oxide and carbon nanosheets.

[0031] The role of the gel modifier is to make the structure of the low molecular weight gel of local anesthetic stronger.

[0032] Preferably, the amount of the gel modifier in the low molecular weight local anesthetic gel is 0.1-1 wt %; more preferably 0.2-0.7 wt %; most preferably 0.5 wt %.

[0033] The present invention also provides a method for preparing a low molecular weight local anesthetic hydrogel, comprising:

[0034] The local anesthetic or a pharmaceutically acceptable salt thereof, the gel modifier and the bile salt are gently sonicated in an aqueous solvent for 10-30 minutes, and then gently stirred or incubated at 25° C. until phase equilibrium is reached;

[0035] Alternatively, bile salts and gel modifiers are gently sonicated in an aqueous solvent for 10-30 minutes, gently stirred or incubated at 25°C to obtain a blank gel; local anesthetics are added to the blank gel, mixed by probe sonication, and gently stirred for 8-15 hours.

[0036] Preferably, the ultrasonic power of the probe is 35%, and the ultrasound is performed twice, each time for 3 minutes, with an interval of 2 minutes between the two ultrasounds.

[0037] Preferably, the mild ultrasound is performed at room temperature, and the mild ultrasound power is 100-200W; most preferably, 100W.

[0038] Preferably, gentle stirring is performed at room temperature, with a stirring speed of 200-400 rpm; most preferably 300 rpm.

[0039] In the local anesthetic low molecular weight hydrogel, the local anesthetic is not simply free in the gel cavity, but participates in the construction of the bile salt gel through hydrophobic interaction and forms a hydrophobic complex with the free bile salt molecules, which can be demonstrated by the following process: (1) adding local anesthetic to the bile salt aqueous solution and gently stirring overnight to obtain a bile salt-local anesthetic complex micro-nano suspension; (2) adding alkali to the local anesthetic low molecular weight hydrogel to destroy the gel structure, and obtaining a suspension similar to (1) (the structure is highly similar under electron microscopy); (3) the local anesthetic low molecular weight gel has excellent stability and can be placed stably at room temperature for more than four months without obvious changes, while the blank bile salt gel without drug will precipitate a large amount of water on the surface after being placed for a few days.

[0040] In some embodiments, the low molecular weight local anesthetic gel exhibits analgesic efficacy for at least 12 hours. In some embodiments, the low molecular weight local anesthetic gel exhibits analgesic efficacy for 12-24 hours. In some embodiments, the low molecular weight local anesthetic gel exhibits analgesic efficacy for at least 24 hours. In some embodiments, the low molecular weight local anesthetic gel exhibits analgesic efficacy for one to two weeks.

[0041] Low-molecular-weight hydrogels for local anesthetics possess a stable structure, and the local anesthetics they carry form a local anesthetic-bile salt complex. The enhanced hydrophobicity of the local anesthetic-bile salt complex facilitates its diffusion into the phospholipid bilayer of liposomes, enabling higher drug loading. Combining the hydrogel with liposomes overcomes the shortcomings of liposomes in physiological environments, such as burst release and rapid metabolic elimination, increasing local drug concentration and enabling better controlled, slow release.

[0042] The inventors preliminarily combined low-molecular-weight hydrogels of local anesthetics with liposomes. Unlike the traditional pharmaceutical method of embedding liposomes in gels, the inventors used liposomes to wrap the drug-containing gel, achieving unexpected drug release performance and supplementing the existing field of single-chamber local anesthetic sustained-release preparations.

[0043] The present invention provides a local anesthetic low molecular weight hydrogel liposome, the raw materials of which include: local anesthetic, bile salt, aqueous solvent or buffer, liposome;

[0044] The local anesthetic is selected from amide local anesthetics;

[0045] The bile salt is selected from at least one of sodium cholate, sodium deoxycholate, sodium chenodeoxycholate, sodium lithocholate, sodium ursocholate, sodium ursodeoxycholate, sodium glycodeoxycholate, sodium taurolithocholate, sodium glycotaurocholate, sodium glycochenodeoxycholate, sodium phenylpropanecholate, sodium casochate, sodium leukocholate, bile acid dimer, bile acid side chain amino acid conjugate, bile acid side chain PEG conjugate and bile acid side chain glucose conjugate;

[0046] The liposomes include phospholipids and cholesterol; the molar percentage of cholesterol in the liposomes is 10-80%;

[0047] The molar ratio of phospholipid to local anesthetic is 0.5-5:1.

[0048] Preferably, the molar percentage of cholesterol in the liposome is 20-40%.

[0049] Preferably, the molar ratio of phospholipid to local anesthetic is 1-2:1.

[0050] The encapsulation efficiency of bile salt gel in the low molecular weight local anesthetic gel liposomes cannot reach 100%. Preferably, the molar ratio of bile salt to local anesthetic in the low molecular weight local anesthetic gel liposomes is 1-5.5:1; preferably 3.5-4.5:1; and most preferably 4:1.

[0051] The phospholipids are selected from one or more of phosphatidylcholine, fatty acylethanolamine, phosphatidylglycerol, phosphatidylserine, phosphatidic acid, and phosphatidylinositol. Including but not limited to lecithin, soybean lecithin, cephalin, sphingomyelin, dipalmitoylphosphatidylcholine (DPPC), distearoylphosphatidylcholine (DSPC), dimyristoylphosphatidylcholine (DMPC), 1-palmitoyl-2-linoleoyl-sn-glycero-3-phosphatidylcholine (PLPC), dioleoylphosphatidylcholine (DOPC), egg yolk phosphatidylcholine (EPC), dieucoylphosphatidylcholine (DEPC), dilauroylphosphatidylcholine (DLPC), 1,2-didecanoyl-sn-glycero-3-phosphocholine (DDPC), hydrogenated soybean phosphatidylcholine (HSPC ), l-myristoyl-2-palmitoylphosphatidylcholine (MPPC), l-palmitoyl-2-myristoylphosphatidylcholine (PMPC), l-palmitoyl-2-stearoylphosphatidylcholine (PSPC), l-stearoyl-2-palmitoylphosphatidylcholine (SPPC), dipalmitoylphosphatidylinositol (DPPI), 1,2-dioleoyl-sn-glycero-3-phosphatidylinositol (DOPI), 1,2-dilinoleoyl-sn-glycero-3-phosphocholine (DLOPC), palmitoyloleoylphosphatidylcholine (POPC), lysophosphatidylcholine, dilinoleoylphosphatidylcholine, Distearoylphosphatidylethanolamine (DSPE), dimyristoylphosphatidylethanolamine (DMPE), dipalmitoylphosphatidylethanolamine (DPPE), dioleoylphosphatidylglycerol (DOPG), dimyristoylphosphatidylglycerol (DMPG), 1-myristoyl-2-stearoyl-sn-glycero-3-phosphocholine (MSPC), 1-stearoyl-2-oleoyl-sn-glycero-3-phosphocholine (SOPC), 1-stearoyl-2-myristoyl-sn-glycero-3-phosphocholine (SMPC), distearoylphosphatidylglycerol (DSPG), dimalmitoylphosphatidylglycerol ... Acylglycerophosphoglycerol (DPPG), dipalmitoylphosphatidylserine (DPPS), 1,2-dioleoyl-sn-glycero-3-phosphatidylserine (DOPS), dimyristoylphosphatidylserine (DMPS), distearoylphosphatidylserine (DSPS), dipalmitoylphosphatidic acid (DPPA), 1,2-dioleoyl-sn-glycero-3-phosphatidic acid (DOPA), dimyristoylphosphatidic acid (DMPA), distearoylphosphatidic acid (DSPA), dimyristoylphosphatidylinositol (DMPI), distearoylphosphatidylinositol (DSPI).

[0052] Preferably, the phospholipid is soybean lecithin.

[0053] The present invention also provides a method for preparing low molecular weight gel liposomes of local anesthetics, comprising:

[0054] (a) Bile salts and gel modifiers were gently sonicated in an aqueous solvent for 10–30 min and incubated with gentle stirring or at 25°C until a blank gel was obtained;

[0055] (b) dissolving the liposomes in a volatile organic solvent and rotary evaporating the liposomes to form a lipid film;

[0056] (c) hydrating the lipid membrane prepared in step (b) with the blank gel prepared in step (a) to obtain blank liposomes;

[0057] (d) The pH of the blank liposomes was adjusted to neutral, and then dialyzed in deionized water for more than 8 h, during which the dialysate was replaced;

[0058] (f) adding a local anesthetic to the blank liposomes after dialyzation in step (d), and performing active drug loading by probe ultrasound to obtain a low molecular weight gel liposome with a local anesthetic.

[0059] Preferably, the volatile organic solvent in step (b) is selected from at least one of chloroform, dichloromethane, methanol, ethanol, diethyl ether, and tert-butanol; more preferably, chloroform.

[0060] Preferably, step (c) comprises: mixing the blank gel with the lipid membrane, performing water bath sonication for 10-30 min at a temperature higher than the lipid phase transition temperature in the lipid membrane, and then performing probe sonication using an ultrasonic cell disruptor.

[0061] Preferably, the probe ultrasound power is 35%, the ultrasound is performed twice, each time for 3 minutes, and the interval between the two probe ultrasounds is 2 minutes.

[0062] The dialysis in step (d) is to remove the free bile salt hydrogel in the blank liposome solution.

[0063] The probe ultrasound conditions for active drug loading in step (f) are: power of 35%, ultrasound twice, each time for 3 minutes, and an interval of 2 minutes between two probe ultrasounds.

[0064] The low-molecular-weight local anesthetic gel and liposomes containing the same of the present invention may further include conventional excipients and pharmaceutically acceptable carriers disclosed in the art, in addition to those described above, to provide suitable pharmaceutical and pharmacological properties for use in various forms and administration routes for postoperative analgesia. Any formulation containing the low-molecular-weight local anesthetic gel of the present invention as a core is considered to be within the scope of protection of the present invention.

[0065] The low molecular weight local anesthetic gel and liposome containing the same of the present invention are injectable and can be administered in a variety of ways, such as implantation, intramuscular administration, subcutaneous administration, etc., preferably subcutaneous injection for infiltration anesthesia.

[0066] Compared with the prior art, the main advantages of the present invention are:

[0067] (1) The preparation process of the low molecular weight local anesthetic gel and the liposome containing the same is simple and controllable, and can be easily scaled up for production.

[0068] (2) The excipients used in the low molecular weight local anesthetic gel and the liposome containing the same of the present invention are all highly safe excipients with high biocompatibility and can be directly injected locally for infiltration anesthesia.

[0069] (3) The low molecular weight local anesthetic gel and the liposome containing the same of the present invention significantly improve the shortcoming of the short half-life of the local anesthetic aqueous solution, and can be sustained-released for more than 24 hours in vitro. The low molecular weight local anesthetic gel can achieve an analgesic duration of up to two weeks in vivo.

[0070] (4) The low molecular weight local anesthetic gel and liposome containing the same prepared by the present invention overcome the great inconvenience of multiple administration of local anesthetic aqueous solutions used in clinical practice, which will greatly improve patient compliance. BRIEF DESCRIPTION OF THE DRAWINGS

[0071] Figure 1 This is the particle size distribution diagram of the ropivacaine-sodium deoxycholate complex suspension prepared in Example 1;

[0072] Figure 2 This is an SEM image of the ropivacaine-sodium deoxycholate complex suspension prepared in Example 1;

[0073] Figure 3 Figure 3 shows the structure of the ropivacaine-sodium deoxycholate gel prepared in Example 3: A is the appearance of the gel, B is an optical microscope image of the gel, C is a SEM image of the gel, and D is a SEM image of the lyophilized gel powder.

[0074] Figure 4 This is a graph showing the in vitro release results of the ropivacaine-sodium deoxycholate gel prepared in Example 3;

[0075] Figure 5 The ropivacaine-bile salt gel liposomes of Example 5 are, from left to right, prescriptions 19, 20, 21, and 22;

[0076] Figure 6 The ropivacaine-bile salt gel liposomes of Example 5 are, from left to right, prescriptions 27, 26, and 25;

[0077] Figure 7 This is the particle size distribution diagram of the ropivacaine-sodium deoxycholate gel liposomes prepared in Example 6;

[0078] Figure 8 TEM image of ropivacaine-sodium deoxycholate gel liposomes prepared in Example 6;

[0079] Figure 9 This is a graph showing the in vitro release results of ropivacaine-sodium deoxycholate gel liposomes prepared in Example 6;

[0080] Figure 10 The graph shows the analgesic effect of the ropivacaine-sodium deoxycholate gel prepared in Example 3 on mice: the left graph shows the analgesic effect for mechanical pain, and the right graph shows the analgesic effect for thermal pain;

[0081] Figure 11 This is a graph showing the in vitro cytotoxicity results of the ropivacaine-sodium deoxycholate gel prepared in Example 3;

[0082] Figure 12 This is the H&E staining result of major organs and sciatic nerve after administration of the ropivacaine-sodium deoxycholate gel prepared in Example 3;

[0083] Figure 13 This is a graph showing the results of serum biochemical indicators after administration of the ropivacaine-sodium deoxycholate gel prepared in Example 3. DETAILED DESCRIPTION

[0084] The present invention will be further described below in conjunction with the accompanying drawings and specific examples. It should be understood that these examples are intended to illustrate the present invention only and are not intended to limit the scope of the invention. The experimental methods in the following examples, for which specific conditions are not specified, are generally carried out under conventional conditions or under conditions recommended by the manufacturer.

[0085] the term:

[0086] The term "mixing" refers to the process of uniformly distributing two or more components in a solution by stirring or heating means known in the pharmaceutical field.

[0087] The term "w / v" refers to the mass concentration of a solute expressed in grams per 100 mL of water. 1% (w / v) means the mass concentration of the solute is 1 g / 100 mL.

[0088] The term "biocompatibility" is defined by the International Standards Organization (ISO) as a property of living tissues in response to inactive materials, generally referring to the compatibility between a material and a host.

[0089] The term "release rate" refers to the rate and extent of drug release from a sustained-release or controlled-release formulation in a specified solvent.

[0090] The term "particle size distribution" refers to the number of particles within different particle size ranges in the formulation solution measured using a BlueWave laser particle size analyzer.

[0091] Example 1 Preparation of Ropivacaine-Sodium Deoxycholate Hydrophobic Complex

[0092] 453.2 mg of sodium deoxycholate was weighed and dissolved in 10 mL of ultrapure water, and then 150 mg of ropivacaine was slowly added under continuous stirring, and the mixture was stirred at 300 rpm overnight to complete the reaction.

[0093] The particle size and distribution of ropivacaine-sodium deoxycholate hydrophobic complex suspension solution were investigated using a BlueWave laser particle size analyzer. Figure 1 As shown. The results show that the particle size of the ropivacaine-sodium deoxycholate hydrophobic complex is 3668nm and the PDI is 0.29. It is revealed that the larger particle size of the complex itself is beneficial to the sustained release of local anesthetics. Figure 2 As shown, the structure of the complex was examined by scanning electron microscopy (SEM), and the results again confirmed the formation of ropivacaine-sodium deoxycholate complex.

[0094] Example 2 Preparation of Ropivacaine-Sodium Deoxycholate Gel

[0095] Table 1 Ropivacaine-sodium deoxycholate gel prescription

[0096]

[0097]

[0098] According to the amounts in Table 1, ropivacaine hydrochloride, a gel modifier, and a bile salt were gently sonicated in a solvent for 30 minutes, followed by stirring at 300 rpm overnight to produce a ropivacaine-sodium deoxycholate gel. Alternatively, the bile salt and gel modifier were first gently sonicated in a solvent for 30 minutes, followed by stirring at 300 rpm overnight to produce a blank gel. Ropivacaine was then added and mixed using probe sonication (power P = 35%, two 3-minute cycles, with a 2-minute interval between each cycle), followed by stirring at 300 rpm overnight to produce a ropivacaine-sodium deoxycholate gel.

[0099] Example 3 Structure of Ropivacaine-Sodium Deoxycholate Gel

[0100] According to recipe 2, 453.2 mg of sodium deoxycholate was weighed and dissolved completely in 5 mL of 1% CMC-Na aqueous solution. Separately, 180 mg of ropivacaine hydrochloride monohydrate was weighed and dissolved completely in 5 mL of 1% CMC-Na aqueous solution to obtain a transparent solution. The two solutions were mixed, gently sonicated in a water bath for 30 minutes, and then stirred at 300 rpm overnight to obtain a milky white ropivacaine-sodium deoxycholate gel with poor fluidity.

[0101] The gel structure was examined visually and by optical microscopy, and the structure of ropivacaine-sodium deoxycholate gel and its lyophilized powder was examined by scanning electron microscopy (SEM). Figure 3 As shown in the figure, wherein A is the appearance of the gel, B is the image of the gel under an optical microscope, C is the SEM image of the gel, and D is the SEM image of the gel lyophilized powder. From B, C, and D, it can be clearly seen that the gel network is a structure formed by irregular cross-linking of fibers. From C and D, it can be seen that some particles are irregularly dispersed in the network on the long fibers that constitute the network skeleton, which is the ropivacaine-sodium deoxycholate complex. The size of the ropivacaine-sodium deoxycholate complex in the gel is smaller than the size of the complex generated by the direct reaction of ropivacaine and sodium deoxycholate (see Example 1), which is attributed to the fact that ropivacaine participates in the construction of the gel skeleton, thereby reducing the mutual aggregation between the ropivacaine-sodium deoxycholate complex.

[0102] Example 4 In vitro release of ropivacaine-sodium deoxycholate gel

[0103] 1 mL of the ropivacaine-sodium deoxycholate gel prepared in Example 3 was placed in a dialysis bag (MWCO: 8000-14000, MD44). Both ends of the dialysis bag were clamped with dialysis clips and placed in a beaker containing 150 mL of release medium (PBS containing 0.2% Tween 20). The beaker was placed in a constant temperature air bath at 37°C and 25 rpm. 1 mL of sample was taken at predetermined time points and 1 mL of fresh mobile phase was added at the same time. The ropivacaine concentration was measured by UV spectrophotometry and the release rate was calculated. The results are shown in FIG. Figure 4 The results showed that ropivacaine-sodium deoxycholate gel had no burst release, sustained release for more than 24 hours in vitro, and then slowly released the remaining drug in the gel.

[0104] Example 5 Preparation of Ropivacaine-Bile Salt Gel Liposomes

[0105] Table 2 Formulation and preparation of ropivacaine-bile salt gel liposomes

[0106]

[0107] Prepare ropivacaine-sodium deoxycholate gel liposomes according to the dosage of the prescription in Table 2. Sodium deoxycholate is added to an aqueous solvent or buffer. Ultrasonicate the solution (power is 100W) for 30 minutes at room temperature, and then stir at 300rpm to react overnight to obtain bile salt water gel. After the phospholipids and cholesterol are completely dissolved in chloroform, they are completely evaporated to dryness using a rotary evaporator at 40°C. Use bile salt water gel to hydrate the lipid film, ultrasonicate in a water bath at 40°C (ultrasonic power is 200W) for 30 minutes, and then ultrasonicate with a probe (power P = 35%, ultrasonicate 2 times, 3 minutes each time, with an interval of 2 minutes between the two times) to obtain blank liposomes. Adjust the pH of the blank liposomes to neutral, and then dialyze in deionized water for more than 8 hours, during which the dialysate is replaced. Finally, ropivacaine is added to the dialyzed blank liposome solution, and the drug is actively loaded by probe ultrasonication (power P = 35%, ultrasonicate 2 times, 3 minutes each time, with an interval of 2 minutes between the two times). The liposomes obtained in prescriptions 19-22 are as follows. Figure 5 As shown, from left to right are prescriptions 19, 20, 21, and 22. The liposomes obtained from prescriptions 25-27 are as follows Figure 6 As shown, from left to right are prescriptions 27, 26, and 25.

[0108] Example 6 Preparation of Ropivacaine-Sodium Deoxycholate Gel Liposomes

[0109] According to the dosage of 27g of the prescription in Example 5, ropivacaine-sodium deoxycholate gel liposomes were prepared:

[0110] (1) Add 900 mg of sodium deoxycholate to 10 mL of hydrochloric acid solution at pH 6.5, sonicate the solution (power 100 W) at room temperature for 30 min, and stir at 300 rpm overnight to obtain sodium deoxycholate gel;

[0111] (2) 828.6 mg of lecithin and 211.3 mg of cholesterol were dissolved in chloroform and completely dried using a rotary evaporator at 40°C to form a film;

[0112] (3) The lipid film in (2) was hydrated with the sodium deoxycholate gel in (1), and the liposome was sonicated in a water bath (ultrasonic power of 200 W) at 40°C for 30 min, and then sonicated with a probe (power P = 35%, sonicated twice, each time for 3 minutes, with an interval of 2 minutes between the two times) to obtain blank liposomes;

[0113] (4) Adjust the pH of the blank liposomes in (3) to neutral, and then dialyze in deionized water for more than 8 h, during which the dialysate was replaced;

[0114] (5) 150 mg of ropivacaine was added to the blank liposome solution after dialyzation in (4), and the drug was actively loaded by probe ultrasound (power P = 35%, ultrasound twice, each time for 3 minutes, with an interval of 2 minutes between the two times).

[0115] The particle size and distribution of liposome solution were investigated using BlueWave laser particle size analyzer. Figure 7 The results showed that the particle size of ropivacaine-sodium deoxycholate gel liposomes was 1755nm and PDI was 0.23. The structure of the gel liposomes was examined by transmission electron microscopy (TEM). Figure 8 As shown, the results showed that a structure of black complex gel encapsulated by liposomes was formed, and the liposome size of large vesicles was basically consistent with the particle size measurement results.

[0116] Example 7 In vitro release of ropivacaine-sodium deoxycholate gel liposomes

[0117] According to the method in Example 4, 1 mL of the ropivacaine-sodium deoxycholate gel liposome solution prepared in Example 6 was placed in a dialysis bag, and the in vitro release of the ropivacaine-sodium deoxycholate gel liposome was investigated in 150 mL of release medium. Figure 9 The results showed that ropivacaine-sodium deoxycholate gel liposomes could sustain release for more than 24 hours in vitro.

[0118] Example 8 Analgesia Experiment of Ropivacaine-Sodium Deoxycholate Gel in Mice

[0119] In order to further verify that the ropivacaine-sodium deoxycholate gel disclosed in the invention has a sustained-release effect, a ropivacaine-sodium deoxycholate gel sample was prepared according to the scheme of prescription 2 (Example 3, and analgesia tests were performed using the Von Frey method and the hot plate method.

[0120] The experimental plan is to conduct pharmacodynamic evaluation through the sciatic nerve block model, that is, inject 0.2mL of local anesthetic gel solution into the muscles around the animal nerve to block the conduction of action potentials and nerve impulses, so as to produce significant anesthetic and analgesic effects in the area controlled by the nerve.

[0121] (1) Three days before modeling, baseline pain levels of C57BL / 6 mice were measured daily using the Von Frey 50% paw withdrawal threshold test and the hot plate analgesia test. Animals with abnormal pain thresholds were removed. Six male mice were randomly divided into two groups: a control group (7.5 mg / mL ropivacaine hydrochloride injection) and a test group (ropivacaine-sodium deoxycholate gel). The outer side of the right leg of the mice was shaved the day before the experiment in preparation for the next day's experiment.

[0122] (2) Prepare a 1.25% tribromoethanol solution with isopropyl alcohol and saline and pass it through a 0.22 μm membrane. Intraperitoneally inject the solution at a dose of 150 mg / kg to briefly anesthetize the mice. After the mice become quiet and the righting reflex is not obvious, fix the limbs in a prone position with medical PE tape (make sure the right sole faces upward). Slightly cut the skin at the femur of the right thigh longitudinally, and then use hemostatic forceps to bluntly dissect the biceps femoris to expose the sciatic nerve. Under direct vision, inject 0.2 mL of local anesthetic solution in parallel into the sciatic nerve root or the muscle around the sciatic nerve, and then suture the skin with absorbable sutures. After injection, at the pre-set time point, each group of mice is tested for sensory nerve block, namely the Von Frey method and the hot plate method. The hot plate method test should be repeated three times.

[0123] (3) Von Frey method and hot plate method procedures:

[0124] Von Frey method: Mice were placed on a 0.5 cm x 0.5 cm metal mesh basket and their activity area was restricted by a beaker. After the mice had been acclimated for 10 minutes and gradually settled, Von Frey fibers (with a force scale of 0.02, 0.04, 0.07, 0.16, 0.4, 0.6, 1.0, 1.4, and 2.0 g) were applied vertically to the skin of the mid-plantar surface of the right foot using an up-and-down method. After the fibers contacted the sole of the foot, pressure was applied until an "S" or "C" shape was formed and maintained for a minimum of 3 seconds, with a maximum stimulation duration of no more than 8 seconds, until the mouse lifted its foot or fled. The right paw's response was then observed. Paw withdrawal or licking was scored as a positive response ("X"), while no or insignificant paw withdrawal or licking was scored as a negative response ("O"). If the first fiber produced a negative response, stimulation was performed with the next higher-scale fiber; otherwise, stimulation was performed with the next higher-scale fiber. The first negative response (i.e., the first transition from a negative to a positive response) is recorded as the starting point, and four consecutive measurements are performed, with no less than 1 minute between stimulations. Testing should be stopped if a negative response is also obtained with the 2.0g filament stimulation, and the subsequent PWT value is recorded as 4.0g to avoid injuring the mouse's foot tissue under anesthesia. Record the "OX" sequence obtained from the five stimulations and the force (f) of the fifth filament stimulation. Calculate the mechanical pain paw withdrawal threshold (PWT) (i.e., the force at which the 50% mechanical paw withdrawal response is achieved) according to Equation 1-1.

[0125]

[0126] Where f is the scaled value of the last applied Von Frey filament, Xf represents the intensity of the last stimulus, and Xf = lg(f * 10000). The k value, provided by the Dixon statistical table, is a constant associated with the pain pattern, i.e., the OX sequence. δ is the mean difference in the scales of the five stimuli, expressed in logarithmic units.

[0127] Hot plate method: At room temperature, place the mouse gently on a constant temperature heating platform at 55°C, start timing, and observe the mouse's reaction. It is generally considered that licking the foot or obviously retracting the foot is a positive reaction, and vice versa. Once a positive reaction occurs, stop timing immediately and remove the mouse from the hot plate, and record the thermal latency time. Repeat the test three times on the same mouse. There should be at least 3 minutes between each hot plate test. The average of the three results represents the thermal latency of the mouse. If there is still no positive reaction after 30 seconds, remove the hot plate to prevent scalding the skin of the mouse's foot under anesthesia. At this time, the thermal latency of the mouse is recorded as 30 seconds. The maximum proportional effect (MPE) is used to analyze the thermal allodynia or analgesia of mice. The calculation formula is shown in 1-2:

[0128]

[0129] Wherein, A is the average thermal latency of the mice at the detection time point, B is the basal thermal latency of the mice, i.e., the baseline pain level before drug administration, and C represents the maximum allowable thermal latency (30 seconds in this disclosure). The effective sensory block duration (effective analgesia time) is the time from drug administration to the recovery of MPE to 50%.

[0130] The analgesic results of ropivacaine-sodium deoxycholate gel in mice Figure 10 The results showed that ropivacaine-sodium deoxycholate gel can achieve significant analgesic effect of mechanical pain for more than 10 days and significant analgesic effect of thermal pain for more than 13 days in sciatic nerve block.

[0131] Example 9 In vitro cytotoxicity of ropivacaine-sodium deoxycholate gel

[0132] The cytotoxicity of the ropivacaine-sodium deoxycholate gel prepared in Example 3 was evaluated using the CCK-8 method.

[0133] To evaluate neurotoxicity, rat adrenal pheochromocytoma cells (PC12 cells) were cultured. This cell line is a powerful cell line that has been widely used in neuroscience research. To evaluate general toxicity, mouse mononuclear macrophages (RAW264.7 cells) were cultured. This cell line is a normal immune cell that is sensitive to stimulation and plays a key role in the relief of inflammatory pain. PC12 cells were cultured in RPMI-1640 cell culture medium supplemented with 10% HS, 5% FBS, and 1% penicillin-streptomycin stock solution, and RAW264.7 cells were cultured in DMEM 1X culture medium supplemented with 10% FBS, and all were cultured in a humidified incubator with 5% CO2 and a constant temperature of 37°C. The cytotoxicity of the gel preparation and ropivacaine hydrochloride solution was evaluated using the conventional cell counting kit-8 assay (CCK-8 method). When cells are growing well and have proliferated to a certain number, PC12 and RAW264.7 cells are seeded into 96-well plates at a density of 1×10⁴ cells per well. Each well is incubated at 37°C, 5% CO₂ for 24 hours, after which the medium is discarded. 100 μL of gel preparation solutions and ropivacaine hydrochloride solutions (final RVC concentrations of 1, 5, 10, 20, 50, and 100 μM) prepared in culture medium are then added to each well. After incubation for 24, 48, and 72 hours, the medium is discarded and 100 μL of 9% (v / v) CCK-8 supplemented culture medium is added for 1-3 hours. The absorbance at 450 nm is measured using a microplate reader. Cell viability = (TE - BK) / (NC - BK) × 100%, where TE (test) represents the experimental group, NC (normal control) represents the control group, and BK (blank) represents the blank group.

[0134] Cytotoxicity results such as Figure 11 As shown. After culturing with ropivacaine hydrochloride or the gel preparation for 24, 48, and 72 hours, the survival rate of RAW264.7 cells did not show a significant decrease, and even increased with time, exceeding 100%, indicating that both ropivacaine hydrochloride and the gel preparation have good biocompatibility. For PC12 cells, which are neuron-like cells, this can reflect the safety of local anesthetics when applied to nerve cells. Figure 11 As can be seen in the figure, the preparation group showed a higher cell survival rate than the ropivacaine hydrochloride-treated group over the three days. The survival rate of PC12 cells treated with the preparation group almost exceeded 100%, while the survival rate of cells treated with ropivacaine hydrochloride was almost less than 100%. This confirms that direct application of ropivacaine has a relatively significant neurotoxicity and also shows that the gel preparation has a high neurological safety.

[0135] Example 10 Biocompatibility of Ropivacaine-Sodium Deoxycholate Gel

[0136] The histopathological and blood biochemical levels of the ropivacaine-sodium deoxycholate gel prepared in Example 3 after administration were evaluated.

[0137] Histology was assessed 4 and 14 days after administration, as these two time points represent the levels of acute and chronic inflammation. The sciatic nerve and surrounding muscle tissue, as well as major organs (heart, liver, spleen, lungs, and kidneys) were dissected and collected on days 4 and 14 after administration. All tissue samples were fixed in 4% buffered paraformaldehyde for more than 24 hours, then embedded in paraffin and sectioned, and stained with hematoxylin and eosin (H&E) to observe whether there was tissue damage or inflammatory response. The sciatic nerve with surrounding muscle should be transected to observe the cross section. The final results are as follows. Figure 12 As shown in the H&E results, mild inflammatory infiltration was observed in various tissues in the saline group. Furthermore, compared with the saline group, the hydrogel formulation and 0.75% ropivacaine hydrochloride did not exacerbate the inflammatory response in major organs and the sciatic nerve, reflecting the excellent biocompatibility of the gel formulation.

[0138] Before the above-mentioned histological collection, blood was collected from the mice through the orbital vein. After standing for 3 hours at room temperature, serum was collected by centrifugation at 4,000 rpm for 10 minutes. If the serum was turbid, it was centrifuged twice. The levels of lactate dehydrogenase (LDH), blood urea nitrogen (BUN), and alkaline phosphatase (ALP) were analyzed by biochemical analyzer. LDH can reflect cardiac toxicity, BUN can reflect renal toxicity, and ALP can reflect hepatotoxicity. The final results are as follows Figure 13 As shown. When ropivacaine is accidentally injected intravascularly or overdosed, it will block the NaV channels of the myocardial cell membrane on a large scale, destroy its structure and release myocardial enzymes, thereby leading to an increase in LDH. ALP and BUN can reflect the abnormalities of liver and kidney function, respectively. Among the three indicators of LDH, ALP, and BUN, on the fourth day after administration, although the results were not significant, the preparation and ropivacaine hydrochloride both showed smaller values than the saline group. On the 14th day after administration, mice treated with the preparation showed lower ALP and BUN levels than the saline group, while the LDH level was similar to that of the saline group and lower than the level on the fourth day. These results indicate that the preparation has good biocompatibility and safety.

[0139] The embodiments described above provide a detailed description of the technical solutions and beneficial effects of the present invention. It should be understood that the above are only specific embodiments of the present invention and are not intended to limit the present invention. Any modifications, supplements and equivalent substitutions made within the scope of the principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A low molecular weight hydrogel for local anesthetic, characterized in that: Its raw materials include: local anesthetic, bile salt, aqueous solvent or buffer; The aqueous solvent or buffer solution is selected from at least one of water, hydrochloric acid with a pH of 6.5, an acid aqueous solution with a pH of 6.5, PBS buffer, Tris-HCl buffer with a pH of 6.5, normal saline, 1 wt% sodium carboxymethylcellulose solution, and 1 wt% sodium hyaluronate solution; the acid aqueous solution refers to an aqueous solution containing an organic acid; The local anesthetic is ropivacaine hydrochloride; The bile salt is selected from at least one of sodium cholate, sodium deoxycholate, sodium chenodeoxycholate, sodium lithocholate, sodium ursocholic acid, sodium ursodeoxycholate, sodium glycodeoxycholate, sodium taurolithocholic acid, sodium glycotaurocholate, sodium glycochenodeoxycholate, sodium phenylpropanecholate, sodium casocholic acid, sodium leukocholic acid, bile acid dimer, bile acid side chain amino acid conjugate, bile acid side chain PEG conjugate and bile acid side chain glucose conjugate.

2. A low molecular weight hydrogel for local anesthetic, characterized in that: Its raw materials include: local anesthetic, bile salt, aqueous solvent or buffer; The aqueous solvent or buffer solution is selected from at least one of hydrochloric acid with a pH of 6.5, an acid aqueous solution with a pH of 6.5, and a Tris-HCl buffer with a pH of 6.5; the acid aqueous solution refers to an aqueous solution containing an organic acid; The local anesthetic is at least one of ropivacaine and a pharmaceutically acceptable salt thereof; The bile salt is selected from at least one of sodium cholate, sodium deoxycholate, sodium chenodeoxycholate, sodium lithocholate, sodium ursocholic acid, sodium ursodeoxycholate, sodium glycodeoxycholate, sodium taurolithocholic acid, sodium glycotaurocholate, sodium glycochenodeoxycholate, sodium phenylpropanecholate, sodium casocholic acid, sodium leukocholic acid, bile acid dimer, bile acid side chain amino acid conjugate, bile acid side chain PEG conjugate and bile acid side chain glucose conjugate.

3. The low molecular weight hydrogel for local anesthetic according to claim 1 or 2, characterized in that: The molar ratio of bile salt to local anesthetic is 1.2-4.5:

1.

4. The low molecular weight hydrogel for local anesthetic according to claim 1 or 2, characterized in that: The low molecular weight local anesthetic gel further contains a gel modifier; the gel modifier is at least one of mannitol, sodium chloride, calcium chloride, glycine, alanine, aspartic acid, glutamic acid, alanine, graphene, graphene oxide and carbon nanosheets; In the low molecular weight gel of local anesthetic, the amount of gel modifier used is 0.1-1wt%.

5. A method for preparing the low molecular weight hydrogel of local anesthetic according to any one of claims 1 to 4, comprising: The local anesthetic and bile salts were gently sonicated in an aqueous solvent or buffer for 10-30 minutes, and then gently stirred or incubated at 25°C until phase equilibrium was reached; Alternatively, bile salts are gently sonicated in an aqueous solvent or buffer for 10-30 minutes, gently stirred or incubated at 25°C to obtain a blank gel; local anesthetic is added to the blank gel, mixed by probe sonication, and gently stirred for 8-15 hours.

6. A low molecular weight hydrogel liposome containing a local anesthetic, characterized in that: Its raw materials include: local anesthetic, bile salt, aqueous solvent or buffer, liposome; The aqueous solvent or buffer solution is selected from at least one of water, hydrochloric acid with a pH of 6.5, an acid aqueous solution with a pH of 6.5, PBS buffer, Tris-HCl buffer with a pH of 6.5, normal saline, 1 wt% sodium carboxymethylcellulose solution, and 1 wt% sodium hyaluronate solution; the acid aqueous solution refers to an aqueous solution containing an organic acid; The local anesthetic is ropivacaine hydrochloride; The bile salt is selected from at least one of sodium cholate, sodium deoxycholate, sodium chenodeoxycholate, sodium lithocholate, sodium ursocholate, sodium ursodeoxycholate, sodium glycodeoxycholate, sodium taurolithocholate, sodium glycotaurocholate, sodium glycochenodeoxycholate, sodium phenylpropanecholate, sodium casochate, sodium leukocholate, bile acid dimer, bile acid side chain amino acid conjugate, bile acid side chain PEG conjugate and bile acid side chain glucose conjugate; The liposomes include phospholipids and cholesterol; the molar percentage of cholesterol in the liposomes is 10-80%; The molar ratio of phospholipid to local anesthetic is 0.5-5:

1.

7. A low molecular weight hydrogel liposome containing a local anesthetic, characterized in that: Its raw materials include: local anesthetic, bile salt, aqueous solvent or buffer, liposome; The aqueous solvent or buffer solution is selected from at least one of hydrochloric acid with a pH of 6.5, an acid aqueous solution with a pH of 6.5, and a Tris-HCl buffer with a pH of 6.5; the acid aqueous solution refers to an aqueous solution containing an organic acid; The local anesthetic is at least one of ropivacaine and a pharmaceutically acceptable salt thereof; The bile salt is selected from at least one of sodium cholate, sodium deoxycholate, sodium chenodeoxycholate, sodium lithocholate, sodium ursocholate, sodium ursodeoxycholate, sodium glycodeoxycholate, sodium taurolithocholate, sodium glycotaurocholate, sodium glycochenodeoxycholate, sodium phenylpropanecholate, sodium casochate, sodium leukocholate, bile acid dimer, bile acid side chain amino acid conjugate, bile acid side chain PEG conjugate and bile acid side chain glucose conjugate; The liposomes include phospholipids and cholesterol; the molar percentage of cholesterol in the liposomes is 10-80%; The molar ratio of phospholipid to local anesthetic is 0.5-5:

1.

8. The low molecular weight hydrogel liposome of local anesthetic according to claim 6 or 7, characterized in that: In the liposome, the molar percentage of cholesterol is 20-40%; and the molar ratio of phospholipid to local anesthetic is 1-2:

1.

9. The low molecular weight hydrogel liposome of local anesthetic according to claim 6 or 7, characterized in that: In the local anesthetic low molecular weight gel liposome, the molar dosage ratio of bile salt to local anesthetic is 1-5.5:

1.

10. A method for preparing low molecular weight hydrogel liposomes of local anesthetic according to any one of claims 7 to 9, characterized in that: include: (a) Bile salts were gently sonicated in aqueous solvent or buffer for 10–30 min and incubated with gentle stirring or at 25°C until a blank gel was obtained; (b) dissolving the liposomes in a volatile organic solvent and rotary evaporating the liposomes to form a lipid film; (c) hydrating the lipid membrane prepared in step (b) with the blank gel prepared in step (a) to obtain blank liposomes; (d) The pH of the blank liposomes was adjusted to neutral and then dialyzed in deionized water for more than 8 h, during which the dialysate was replaced; (f) Adding local anesthetic to the blank liposomes after dialyzation in step (d), and performing active drug loading by probe ultrasound to obtain low molecular weight gel liposomes with local anesthetic.

Images