Microsphere-oil gel composite sustained-release injection and preparation method thereof

Abstract

This invention discloses a microsphere-oil gel composite sustained-release injection and its preparation method. The method includes the following steps: dissolving PVA in pure water to obtain an aqueous phase; dissolving PLGA in an organic solvent to form an organic phase; adding vitamin B12 in solid form to the organic phase to form a solid-oil phase suspension system; adding the solid-oil phase suspension system to the aqueous phase for emulsification to form a solid-oil-aqueous emulsion; adding the emulsion to excess pure water to form drug-loaded PLGA microspheres and freeze-drying; using peanut oil as the oil phase, heating to 60-65°C, adding a gelling agent (a mixture of glyceryl monostearate and beeswax) to the oil phase to form a clear and homogeneous oil phase system; cooling the oil phase system to 30-40°C, adding drug-loaded PLGA microspheres, and uniformly dispersing them under stirring conditions, then continuing to cool naturally to room temperature to obtain the microsphere-oil gel composite sustained-release injection.

Description

Technical Field

[0001] This invention belongs to the field of medicine, specifically relating to a microsphere-oil gel composite sustained-release injection and its preparation method. Background Technology

[0002] Ruminants have a continuous and stable need for various vitamins during their growth, development, reproduction, and lactation, among which vitamin B is essential. 12 Cobalamin, a cobalt-containing water-soluble vitamin, plays an important role in the metabolism of ruminants. Vitamin B1 12 Vitamin B1 participates in one-carbon unit metabolism and propionic acid metabolism, and is closely related to energy utilization efficiency, protein synthesis, and erythrocyte production. Its supply level directly affects the production performance and health of ruminants. Unlike monogastric animals, ruminants have higher levels of vitamin B1. 12 Vitamin B1 primarily relies on rumen microbial synthesis, and this process is influenced by various factors, including the cobalt content in the diet, feed composition, rumen fermentation environment, and the animal's physiological state. When cobalt intake is insufficient or rumen function is impaired, rumen microorganisms synthesize vitamin B1. 12 A decline in the body's ability to produce vitamin B can easily lead to a decrease in vitamin B levels. 12 Insufficient levels. In actual production, ruminants lack vitamin B. 12 Vitamin B deficiency is relatively common, especially in peripartum cows, fast-growing fattening cattle, and animal populations in long-term low-cobalt diets. 12 A lack of these nutrients can cause problems such as stunted growth, decreased appetite, anemia, reduced reproductive performance, and decreased milk production. In severe cases, it can also affect the overall health and productivity of animals.

[0003] Vitamin B in ruminants 12 The deficiency problem has been addressed through various supplementation methods in livestock production and veterinary clinical practice, primarily including injections and supplementation via feed or licks. Among these, vitamin B... 12 Injectable solutions are widely used in clinical and manufacturing practices due to their rapid onset of action and relatively direct administration method. Existing vitamin B... 12 Injectable preparations are mostly water-soluble, short-acting formulations. After entering the body, they can increase the level of vitamin B in the blood or tissues within a short period of time. 12 Levels of vitamin B12 have a certain ameliorative effect on acute or obvious deficiency states. However, due to vitamin B12 deficiency... 12Due to their rapid metabolism and excretion in the body, these short-acting preparations often fail to maintain a stable effective concentration after taking effect, typically requiring repeated injections to maintain the supplementation effect. This not only increases labor costs and operational frequency but may also cause repeated stress to animals, affecting their production performance and welfare. In addition to injection administration, vitamin B can be supplemented through feed additives or licks. 12 This is also a commonly used method in production. However, this type of supplementation is affected by various factors in practical application, such as differences in individual animal feed intake, group competition, reduced feed intake due to disease or stress, etc., leading to vitamin B... 12 The actual intake of vitamin B is difficult to control precisely, and the effectiveness of supplementation is highly uncertain. Especially during the peripartum period or high production load stages, relying solely on feed or licks for supplementation often fails to meet the animal's vitamin B requirements. 12 The continued demand.

[0004] To prolong the duration of drug action and reduce dosing frequency, sustained-release and controlled-release formulations have received widespread attention in the veterinary and pharmaceutical fields in recent years. Among them, biodegradable polymers, such as polylactic-co-glycolic acid copolymer (PLGA), are widely used in the preparation of microsphere sustained-release injection formulations due to their good biocompatibility and controllable degradation characteristics. PLGA microspheres can achieve sustained drug release through gradual degradation in vivo, thereby reducing dosing frequency and improving medication adherence to some extent. For various small molecule drugs and some bioactive substances, studies have shown that microsphere sustained-release formulations have certain advantages in maintaining effective drug concentrations, thus showing good application prospects in the field of long-acting injection formulations. However, in practical applications, the release behavior of microsphere sustained-release formulations is significantly affected by the physicochemical properties of the drug and the preparation process. For vitamin B... 12 For these highly water-soluble hydrophilic small molecule drugs, during microsphere preparation and solidification, the drug tends to migrate to the surface of the microspheres or distribute in the near-surface region, leading to a significant initial burst release at the beginning of administration. This burst release not only weakens the long-acting sustained-release advantage of microsphere formulations but may also cause fluctuations in drug concentration in vivo, affecting the safety and stability of administration. Furthermore, the release process of microsphere injection formulations in vivo is closely related to the external environment, including the tissue fluid environment at the injection site, the dispersion state of the microspheres in the carrier, and the properties of the initial contact medium after administration. All of these factors may further amplify the burst release problem of hydrophilic drugs in microsphere systems, making it difficult to effectively control the initial release behavior simply by relying on the microsphere structure itself.

[0005] Therefore, developing a novel microsphere-oil gel composite injection that can overcome the above-mentioned defects is of great practical significance. Summary of the Invention

[0006] To address the shortcomings of existing technologies, this invention provides a microsphere-oil gel composite sustained-release injection and its preparation method. This injection significantly reduces the initial burst release of the drug (vitamin B12), and its low-temperature processing reduces the risk of thermal degradation of the drug (vitamin B12).

[0007] The preparation method of the microsphere-oleogel composite sustained-release injection provided by the present invention includes the following steps: I. Preparation of PLGA microspheres (s / o / w) (1) The emulsifying stabilizer is dissolved in pure water and a homogeneous aqueous phase is obtained under heating and stirring conditions; the emulsifying stabilizer is polyvinyl alcohol; (2) A biodegradable polymer material is dissolved in an organic solvent and a homogeneous organic phase is formed under heating and stirring conditions; the polymer material is polylactic acid-glycolic acid copolymer (PLGA) and the organic solvent is ethyl acetate; (3) Add vitamin B12 in solid form to the organic phase obtained in step (2), and under stirring conditions, make the drug uniformly distributed in the organic phase in a solid dispersion state to form a solid-oil suspension system (S / O). (4) Add the solid-oil suspension system obtained in step (3) to the aqueous phase prepared in step (1) and emulsify it under stirring conditions to form a solid-oil-aqueous (S / O / W) emulsion. (5) Add the emulsion obtained in step (4) to excess pure water, and under stirring conditions, allow the organic solvent to evaporate and promote the solidification of the polymer material to form drug-loaded PLGA microspheres; (6) The drug-loaded microspheres after curing are separated and washed, and the residual moisture is removed by freeze drying to obtain dried drug-loaded PLGA microspheres; II. Preparation of Microsphere-Olegel Composite Injection (7) Peanut oil or soybean oil is used as the oil phase and heated to a temperature range in which the gelling agent can dissolve. The gelling agent is added to the oil phase under stirring to fully dissolve it and form a clear and homogeneous oil phase system. The gelling agent is a mixture of glyceryl monostearate (GMS) and beeswax. (8) Cool the clear and uniform oil phase system obtained in step (7). When the system temperature drops to above the gelation temperature of the gelling agent and below the tolerance temperature of the hydrophilic drug or microspheres, add the dried drug-loaded PLGA microspheres obtained in step (6) and disperse them uniformly under stirring conditions. Then continue to cool naturally to room temperature so that GMS and beeswax crystallize and form a three-dimensional network structure, thereby obtaining an oil gel matrix in which microspheres are uniformly dispersed, and obtain a microsphere-oil gel composite sustained-release injection.

[0008] In step (1) of the above method, the weight-average molecular weight (Mw) of the polyvinyl alcohol is 30,000-50,000; the mass ratio of the polyvinyl alcohol to pure water is 1%-3.5%; the heating temperature can be 30-35 ℃; the stirring speed can be 700-800 rpm; and the stirring time can be 20-30 min.

[0009] According to a specific embodiment of the present invention, the ratio of polyvinyl alcohol to pure water can be 1.2g:48mL; the heating temperature is 75℃, the stirring speed is 700rpm, and the stirring time is 20min.

[0010] In step (2) of the above method, the weight-average molecular weight (Mw) of the polylactic acid-glycolic acid copolymer (PLGA) is 87,000-106,000; the mass-volume ratio (g / mL) of the polylactic acid-glycolic acid copolymer (PLGA) to the organic solvent is 7.5%-12.5%; the heating temperature is 30-35 ℃; the stirring speed is 300-400 rpm, and the stirring time can be 10-20 min.

[0011] According to a specific embodiment of the present invention, the ratio of polylactic acid-glycolic acid copolymer (PLGA) to organic solvent is 1.2 g: 12 mL; the heating temperature is 30 °C; the stirring speed is 300 rpm and the stirring time is 10 min.

[0012] In step (3) of the above method, the vitamin B12 includes hydroxycobalamin hydrochloride, cyanocobalamin, methylcobalamin, etc.

[0013] In step (3) of the above method, the ratio of vitamin B12 to the organic phase is 1 g: (75-125) mL.

[0014] According to one specific embodiment of the present invention, the ratio of hydroxycobalamin hydrochloride to the organic phase is 0.12 g: 12 mL.

[0015] In step (4) of the above method, the volume ratio of the solid-oil suspension system to the aqueous phase is 1:(2-6); the stirring speed of the emulsification is 400-800 rpm, and the stirring time is 5-20 min.

[0016] According to a specific embodiment of the present invention, the volume ratio of the solid-oil suspension system to the aqueous phase is 1:4; the stirring speed of the emulsification is 600 rpm, and the stirring time is 10 min.

[0017] In step (6) of the above method, the separation can be carried out by vacuum filtration; the washing is carried out by pure water; the freeze-drying conditions are: first freeze at -80 ~ -90 ℃ for 24-36 h, and then freeze at a vacuum degree below 50 Pa and a temperature between -40 and -60 ℃ for 36-48 h.

[0018] According to a specific embodiment of the present invention, the freeze-drying conditions are as follows: first, freezing at -80 ℃ for 24 h, and then freeze-drying at a vacuum degree of less than 50 Pa and a cold trap temperature of -40 to -60 ℃ for 48 h.

[0019] In step (7) of the above method, the mass ratio of glyceryl monostearate (GMS) to beeswax is (1-1.5):1; the amount of gelling agent is 1-10% of the mass of the oil phase; the heating temperature is 60-65 ℃ and the stirring speed is 1200-1500 rpm.

[0020] According to one embodiment of the present invention, the mass ratio of glyceryl monostearate (GMS) to beeswax is 1.5:1.

[0021] According to one embodiment of the present invention, the amount of gelling agent used is 3% of the mass of the oil phase.

[0022] According to another embodiment of the invention, the amount of gelling agent used is 10% of the mass of the oil phase.

[0023] According to one embodiment of the present invention, the heating temperature is 65 °C and the stirring speed is 1500 rpm.

[0024] In step (8) of the above method, the system temperature is 30-40℃; the mass ratio of the oil phase system to the drug-loaded PLGA microspheres is (8-12.5):1; the stirring speed is 1200-1500 rpm, and the stirring time is 3-5 min.

[0025] According to one embodiment of the present invention, the system temperature is 35 °C; the mass ratio of the oil phase system to the drug-loaded PLGA microspheres is 10:1; the stirring speed is 1500 rpm and the stirring time is 3 min.

[0026] The microsphere-oil gel composite sustained-release injection prepared by the above method is also within the scope of protection of this invention.

[0027] Compared with the prior art, the present invention has the following beneficial effects: This invention introduces a two-component structured system with synergistic crystallization behavior by compounding glyceryl monostearate (GMS) and beeswax as gelling agents in an oil-phase system. During cooling, this compound system allows GMS to initially form a primary crystalline structure, providing a nucleation basis for the further growth of beeswax crystals, thereby lowering the initial temperature required for the formation of the overall gel network. The GMS / beeswax compound oleogel system used in this invention, by controlling the gelation behavior and rheological evolution process, achieves a lower processing temperature and a wider operating window for microsphere dispersion, providing milder and more controllable process conditions for subsequent preparations.

[0028] This invention constructs a multi-level diffusion pathway between the microspheres and the external medium by dispersing drug-loaded PLGA microspheres in an oleogel continuous phase, thereby regulating the drug release behavior in the early stages of drug administration. The hydrophobic continuous phase and three-dimensional network structure of the oleogel system can structurally slow down the permeation rate of water molecules to the surface of the microspheres, further restricting the outward diffusion of the drug from the surface of the microspheres. In the early time points of in vitro release experiments, the drug release amount detected by the compounded oleogel system was low in the initial stage, and no obvious instantaneous release peak was observed. This release characteristic helps to avoid the problem of excessively high local drug concentration caused by a large release of the drug in a short period of time, making the drug release process more gradual. Attached Figure Description

[0029] Figure 1 The in vitro drug release curves within 48 hours for the microsphere-oil gel composite formulations prepared in Example 1 (GMS / Beeswax oleogel), Comparative Example 1 (Beeswax oleogel), and Comparative Example 2 (Peanut oil) are shown. Detailed Implementation

[0030] The present invention will now be described in further detail with reference to specific embodiments. The given embodiments are merely illustrative of the invention and not intended to limit its scope. The embodiments provided below can serve as a guide for further improvements by those skilled in the art and do not constitute a limitation on the invention in any way.

[0031] Unless otherwise specified, the experimental methods used in the following examples are conventional methods, performed according to the techniques or conditions described in the literature in this field or according to the product instructions. Unless otherwise specified, the materials and reagents used in the following examples are commercially available.

[0032] Example 1: Preparation of microsphere-oil gel composite sustained-release injection (I) Preparation of PLGA microspheres (1) Weigh 1.2 g of polyvinyl alcohol (PVA) 4Mw (ten thousand) and add it to 48 mL of pure water. Stir at 700 rpm for 20 min under 75 ℃ water bath conditions to completely dissolve it and obtain a homogeneous aqueous phase for later use.

[0033] (2) Weigh 1.2 g of polylactic acid-glycolic acid copolymer (PLGA) with a molecular weight of 9 Mw (ten thousand) and add it to 12 mL of ethyl acetate. Stir at 300 rpm for 10 min at 30 ℃ to completely dissolve PLGA and form a clear organic phase.

[0034] (3) Weigh 0.12 g of hydroxycobalamin hydrochloride (vitamin B12) solid and add it to the above organic phase. Under stirring conditions, the drug is evenly distributed in the organic phase in a solid dispersion state to form a solid-oil phase suspension system (S / O).

[0035] (4) The solid-oil suspension system is slowly added to the aqueous phase and stirred and emulsified at 600 rpm for 10 min to form a solid-oil-aqueous (S / O / W) emulsion.

[0036] (5) Pour the obtained emulsion into 200 mL of pure water and stir continuously at room temperature for 2 h to allow ethyl acetate to gradually evaporate and promote PLGA solidification, forming drug-loaded PLGA microspheres.

[0037] (6) After curing, the microspheres were collected by vacuum filtration and washed three times with pure water. The resulting wet microspheres were then frozen at -80 ℃ for 24 h and then freeze-dried at a vacuum of less than 50 Pa and a cold trap temperature of -40 to -60 ℃ for 48 h to obtain dried hydroxycobalamin hydrochloride-supported PLGA microspheres.

[0038] (II) Preparation of microsphere-oil gel composite injection (7) Weigh 5.0 g of peanut oil as the oil phase, place it in a water bath and heat it to 65 °C. Under stirring conditions, add 0.09 g of glyceryl monostearate (GMS) and 0.06 g of beeswax in sequence (the total amount of gelling agent is 3% of the mass of the oil phase), and stir at 1200 rpm until the gelling agent is completely dissolved to form a clear and homogeneous oil phase system.

[0039] (8) Cool the above-mentioned clear and uniform oil phase system. When the system temperature drops to 35°C, add the above-prepared PLGA microspheres loaded with hydroxycobalamin hydrochloride and stir at 1200 rpm for 3 min to make the microspheres uniformly dispersed in the oil phase system.

[0040] (9) Continue to cool naturally to room temperature, so that GMS and beeswax crystallize and form a three-dimensional network structure, thereby obtaining an oleogel matrix in which microspheres are uniformly dispersed, and obtaining a microsphere-oleogel composite sustained-release injection.

[0041] Example 2: Preparation of microsphere-oil gel composite sustained-release injection (I) Preparation of PLGA microspheres Consistent with steps (1)-(6) in Example 1, repeated content is omitted here.

[0042] (II) Preparation of microsphere-oil gel composite injection (7) Weigh 5.0 g of soybean oil as the oil phase, place it in a water bath and heat it to 65 °C. Under stirring conditions, add 0.3 g of glyceryl monostearate (GMS) and 0.2 g of beeswax in sequence (the total amount of gelling agent is 10% of the mass of the oil phase), and stir at 1500 rpm until the gelling agent is completely dissolved to form a clear and homogeneous oil phase system.

[0043] (8) Cool the above-mentioned clarified oil phase system. When the system temperature drops to 35°C, add the above-prepared PLGA microspheres loaded with hydroxycobalamin hydrochloride and stir at 1500 rpm for 3 min to make the microspheres uniformly dispersed in the oil phase system.

[0044] (9) Continue to cool naturally to room temperature, so that GMS and beeswax crystallize and form a three-dimensional network structure, thereby obtaining an oleogel matrix in which microspheres are uniformly dispersed, and obtaining a microsphere-oleogel composite sustained-release injection.

[0045] Comparative Example 1: Preparation of Microsphere-Olegel Composite Injection Steps (1)-(6) are the same as in Example 1, and repeated content is omitted here.

[0046] (7) Weigh 5.0 g of peanut oil as the oil phase, place it in a water bath and heat it to 75 °C. Add 0.15 g of beeswax (total amount is 3% of the oil phase mass) under stirring conditions, and stir at 1200 rpm until the gelling agent is completely dissolved to form a clear and uniform oil phase system.

[0047] (8) Cool the above-mentioned clarified oil phase system. When the system temperature drops to 55°C, add the above-prepared PLGA microspheres loaded with hydroxycobalamin hydrochloride and stir at 1200 rpm for 3 min to make the microspheres uniformly dispersed in the oil phase system.

[0048] (9) Continue to cool naturally to room temperature to obtain an oleogel matrix in which microspheres are uniformly dispersed, and obtain a microsphere-oleogel composite sustained-release injection.

[0049] Comparative Example 2: Preparation of Microsphere-Oil Phase Composite Injection Steps (1)-(6) are the same as in Example 1, and repeated content is omitted here.

[0050] (7) Weigh 5.0 g of peanut oil as the oil phase, place it in a water bath and heat it to 35°C. Add the PLGA microspheres supported by the above-prepared hydroxycobalamin hydrochloride and stir at 1200 rpm for 3 min to make the microspheres uniformly dispersed in the oil phase system.

[0051] (8) Continue to cool naturally to room temperature to obtain an oleogel matrix in which microspheres are uniformly dispersed, and obtain a microsphere sustained-release injection.

[0052] Comparative Example 3: Preparation of Microsphere-Olegel Composite Injection Steps (1)-(6) are the same as in Example 1, and repeated content is omitted here.

[0053] (7) Weigh 5.0 g of soybean oil as the oil phase, and add 0.3 g of soybean lecithin and 0.2 g of stearic acid in sequence under stirring conditions (the total amount of gelling agent is 10% of the mass of the oil phase). Heat to 80 °C and stir to completely dissolve the gelling agent to form a clear and homogeneous oil phase system.

[0054] (8) When the obtained clear oil phase system is cooled to 45 °C, drug-loaded PLGA microspheres are added and dispersed under stirring conditions.

[0055] (9) Continue cooling to room temperature to allow the oil phase to solidify rapidly and form a gel structure, thereby obtaining a microsphere-oil gel composite formulation.

[0056] Comparison of the effects of Examples 1-2 and Comparative Examples 1-3 above: (a) Comparison of preparation temperatures: Table 1

[0057] This invention introduces a two-component structured system with synergistic crystallization behavior by combining glyceryl monostearate (GMS) and beeswax as gelling agents in an oil phase system. Compared to oleogel systems using beeswax as a single gelling agent, this compound system allows GMS to form a primary crystalline structure first during cooling, providing a nucleation basis for the further growth of beeswax crystals, thereby reducing the onset temperature required for the formation of the overall gel network.

[0058] Under this synergistic crystallization mechanism, the oil phase system maintains suitable fluidity and operability in the 30-40 ℃ range, allowing the drug-loaded PLGA microspheres to be dispersed before the gel network is fully established. In contrast, in a single beeswax system or other different oleogel systems, due to the dependence of crystallization on higher temperatures, the viscosity of the system increases more rapidly during the cooling process. Usually, the addition of microspheres needs to be completed at a higher temperature; otherwise, the system may thicken rapidly or even fail to disperse evenly.

[0059] Therefore, it can be seen that the GMS / beeswax compound oleogel system used in this invention achieves a decrease in the microsphere dispersion processing temperature and a widening of the operating window by regulating the gelation behavior and rheological evolution process, providing milder and more controllable process conditions for subsequent preparation.

[0060] (II) Comparison of sudden release situations The specific testing method is as follows: (1) In vitro release experiment A certain amount of the prepared sample was placed in a pre-treated dialysis bag, which was then sealed and immersed in a beaker containing pure water as the release medium. The system was placed on a magnetic stirrer and subjected to an in vitro release experiment at 37 °C and a stirring speed of 100 rpm. At preset time points, a certain volume of the release medium was collected and replaced with an equal volume of release medium. The collected samples were then appropriately processed for subsequent liquid chromatography detection.

[0061] (2) Sample processing The collected release medium samples were filtered through a 0.22 μm microporous membrane to remove any possible particulate or oil phase impurities. The processed samples were then analyzed by high-performance liquid chromatography (HPLC).

[0062] (3) High performance liquid chromatography detection The drug concentration in the release medium was determined using high-performance liquid chromatography (HPLC). The drug concentration in the release medium at each time point was calculated by comparing the peak area of ​​the sample with that of a standard of known concentration. (4) Data processing Based on the drug concentrations detected at each time point and the total volume of the release system, the drug release amount is calculated, and drug release curves are plotted to evaluate the in vitro sustained-release performance of different formulation systems.

[0063] See results Figure 1 And Table 2.

[0064] Table 2

[0065] This invention constructs a multi-level diffusion pathway between the microspheres and the external medium by dispersing drug-loaded PLGA microspheres in an olegel continuous phase, thereby regulating the drug release behavior in the early stages of drug administration. Compared to microspheres being directly exposed to an aqueous phase or body fluid environment, the hydrophobic continuous phase and its three-dimensional network structure of the olegel system can structurally slow down the rate of water molecule penetration to the microsphere surface, further restricting the outward diffusion of the drug from the microsphere surface.

[0066] In the early stages of the in vitro release experiment, different carrier systems exhibited different release behaviors. Among them, the compound oleogel system showed a low amount of drug release in the initial stage and did not show a significant instantaneous release peak. This release characteristic helps to avoid the problem of excessively high local drug concentrations caused by a large amount of drug release in a short period of time, making the drug release process more gradual.

[0067] (III) Suspension uniformity and microsphere sedimentation characteristics A certain volume of the microsphere-oleogel composite injection sample was placed in a transparent sample vial and allowed to stand at room temperature for a certain period of time. The microsphere sedimentation or stratification of the system was observed. The sample vial was then inverted to remix the system, and the number of inversions required for the system to return to a uniform dispersion state was recorded. The results are shown in Table 3.

[0068] Table 3

[0069] The GMS / beeswax compound oleogel system can provide a more stable spatial support structure for microspheres, effectively inhibiting microsphere sedimentation under short-term static conditions, and restoring a uniform dispersion state under slight disturbance, demonstrating better suspension stability and redispersion performance.

[0070] The present invention has been described in detail above. For those skilled in the art, the invention can be practiced in a wide range of ways with equivalent parameters, concentrations, and conditions without departing from its spirit and scope, and without requiring unnecessary experiments. Although specific embodiments have been given, it should be understood that further modifications can be made to the invention. In summary, according to the principles of the invention, this application is intended to include any changes, uses, or improvements to the invention, including changes made using conventional techniques known in the art that depart from the scope disclosed herein. Some of the essential features can be applied within the scope of the following appended claims.

Claims

1. A method for preparing a microsphere-oil gel composite sustained-release injection, comprising the following steps: (1) The emulsifying stabilizer is dissolved in pure water and a homogeneous aqueous phase is obtained under heating and stirring conditions; the emulsifying stabilizer is polyvinyl alcohol; (2) A biodegradable polymer material is dissolved in an organic solvent and a homogeneous organic phase is formed under heating and stirring conditions; the polymer material is polylactic acid-glycolic acid copolymer and the organic solvent is ethyl acetate; (3) The hydrophilic drug is added in solid form to the organic phase obtained in step (2), and the drug is uniformly distributed in the organic phase in a solid dispersion state under stirring conditions to form a solid-oil phase suspension system; the hydrophilic drug is vitamin B12. (4) Add the solid-oil suspension system obtained in step (3) to the aqueous phase prepared in step (1) and emulsify it under stirring conditions to form a solid-oil-aqueous emulsion. (5) Add the emulsion obtained in step (4) to excess pure water, and under stirring conditions, allow the organic solvent to evaporate and promote the solidification of the polymer material to form drug-loaded PLGA microspheres; (6) The drug-loaded microspheres after curing are separated and washed, and the residual moisture is removed by freeze drying to obtain dried drug-loaded PLGA microspheres; (7) Peanut oil or soybean oil is used as the oil phase and heated to a temperature range in which the gelling agent can dissolve. The gelling agent is added to the oil phase under stirring to fully dissolve it and form a clear and homogeneous oil phase system. The gelling agent is a mixture of glyceryl monostearate and beeswax. In step (7), the mass ratio of glyceryl monostearate to beeswax is (1-1.5):1; And / or, in step (7), the amount of gelling agent used is 1%-10% of the mass of the oil phase; And / or, in step (7), the heating temperature is 60-65 ℃; (8) Cool the clear and uniform oil phase system obtained in step (7). When the system temperature drops to above the gelation temperature of the gelling agent and below the tolerance temperature of the hydrophilic drug or microspheres, add the dried drug-loaded PLGA microspheres obtained in step (6) and disperse them uniformly under stirring conditions. Then continue to cool naturally to room temperature to obtain the microsphere-oil gel composite sustained-release injection.

2. The preparation method according to claim 1, characterized in that: In step (8), the system temperature is 30-40 ℃.

3. The preparation method according to claim 1, characterized in that: In step (1), the weight-average molecular weight of the polyvinyl alcohol is 30,000 to 50,000. And / or, the mass ratio of the polyvinyl alcohol to pure water is 1%-3.5%; And / or, the heating temperature is 30-35 °C; And / or, the stirring speed is 700-800 rpm, and the stirring time is 20-30 min.

4. The preparation method according to claim 1, characterized in that: In step (2), the weight-average molecular weight of the polylactic acid-glycolic acid copolymer is 87,000 to 106,000. And / or, the mass-to-volume ratio of the polylactic acid-glycolic acid copolymer to the organic solvent is 7.5%-12.5%; And / or, the heating temperature is 30-35 °C; And / or, the stirring speed is 300-400 rpm, and the stirring time is 10-20 min.

5. The preparation method according to claim 1, characterized in that: In step (3), the vitamin B12 includes hydroxycobalamin hydrochloride, cyanocobalamin and / or methylcobalamin.

6. The preparation method according to claim 1, characterized in that: In step (3), the ratio of vitamin B12 to the organic phase is 1g:(75-125)mL.

7. The preparation method according to claim 1, characterized in that: In step (4), the volume ratio of the solid-oil suspension system to the aqueous phase is 1:(2-6). And / or, in step (4), the stirring speed of the emulsification is 400-800 rpm and the stirring time is 5-20 min.

8. The preparation method according to claim 1, characterized in that: In step (6), the separation is performed by vacuum filtration; And / or, in step (6), the washing is performed using pure water; And / or, in step (6), the freeze-drying conditions are: first freeze at -80 ~ -90 ℃ for 24-36 h, then freeze at a vacuum of less than 50 Pa and a temperature maintained between -40 and -60 ℃ for 36-48 h.

9. The preparation method according to claim 1, characterized in that: In step (7), the stirring speed is 1200-1500 rpm; And / or, in step (8), the mass ratio of the oil phase system to the drug-loaded PLGA microspheres is (8-12.5):1; And / or, in step (8), the stirring speed is 1200-1500 rpm and the stirring time is 3-5 min.

10. The microsphere-oil gel composite sustained-release injection prepared by the method of any one of claims 1-9.

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