Chitosan / polycaprolactone composite microsphere gel

Abstract

The present invention relates to a chitosan / polycaprolactone composite microsphere gel, which has increased hydrophilicity and water absorption compared with the existing microsphere gel, has better tissue compatibility, and the prepared microsphere particle size distribution is narrower. It comprises chitosan / polycaprolactone composite microspheres and carboxymethyl cellulose (CMC) hydrogel, wherein the polycaprolactone microspheres are uniformly dispersed in the carboxymethyl cellulose (CMC) hydrogel, the chitosan / polycaprolactone composite is a molten blend of chitosan and polycaprolactone, and the chitosan / polycaprolactone composite microsphere gel is an injectable implant.

Description

Technical Field

[0001] The invention belongs to the field of medicine, and in particular relates to a chitosan / polycaprolactone composite microsphere gel. Background Art

[0002] At present, the skin filling injection materials are mainly divided into degradable and non-degradable types, among which the degradable materials are usually polymers such as hyaluronic acid, collagen, poly-L-lactic acid and hydroxyapatite. At present, the skin fillers have developed to the third generation of synthetic polymer fillers, such as polylactic acid (PLA) or polycaprolactone (PCL). Because they decompose very slowly in the human body, the third generation fillers have a longer duration than the first generation collagen and second generation hyaluronic acid fillers (which are absorbent fillers). However, it still faces various problems that need to be solved.

[0003] WO2009 / 014441A1 discloses microparticles containing PCL and their uses, microspheres with good flow properties, wherein an initial mixture containing solubilized PCL and a surfactant is used with a relatively high viscosity, and methylcellulose is used as a surfactant in the preparation of the microspheres, rather than a surfactant with limited biocompatibility such as polyvinyl alcohol (PVA) as described in EP 1872803 or US2003 / 0157187. Viscous aqueous solutions made with relatively high concentrations of PVA enable the preparation of PCL microspheres by rapidly adding a PCL solution to a vigorously stirred surfactant solution, and very small particles with suitable morphology can be prepared, but the yield of particles in the size range of 38-75 um is low. When MC is used as a surfactant, the yield of the method is greatly improved. However, the microspheres prepared by the method disclosed in WO2009 / 014441A1 cannot well control the size of the polymer microspheres, resulting in dispersed particle size distribution. In order to further obtain a narrow distribution of microsphere sizes, a separation method such as filtration removal is required, but this will lead to a complicated production process and is not conducive to mass production.

[0004] Polycaprolactone is a hydrophobic carrier and a semi-crystalline polymer. Its amorphous phase structure is conducive to improving the elasticity of nanofibers, and its crystalline phase structure is conducive to improving the mechanical strength of nanofibers. Therefore, the crystal phase morphology of polycaprolactone in the system directly affects the fluidity, viscosity, strength, etc. of the microspheres. During the injection process, the larger the particle size of the degradable polyester microspheres, the larger the needle and thrust used, which will cause discomfort to the user and even cause needle blockage in severe cases. At the same time, the temperature difference of polycaprolactone changes repeatedly during transportation and storage. In some reports, it was found that although the thread embedding material products were not opened, the transportation and storage temperature directly determined the formation of product vitrification, i.e. "embrittlement" (see "Comprehensive Clinical Practical Guidelines for Refining Thread Sculpting and Thread Embedding for Anti-Aging", page 12). It can be seen that polycaprolactone can maintain stability in the system, which has an important influence on maintaining the fluidity of the product.

[0005] CN 106063948 A discloses a long-acting subcutaneous implant and a preparation method thereof, comprising composite particles of collagen wrapped with degradable polyurethane, wherein the weight percentage of degradable polyurethane is 0.1-50%, the percentage of collagen is 0.1-50%, and the content of other components is 0.1-80%, and the prepared composite particles have a size range of 60um-400um. CN 106492284 A discloses a preparation method of a biodegradable filling material, its product and application, (1) mixing a matrix material and a dispersed phase material in a mass ratio of 10:0 to 6:4 and dissolving them in an organic solvent to prepare a polymer organic solvent; the matrix material is polydioxanone; the dispersed phase material is one or more of poly-L-lactic acid, polycaprolactone, polylactic acid or polyglycolic acid; (2) treating the polymer organic solvent prepared in step (1) by a mechanical method or an emulsification method to prepare microspheres. The obtained microspheres have similar and controllable particle sizes, good filling performance, and are safe and degradable. CN110327497A discloses a microsphere-containing injection gel and a preparation method thereof, which comprises a carrier and degradable polyester microspheres dispersed in the carrier for filling and supporting functions, wherein the carrier is prepared from polymer material particles and physiological buffer, and the degradable polyester microspheres are uniformly dispersed in the carrier, which can avoid problems such as uneven filling caused by local injection.

[0006] CN110623944 A discloses a glucagon-like peptide-1 analog sustained-release microsphere preparation, microsphere glucagon-like peptide-1 analog, β-cyclodextrin derivative, PLGA and polycaprolactone mixture and PEG. After adding a small amount of polycaprolactone (PCL) to PLGA for blending, under the action of PEG, the phase separation of PLGA and PCL can be accelerated to form a PLGA / PCL double-layer microsphere structure. The sudden release phenomenon of the microsphere is avoided, the drug release characteristics are improved, and the drug release cycle of the microsphere can be extended. However, the blending method is to add PLGA, polycaprolactone (PCL) and PEG to a mixed solution of dichloromethane and ethyl acetate for dissolution, that is, simple physical mixing, which does not affect the properties of each polymer. CN110882232 A discloses a vaccine, which includes an antigen and a biodegradable polymer blend matrix, wherein the polymer blend contains a hydrophobic polymer polycaprolactone and an amphiphilic block copolymer, and the blend is also the above two polymers dissolved in an oil phase containing chloroform and MPLA. Therefore, the current blending of polycaprolactone polymers in polycaprolactone microspheres is only a simple dissolution and mixing of a variety of different polymers, which does not solve the shortcomings of polycaprolactone microspheres. Summary of the invention

[0007] The technical problem to be solved by the present application is to provide a chitosan / polycaprolactone composite microsphere gel, which is suitable for in vivo injection, implantation or filling. Compared with the existing microsphere gel, it has increased hydrophilicity and water absorption, has better tissue compatibility, and at the same time, the prepared microsphere particle size distribution is narrower and the preparation efficiency is higher; at the same time, due to the improved suspension performance, the adhesion and aggregation of the microspheres are reduced during long-term storage, which is more suitable for clinical safety application.

[0008] In order to solve the above technical problems, the technical solution adopted by the present invention is as follows:

[0009] The invention provides a chitosan / polycaprolactone composite microsphere gel, which is characterized in that: the chitosan / polycaprolactone composite microsphere gel comprises chitosan / polycaprolactone composite microspheres and carboxymethyl cellulose (CMC) hydrogel, wherein the polycaprolactone microspheres are uniformly dispersed in the carboxymethyl cellulose (CMC) hydrogel, the chitosan / polycaprolactone composite is a molten blend of chitosan and polycaprolactone, and the chitosan / polycaprolactone composite microsphere gel is an injectable implant.

[0010] By weight percentage, it comprises 20-40% chitosan / polycaprolactone complex, 60-80% carboxymethyl cellulose (CMC) hydrogel, and further comprises 0.3-1% glycerol, preferably 0.8%.

[0011] The chitosan has a viscosity-average molecular weight between 50 and 70 kDa, preferably 55 kDa, and a deacetylation degree between 80 and 85%.

[0012] The chitosan / polycaprolactone composite microspheres have a D10 of 9-12 μm, preferably 10 μm and 11 μm, a D50 of 30-35 μm, preferably 32 μm, 33 μm and 34 μm, and a D90 of 35-42 μm, preferably 36 μm, 38 μm and 40 μm.

[0013] The particle size span value of the chitosan / polycaprolactone composite microspheres is 0.8-0.9, preferably 0.85 or 0.87, and the span value is (D90-D10) / D50.

[0014] In the chitosan / polycaprolactone composite, the weight ratio of chitosan to polycaprolactone is (0.5-5):(99.5-95), preferably 1:99.

[0015] The number average molecular weight Mn of the polycaprolactone is 25,000-40,000, preferably 30,000.

[0016] The chitosan / polycaprolactone composite is prepared by the following method: dry polycaprolactone PCL and chitosan CS are melt-blended at 150-180° C., preferably 160° C. or 165° C., to obtain a chitosan / polycaprolactone blend.

[0017] The present invention further provides a method for preparing chitosan / polycaprolactone composite microspheres, comprising the following steps:

[0018] (1) preparing chitosan / polycaprolactone composite blends;

[0019] (2) dissolving the chitosan / polycaprolactone blend in dichloromethane-ethanol to prepare an organic phase with a concentration of 10-30 w / w%;

[0020] (3) preparing a 1.5 w / v% aqueous solution of a surfactant, wherein the surfactant is selected from polyvinyl alcohol, methyl cellulose, and povidone, preferably polyvinyl alcohol;

[0021] (4) The organic phase is poured into the aqueous phase and sheared at high speed to obtain a microsphere suspension, and then the stirring is continued, the organic solvent is removed, and the microspheres are washed with water to obtain microspheres.

[0022] The volume ratio of dichloromethane to ethanol is 9:1.

[0023] The present invention further provides a method for preparing chitosan / polycaprolactone composite microsphere gel:

[0024] The polycaprolactone composite microspheres are mixed with carboxymethyl cellulose (CMC) hydrogel, glycerol is added, and the mixture is continuously mixed to prepare the polycaprolactone microsphere gel.

[0025] The concentration of the carboxymethyl cellulose (CMC) hydrogel is 9%.

[0026] Beneficial effects:

[0027] 1. The microsphere gel of the present invention has better hydrophilicity and water absorption by using a melt blend of chitosan / polycaprolactone, thereby improving tissue compatibility. On the other hand, it also makes the particle size span of the prepared microspheres smaller and the distribution more uniform and concentrated.

[0028] 2. The microspheres prepared by the microsphere gel of the present invention have a particle size span of 0.8-0.9, a narrower particle size distribution, and a higher preparation efficiency.

[0029] 3. The microsphere gel of the present invention can reduce the adhesion and aggregation of microspheres during long-term storage and is more suitable for injection. DETAILED DESCRIPTION

[0030] The following examples are used to illustrate the present invention, but do not limit the invention itself.

[0031] Example 1

[0032] Preparation of chitosan / polycaprolactone composite blends:

[0033] Place 99g of dried polycaprolactone PCL (number average molecular weight Mn=30000) and 1g of chitosan CS (viscosity average molecular weight 55kDa, degree of deacetylation 82.3%) in a torque rheometer, and then melt-blend at a rotor speed of 150r / min and 165°C for 10min. Stop when the torque level is reached to obtain the chitosan / polycaprolactone blend.

[0034] The chitosan / polycaprolactone blend was crushed into fine powder, and 10 g of the chitosan / polycaprolactone blend was dissolved in dichloromethane-ethanol (volume ratio 9:1) to prepare an organic phase with a concentration of 20 w / w%.

[0035] A 1.5 w / v% aqueous solution of a surfactant polyvinyl alcohol was prepared as the aqueous phase. The aqueous phase solution was pre-saturated with 2% volume fraction of dichloromethane. This step can reduce the precipitation of PCL on the surface of the solution when the solvent is volatilized. The organic phase was then poured into the aqueous phase and sheared at high speed to obtain a microsphere suspension.

[0036] The microsphere suspension was stirred at 200 rpm for 12 hours at 25° C., the organic solvent was removed, and then the suspension was repeatedly washed with water to obtain microspheres.

[0037] Preparation of CMC hydrogel: gradually add sodium carboxymethylcellulose powder into 60°C hot water and stir, sterilize with wet heat steam (121°C for 30min) after being evenly dissolved, cool and set aside to obtain 9% CMC hydrogel.

[0038] The above-mentioned dried microspheres were mixed with CMC hydrogel in a ratio of 3:7, and glycerol (the weight content in the gel system was 0.8%) was added to uniformly disperse it in the CMC hydrogel.

[0039] Example 2

[0040] Preparation of chitosan / polycaprolactone composite blends:

[0041] Place 95g of dried polycaprolactone PCL (number average molecular weight Mn=30000) and 5g of chitosan CS (viscosity average molecular weight 55kDa, degree of deacetylation 82.3%) in a torque rheometer, and then melt-blend at a rotor speed of 150r / min and 165°C for 10min. Stop when the torque level is reached to obtain the chitosan / polycaprolactone blend.

[0042] Then continue to prepare chitosan / polycaprolactone microsphere gel, and the remaining steps are the same as Example 1.

[0043] Example 3

[0044] Preparation of chitosan / polycaprolactone composite blends:

[0045] Place 90g of dried polycaprolactone PCL (number average molecular weight Mn=30000) and 10g of chitosan CS (viscosity average molecular weight 55kDa, degree of deacetylation 82.3%) in a torque rheometer, and then melt-blend at a rotor speed of 150r / min and 165°C for 10min. Stop when the torque level is reached to obtain the chitosan / polycaprolactone blend.

[0046] Then continue to prepare chitosan / polycaprolactone microsphere gel, and the remaining steps are the same as Example 1.

[0047] Example 4

[0048] Preparation of chitosan / polycaprolactone composite blends:

[0049] Place 99.5 g of dried polycaprolactone PCL (number average molecular weight Mn=30000) and 0.5 g of chitosan CS (viscosity average molecular weight 55 kDa, degree of deacetylation 82.3%) in a torque rheometer, and then melt-blend at a rotor speed of 150 r / min and 165°C for 10 min. Stop when the torque level is reached to obtain the chitosan / polycaprolactone blend.

[0050] Then continue to prepare chitosan / polycaprolactone microsphere gel, and the remaining steps are the same as Example 1.

[0051] Example 5

[0052] Preparation of chitosan / polycaprolactone composite blends:

[0053] Place 99g of dried polycaprolactone PCL (number average molecular weight Mn=45000) and 1g of chitosan CS (viscosity average molecular weight 55kDa, deacetylation degree 82.3%) in a torque rheometer, and then melt-blend at a rotor speed of 150r / min and 165°C for 10min. Stop when the torque level is reached to obtain the chitosan / polycaprolactone blend.

[0054] Then continue to prepare chitosan / polycaprolactone microsphere gel, and the remaining steps are the same as Example 1.

[0055] Example 6

[0056] Preparation of chitosan / polycaprolactone composite blends:

[0057] Place 99g of dried polycaprolactone PCL (number average molecular weight Mn=30000) and 1g of chitosan CS (viscosity average molecular weight 90kDa, degree of deacetylation 88.7%) in a torque rheometer, and then melt-blend at a rotor speed of 150r / min and 165°C for 10min. Stop when the torque level is reached to obtain the chitosan / polycaprolactone blend.

[0058] Then continue to prepare chitosan / polycaprolactone microsphere gel, and the remaining steps are the same as Example 1.

[0059] Example 7

[0060] Preparation of chitosan / polycaprolactone composite blends:

[0061] Place 99g of dried polycaprolactone PCL (number average molecular weight Mn=30000) and 1g of chitosan CS (viscosity average molecular weight 160kDa, degree of deacetylation 86.7%) in a torque rheometer, and then melt-blend at a rotor speed of 150r / min and 165°C for 10min. Stop when the torque level is reached to obtain the chitosan / polycaprolactone blend.

[0062] Then continue to prepare chitosan / polycaprolactone microsphere gel, and the remaining steps are the same as Example 1.

[0063] Example 8

[0064] Preparation of chitosan / polycaprolactone composite blends:

[0065] Place 99g of dried polycaprolactone PCL (number average molecular weight Mn=30000) and 1g of chitosan CS (viscosity average molecular weight 55kDa, degree of deacetylation 82.3%) in a torque rheometer, and then melt-blend at a rotor speed of 150r / min and 165°C for 10min. Stop when the torque level is reached to obtain the chitosan / polycaprolactone blend.

[0066] The chitosan / polycaprolactone blend was crushed into fine powder, and 10 g of the chitosan / polycaprolactone blend was dissolved in dichloromethane to prepare an organic phase with a concentration of 20 w / w%.

[0067] The remaining steps are the same as in Example 1.

[0068] Example 9

[0069] Preparation of chitosan / polycaprolactone composite blends:

[0070] Place 99g of dried polycaprolactone PCL (number average molecular weight Mn=30000) and 1g of chitosan CS (viscosity average molecular weight 55kDa, degree of deacetylation 82.3%) in a torque rheometer, and then melt blend at a rotor speed of 100r / min and 160°C for 15min. Stop when the torque level is reached to obtain the chitosan / polycaprolactone blend.

[0071] The chitosan / polycaprolactone blend was crushed into fine powder, and 10 g of the chitosan / polycaprolactone blend was dissolved in dichloromethane-ethanol (volume ratio 9:1) to prepare an organic phase with a concentration of 30 w / w%.

[0072] A 1.5 w / v% aqueous solution of a surfactant polyvinyl alcohol was prepared as the aqueous phase. The aqueous phase solution was pre-saturated with 2% volume fraction of dichloromethane. This step can reduce the precipitation of PCL on the surface of the solution when the solvent is volatilized. The organic phase was then poured into the aqueous phase and sheared at high speed to obtain a microsphere suspension.

[0073] The microsphere suspension was stirred at 200 rpm for 12 hours at 25° C., the organic solvent was removed, and then the suspension was repeatedly washed with water to obtain microspheres.

[0074] Preparation of CMC hydrogel: gradually add sodium carboxymethylcellulose powder into 60°C hot water and stir, sterilize with wet heat steam (121°C for 30min) after being evenly dissolved, cool and set aside to obtain 9% CMC hydrogel.

[0075] The above-mentioned dried microspheres were mixed with CMC hydrogel in a ratio of 3:7, and glycerol (the weight content in the gel system was 0.8%) was added to uniformly disperse it in the CMC hydrogel.

[0076] Example 10

[0077] Preparation of chitosan / polycaprolactone composite blends:

[0078] Place 99g of dried polycaprolactone PCL (number average molecular weight Mn=30000) and 1g of chitosan CS (viscosity average molecular weight 55kDa, degree of deacetylation 82.3%) in a torque rheometer, and then melt blend at a rotor speed of 100r / min and 180°C for 10min. Stop when the torque level is reached to obtain the chitosan / polycaprolactone blend.

[0079] The chitosan / polycaprolactone blend was crushed into fine powder, and 10 g of the chitosan / polycaprolactone blend was dissolved in dichloromethane-ethanol (volume ratio 9:1) to prepare an organic phase with a concentration of 20 w / w%.

[0080] A 2 w / v% aqueous solution of surfactant methylcellulose was prepared as the aqueous phase. The aqueous phase solution was pre-saturated with 2% volume fraction of dichloromethane. This step can reduce the precipitation of PCL on the surface of the solution when the solvent is volatilized. The organic phase was then poured into the aqueous phase and sheared and homogenized at high speed to obtain a microsphere suspension.

[0081] The microsphere suspension was stirred at 200 rpm for 12 hours at 25° C., the organic solvent was removed, and then the suspension was repeatedly washed with water to obtain microspheres.

[0082] Preparation of CMC hydrogel: gradually add sodium carboxymethylcellulose powder into 60°C hot water and stir, sterilize with wet heat steam (121°C for 30min) after being evenly dissolved, cool and set aside to obtain 9% CMC hydrogel.

[0083] The above-mentioned dried microspheres were mixed with CMC hydrogel in a ratio of 3:7, and glycerol (the weight content in the gel system was 0.8%) was added to uniformly disperse it in the CMC hydrogel.

[0084] Embodiment 11

[0085] Preparation of chitosan / polycaprolactone composite blends:

[0086] Place 99g of dried polycaprolactone PCL (number average molecular weight Mn=30000) and 1g of chitosan CS (viscosity average molecular weight 55kDa, deacetylation degree 82.3%) in a torque rheometer, and then melt-blend at a rotor speed of 150r / min and 160°C for 15min. Stop when the torque level is reached to obtain the chitosan / polycaprolactone blend.

[0087] The chitosan / polycaprolactone blend was crushed into fine powder, and 10 g of the chitosan / polycaprolactone blend was dissolved in dichloromethane-ethanol (volume ratio 9:1) to prepare an organic phase with a concentration of 10 w / w%.

[0088] A 2 w / v% aqueous solution of surfactant povidone was prepared as the aqueous phase. The aqueous phase solution was pre-saturated with 2% volume fraction of dichloromethane. This step can reduce the precipitation of PCL on the surface of the solution when the solvent is volatilized. The organic phase was then poured into the aqueous phase and sheared at high speed to obtain a microsphere suspension.

[0089] The microsphere suspension was stirred at 200 rpm for 12 hours at 25° C., the organic solvent was removed, and then the suspension was repeatedly washed with water to obtain microspheres.

[0090] Preparation of CMC hydrogel: gradually add sodium carboxymethylcellulose powder into 60°C hot water and stir, sterilize with wet heat steam (121°C for 30min) after being evenly dissolved, cool and set aside to obtain 9% CMC hydrogel.

[0091] The above-mentioned dried microspheres were mixed with CMC hydrogel in a ratio of 3:7, and glycerol (the weight content in the gel system was 0.8%) was added to uniformly disperse it in the CMC hydrogel.

[0092] Comparative Example 1

[0093] 10 g of PCL with Mn of 42500 was dissolved in DCM (10 w / w%), the solution was dispersed in 1000 ml of water containing 0.8% methylcellulose MC, stirred (1000 rpm), the resulting microspheres were filtered, washed and dried to obtain microspheres. Subsequently, 30% of the microspheres were dispersed in 9% CMC hydrogel containing 0.1% glycerol to obtain a microsphere gel.

[0094] Comparative Example 2

[0095] Preparation of chitosan / polycaprolactone blends:

[0096] 9.95 g of dried polycaprolactone PCL (number average molecular weight Mn=30000) and 0.05 g of chitosan CS (viscosity average molecular weight 55 kDa, deacetylation degree 82.3%) were dissolved in dichloromethane-trifluoroacetic acid (volume ratio 9.9:0.1) to prepare an organic phase with a concentration of 20 w / w%.

[0097] A 1.5 w / v% aqueous solution of a surfactant polyvinyl alcohol was prepared as the aqueous phase. The aqueous phase solution was pre-saturated with 2% volume fraction of dichloromethane. This step can reduce the precipitation of PCL on the surface of the solution when the solvent is volatilized. The organic phase was then poured into the aqueous phase and sheared at high speed to obtain a microsphere suspension.

[0098] The microsphere suspension was stirred at 200 rpm for 12 hours at 25° C., the organic solvent was removed, and then the suspension was repeatedly washed with water to obtain microspheres.

[0099] Preparation of CMC hydrogel: gradually add sodium carboxymethylcellulose powder into 60°C hot water and stir, sterilize with wet heat steam (121°C for 30min) after being evenly dissolved, cool and set aside to obtain 9% CMC hydrogel.

[0100] The above-mentioned dried microspheres were mixed with CMC hydrogel in a ratio of 3:7, and glycerol (the weight content in the gel system was 0.8%) was added to uniformly disperse it in the CMC hydrogel.

[0101] Experimental Example 1: In vitro degradation experiment of chitosan / polycaprolactone blends

[0102] Take the chitosan / polycaprolactone blends of Examples 1-7 and weigh (W 0 ) and then immersed in 10mL PBS (0.01M, pH=7.4) solution, placed in a 37℃ shaker at a shaking speed of 60r / min. The PBS solution was replaced weekly, with a degradation period of 4 weeks, and the measurement was carried out for 24 weeks. At the end of each degradation period, the sample was taken out, thoroughly rinsed with distilled water, and vacuum freeze-dried to constant weight (Wt). Degradation rate = (Wt) 0 -Wt) / W 0 ×100%.

[0103] Table 1 Degradation rate of chitosan / polycaprolactone blends

[0104]

[0105]

[0106] The experimental results show that when the chitosan content is above 10%, the in vitro degradation rate of the chitosan / polycaprolactone blend increases significantly, which is not conducive to injection filling. Between 0.5-5%, the in vitro degradation rate of the chitosan / polycaprolactone blend has no significant change.

[0107] Experimental Example 2: Water absorption and re-dissolution performance test of microspheres

[0108] Test methods for contact angle and water absorption rate: The contact angle test adopts the appearance image analysis method. A liquid drop is dropped on the surface of a solid sample, and the external image of the liquid drop is obtained through a microscope lens and a camera. Then, digital image processing and some algorithms are used to calculate the contact angle of the liquid drop in the image.

[0109] Water absorption test method: Take a certain weight of dried microspheres W 0 Grams, put into a stainless steel mesh cage, placed in 500mL distilled water, leave for 8 hours, take out until the stainless steel mesh cage stops dripping, weigh the weight of the microspheres W 1 grams. Water absorption rate = (W 1 -W 0 ) / W 0×100%.

[0110] Method for determining suspension time: The dried microspheres obtained in the example are redissolved in 4 mL of sterile water for injection to form a suspension of composite microspheres, and the suspension time is determined. The suspension time is the time from when the suspension is shaken to when stratification begins to appear on the surface of the suspension.

[0111] Table 2 Water absorption and re-dissolution properties of chitosan / polycaprolactone blend microspheres

[0112] serial number Contact angle (°) Water absorption (%) Redissolution time (min) Example 1 67 17.6 27 Example 2 63 20.4 29 Example 3 60 21.9 28 Example 4 80 13.4 24 Example 5 91 10.8 20 Example 6 95 13.3 22 Example 7 97 15.6 24 Example 8 82 14.6 19 Comparative Example 1 128 3.8 16 Comparative Example 2 120 4.2 17

[0113] The experimental results show that the chitosan / polycaprolactone blend microspheres of the present invention have good water absorption and re-dissolution properties, and have better water absorption properties than existing pure polycaprolactone microspheres. Since polycaprolactone is a hydrophobic polymer and has insufficient compatibility with body tissues, the improvement of its hydrophilic properties is beneficial to reducing the adverse reactions caused by insufficient tissue compatibility.

[0114] Experimental Example 3: Particle Size Detection of Microspheres

[0115] The particle size of the microspheres was determined by laser diffraction. 50 mg of microspheres were mixed with 1 mL of ultrapure water, vortexed for 20 seconds, and then dispersed by ultrasound. The microsphere dispersion was placed in a particle size analyzer to measure D10, D50, and D90, and the span value was calculated as (D90-D10) / D50. The results are shown in Table 3.

[0116] Table 3 Microsphere particle size test results

[0117]

[0118] The experimental results show that, compared with pure polycaprolactone microspheres, the chitosan / polycaprolactone blend microspheres of the present invention can obtain microspheres with a more concentrated particle size distribution, with D10 at 9-12 μm, D50 at 30-35 μm, D90 at 35-42 μm, and a span value of 0.8-0.9. Therefore, compared with the current polycaprolactone microspheres, the microspheres of the present invention have a narrower particle size distribution, improve the microsphere yield, reduce unnecessary sieving and screening microsphere operations, and are conducive to clinical safety applications.

[0119] Experimental Example 4: Microsphere Gel Storage Stability Experiment

[0120] The microsphere gel prepared in Examples 1, 5, 6, 7 and Comparative Example 1 was placed at 40°C for 6 months. The prepared microsphere gel was fully stirred and mixed, and then the viscosity of the system was tested. The sample was aspirated with a 1 mL syringe, a needle was put on and fixed, and the sample was pushed out of the needle to test the needle passability. The needle pass success rate of a 30G needle (inner diameter 133 μm) was measured, where the needle pass success rate = number of complete passes / number of attempts. The results are shown in the table below.

[0121] Table 4 Microsphere gel storage stability test results

[0122] serial number 0 month June Example 1 96 / 100 93 / 100 Example 5 94 / 100 78 / 100 Example 6 95 / 100 82 / 100 Example 7 97 / 100 83 / 100 Comparative Example 1 92 / 100 80 / 100

[0123] The experimental results show that the chitosan viscosity-average molecular weight is between 50-70 kDa, the deacetylation degree is between 80-85%, and the prepared chitosan / polycaprolactone blend microspheres are not easily affected by temperature changes. This may be because the microspheres are not easy to stick together after storage and can maintain a relatively uniform dispersion state.

Claims

1. A method for preparing a chitosan / polycaprolactone composite microsphere gel, the microsphere gel comprising chitosan / polycaprolactone composite microspheres and carboxymethyl cellulose (CMC) hydrogel, wherein the polycaprolactone microspheres are uniformly dispersed in the carboxymethyl cellulose (CMC) hydrogel, the chitosan / polycaprolactone composite is a melt blend of chitosan and polycaprolactone, and the chitosan / polycaprolactone composite microsphere gel is an injectable implant. Features The preparation method comprises: (1) Melting and blending dried polycaprolactone PCL and chitosan CS at 160-180° C. to prepare a chitosan / polycaprolactone composite blend; (2) dissolving the chitosan / polycaprolactone composite blend in dichloromethane-ethanol to prepare an organic phase with a concentration of 10-30 w / w%; (3) preparing a 1.5 w / v% aqueous solution of a surfactant, wherein the surfactant is selected from polyvinyl alcohol, methyl cellulose, and povidone; (4) The organic phase is poured into the aqueous phase and sheared at high speed to obtain a microsphere suspension, and then the stirring is continued, the organic solvent is removed, and the microspheres are washed with water to obtain microspheres.

2. The preparation method according to claim 1, Features: The volume ratio of dichloromethane to ethanol is 9:

1.

3. The preparation method according to claim 1, Features: The chitosan has a viscosity-average molecular weight between 50 and 70 kDa.

4. The preparation method according to claim 1, Features: The chitosan / polycaprolactone composite microspheres have a D10 of 9-12 μm, a D50 of 30-35 μm, and a D90 of 35-42 μm.

5. The preparation method according to claim 1, Features: The particle size span value of the chitosan / polycaprolactone composite microspheres is 0.8-0.

9.

6. The preparation method according to claim 2, Features: In the chitosan / polycaprolactone composite, the weight ratio of chitosan to polycaprolactone is (0.5-5):(99.5-95).

7. The preparation method according to claim 1, Features: The number average molecular weight Mn of the polycaprolactone is 25000-40000.

8. The preparation method according to claim 1, Features: The chitosan / polycaprolactone complex microsphere gel comprises 20-40% chitosan / polycaprolactone complex and 60-80% carboxymethyl cellulose CMC hydrogel, calculated by weight percentage.

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