A method for preparing cross-linked polyester microspheres, cross-linked polyester microspheres and their applications

Abstract

This invention relates to a method for preparing cross-linked polyester microspheres, the cross-linked polyester microspheres themselves, and their applications, belonging to the field of biomedical materials technology. The method for preparing cross-linked polyester microspheres provided by this invention does not require blending with other high-molecular-weight polyester materials or modifying the prepolymer to improve microsphere molding stability. The resulting cross-linked polyester microspheres exhibit excellent morphology retention and mechanical stability, show low inflammatory response and good tissue collagen production in biological experiments, making them suitable as soft tissue filler materials.

Description

Technical Field

[0001] This invention relates to the field of biomedical materials technology, and in particular to a method for preparing cross-linked polyester microspheres, the cross-linked polyester microspheres and their applications. Background Technology

[0002] With the rapid development of medical aesthetics technology, minimally invasive, reversible, and injectable soft tissue filler materials have been widely used in areas such as facial rejuvenation, contouring, and tissue volume reconstruction due to their advantages of simple operation, short recovery period, and high safety.

[0003] Currently, commonly used cosmetic fillers in clinical practice mainly include hyaluronic acid fillers and collagen fillers. However, these materials have drawbacks such as short-lived filling effects and insufficient support. To prolong the filling effect and improve tissue support, polymer microspheres, as functional filler components, have been extensively studied. By forming a stable spatial scaffold structure in vivo, microspheres can induce collagen regeneration and maintain tissue volume.

[0004] Commonly used polymer microspheres include polylactic acid microspheres or polycaprolactone microspheres, but they are mostly linear polyester structures. Their molecular chains mainly rely on physical entanglement to maintain morphological stability. Under body fluid environment and long-term stress conditions, they are prone to deformation, collapse or breakage, making it difficult to provide continuous and stable tissue support. At the same time, these microspheres usually undergo rapid molecular weight reduction through bulk degradation, and their mechanical properties decrease significantly with the degradation process. They may also accumulate acidic degradation products locally, thereby triggering adverse clinical reactions such as inflammatory reactions, nodules or hardening to the touch.

[0005] Compared to linear polyester microspheres, cross-linked polyester microspheres significantly improve the morphology retention and mechanical stability of the microspheres by introducing a stable three-dimensional cross-linked network structure between the molecular chains. Even under partial degradation conditions, they can still maintain the overall structure and spatial support function. Their mechanical properties and viscoelasticity can be controlled by the degree of cross-linking, making them closer to the characteristics of natural soft tissue. This ensures good injection smoothness while achieving long-term stable filling effect.

[0006] However, cross-linked polyester materials are difficult to prepare into cross-linked polyester microspheres using traditional microsphere preparation methods. The fundamental reason is that these materials typically require the preparation of low-molecular-weight prepolymers to ensure operability for melt or solution processing. However, due to the low molecular weight of the prepolymers, the molecular chain entanglement within the system is insufficient, making it difficult to achieve stable curing and structural retention during microsphere molding. For example, the number-average molecular weight of polycitric acid ester prepolymers is typically only about 1000-5000, making it difficult to form a stable microsphere structure without further cross-linking or reinforcement. Existing technologies usually require the introduction of other high-molecular-weight polyester materials for blending or chemical modification of the prepolymer to improve molding stability. However, these methods inevitably introduce other components into the system, making it difficult to obtain cross-linked polyester microspheres with a single composition and pure structure. If cross-linked polyester materials are prepared in advance, the formation of a three-dimensional network structure causes the polyester material to lose its thermoplasticity or solubility, limiting the feasibility of preparing microspheres using conventional melt molding or solution emulsification methods.

[0007] Therefore, how to prepare a cross-linked polyester microsphere with a single component, pure structure, and excellent morphological retention and mechanical stability has become an urgent problem to be solved. Summary of the Invention

[0008] To address the aforementioned technical problems, this invention relates to a method for preparing cross-linked polyester microspheres, the cross-linked polyester microspheres themselves, and their applications. This method eliminates the need for blending with other high-molecular-weight polyester materials or chemically modifying the prepolymer to improve the stability of microsphere molding. The resulting cross-linked polyester microspheres exhibit excellent morphological retention and mechanical stability, maintaining their overall structure and spatial support function even under partial degradation conditions. Furthermore, they are characterized by their single composition and pure structure, exhibiting low inflammatory response, good biocompatibility, and good tissue collagen production in biological experiments, making them suitable as soft tissue filling materials.

[0009] To achieve this objective, the present invention adopts the following technical solution:

[0010] In a first aspect, the present invention provides a method for preparing cross-linked polyester microspheres, the method comprising:

[0011] (1) Mix polyacids and polyols and carry out melt polycondensation reaction to obtain polyester prepolymer;

[0012] (2) The polyester prepolymer obtained in step (1) is mixed with solvent A to obtain oil phase solution A;

[0013] (3) Mix the oil phase solution A obtained in step (2) with the oil phase solution B to obtain a polyester prepolymer emulsion;

[0014] (4) The polyester prepolymer emulsion obtained in step (3) undergoes a thermal crosslinking reaction to obtain the crosslinked polyester microspheres;

[0015] The polyacids include polyacids with a functionality of 2 or polyacids with a functionality of 3.

[0016] The polyols include polyols with a functionality of 2 or polyols with a functionality of 3.

[0017] When the polyacid is a polyacid with a functionality of 2, the polyol is selected from polyols with a functionality of 3.

[0018] When the polyacid is a polyacid with a functionality of 3, the polyol is selected from polyols with a functionality of 2.

[0019] The preparation method provided by this invention first prepares a single-component polyester prepolymer through melt polycondensation reaction, then constructs a polyester prepolymer emulsion with an oil-in-oil emulsion system and performs thermal crosslinking. Without introducing other high-molecular-weight polyester materials, the simultaneous construction of microsphere morphology is achieved during the crosslinking process, resulting in crosslinked polyester microspheres with high sphericity, controllable particle size, and suitable for injection.

[0020] Preferably, the polyacid with a functionality of 2 includes any one or a combination of at least two of malic acid, sebacic acid, succinic acid, fumaric acid, tartaric acid, or α-ketoglutarate.

[0021] Preferably, the polyacid with a functionality of 3 includes any one or a combination of at least two of citric acid, propane-1,2,3-tricarboxylic acid, or propylene-1,2,3-tricarboxylic acid.

[0022] Preferably, the polyacid is selected from citric acid and / or malic acid.

[0023] This invention preferably uses citric acid and / or malic acid as the polyacids. Both citric acid and malic acid are natural metabolites in the human body, participating in the tricarboxylic acid cycle, and possess excellent biocompatibility and biosafety. Their degradation products can be metabolized and utilized by the human body, resulting in high safety. Furthermore, citric acid molecules contain multiple carboxyl and hydroxyl groups, providing high functionality and forming a stable three-dimensional cross-linked structure. Simultaneously, the carboxyl groups retained on the microsphere surface enhance hydrophilicity and cell compatibility, facilitating tissue integration. Malic acid, on the other hand, has relatively low functionality, allowing for adjustment of the cross-linking density during copolymerization, making the microsphere network structure more flexible and preventing excessive hardness, thereby improving injection performance, deformation recovery ability, and tissue feel. In addition, these two natural polyacids can also endow the microspheres with certain antioxidant and microenvironment regulation capabilities, helping to reduce local inflammatory responses and promote skin tissue repair and collagen reconstruction. Therefore, the cross-linked polyester system based on citric acid and malic acid has comprehensive advantages in medical aesthetic fillers or skin regeneration materials, including high safety, adjustable mechanical properties, mild degradation, and good bioactivity.

[0024] Preferably, the polyol with a functionality of 2 includes any one or a combination of at least two of the following: ethylene glycol, polyethylene glycol, 1,3-propanediol, 1,4-butanediol, 1,8-octanediol, 1,2-propanediol, 1,2-octanediol, methylpropanediol, 1,5-pentanediol, neopentanediol, 1,2-pentanediol, 1,6-hexanediol, or 1,2-hexanediol.

[0025] Preferably, the polyol with a functionality of 3 includes any one or a combination of at least two of glycerol, trimethylolpropane, trimethylolethane, or hexanetriol.

[0026] Preferably, the polyol is selected from any one or a combination of at least two of ethylene glycol, 1,4-butanediol or 1,8-octanediol.

[0027] The preferred polyol of this invention is any one or a combination of at least two of ethylene glycol, 1,4-butanediol or 1,8-octanediol. The above polyols have linear structures and high reactivity, and can efficiently polycondense with polybasic acids to form polyester chains. At the same time, different carbon chain lengths can control the flexibility, mechanical properties, glass transition temperature and degradation rate of the polyester. Moreover, the degradation products are biocompatible and safe and can be metabolized and utilized in vivo.

[0028] Preferably, the molar ratio of the polyacid to the polyol in step (1) is 1:(0.5-2), for example, it can be 1:0.5, 1:0.6, 1:0.8, 1:1, 1:1.2, 1:1.4, 1:1.5, 1:1.6, 1:18 or 1:2, etc.

[0029] The present invention specifies that the molar ratio of the polyacid to the polyol is 1:(0.5-2). This molar ratio allows the system to undergo a full cross-linking reaction, forming cross-linked polyester microspheres with stable structure and uniform morphology. Moreover, this molar ratio not only ensures a stable and controllable reaction and reduces the residue of reacting monomers, but also allows for flexible control of the cross-linking density of the microspheres by fine-tuning the ratio, giving the product good mechanical strength and biodegradability.

[0030] Preferably, the reaction temperature of the melt polycondensation reaction in step (1) is 100-200℃, for example, it can be 100℃, 110℃, 120℃, 130℃, 140℃, 150℃, 160℃, 170℃, 180℃, 190℃ or 200℃, etc., and the reaction time of the melt polycondensation reaction is 0.5-5 h, for example, it can be 0.5 h, 1 h, 1.5, 2 h, 2.5 h, 3 h, 3.5 h, 4 h, 4.5 h or 5 h, etc.

[0031] Preferably, the number average molecular weight of the polyester prepolymer obtained in step (1) is 500-12000, for example, it can be 500, 600, 800, 1000, 1500, 2000, 2500, 3000, 3500, 4000, 4500, 5000, 5500, 6000, 6500, 7000, 7500, 8000, 8500, 9000, 9500, 10000, 10500, 11000, 11500 or 12000, etc.

[0032] The number-average molecular weight was obtained by gel permeation chromatography (GPC).

[0033] Preferably, solvent A in step (2) includes an organic solvent.

[0034] Preferably, the organic solvent includes any one or a combination of at least two of N,N-dimethylformamide, dimethylacetamide, dimethyl sulfoxide, diphenyl ether, N-methylpyrrolidone, 1,2,3,4-tetrahydronaphthalene, xylene, toluene, or cyclohexanone.

[0035] Preferably, the mass ratio of solvent A to polyester prepolymer is (0.1-10):1, for example, it can be 0.1:1, 0.5:1, 1:1, 2:1, 3:1, 4:1, 5:1, 6:1, 7:1, 8:1, 9:1 or 10:1, etc.

[0036] Preferably, the oil phase solution A in step (2) further includes a catalyst.

[0037] Preferably, the catalyst comprises any one or a combination of at least two of the following: methylbenzenesulfonic acid, thionyl chloride, acetamide, tetrabutyl titanate, sodium methoxide, sodium ethoxide, tetraethyl titanate, tetraisopropyl titanate, boron trifluoride, stannous octoate, stannous tetrachloride, stannous oxalate, stannous chloride, p-toluenesulfonic acid, or butylstannic acid.

[0038] Preferably, the mass ratio of the catalyst to the polyester prepolymer is (0.001-0.1):1, for example, it can be 0.001:1, 0.005:1, 0.01:1, 0.02:1, 0.03:1, 0.04:1, 0.05:1, 0.06:1, 0.07:1, 0.08:1, 0.09:1 or 0.1:1, etc.

[0039] Preferably, the mass ratio of oil phase solution A to oil phase solution B in step (3) is (0.01-0.5):1, for example, it can be 0.01:1, 0.05:1, 0.1:1, 0.2:1, 0.3:1, 0.4:1 or 0.5:1, etc.

[0040] Preferably, the oil phase solution B includes solvent B.

[0041] Preferably, solvent B comprises any one or a combination of at least two of liquid paraffin, white oil, n-hexadecane, n-heptane, isoalkanes, silicone oil, or mineral oil.

[0042] Preferably, the oil phase solution B further includes a dispersant.

[0043] Preferably, the dispersant comprises any one or a combination of at least two of the following: sorbitan monooleate, glyceryl monooleate, polyisobutylene, polymethacrylate dispersants, PVP, PEG-fatty chain copolymer, hydrophobic silica, hydrophobic nanoclay, or surface-modified bioactive glass nanoparticles.

[0044] Preferably, the mass ratio of solvent B to dispersant in the oil phase solution B is (50-500):1, for example, it can be 50:1, 60:1, 80:1, 100:1, 150:1, 200:1, 250:1, 300:1, 350:1, 400:1, 450:1 or 500:1, etc.

[0045] Preferably, the mixing in step (3) is carried out under stirring.

[0046] Preferably, the stirring speed is 100-5000 r / min, for example, it can be 100 r / min, 500 r / min, 1000 r / min, 2000 r / min, 3000 r / min, 4000 r / min or 5000 r / min, etc., and the time is 10-60 min, for example, it can be 10 min, 20 min, 30 min, 40 min, 50 min or 60 min, etc.

[0047] Preferably, the reaction temperature of the thermal crosslinking reaction in step (4) is 30-150℃, for example, it can be 30℃, 40℃, 50℃, 60℃, 80℃, 90℃, 100℃, 110℃, 120℃, 140℃ or 150℃, etc., and the reaction time of the thermal crosslinking reaction is 1-200 h, for example, it can be 1 h, 20 h, 40 h, 50 h, 60 h, 80 h, 100 h, 120 h, 140 h, 150 h, 160 h, 180 h or 200 h, etc.

[0048] The present invention specifies that the temperature of the thermal crosslinking reaction in step (4) is 30-150°C. Conducting the reaction within this temperature range maintains the stability of the emulsion, ensuring a uniform and stable crosslinking reaction.

[0049] Preferably, the thermal crosslinking reaction in step (4) is carried out in a vacuum environment.

[0050] Preferably, the vacuum level of the vacuum environment is 10-1000 Pa, for example, it can be 10 Pa, 100 Pa, 200 Pa, 300 Pa, 400 Pa, 500 Pa, 600 Pa, 700 Pa, 800 Pa, 900 Pa or 1000 Pa.

[0051] Preferably, the thermal crosslinking reaction in step (4) further includes a post-processing step.

[0052] Preferably, the post-processing steps include filtration, washing, drying, and sieving.

[0053] Preferably, the washing includes washing with ethanol and water 2-5 times in sequence, for example, 2 times, 3 times, 4 times or 5 times.

[0054] The purpose of the post-treatment step is to remove the catalyst from oil phase solution B and oil phase solution A.

[0055] Secondly, the present invention provides a method for preparing cross-linked polyester microspheres as described in the first aspect, resulting in cross-linked polyester microspheres.

[0056] Preferably, the cross-linked polyester microspheres have a particle size of 0.1-150 μm, such as 0.1 μm, 0.5 μm, 1 μm, 5 μm, 10 μm, 20 μm, 40 μm, 50 μm, 60 μm, 80 μm, 100 μm, 120 μm, 140 μm or 150 μm.

[0057] The particle size refers to the particle size distribution range of the cross-linked polyester microspheres prepared by observation using an optical microscope or a scanning electron microscope.

[0058] Thirdly, the present invention provides the application of cross-linked polyester microspheres as described in the second aspect in soft tissue filling materials.

[0059] Compared with the prior art, the present invention has at least the following beneficial effects:

[0060] (1) This invention provides a method for preparing cross-linked polyester microspheres. First, a polyester prepolymer with a single component is prepared by melt polycondensation reaction. Then, a polyester prepolymer emulsion with an oil-in-oil emulsion system is constructed and thermally cross-linked. Without introducing other high-molecular polyester materials, the morphology of microspheres is constructed simultaneously during the cross-linking process. Cross-linked polyester microspheres with high sphericity, controllable particle size, suitable for injection, single component, pure structure, low inflammatory response in biological experiments, good biocompatibility and tissue collagen generation are obtained. They are suitable for soft tissue filling materials.

[0061] (2) The preparation method of cross-linked polyester microspheres provided by the present invention can precisely adjust its elastic modulus within a wide range through molecular structure design, cross-linking degree control and other means, so as to achieve matching of mechanical requirements for different injection layers.

[0062] (3) The cross-linked polyester microspheres prepared by the present invention significantly improve the morphological retention and mechanical stability of the microspheres by introducing a stable three-dimensional cross-linked network structure between the molecular chains. Even under partial degradation conditions, they can still maintain the overall structure and spatial support function. Moreover, the cross-linked polyester microspheres exhibit typical viscoelastic characteristics. When subjected to external forces such as compression or shear, they can release the external forces through a viscoelastic energy dissipation mechanism, making them less prone to instantaneous rupture or irreversible deformation, which is beneficial for maintaining the filling volume and morphological stability. Attached Figure Description

[0063] Figure 1 This is a surface morphology image of the cross-linked polyester microspheres prepared in Example 1 of the present invention, taken using an optical microscope. The scale bar is 200 μm.

[0064] Figure 2 The image shows the surface morphology of the cross-linked polyester microspheres prepared in Example 2 of this invention, taken using an optical microscope. The scale bar is 200 μm.

[0065] Figure 3 This is a surface morphology image of the cross-linked polyester microspheres prepared in Example 3 of the present invention, taken using an optical microscope. The scale bar is 200 μm.

[0066] Figure 4 This is a surface morphology image of the cross-linked polyester microspheres prepared in Comparative Example 1 of the present invention, taken using an optical microscope. The scale bar is 200 μm. Detailed Implementation

[0067] The technical solution of the present invention will be further described below with reference to the accompanying drawings and specific embodiments. However, the following examples are merely simplified examples of the present invention and do not represent or limit the scope of protection of the present invention. The scope of protection of the present invention is determined by the claims.

[0068] To facilitate understanding of the present invention, the following embodiments are provided. Those skilled in the art should understand that these embodiments are merely illustrative and should not be construed as limiting the scope of the invention.

[0069] The specific information of the materials used in the following specific embodiments of the present invention is as follows:

[0070] PEG-fatty chain copolymer, PEG-100 stearate (SE-100), purchased from Hubei Xinjiecheng Chemical Co., Ltd.

[0071] Mineral oil, L-QB300 mineral oil-type heat transfer oil, purchased from Great Wall Lubricating Oil.

[0072] Hydrophobic silica, TY-510 hydrophobic silica, purchased from Yuejiang Chemical.

[0073] Silicone oil, dimethyl silicone oil DC 200, viscosity 50~10000 cSt, purchased from Dow Corning.

[0074] Example 1

[0075] This embodiment provides a method for preparing cross-linked polyester microspheres and the cross-linked polyester microspheres. The preparation method includes:

[0076] (1) Citric acid and 1,8-octanediol were mixed at a molar ratio of 1:1 and subjected to melt polycondensation reaction at (140℃, 1 h) to obtain a polyester prepolymer with a number average molecular weight of 1000.

[0077] (2) The polyester prepolymer obtained in step (1) is mixed with xylene and tetraethyl titanate, and the mass ratio of polyester prepolymer, xylene and tetraethyl titanate is 1:1:0.01 to obtain oil phase solution A;

[0078] (3) The oil phase solution A obtained in step (2) and the oil phase solution B (oil phase solution B includes sorbitan monooleate and silicone oil in a mass ratio of 1:100, and the mass ratio of oil phase solution A to oil phase solution B is 0.1:1) are mixed at 4000 r / min for 30 min to obtain a polyester prepolymer emulsion.

[0079] (4) After the polyester prepolymer emulsion obtained in step (3) is subjected to thermal crosslinking reaction at 80°C and 100 Pa vacuum for 120 h, the oil phase solution B is removed by filtration, and after washing, drying and sieving, crosslinked polyester microspheres with a particle size of 20-50 μm are obtained.

[0080] Example 2

[0081] This embodiment provides a method for preparing cross-linked polyester microspheres and the cross-linked polyester microspheres. The preparation method includes:

[0082] (1) Malic acid and glycerol were mixed at a molar ratio of 1:0.75 and subjected to melt polycondensation reaction at (120℃, 3 h) to obtain a polyester prepolymer with a number average molecular weight of 5000.

[0083] (2) The polyester prepolymer obtained in step (1) is mixed with dimethyl sulfoxide and toluenesulfonic acid, and the mass ratio of polyester prepolymer, dimethyl sulfoxide and toluenesulfonic acid is 1:2:0.02 to obtain oil phase solution A;

[0084] (3) The oil phase solution A obtained in step (2) and the oil phase solution B (oil phase solution B includes PEG-fatty chain copolymer and mineral oil in a mass ratio of 1:150, and the mass ratio of oil phase solution A to oil phase solution B is 0.2:1) are mixed at 2000 r / min for 20 min to obtain polyester prepolymer emulsion;

[0085] (4) The polyester prepolymer emulsion obtained in step (3) was subjected to thermal crosslinking reaction at 100℃ and 20 Pa vacuum for 72 hours. After filtering to remove oil phase solution B, it was washed, dried and refined to obtain crosslinked polyester microspheres with a particle size of 30-70 μm.

[0086] Example 3

[0087] This embodiment provides a method for preparing cross-linked polyester microspheres and the cross-linked polyester microspheres. The preparation method includes:

[0088] (1) Propane-1,2,3-tricarboxylic acid and ethylene glycol were mixed at a molar ratio of 1:1.25 and subjected to melt polycondensation reaction at (170℃, 2 h) to obtain a polyester prepolymer with a number average molecular weight of 8000;

[0089] (2) The polyester prepolymer obtained in step (1) is mixed with N,N-dimethylformamide and stannous chloride. The mass ratio of polyester prepolymer, N,N-dimethylformamide and stannous chloride is 1:1.5:0.03 to obtain oil phase solution A.

[0090] (3) The oil phase solution A obtained in step (2) and the oil phase solution B (oil phase solution B includes hydrophobic silica and liquid paraffin in a mass ratio of 1:400, and the mass ratio of oil phase solution A to oil phase solution B is 0.15:1) are mixed at 1000 r / min for 40 min to obtain a polyester prepolymer emulsion.

[0091] (4) After the polyester prepolymer emulsion obtained in step (3) is subjected to thermal crosslinking reaction at 120℃ and 500 Pa for 24 h, the oil phase solution B is removed by filtration, and after washing, drying and refining, crosslinked polyester microspheres with a particle size of 50-80 μm are obtained.

[0092] Example 4

[0093] This embodiment provides a method for preparing cross-linked polyester microspheres and the cross-linked polyester microspheres. The preparation method includes:

[0094] (1) Fumaric acid and trimethylolpropane were mixed at a molar ratio of 1:1 and subjected to melt polycondensation reaction at (140℃, 1 h) to obtain a polyester prepolymer with a number average molecular weight of 1500.

[0095] (2) The polyester prepolymer obtained in step (1) is mixed with xylene and tetraethyl titanate, and the mass ratio of polyester prepolymer, xylene and tetraethyl titanate is 1:1:0.01 to obtain oil phase solution A;

[0096] (3) The oil phase solution A obtained in step (2) and the oil phase solution B (oil phase solution B includes sorbitan monooleate and silicone oil in a mass ratio of 1:100, and the mass ratio of oil phase solution A to oil phase solution B is 0.1:1) are mixed at 4000 r / min for 30 min to obtain a polyester prepolymer emulsion.

[0097] (4) After the polyester prepolymer emulsion obtained in step (3) is subjected to thermal crosslinking reaction at 80°C and 100 Pa vacuum for 120 h, the oil phase solution B is removed by filtration, and after washing, drying and sieving, crosslinked polyester microspheres with a particle size of 20-50 μm are obtained.

[0098] Example 5

[0099] This embodiment provides a method for preparing cross-linked polyester microspheres and the cross-linked polyester microspheres. The preparation method includes:

[0100] (1) Citric acid and 1,2-pentanediol were mixed at a molar ratio of 1:1 and subjected to melt polycondensation reaction at 140℃ for 1 h to obtain a polyester prepolymer with a number average molecular weight of 1500.

[0101] (2) The polyester prepolymer obtained in step (1) is mixed with xylene and tetraethyl titanate, and the mass ratio of polyester prepolymer, xylene and tetraethyl titanate is 1:1:0.01 to obtain oil phase solution A;

[0102] (3) The oil phase solution A obtained in step (2) and the oil phase solution B (oil phase solution B includes sorbitan monooleate and silicone oil in a mass ratio of 1:100, and the mass ratio of oil phase solution A to oil phase solution B is 0.1:1) are mixed at 4000 r / min for 30 min to obtain a polyester prepolymer emulsion.

[0103] (4) After the polyester prepolymer emulsion obtained in step (3) is subjected to thermal crosslinking reaction at 80°C and 100 Pa vacuum for 120 h, the oil phase solution B is removed by filtration, and after washing, drying and sieving, crosslinked polyester microspheres with a particle size of 20-50 μm are obtained.

[0104] Example 6

[0105] This embodiment provides a method for preparing cross-linked polyester microspheres and the cross-linked polyester microspheres. The preparation method includes:

[0106] (1) Propylene-1,2,3-tricarboxylic acid and 1,8-octanediol were mixed at a molar ratio of 1:1 and subjected to melt polycondensation reaction at (140℃, 1 h) to obtain a polyester prepolymer with a number average molecular weight of 1500.

[0107] (2) The polyester prepolymer obtained in step (1) is mixed with xylene and tetraethyl titanate, and the mass ratio of polyester prepolymer, xylene and tetraethyl titanate is 1:1:0.01 to obtain oil phase solution A;

[0108] (3) The oil phase solution A obtained in step (2) and the oil phase solution B (oil phase solution B includes sorbitan monooleate and silicone oil in a mass ratio of 1:100, and the mass ratio of oil phase solution A to oil phase solution B is 0.1:1) are mixed at 4000 r / min for 30 min to obtain a polyester prepolymer emulsion.

[0109] (4) After the polyester prepolymer emulsion obtained in step (3) is subjected to thermal crosslinking reaction at 80°C and 100 Pa vacuum for 120 h, the oil phase solution B is removed by filtration, and after washing, drying and sieving, crosslinked polyester microspheres with a particle size of 20-50 μm are obtained.

[0110] Example 7

[0111] This embodiment provides a method for preparing cross-linked polyester microspheres and the cross-linked polyester microspheres. The difference between the preparation method and that in Example 1 is that the molar ratio of citric acid to 1,8-octanediol is 1:0.5, and the number average molecular weight of the obtained polyester prepolymer is 800.

[0112] Example 8

[0113] This embodiment provides a method for preparing cross-linked polyester microspheres and the cross-linked polyester microspheres. The difference between the preparation method and that in Example 1 is that the molar ratio of citric acid to 1,8-octanediol is 1:1.8, and the number average molecular weight of the obtained polyester prepolymer is 1500.

[0114] Example 9

[0115] This embodiment provides a method for preparing cross-linked polyester microspheres and the cross-linked polyester microspheres. The difference between the preparation method and that in Example 1 is that the molar ratio of citric acid to 1,8-octanediol is 1:2.5, and the number average molecular weight of the obtained polyester prepolymer is 1600.

[0116] Example 10

[0117] This embodiment provides a method for preparing cross-linked polyester microspheres and cross-linked polyester microspheres. The difference between the preparation method and that in Embodiment 1 is that the temperature of the thermal cross-linking reaction in step (4) is adjusted to 60°C.

[0118] Example 11

[0119] This embodiment provides a method for preparing cross-linked polyester microspheres and cross-linked polyester microspheres. The difference between the preparation method and that in Embodiment 1 is that the temperature of the thermal cross-linking reaction in step (4) is adjusted to 120°C.

[0120] Example 12

[0121] This embodiment provides a method for preparing cross-linked polyester microspheres and cross-linked polyester microspheres. The difference between the preparation method and that in Embodiment 1 is that the temperature of the thermal cross-linking reaction in step (4) is adjusted to 180°C.

[0122] Comparative Example 1

[0123] This comparative example provides a method for preparing cross-linked polyester microspheres and the cross-linked polyester microspheres. The preparation method includes:

[0124] (1) Citric acid and 1,8-octanediol were mixed at a molar ratio of 1:1 and subjected to melt polycondensation reaction at (140℃, 60 min) to obtain a polyester prepolymer with a number average molecular weight of 1000.

[0125] (2) The polyester prepolymer obtained in step (1) was subjected to thermal crosslinking reaction at 80°C and 100 Pa vacuum for 12 h, and then mechanically ground in a ball mill at 150 rpm for 1 h. After sieving, crosslinked polyester microspheres with a particle size of 20-50 μm were obtained.

[0126] The microstructure of the cross-linked polyester microspheres prepared in Examples 1-3 and Comparative Example 1 was characterized using an optical microscope (XSP-00). The results for Examples 1-3 and Comparative Example 1 are as follows: Figure 1-4 As shown, the scale bar is 200 μm.

[0127] from Figure 1-3 As can be seen, the cross-linked polyester microspheres prepared in Examples 1-3 of this invention have high sphericity and uniform particle size. Figure 4 As can be seen from the above, the cross-linked polyester microspheres prepared in Comparative Example 1 of this invention are irregular particles and do not have a complete spherical structure.

[0128] Test methods

[0129] The cross-linked polyester microspheres provided in the examples and comparative examples were subjected to the following performance tests:

[0130] (1) Spherical formation performance: The spherical formation of cross-linked polyester microspheres was observed using an optical microscope (XSP-00).

[0131] (2) Elastic modulus (GPa): The elastic modulus of cross-linked polyester microspheres was tested by atomic force microscopy compression test (Multimode-8). The atomic force microscopy probe was pressed into the surface of the microspheres, and the elastic modulus of the cross-linked polyester microspheres was calculated by force-displacement curve. The elastic modulus of cross-linked polyester microspheres should be moderate (0.4-4.0 GPa). If the elastic modulus is too low, the cross-linked polyester microspheres will have insufficient support capacity and poor shape maintenance performance; if the elastic modulus is too high, the injection will be difficult, and the surrounding soft tissue will be easily compressed, causing adverse effects such as inflammation.

[0132] The cross-linked polyester microspheres provided in the examples and comparative examples were mixed with 20 mg / mL sodium hyaluronate gel (purchased from Bloomage Biotechnology Co., Ltd.) to prepare a cross-linked polyester microsphere composite gel (the cross-linked polyester microspheres accounted for 30% of the total mass of the composite gel) and the following performance tests were performed.

[0133] (3) Appearance: Observe whether the cross-linked polyester microsphere composite gel has fluidity and dispersibility (observe whether the system is homogeneous or has obvious agglomerated particles).

[0134] (4) Pushing force (N): The above cross-linked polyester microsphere composite gel was filled into a syringe, and the pushing force was tested using a universal testing machine. A 27 G needle was used, the pushing rate was set to 30 mm / min, and the pushing force was measured.

[0135] (5) Local inflammatory response: The above-mentioned cross-linked polyester microsphere composite gel was injected into the skin tissue of SD rats. Skin tissue samples were taken at 1, 4 and 13 weeks after implantation. Tissue sections were prepared from the implantation site and HE stained to observe the inflammatory response. By observing the HE stained sections, the "amount of inflammatory cell infiltration around the implantation site" and "severity of the overall tissue response" were scored. The scoring results can directly reflect whether the microspheres have caused obvious inflammation (the lower the score, the milder the inflammatory response and the better the biocompatibility of the cross-linked polyester microspheres).

[0136] (6) Collagen content (%): The above-mentioned cross-linked polyester microsphere composite gel was injected into the skin tissue of SD rats. Skin tissue samples were taken at 1, 4 and 13 weeks after implantation. Tissue sections were made from the implantation site and Masson staining was performed to observe the collagen production in the tissue. By analyzing the collagen content (such as the proportion of collagen area) in the Masson stained sections, the effect of cross-linked polyester microspheres in promoting collagen production was quantitatively judged (the higher the collagen content, the better the collagen regeneration performance of cross-linked polyester microspheres and the longer the filling effect).

[0137] The test results are shown in Tables 1 and 2:

[0138] Table 1

[0139]

[0140] Table 2

[0141]

[0142] The test results show that:

[0143] (1) As can be seen from Examples 1-12, the preparation method provided by the present invention effectively prepared a cross-linked polyester microsphere with an elastic modulus of 0.21-4.56 GPa. The cross-linked polyester microsphere has good flowability and dispersibility in sodium hyaluronate gel. The extrusion force of the cross-linked polyester microsphere composite gel is 18.10-49.50 N, the local inflammation response score is 2.2-8.9 after 1 week, 2.1-6.9 after 4 weeks, and 0.5-3.8 after 13 weeks. The inflammation response is mild and the biocompatibility is good. The collagen content is 15-32% after 1 week, 36-55% after 4 weeks, and 55-81% after 13 weeks. The cross-linked polyester microsphere has good collagen regeneration performance and a more lasting filling effect.

[0144] (2) As can be seen from Examples 1 and 4-6, the cross-linked polyester microspheres prepared by using preferred polyacids and polyols have a suitable elastic modulus and excellent biocompatibility and collagen regeneration promotion performance.

[0145] (3) As can be seen from Examples 1 and 7-9, by limiting the molar ratio of polyacid to polyol, the cross-linked polyester microspheres prepared by the present invention have controllable cross-linking degree, moderate elastic modulus, and less residual reactive monomers, thus avoiding local inflammatory reactions caused by residual reactive monomers due to insufficient cross-linking reaction. If the molar ratio of polyacid to polyol is too low, there will be insufficient cross-linking sites and low cross-linking density, resulting in a small elastic modulus and loose structure of the microspheres, which are prone to rapid degradation of the bulk phase and insufficient support. After implantation, the microspheres are prone to collapse and displacement, and the collagen induction effect will be poor. If the molar ratio of polyacid to polyol is too high, the unreacted residual raw materials will play an internal plasticizing role, enhance the molecular chain mobility, and ultimately weaken the microspheres' resistance to deformation and reduce the elastic modulus.

[0146] (4) As can be seen from Examples 1 and 10-12, the present invention limits the temperature of the thermal crosslinking reaction. The reaction can maintain the stability of the emulsion within this temperature range, so that the crosslinking reaction proceeds uniformly and stably, and the obtained crosslinked polyester microspheres have excellent morphological characteristics, avoiding defects such as agglomeration, poor sphericity, and uneven particle size of the microspheres. If the reaction temperature is too high, the obtained crosslinked polyester microspheres will undergo excessive crosslinking and thermal degradation of molecular chains at high temperature.

[0147] (5) As can be seen from Examples 1, 9 and 12, the cross-linked polyester microspheres provided in Examples 9 and 12 have problems such as unstable emulsion and inability of microspheres to be stably cross-linked and cured due to the excessively high molar ratio of polyacid to polyol or the excessively high cross-linking temperature. Some of them cannot be formed into spheres, and the formed spheres often have problems such as morphological collapse and unstable morphology. After implantation, they are prone to induce obvious local inflammatory reactions.

[0148] (6) As can be seen from the examples and Comparative Example 1, the microspheres prepared by conventional microsphere molding methods such as ball milling are irregular particles with poor flowability and injectability, and irregular edge morphology, which can easily induce obvious local inflammatory reactions after implantation.

[0149] The above description is only a specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Those skilled in the art should understand that any changes or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention fall within the protection and disclosure scope of the present invention.

Claims

1. A method for producing crosslinked polyester microspheres, characterized by, The preparation method includes: (1) Mix polyacids and polyols and carry out melt polycondensation reaction to obtain polyester prepolymer; (2) The polyester prepolymer obtained in step (1) is mixed with solvent A to obtain oil phase solution A; (3) Mix the oil phase solution A obtained in step (2) with the oil phase solution B to obtain a polyester prepolymer emulsion; (4) The polyester prepolymer emulsion obtained in step (3) undergoes a thermal crosslinking reaction to obtain the crosslinked polyester microspheres; The polyacids include polyacids with a functionality of 2 or polyacids with a functionality of 3. The polyols include polyols with a functionality of 2 or polyols with a functionality of 3. When the polyacid is a polyacid with a functionality of 2, the polyol is selected from polyols with a functionality of 3. When the polyacid is a polyacid with a functionality of 3, the polyol is selected from polyols with a functionality of 2. The molar ratio of the polyacid to the polyol in step (1) is 1:(0.5-2); The reaction temperature of the melt polycondensation reaction in step (1) is 100-200℃, and the reaction time of the melt polycondensation reaction is 0.5-5 h; The mass ratio of oil phase solution A to oil phase solution B in step (3) is (0.01-0.5):1; The reaction temperature of the thermal crosslinking reaction in step (4) is 30-150℃, and the reaction time of the thermal crosslinking reaction is 1-200 h; The thermal crosslinking reaction described in step (4) is carried out in a vacuum environment; The vacuum level of the vacuum environment is 10-1000 Pa.

2. The method for producing crosslinked polyester microspheres according to claim 1, characterized by, The polyacids with a functionality of 2 include any one or a combination of at least two of malic acid, sebacic acid, succinic acid, fumaric acid, tartaric acid, or α-ketoglutaric acid. The polyacid with a functionality of 3 includes any one or a combination of at least two of citric acid, propane-1,2,3-tricarboxylic acid, or propylene-1,2,3-tricarboxylic acid. The polyols with a functionality of 2 include any one or a combination of at least two of the following: ethylene glycol, polyethylene glycol, 1,3-propanediol, 1,4-butanediol, 1,8-octanediol, 1,2-propanediol, 1,2-octanediol, methylpropanediol, 1,5-pentanediol, neopentanediol, 1,2-pentanediol, 1,6-hexanediol, or 1,2-hexanediol. The polyol with a functionality of 3 includes any one or a combination of at least two of glycerol, trimethylolpropane, trimethylolethane, or hexanetriol.

3. The method for preparing cross-linked polyester microspheres according to claim 1, characterized in that, The number average molecular weight of the polyester prepolymer obtained in step (1) is 500-12000.

4. The method for preparing cross-linked polyester microspheres according to claim 1, characterized in that, Solvent A mentioned in step (2) includes organic solvents; The organic solvent includes any one or a combination of at least two of N,N-dimethylformamide, dimethylacetamide, dimethyl sulfoxide, diphenyl ether, N-methylpyrrolidone, 1,2,3,4-tetrahydronaphthalene, xylene, toluene, or cyclohexanone; The mass ratio of solvent A to polyester prepolymer is (0.1-10):1; The oil phase solution A mentioned in step (2) also includes a catalyst; The catalyst comprises any one or a combination of at least two of the following: methylbenzenesulfonic acid, thionyl chloride, acetamide, tetrabutyl titanate, sodium methoxide, sodium ethoxide, tetraethyl titanate, tetraisopropyl titanate, boron trifluoride, stannous octoate, stannous tetrachloride, stannous oxalate, stannous chloride, p-toluenesulfonic acid, or butylstannic acid. The mass ratio of the catalyst to the polyester prepolymer is (0.001-0.1):

1.

5. The method for preparing cross-linked polyester microspheres according to claim 1, characterized in that, The oil phase solution B includes solvent B; Solvent B includes any one or a combination of at least two of the following: liquid paraffin, white oil, n-hexadecane, n-heptane, isoalkanes, silicone oil, or mineral oil. The oil phase solution B also includes a dispersant; The dispersant includes any one or a combination of at least two of the following: sorbitan monooleate, glyceryl monooleate, polyisobutylene, polymethyl methacrylate dispersants, PVP, PEG-fatty chain copolymer, hydrophobic silica, hydrophobic nanoclay, or surface-modified bioactive glass nanoparticles. The mass ratio of solvent B to dispersant in the oil phase solution B is (50-500):1; The mixing described in step (3) is carried out under stirring; The stirring speed is 100-5000 r / min, and the stirring time is 10-60 min.

6. The method for preparing cross-linked polyester microspheres according to claim 1, characterized in that, The thermal crosslinking reaction described in step (4) also includes a post-processing step; The post-processing steps include filtration, washing, drying, and sieving.

7. Crosslinked polyester microspheres prepared by a method according to any one of claims 1-6.

8. The cross-linked polyester microspheres according to claim 7, characterized in that, The cross-linked polyester microspheres have a particle size of 0.1-150 μm.

9. The application of a cross-linked polyester microsphere as described in claim 7 or 8 in a soft tissue filling material.

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