A porous poly-l-lactic acid microsphere and a preparation method thereof, and an injection preparation

Abstract

The present application provides a kind of porous poly-L-lactic acid microspheres, and its preparation method and injection preparation comprising porous poly-L-lactic acid microspheres, the porous poly-L-lactic acid microspheres are prepared by emulsification-solvent evaporation method from first component, second component and optional auxiliary component, wherein the first component is poly-L-lactic acid, the second component is sodium carboxymethyl cellulose, the content of the first component is 98%-99.9% of the total mass of the first component and the second component, the content of the second component is 0.1%-2% of the total mass of the first component and the second component, and the porous poly-L-lactic acid microspheres have topological morphology.

Description

A porous poly-L-lactic acid microsphere, its preparation method, and its injectable formulation Technical Field

[0001] This invention relates to the field of medical materials, and more particularly to a porous poly-L-lactic acid microsphere with a topological morphology, a method for preparing the same, and an injectable formulation containing the porous poly-L-lactic acid microsphere. Background Technology

[0002] Poly-L-lactic acid (PLLA) injectable filler is a medical material specifically designed for facial filling and wrinkle reduction. It is made from poly-L-lactic acid, a biodegradable polymer that can be extracted from natural plants and animals. After years of research and clinical trials, it has been proven to be a safe and effective medical aesthetic and plastic surgery injectable material.

[0003] Currently available medical aesthetic microspheres are mostly solid microspheres with smooth surfaces. However, the smooth surface of these microspheres is not conducive to the adhesion of fibroblasts and the production of collagen, resulting in insufficient ability to stimulate collagen regeneration. At the same time, the solid internal structure does not provide enough growth space for fibroblasts and collagen, thus the medical aesthetic effect needs to be improved.

[0004] While there have been some reports on the development of porous microspheres, there are very few publications on porous poly-L-lactic acid microspheres. Furthermore, existing porous microspheres have relatively small pore sizes, and there are no reports on microspheres with stable topological structures. Summary of the Invention

[0005] To address the technical problems existing in the prior art, this invention provides poly-L-lactic acid porous microspheres, a method for preparing the same, and an injectable formulation comprising the poly-L-lactic acid porous microspheres. The poly-L-lactic acid porous microspheres of this invention possess a distinctive topological morphology and clearly defined pores, exhibiting a stronger ability to stimulate collagen regeneration and promoting fibroblast proliferation, resulting in excellent aesthetic effects.

[0006] This invention provides a method for preparing poly-L-lactic acid porous microspheres. The poly-L-lactic acid porous microspheres are prepared by an emulsification-solvent evaporation method from a first component, a second component, and optional auxiliary components. The first component is poly-L-lactic acid, and the second component is sodium carboxymethyl cellulose. The content of the first component is 98%-99.9% of the total mass of the first and second components, and the content of the second component is 0.1%-2% of the total mass of the first and second components. The poly-L-lactic acid porous microspheres have a specific topological morphology.

[0007] Preferably, the intrinsic viscosity of the poly-L-lactic acid is 0.2-4.0 dL / g.

[0008] Preferably, the auxiliary component is selected from at least one of the following groups: vitamins or their esters, amino acids, hyaluronic acid, small molecule active peptides, collagen, polyracemic lactic acid, polydextral lactic acid, block copolymers of polylactic acid and other components, and the content of the auxiliary component is 0-30% of the total mass of the first component and the second component.

[0009] Preferably, the emulsification-solvent evaporation method is a double emulsification-solvent evaporation method, and the method includes:

[0010] (A) The first component and optionally the oil-soluble auxiliary component are dissolved in an organic solvent to form an oil phase;

[0011] (B) Dissolve the second component and optionally the water-soluble auxiliary component in water to form an internal aqueous phase;

[0012] (C) Dissolving the surfactant in water to form an external aqueous phase;

[0013] (D) The oil phase and the inner aqueous phase are mixed to form a primary emulsion, and the primary emulsion is added to the outer aqueous phase to form a secondary emulsion;

[0014] (E) Stir the double emulsion to evaporate the organic solvent, obtaining a suspension;

[0015] (F) The suspension is sieved, washed, and freeze-dried to obtain the poly-L-lactic acid porous microspheres.

[0016] Preferably, the mass-to-volume ratio of the second component to the water is 0.01g-0.06g:2mL, and the volume ratio of water in step (B) to the organic solvent in step (A) is 1:5-1:30.

[0017] Preferably, the particle size of the poly-L-lactic acid porous microspheres is 10-150 µm.

[0018] More preferably, the particle size of the poly-L-lactic acid porous microspheres is 25-100µm.

[0019] The present invention also provides a poly-L-lactic acid porous microsphere, which is prepared by the preparation method described in the present invention, and the poly-L-lactic acid porous microsphere has a topological morphology.

[0020] The present invention also provides an injectable formulation comprising poly-L-lactic acid porous microspheres prepared according to the preparation method of the present invention, or poly-L-lactic acid porous microspheres provided by the present invention.

[0021] Preferably, the injectable formulation is used for medical aesthetics and plastic surgery.

[0022] Sodium carboxymethyl cellulose is a commonly used suspending agent in medical aesthetic microspheres, typically dissolved in the solvent of the microspheres to increase the viscosity of the solvent. During their research, the inventors of this invention unexpectedly discovered that adding sodium carboxymethyl cellulose during the microsphere preparation process can produce microspheres with a porous topology and significant pore size; moreover, only a small amount of sodium carboxymethyl cellulose is needed to achieve a very noticeable pore-forming effect.

[0023] The poly-L-lactic acid porous microspheres of this invention possess a unique topological morphology, with depressions and protrusions on their surface, which facilitates better adhesion and proliferation of fibroblasts and exhibits a strong ability to stimulate collagen regeneration. Simultaneously, the significant porosity provides sufficient growth space for fibroblasts and collagen, resulting in excellent aesthetic effects. Furthermore, the poly-L-lactic acid porous microspheres of this invention are in the micrometer range in size, which is advantageous for preparing injectable formulations. They not only provide excellent physical filling effects but, as mentioned above, also stimulate the proliferation and regeneration of fibroblasts and collagen, promoting self-repair at the filling site. Attached Figure Description

[0024] Figure 1 is an electron microscope image of the poly-L-lactic acid porous microspheres prepared in Example 1, wherein Figure 1A is an image magnified 1000 times and Figure 1B is an image magnified 300 times.

[0025] Figure 2 shows electron micrographs of the poly-L-lactic acid porous microspheres prepared in Example 2, where Figure 2A is an image magnified 800 times and Figure 2B is an image magnified 200 times.

[0026] Figure 3 shows electron micrographs of the poly-L-lactic acid porous microspheres prepared in Example 3, where Figure 3A is an image magnified 500 times and Figure 3B is an image magnified 200 times.

[0027] Figure 4 shows electron micrographs of the poly-L-lactic acid porous microspheres prepared in Comparative Example 1, where Figure 4A is an image magnified 800 times and Figure 4B is an image magnified 500 times.

[0028] Figure 5 is an electron microscope image of the poly-L-lactic acid porous microspheres prepared in Comparative Example 2;

[0029] Figure 6 shows electron micrographs of the poly-L-lactic acid porous microspheres prepared in Comparative Example 3, where Figure 6A is an image magnified 400 times and Figure 6B is an image magnified 200 times.

[0030] Figure 7 is an electron microscope image of the poly-L-lactic acid porous microspheres prepared in Comparative Example 4. Detailed Implementation

[0031] The technical solutions of the present invention will be further described below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are for illustration and explanation only and are not intended to limit the invention. Unless otherwise specified, the methods used in this invention are conventional production methods; the raw materials used, unless otherwise specified, are conventional commercially available products. Unless otherwise specified, all percentages in this invention are by mass.

[0032] the term

[0033] Polylactic acid, also known as polylactide, is a polyester polymer obtained by polymerizing lactic acid as the main raw material. Because the lactic acid molecule contains an asymmetric carbon atom, it exhibits optical activity. Therefore, polylactic acid is also classified into dextrorotatory polylactic acid (also known as poly-D-lactic acid, PDLA), levorotatory polylactic acid (also known as poly-L-lactic acid, PLLA), racemic polylactic acid (also known as poly-racemic lactic acid, PDLLA), and non-optically active polylactic acid (Meso-PLA).

[0034] In this invention, a microsphere with a topological morphology refers to a microsphere with a honeycomb-like pore structure inside and extending to form a grooved morphology on the surface. The surface of the microsphere has depressions and protrusions and obvious pores.

[0035] In this invention, the "auxiliary component" is only required to not affect the preparation and efficacy (such as the ability to stimulate collagen regeneration, safety, and onset time) of the poly-L-lactic acid composite porous microspheres of this invention, without any other additional restrictions. For example, it can be selected from at least one of the following groups: vitamins or their esters, amino acids, small molecule active peptides, collagen, polyracemic lactic acid, polydextral lactic acid, block copolymers of polylactic acid and other components. When preparing the poly-L-lactic acid composite porous microspheres of this invention, auxiliary components may or may not be added according to actual needs.

[0036] In this invention, the "emulsification-solvent evaporation method" is a known technique in the art. Simply put, it involves preparing an emulsion by mixing an aqueous phase containing a surfactant and an oil phase containing an organic solvent, and then evaporating the organic solvent from the emulsion to obtain spherical particles. Preferably, this invention uses a double emulsification-solvent evaporation method. The double emulsification-solvent evaporation method refers to first preparing a primary emulsion by mixing an inner aqueous phase and an oil phase, and then mixing the primary emulsion with an outer aqueous phase to prepare another emulsion. Unless otherwise specified, in addition to the raw materials and parameters defined in this invention, such as the first component, the second component, and auxiliary components, reagents and experimental parameters commonly used in the emulsification-solvent evaporation method in the art can be used to prepare the poly-L-lactic acid porous microspheres of this invention.

[0037] The poly-L-lactic acid porous microspheres of the present invention are prepared by an emulsification-solvent evaporation method from a first component, a second component, and optional auxiliary components. The first component is poly-L-lactic acid, and the second component is sodium carboxymethyl cellulose. The content of the first component is 98%-99.9% of the total mass of the first and second components, and the content of the second component is 0.1%-2% of the total mass of the first and second components. The present invention achieves the preparation of porous microspheres with specific topological morphologies by using the combined use of the first and second components and adjusting their amounts through an emulsification-solvent evaporation method.

[0038] Preferably, the content of the second component is 0.1%-1.5% of the total mass of the first and second components. When the content of the second component is less than 0.1% relative to the total mass of the first and second components, the prepared microspheres do not have a topological morphology; the microspheres are solid structures with only shallow pits on the surface and almost no pores. When the content of the second component is greater than 2% relative to the total mass of the first and second components, the prepared microspheres have an unstable structure and are prone to collapse. Preferably, the emulsification-solvent evaporation method is a double emulsification-solvent evaporation method. The microspheres prepared by the method of the present invention have a topological morphology, with depressions and protrusions on the surface, which is conducive to better adhesion and proliferation of fibroblasts, and has a strong ability to stimulate collagen regeneration. At the same time, they have obvious pores, which can provide sufficient growth space for fibroblasts and collagen, resulting in good medical aesthetic effects.

[0039] In a preferred embodiment of the present invention, the intrinsic viscosity of the poly-L-lactic acid (PLLA) is 0.2-4.0 dL / g. PLLA with an intrinsic viscosity within this range exhibits a suitable degradation rate, allowing the prepared porous microspheres with a specific topological structure to remain in vivo for a certain period to achieve effects such as filling, stimulating fibroblast and collagen proliferation and regeneration, and degrading after a certain time without causing long-term effects on the human body.

[0040] In a preferred embodiment of the present invention, the auxiliary component is selected from at least one of the following groups: vitamins or their esters, amino acids, hyaluronic acid, small molecule active peptides, collagen, polyracemic lactic acid, polydextral lactic acid, block copolymers of polylactic acid and other components, and the content of the auxiliary component is 0-30% of the total mass of the first component and the second component. Depending on actual needs, other auxiliary components can be added during the preparation of the porous microspheres of the present invention to achieve additional effects, such as adding vitamin C to achieve effects such as brightening skin tone and anti-oxidation.

[0041] In a preferred embodiment of the present invention, the mass-to-volume ratio of the first component to the organic solvent is 1:5, the mass-to-volume ratio of the second component to the water is 0.01g-0.06g:2mL, the volume ratio of water in step (B) to organic solvent in step (A) is 1:5-1:30, and more preferably, the volume ratio of water in step (B) to organic solvent in step (A) is 1:10-1:20.

[0042] In a preferred embodiment of the present invention, the particle size of the poly-L-lactic acid porous microspheres is 10-150µm, more preferably, the particle size of the poly-L-lactic acid porous microspheres is 25-100µm, and even more preferably, the particle size D10 of the poly-L-lactic acid porous microspheres is 25µm-45µm, D50 is 40.0µm-65µm, and D90 is 60.0µm-100.3µm.

[0043] The present invention also provides an injectable formulation comprising porous poly-L-lactic acid microspheres prepared according to the method of the present invention. Preferably, the injectable formulation is used for medical aesthetics and plastic surgery.

[0044] In addition to the aforementioned active ingredient, poly-L-lactic acid porous microspheres, the injectable formulation of the present invention may optionally include medical excipients, including but not limited to solvents, surfactants, preservatives, buffers, and isotonic adjusters. Solvents are used to disperse the poly-L-lactic acid porous microspheres, such as an aqueous solution of sodium carboxymethyl cellulose; surfactants can reduce interfacial tension and enhance the redispersibility of microspheres, such as polysorbate 80 and polysorbate 20; preservatives are used to prevent or inhibit the growth and reproduction of microorganisms in the formulation, ensuring the microbial safety of the formulation, such as benzyl alcohol, sodium benzoate, potassium sorbate, and parabens; buffers are used to maintain the formulation within a suitable and stable pH range, ensuring the stability and solubility of the active ingredient or reducing irritation, such as phosphate buffer (sodium dihydrogen phosphate / disodium hydrogen phosphate), acetate buffer (acetic acid / sodium acetate), and citrate buffer; isotonic adjusters regulate the osmotic pressure of the injection to be comparable to body fluids (blood), reducing irritation, such as sodium chloride, glucose, glycerol, and mannitol. Those skilled in the art can select commonly used medical excipients in the field to prepare the injectable formulation of the present invention according to actual needs.

[0045] The electron microscope used in the following examples was a Zeiss EVO LS15. In this invention, a Malvern 3000 laser particle size analyzer was used to detect the microsphere size according to the third method (light scattering method) of General Chapter 0982, Part IV, of the Chinese Pharmacopoeia (2020 Edition). Example 1

[0046] 4g of PLLA (intrinsic viscosity 1.1 dL / g) was dissolved in 20mL of dichloromethane to form an oil phase. 0.01g of sodium carboxymethyl cellulose was dissolved in 2mL of purified water to form an inner aqueous phase. The inner aqueous phase was added to the oil phase and homogenized at 10000rpm for 90s to obtain a primary emulsion. The primary emulsion was added to 1000mL of 1% (w / v) polyvinyl alcohol (PVA) solution at 15℃ under homogenization at 5000rpm, and homogenized for 2min to obtain an emulsion. The emulsion was transferred to a cantilever mixer and stirred at 200rpm for 5h to evaporate and remove the organic solvent. The mixture was filtered through a sieve, washed with deionized water, and lyophilized to obtain powdered microspheres. The electron micrograph of the prepared microspheres is shown in Figure 1. The microspheres have obvious topological structure and pores. The particle size distribution is shown in Table 1 below. Example 2

[0047] 4g of PLLA (intrinsic viscosity 0.5dL / g) was weighed and dissolved in 20mL of dichloromethane to form an oil phase. 0.005g of sodium carboxymethyl cellulose was weighed and dissolved in 1mL of purified water to form an inner aqueous phase. The inner aqueous phase was added to the oil phase and homogenized at 10000rpm for 90s to obtain a primary emulsion. The primary emulsion was added to 1000mL of 1% (w / v) PVA solution at 15℃ under homogenization at 5000rpm and homogenized for 2min to obtain an emulsion. The emulsion was transferred to a cantilever mixer and stirred at 200rpm for 5h to evaporate and remove the organic solvent. The mixture was filtered through a sieve, washed with deionized water, and lyophilized to obtain powdered microspheres. The electron microscopy image of the prepared microspheres is shown in Figure 2. The microspheres have obvious topological structure and pores. The particle size distribution is shown in Table 1 below. Example 3

[0048] 4 g of PLLA (intrinsic viscosity 3.3 dL / g) was dissolved in 20 mL of dichloromethane to form the oil phase. 0.06 g of sodium carboxymethyl cellulose and 0.2 g of recombinant type III collagen were dissolved in 2 mL of purified water to form the inner aqueous phase. The inner aqueous phase was added to the oil phase and homogenized at 10,000 rpm for 90 s to obtain the primary emulsion. The primary emulsion was added to 1000 mL of 1% (w / v) PVA solution at 15℃ under homogenization at 5000 rpm and homogenized for 2 min to obtain the emulsion. The emulsion was transferred to a cantilever mixer and stirred at 200 rpm for 5 h to evaporate and remove the organic solvent. The mixture was filtered through a sieve, washed with deionized water, and lyophilized to obtain powdered microspheres. Electron microscopy images of the prepared microspheres are shown in Figure 3. The microspheres exhibit a distinct topological structure and pore size. The particle size distribution is shown in Table 1 below.

[0049] Table 1

[0050]

[0051] Comparative Example 1

[0052] 4 g of PLLA (intrinsic viscosity 1.1 dL / g) was dissolved in 20 mL of dichloromethane to form the oil phase. 0.002 g of sodium carboxymethyl cellulose was dissolved in 2 mL of purified water to form the aqueous phase. The aqueous phase was added to the oil phase and homogenized at 10,000 rpm for 90 s to obtain the primary emulsion. The primary emulsion was then added to 1000 mL of 1% (w / v) PVA solution at 15 °C under homogenization at 5,000 rpm and homogenized for 2 min to obtain the emulsion. The emulsion was transferred to a cantilever mixer and stirred at 200 rpm for 5 h to evaporate and remove the organic solvent. The mixture was filtered through a sieve, washed with deionized water, and lyophilized to obtain powdered microspheres.

[0053] In Comparative Example 1, the content of sodium carboxymethyl cellulose relative to the total mass of PLLA and sodium carboxymethyl cellulose was 0.05%. The electron microscopy image of the prepared microspheres is shown in Figure 4. It can be seen that the prepared microspheres are solid structures with only very shallow pits on the surface and very inconspicuous pores.

[0054] Comparative Example 2

[0055] 4 g of PLLA (intrinsic viscosity 2.5 dL / g) was weighed and dissolved in 20 mL of dichloromethane to form the oil phase. 0.5 g of sodium carboxymethyl cellulose was weighed and dissolved in 2 mL of purified water to form the inner aqueous phase. The inner aqueous phase was added to the oil phase and homogenized at 10,000 rpm for 90 s to obtain the primary emulsion. The primary emulsion was then added to 1000 mL of 1% (w / v) PVA solution at 15 °C under homogenization at 5,000 rpm and homogenized for 2 min to obtain the emulsion. The emulsion was transferred to a cantilever mixer and stirred at 200 rpm for 5 h to evaporate and remove the organic solvent. The mixture was filtered through a sieve, washed with deionized water, and lyophilized to obtain powdered microspheres.

[0056] In Comparative Example 2, the content of sodium carboxymethyl cellulose relative to the total mass of PLLA and sodium carboxymethyl cellulose was 11.11%. The electron microscopy image of the prepared microspheres is shown in Figure 5. The microsphere structure is not firm and is prone to collapse, and cannot form a stable topological structure.

[0057] Comparative Example 3

[0058] 4 g of PLLA (intrinsic viscosity 1.1 dL / g) was weighed and dissolved in 20 mL of dichloromethane to form an oil phase. The oil phase was added to 1000 mL of a 1% (w / v) PVA solution at 15 °C under homogenization at 5000 rpm, and the mixture was homogenized and emulsified for 2 min to obtain an emulsion. The emulsion was transferred to a cantilever mixer and stirred at 200 rpm for 5 h to evaporate and remove the organic solvent. The mixture was filtered through a sieve, washed with deionized water, and lyophilized to obtain powdered microspheres.

[0059] No sodium carboxymethyl cellulose was added during the preparation of the microspheres. The electron microscope image of the prepared microspheres is shown in Figure 6. The obtained microspheres have a solid structure, a smooth surface, and no pores.

[0060] Comparative Example 4

[0061] Dissolve approximately 500 mg of galantamine in 4 ml of sodium carboxymethyl cellulose aqueous solution (emulsifier), add it to 20 ml of PLGA (50:50, MW25000) chloroform solution containing 85% of the total weight of microspheres, emulsify by high-speed stirring (20,000 rpm), then add it to 500 ml of 6% PVA aqueous solution while stirring at 1500 rpm to form a double emulsion. After magnetic stirring for 15 minutes, dilute the PVA 3 times, stir for 3 hours to evaporate the solvent, then wash, centrifuge, freeze dry, and collect the product.

[0062] Comparative Example 4: Microspheres were prepared by combining PLGA with sodium carboxymethyl cellulose. Electron microscopy images of the microspheres are shown in Figure 7. The microspheres have a solid structure, a smooth surface, and are essentially non-porous. Example 4

[0063] This embodiment uses the microspheres of Examples 1-2 and Comparative Example 3 as examples to test the ability of microspheres to promote the proliferation of fibroblasts.

[0064] Solution preparation:

[0065] Sterile culture medium: 10% fetal bovine serum (Gibco, USA) was prepared using DMEM medium (Gibco, USA).

[0066] Microsphere solutions: For the microspheres of Examples 1-2 and Comparative Example 3, solutions of each microsphere were prepared with five different gradient concentrations of 0.20% (w / v), 0.40% (w / v), 0.80% (w / v), 1.6% (w / v), and 3.2% (w / v) using sterile culture medium.

[0067] Assay: The example group, comparative group, and control group were each seeded with 10,000 fibroblasts (human dermal fibroblasts (Guangdong Boxi Biotechnology Co., Ltd.)) per well, with six replicates for each concentration. The culture plates were incubated at 37°C in a 5% CO2 incubator for 24 hours. After incubation, the original culture medium was aspirated. 100 μL of microsphere solution of different concentrations was added to the example group and comparative group, respectively, while 100 μL of sterile culture medium was added to the control group. Incubation continued for 48 hours. 10 μL of 5 mg / mL MTT solution was added, followed by incubation for another 4 hours. Then, 200 μL of dimethyl sulfoxide was added, and the mixture was shaken for 10 minutes. The absorbance (A) at 490 nm was measured using a microplate reader (model: SPARK, Tecan Austria GmbH).

[0068] The experimental data on fibroblast proliferation obtained from the test are shown in Table 2.

[0069] Table 2

[0070]

[0071] As shown in Table 2, at all concentrations, the poly-L-lactic acid porous microspheres of the present invention exhibited significantly enhanced fibroblast proliferation capacity compared to the solid microspheres of Comparative Example 3. Example 5

[0072] This embodiment uses the microspheres from Examples 1-2 and Comparative Example 3 as examples to test the ability of microspheres to stimulate collagen regeneration in rats.

[0073] Experimental principle:

[0074] After being administered to rats via subcutaneous injection, the poly-L-lactic acid porous microspheres were rapidly absorbed by the skin surrounding the injection site. The collagen level in the subcutaneous tissue at the injection site was measured as a quantitative indicator at the experimental endpoint.

[0075] Experimental methods:

[0076] Experimental animals: SD rats, which were purchased from Spiford (Suzhou) Biotechnology Co., Ltd.

[0077] Half male and half female, 180-220g.

[0078] Experimental plan:

[0079] After acclimatization, 12 rats were randomly divided into three groups (Example 1 group, Example 2 group, and Comparative Example 3 group, with 4 rats in each group), with half males and half females. Each group was then given a single subcutaneous injection of 0.1 mL of the injection solution (2.5% sodium carboxymethyl cellulose aqueous solution, containing 9 mg of microspheres per 0.1 mL) into the subcutaneous fat layer. At week 12 post-injection, the rats were sacrificed, and skin from the injection site on the back was harvested, dehydrated, paraffin-embedded, and stained with Masson's stain. The stained areas were imaged using an optical microscope (CX33RTFS2, Olympus Corporation, Japan) to evaluate the subcutaneous collagen area. Using ImageJ software, three fields of view were selected from the Masson-stained images, and the total area and collagen coverage of each field of view were measured. The collagen area percentage was calculated as (collagen pixel area / total pixel area) × 100%, and the average of the three fields of view was taken as the collagen area percentage of the image.

[0080] The experimental data on the collagen area obtained from the detection are shown in Table 3.

[0081] Table 3

[0082]

[0083] As can be seen from Table 3, the poly-L-lactic acid porous microspheres of the present invention have a better collagen generation effect compared with the solid microspheres of Comparative Example 3.

[0084] As can be seen from the above examples and comparative examples, the present invention achieves the preparation of porous microspheres with topological morphology by using PLLA in combination with sodium carboxymethyl cellulose and adjusting the content of sodium carboxymethyl cellulose, combined with a reemulsification-solvent evaporation method. The porous microspheres with topological morphology of the present invention have a stronger ability to stimulate fibroblast proliferation and collagen regeneration.

[0085] This invention may have other various embodiments. Without departing from the spirit and essence of this invention, those skilled in the art can make various corresponding changes and modifications according to this invention, but these corresponding changes and modifications should all fall within the protection scope of the appended claims.

Claims

1. A method for preparing porous poly-L-lactic acid microspheres, characterized in that, The poly-L-lactic acid porous microspheres are prepared by an emulsification-solvent evaporation method from a first component, a second component, and optional auxiliary components. The first component is poly-L-lactic acid, and the second component is sodium carboxymethyl cellulose. The intrinsic viscosity of the poly-L-lactic acid is 0.2-4.0 dL / g. The content of the first component is 98%-99.9% of the total mass of the first and second components, and the content of the second component is 0.1%-2% of the total mass of the first and second components. The poly-L-lactic acid porous microspheres have a specific topological morphology. The poly-L-lactic acid porous microspheres with topological morphology refer to microspheres with a honeycomb-like pore structure inside and extending to form a grooved morphology on the surface. The surface of the microspheres has depressions and protrusions and obvious pores. The emulsification-solvent evaporation method is a double emulsification-solvent evaporation method. The method includes: (A) dissolving the first component and optionally an oil-soluble auxiliary component in an organic solvent to form an oil phase; (B) dissolving the second component and optionally a water-soluble auxiliary component in water to form an inner aqueous phase, wherein the mass-volume ratio of the second component to water is 0.01 g - 0.06 g: 2 mL; (C) dissolving a surfactant in water to form an outer aqueous phase; (D) mixing the oil phase and the inner aqueous phase to form a primary emulsion, and adding the primary emulsion to the outer aqueous phase to form a double emulsion; (E) stirring the double emulsion to evaporate the organic solvent and obtain a suspension; (F) sieving, washing, and freeze-drying the suspension to obtain the poly-L-lactic acid porous microspheres.

2. The preparation method according to claim 1, characterized in that, The auxiliary ingredient is selected from at least one of the following groups: vitamins or their esters, amino acids, hyaluronic acid, collagen, polyracemic lactic acid, and polydextral lactic acid. The content of the auxiliary ingredient is 0-30% of the total mass of the first and second ingredients.

3. The preparation method according to claim 1, characterized in that, The volume ratio of water in step (B) to organic solvent in step (A) is 1:5 to 1:

30.

4. The preparation method according to claim 1, characterized in that, The particle size of the poly-L-lactic acid porous microspheres is 10-150µm.

5. The preparation method according to claim 4, characterized in that, The particle size of the poly-L-lactic acid porous microspheres is 25-100µm.

6. A porous microsphere of poly-L-lactic acid, characterized in that, The poly-L-lactic acid porous microspheres prepared according to any one of claims 1-5 have a topological morphology.

7. An injectable formulation, characterized in that, This includes poly-L-lactic acid porous microspheres prepared by the preparation method according to any one of claims 1-5, or poly-L-lactic acid porous microspheres according to claim 6.

8. The injectable formulation according to claim 7, characterized in that, The injectable formulation is used for medical aesthetics and plastic surgery.

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