A method for preparing a polymer microsphere

Abstract

The application provides a preparation method of polymer microspheres, which comprises the following steps: (1) dissolving a polymer material and an optional active component in a solvent to form a precursor solution; and (2) injecting the precursor solution into a receiving liquid by a wet electrostatic spraying method to form polymer microspheres, wherein the polymer microspheres have a structure with smooth and compact surfaces and loose and porous interiors. The preparation method has the characteristics of high yield, simplicity, strong controllability, stable process and suitability for different types of polymers, and is easy to realize large-scale industrial production.

Description

Technical Field

[0001] This invention relates to the field of biomedical technology, and in particular to a method for preparing polymer microspheres. Background Technology

[0002] Polymer microspheres such as polycaprolactone (PCL), polylactic acid (PLA), and polylactic-glycolic acid copolymer (PLGA) have been proven to have excellent biocompatibility and have been widely used in drug delivery, tissue filling, and other fields. Traditional methods for preparing polymer microspheres include sol-gel methods, emulsion polymerization methods, template methods, and reactive template methods, but these methods have some drawbacks and challenges:

[0003] 1. Uncontrollable microsphere structure: Although there are some methods to control the solid or hollow and porous structure of polymer microspheres, the preparation of polymer microspheres with a smooth and dense surface and a loose and porous internal structure remains a challenge.

[0004] 2. Complex processes: Some methods for preparing polymer microspheres require multiple steps and complex process conditions, such as emulsion polymerization, suspension polymerization, or solvent evaporation. These complex steps and conditions may lead to operational difficulties and process instability.

[0005] 3. Low yield: The yield of some preparation methods is relatively low, especially for polymer microspheres with limited size range. Low yield limits the feasibility of large-scale preparation and increases cost and time.

[0006] 4. Control of microsphere size and morphology: Although there are some methods to control the size and morphology of polymer microspheres, in practice, controlling size and morphology remains a challenge, especially for hollow microspheres, where controlling their wall thickness and pore size is even more complex.

[0007] 5. Challenges in mass production: Many methods for preparing polymer microspheres are suitable for small-batch laboratory preparation, but large-scale production on an industrial scale remains challenging. More efficient and scalable preparation methods need to be developed to meet the demands of industrial production.

[0008] Therefore, the urgent problem to be solved is to find an efficient method for preparing polymer microspheres with advantages such as high yield, simplicity and ease of implementation and strong controllability. Summary of the Invention

[0009] This invention overcomes the shortcomings of existing technologies and provides a method for preparing polymer microspheres with smooth, dense surfaces and porous interiors. This method utilizes wet electrostatic spraying, employing high-voltage electrostatic force to break a liquid stream containing polymer materials and optionally bioactive components into charged droplets. The droplets are then rapidly solidified by receiving the solution to form microspheres. This method is simple and efficient, and offers excellent control over the shape, structure, and size of the microparticles, particularly for preparing microspheres with a unique structure characterized by a smooth, dense surface and porous interior.

[0010] This invention is achieved through the following technical solution:

[0011] On one hand, the present invention provides a method for preparing polymer microspheres, which includes the following steps:

[0012] (1) Dissolve the polymer material and optional active components in a solvent to form a precursor solution;

[0013] Preferably, the polymer material is selected from one or more of polylactic acid (PLA), polycaprolactone (PCL), polylactic acid-caprolactone copolymer (PLCL), block copolymer of polylactic acid and polyethylene glycol (PLA-PEG), and polylactic acid-glycolic acid copolymer (PLGA); the active component is a biologically active substance.

[0014] (2) The precursor solution is injected into the receiving liquid by wet electrostatic spraying to form polymer microspheres.

[0015] The polymer microspheres have a smooth and dense surface and a loose and porous internal structure.

[0016] The wet electrostatic spraying process of this invention is based on most processes based on the principle of electrostatic atomization, that is, processes derived from electrostatic atomization, including electrostatic spraying, electrostatic spinning, and multi-fluid composite electrostatic spraying technology.

[0017] According to some embodiments of the present invention, the solvent is an organic solvent, preferably selected from one or more of hexafluoroisopropanol, chloroform, dichloromethane, toluene, tetrahydrofuran, and ethyl acetate.

[0018] According to some embodiments of the present invention, the molecular weight of the polymer material is 30,000 to 500,000 Da, preferably 35,000 to 230,000 Da.

[0019] According to some embodiments of the present invention, the concentration of the polymer material in the precursor solution is 0.1~30% w / v.

[0020] According to some embodiments of the present invention, the concentration of the active component in the precursor solution is 0.1-10% w / v, preferably 0.1-5% w / v.

[0021] According to some embodiments of the present invention, the mass ratio of the active component to the polymer material in the precursor solution is 0.01 to 0.2:1, preferably 0.02 to 0.05:1.

[0022] According to some embodiments of the present invention, the receiving liquid is an aqueous solution of ethanol with an ethanol concentration greater than 75 wt%, preferably an aqueous solution of ethanol with an ethanol concentration of 80 wt%.

[0023] According to some embodiments of the present invention, in step (2), the injection is performed at a rate of 0.1 to 10 mm / min, preferably 0.5 to 5 mm / min, and more preferably 0.5 to 2 mm / min.

[0024] According to some embodiments of the present invention, in step (2), the injection is performed at a rate of 0.5~1.0 mm / min.

[0025] According to some embodiments of the present invention, in step (2), the wet electrostatic spraying method is carried out at a voltage of 2.0~15.0 kV, preferably 2~10 kV, and more preferably 3~5 kV.

[0026] According to some embodiments of the present invention, in step (2), the wet electrostatic spraying method is carried out at a voltage of 3.5~4.2 kV.

[0027] According to some embodiments of the present invention, in step (2), the wet electrostatic spraying is carried out at a temperature of 15 ℃ to 50 ℃, preferably 25 ℃ to 45 ℃, and more preferably 37 ℃ to 45 ℃.

[0028] According to some embodiments of the present invention, in step (2), the wet electrostatic spraying is carried out at a temperature of 40°C to 43°C.

[0029] According to some embodiments of the present invention, the active component is selected from one or more of nanoscale bioactive inorganic materials, cell growth factors, drugs, and nutrients;

[0030] Preferably, the nanoscale bioactive inorganic material is a bioactive glass and / or a silicate bioactive ceramic;

[0031] Preferably, the bioactive glass is 45S5 bioactive glass;

[0032] Preferably, the silicate bioactive ceramic is CaSiO3, FeSiO4, or CaCuSi4O.10 ;

[0033] Preferably, the cell growth factor is vascular endothelial growth factor (VEGF) or basic fibroblast growth factor (bFGF).

[0034] Preferably, the drug is rapamycin, sirolimus, or paclitaxel;

[0035] Preferably, the nutrient is vitamin C, amino acids, or collagen.

[0036] This invention utilizes a wet electrostatic spraying method to treat a precursor solution containing polymer materials and optional active components. During the experiment, a high-voltage generator outputs a fixed voltage, and a micro-injection pump is set to a specific injection speed. The precursor solution is drawn into a syringe, which is then fixed onto the injection pump and vertically positioned above a receiving container. The positive terminal of the high-voltage generator is connected to the syringe needle, and the negative terminal is connected to a large-diameter metal container containing a large volume of receiving liquid. The power switch of the high-voltage generator is turned on, followed by the injection pump. The injection pump pushes the precursor solution downwards at a certain speed, dispersing it into droplets of a specific size under the influence of the electric field. When the droplets generated by the electrostatic spraying are injected into the large volume of receiving liquid, they begin to solidify. After the injection is completed, the received suspension is allowed to stand overnight, and the precipitate in the receiving liquid is collected, freeze-dried, and a white powder is obtained.

[0037] On the other hand, the present invention provides polymer microspheres prepared by the above preparation method.

[0038] According to some embodiments of the present invention, the diameter of the polymer microspheres is preferably 0.1 to 200 mm. More preferably 20-50 .

[0039] In another aspect, the present invention provides the use of the above-mentioned polymer microspheres in the preparation of biomedical materials, especially as tissue fillers.

[0040] Compared with the prior art, the preparation method provided by the present invention has the following beneficial effects:

[0041] 1. This invention utilizes a special wet electrostatic spraying method to solve the technical problems of low yield and uncontrollable structure in traditional polymer microsphere preparation methods, and provides a solution for efficiently preparing polymer microspheres with a smooth and dense surface and a loose and porous internal structure;

[0042] 2. The preparation method of the present invention has a high yield and can prepare a large number of polymer microspheres in batches; it is simple and easy to implement, requiring no complicated equipment and steps; it is highly controllable, and the structure, size and morphology of the microspheres can be controlled by adjusting the preparation conditions and polymer formulation;

[0043] 3. This invention optimizes and screens the conditions involved in the preparation method, such as polymer molecular weight, temperature, injection rate, voltage, reactant ratio, and types of bioactive components. In addition, further in-depth research and improvement can optimize the preparation process to improve yield and microsphere quality, thereby meeting the needs of different application fields. Attached Figure Description

[0044] The embodiments of the present invention will now be described in detail with reference to the accompanying drawings, wherein:

[0045] Figure 1 This is a SEM image of the PCL microspheres prepared in Example 1 of the present invention;

[0046] Figure 2 This is a SEM image of the PLCL microspheres prepared in Example 2 of the present invention;

[0047] Figure 3 This is a microscopic observation image of the PLCL microspheres containing active components prepared in Example 3 of the present invention;

[0048] Figure 4 This demonstrates that the microsphere composite gel obtained in Example 9 of the present invention has good injectability;

[0049] Figure 5 This demonstrates that the microsphere composite gel obtained in Example 9 of the present invention has a good tissue filling effect.

[0050] Figure 6 A schematic diagram illustrating the effect of the microsphere composite gel obtained in Example 9 of the present invention on inducing collagen regeneration is shown. Detailed Implementation

[0051] The present invention will now be described in further detail with reference to specific embodiments, which will provide a better understanding of the invention. However, those skilled in the art should readily understand that the following embodiments are merely descriptive and do not imply that the invention is limited to these specific embodiments. Those skilled in the art should recognize that the present invention covers all improvements, alternatives, and equivalents that may be included within the scope of the claims.

[0052] Example 1: Preparation of PCL polymer microspheres without added active components

[0053] 1) Weigh a certain amount of 1g of PCL particles with a molecular weight of 35000 Da, add it to 10mL of dichloromethane, and stir magnetically for 2 hours to obtain a homogeneous precursor solution with a concentration of 10% (w / v).

[0054] 2) At room temperature of 25°C, take an appropriate amount of the precursor solution and put it into an injection syringe;

[0055] 3) Try to position the needle in the center above the receiver, keeping the tip of the needle 3 cm away from the surface of the receiving liquid;

[0056] 4) Turn on the high-voltage power supply and adjust the voltage to 3.0 kV;

[0057] 5) Turn on the injection device, set the injection speed to 2 mm / min, and continuously receive microspheres;

[0058] 6) After preparation, collect the precipitated particles, freeze-dry them, and obtain the microsphere product.

[0059] like Figure 1 The image shown is a SEM image of the surface morphology of the PCL microspheres prepared in this embodiment. Figure 1 It can be seen that the surface of the microspheres is smooth and dense, and after being broken, the internal structure is observed to be loose and honeycomb-like.

[0060] Example 2: Preparation of PLCL polymer microspheres without added active components

[0061] 1) Weigh a certain amount of 1g of PLCL particles with a molecular weight of 230000 Da, add it to 20mL of dichloromethane, and stir magnetically for 4 hours to obtain a homogeneous precursor solution with a concentration of 5% (w / v).

[0062] 2) Turn on the 42℃ water bath 2 hours in advance to preheat the receiving solution;

[0063] 3) At room temperature of 25°C, take an appropriate amount of the precursor solution and put it into an injection syringe;

[0064] 4) Try to position the needle in the center above the receiver, keeping the tip of the needle 3 cm away from the surface of the receiving liquid;

[0065] 5) Turn on the high-voltage power supply and adjust the voltage to 3.5 kV;

[0066] 6) Turn on the injection device, set the injection speed to 1 mm / min, and continuously receive microspheres;

[0067] 7) After preparation, the receiving liquid was heated for another 3 hours to accelerate the precipitation of dichloromethane and solidify the microspheres; then heating was stopped, the mixture was left to stand overnight, the precipitated particles were collected, and the microspheres were freeze-dried to obtain the microsphere product.

[0068] like Figure 2 The image shown is a SEM image of the surface morphology of the PLCL microspheres prepared in this embodiment. Figure 2 It can be seen that the surface of the microspheres is smooth and dense, and after being broken, the internal structure is observed to be loose and honeycomb-like.

[0069] Example 3: Preparation of polymer microspheres with added active components

[0070] 1) Weigh a certain amount of 1g of PLCL particles with a molecular weight of 230000 Da and 0.02g of 45S5 bioactive glass powder (BG), add them to 20mL of dichloromethane, and stir magnetically for 4 hours to obtain a homogeneous precursor solution; in the precursor solution, the mass concentration of PLCL particles is 0.05 g / ml, the mass concentration of BG is 0.001g / ml, and the mass ratio of BG to PLCL particles is 0.02:1;

[0071] 2) Turn on the 42℃ water bath 2 hours in advance to preheat the receiving solution;

[0072] 3) At room temperature of 25°C, take an appropriate amount of the precursor solution and put it into an injection syringe;

[0073] 4) Try to position the needle in the center above the receiver, keeping the tip of the needle 3 cm away from the surface of the receiving liquid;

[0074] 5) Turn on the high-voltage power supply and adjust the voltage to 3.5 kV;

[0075] 6) Turn on the injection device, set the injection speed to 1 mm / min, and continuously receive microspheres;

[0076] 7) After preparation, the receiving liquid was heated for another 3 hours to accelerate the precipitation of dichloromethane and solidify the microspheres; then heating was stopped, the mixture was left to stand overnight, the precipitated particles were collected, and the microspheres were freeze-dried to obtain the microsphere product.

[0077] like Figure 3 The microscopic image of the PLCL microspheres containing the active component prepared in this embodiment is obtained by... Figure 3 As can be seen, even with the addition of bioactive components, the microspheres still maintain a regular shape, with a smooth surface and internal pores.

[0078] Example 4: Study on Temperature

[0079] According to the preparation method of Example 2, the temperature conditions in step 2) were changed. The specific temperatures and the results are listed in Table 1 below.

[0080] Table 1

[0081]

[0082] As can be seen from the above, at a slightly higher temperature (42℃), the microspheres are more likely to remain dispersed after being received and are easier to collect.

[0083] Example 5: Study on injection rate

[0084] According to the preparation method of Example 2, the injection rate in step 6) was changed. The specific injection rates and the results are listed in Table 2 below.

[0085] Table 2

[0086]

[0087] As can be seen from the above, microspheres are easy to form under relatively low injection speeds (0.5~1.0 mm / min).

[0088] Example 6: Study of Voltage

[0089] According to the preparation method of Example 2, the voltage in step 5) was changed. The specific voltage and the results are listed in Table 3 below.

[0090] Table 3

[0091]

[0092] As can be seen from the above, microspheres are easy to form under slightly higher voltage conditions (3.5~4.2 kV).

[0093] Example 7: Study on the proportion of active components

[0094] According to the preparation method of Example 3, the amount of active component in step 1) was changed. The specific mass ratio and the results are listed in Table 4 below.

[0095] Table 4

[0096]

[0097] As can be seen from the above, the microspheres exhibit the best forming state when the mass ratio of the active component to the polymer material is 0.02~0.05:1.

[0098] Example 8: Study on the molecular weight of the polymer

[0099] Following the preparation method of Example 2, the proportion of reactants in step 1 was changed. The specific proportions of reactants and the results are listed in Table 5 below.

[0100] Table 5

[0101]

[0102] As can be seen from the above, microspheres are easy to form under conditions of lower molecular weight (35~230 kDa); microspheres are not easy to form when using polymers with larger molecular weight (such as 70 kDa).

[0103] Example 9: Application of polymer microspheres in tissue fillers

[0104] The PCL polymer microspheres from Example 1 were used as tissue fillers, with the following specific applications:

[0105] 1) Take 2.0g of PCL microspheres from Example 1 and mix them with 0.5g of sodium carboxymethyl cellulose, 0.1mL of glycerol and 9.9mL of phosphate buffer to prepare approximately 10mL of composite gel. Figure 4 );

[0106] 2) After injecting the compound gel under the skin on the rabbit's back, a noticeable bulge was observed on the skin of the rabbit's back after the injection. The bulge was still obvious at the 1- and 2-week follow-up examinations. After removing the skin, the microspheres could still be seen at the injection site. Figure 5 ).

[0107] Depend on Figure 6 It is known that PLC composite gel can effectively promote collagen regeneration after being injected into the body.

[0108] It is evident that the PCL and PLC microspheres prepared in the embodiments of the present invention both exhibit excellent tissue filling effects.

[0109] While various aspects and embodiments of the invention have been disclosed herein, other aspects and embodiments will be apparent to those skilled in the art. The aspects and embodiments disclosed herein are for illustrative purposes only and not for limiting purposes. The scope and spirit of the invention are determined solely by the appended claims.

Claims

1. A method for preparing polymer microspheres, comprising the following steps: (1) Dissolve the polymer material and optional active components in a solvent to form a precursor solution; Preferably, the polymer material is selected from one or more of polylactic acid, polycaprolactone, polylactic acid-caprolactone copolymer, block copolymer of polylactic acid and polyethylene glycol, and polylactic acid-glycolic acid copolymer; the active component is a biologically active substance. (2) The precursor solution is injected into the receiving liquid by wet electrostatic spraying to form polymer microspheres. The polymer microspheres have a smooth and dense surface and a loose and porous internal structure.

2. The preparation method according to claim 1, characterized in that, The solvent is an organic solvent, preferably selected from one or more of hexafluoroisopropanol, chloroform, dichloromethane, toluene, tetrahydrofuran, and ethyl acetate. Preferably, the molecular weight of the polymer material is 1,000 to 500,000 Da, and more preferably 35,000 to 230,000 Da.

3. The preparation method according to claim 1 or 2, characterized in that, The concentration of the polymer material in the precursor solution is 0.1~30% w / v; Preferably, the concentration of the active component in the precursor solution is 0.1-10% w / v, more preferably 0.1-5% w / v; Preferably, the mass ratio of the active component to the polymer material in the precursor solution is 0.01~0.2:1, more preferably 0.02~0.05:

1.

4. The preparation method according to any one of claims 1 to 3, characterized in that, The receiving liquid is an aqueous solution of ethanol with an ethanol concentration greater than 75 wt%, preferably an aqueous solution of ethanol with an ethanol concentration of 80 wt%.

5. The preparation method according to any one of claims 1 to 4, characterized in that, In step (2), the injection is performed at a rate of 0.1~10 mm / min, preferably 0.5~5 mm / min, more preferably 0.5~2 mm / min, and most preferably 0.5~1.0 mm / min; Preferably, the wet electrostatic spraying is performed at a voltage of 2.0~15.0 kV, more preferably 2~10 kV, more preferably 3~5 kV, and most preferably 3.5~4.2 kV. Preferably, the wet electrostatic spraying is carried out at a temperature of 15°C to 50°C, more preferably at 25°C to 45°C, even more preferably at 37°C to 45°C, and most preferably at 40°C to 43°C.

6. The preparation method according to any one of claims 1 to 5, characterized in that, The active component is selected from one or more of nanoscale bioactive inorganic materials, cell growth factors, drugs, and nutrients; Preferably, the nanoscale bioactive inorganic material is a bioactive glass and / or a silicate bioactive ceramic; Preferably, the bioactive glass is 45S5 bioactive glass; Preferably, the silicate bioactive ceramic is CaSiO3, FeSiO4, or CaCuSi4O. 10 ; Preferably, the cell growth factor is VEGF or bFGF; Preferably, the drug is rapamycin, sirolimus, or paclitaxel; Preferably, the nutrient is vitamin C, amino acids, or collagen.

7. The polymer microspheres prepared by the method according to any one of claims 1 to 6, wherein the diameter of the polymer microspheres is preferably 0.1 to 200 mm. More preferably 20-50 .

8. Use of the polymer microspheres prepared by the method according to any one of claims 1 to 6 or the polymer microspheres according to claim 7 in the preparation of biomedical materials, especially as tissue fillers.

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