Polylactic acid microspheres with controllable degradation performance as well as preparation method and application of polylactic acid microspheres

Abstract

The invention relates to the technical field of biodegradable materials, in particular to a polylactic acid microsphere with controllable degradation performance and a preparation method and application thereof. Comprising the following steps: S1, dissolving polylactic acid with the molecular weight of 50-200kDa in an organic solvent to obtain an oil phase, and dissolving a medicine in the solvent to obtain a water phase; s2, adding the water phase into the oil phase to form a W / O primary emulsion; s3, adding the W / O primary emulsion into a solution containing a surfactant with the mass volume concentration of 0.5%-2%, and stirring to form a W / O / W system; s4, performing solvent volatilization on the W / O / W system; and S5, collecting the microspheres, and drying. The particle size of the polylactic acid microspheres can be controlled, the high-quality polylactic acid microspheres with controllable degradation performance and drug release performance are prepared, and different biomedical application requirements are met.

Description

Technical Field

[0001] The present invention relates to the technical field of biodegradable materials, and specifically to a poly(lactic acid) microsphere with controllable degradation performance, its preparation method and application. Background Art

[0002] Poly(lactic acid) (PLA) is a biodegradable material widely used in the fields of biomedicine, food packaging and tissue engineering. Due to its good biocompatibility and controllable degradation characteristics, PLA microspheres are widely used in drug delivery systems, cell carriers and tissue regeneration. However, existing preparation methods of PLA microspheres (such as the emulsion solvent evaporation method and spray drying method) have certain limitations in terms of microsphere size, morphology control, drug loading capacity and degradation performance, and it is difficult to meet the diverse needs of microspheres in different application fields.

[0003] Therefore, the development of an innovative preparation method to achieve controllable degradation, precise morphology regulation and drug release characteristics of PLA microspheres can provide a more effective solution for biomedical and material applications. Summary of the Invention

[0004] In order to solve the defects existing in the prior art, the present invention provides a poly(lactic acid) microsphere with controllable degradation performance, its preparation method and application. Under the preparation process of the present invention, it is only necessary to adjust relevant process parameters such as the molecular weight of poly(lactic acid) and the proportion of dopants to control the particle size of the poly(lactic acid) microspheres, and prepare high-quality poly(lactic acid) microspheres with controllable degradation performance and drug release performance to meet the requirements of different biomedical applications.

[0005] To achieve the above object, the present invention adopts the following technical solutions:

[0006] In the first aspect, the present invention provides a preparation method of a poly(lactic acid) microsphere with controllable degradation performance, comprising the following steps:

[0007] S1. Dissolve poly(lactic acid) with a molecular weight of 50 - 200 kDa in an organic solvent to obtain an oil phase, and dissolve a drug in a solvent to obtain an aqueous phase;

[0008] S2. Add the aqueous phase to the oil phase to form a W / O primary emulsion;

[0009] S3. Add the W / O primary emulsion to a solution containing a surfactant with a mass - volume concentration of 0.5% - 2%, and stir to form a W / O / W system;

[0010] S4. Carry out solvent evaporation on the W / O / W system;

[0011] S5. Collect the microspheres and dry them to obtain the product.

[0012] In some embodiments of the present invention, the molecular weight of the polylactic acid is any one of 50 kDa, 100 kDa, 150 kDa, 200 kDa or a value between any two of them.

[0013] Preferably, in S1, a dopant is further added to the oil phase, and the dopant is selected from any one or more of hydroxyapatite, chitosan, nano-hydroxyapatite, silica nanoparticles, calcium carbonate, gelatin, and chitosan.

[0014] Preferably, the mass concentration of the dopant is 10-40%. Exemplarily, the mass concentration of the dopant is any one of 10%, 20%, 30%, 40% or a value between any two of them.

[0015] Preferably, in S1, the mass-volume concentration of the polylactic acid is 6%.

[0016] Preferably, in S1, the concentration of the drug in the aqueous phase is 1 mg / mL to 10 mg / mL. Exemplarily, the concentration of the drug in the aqueous phase is any one of 1 mg / mL, 5 mg / mL, 10 mg / mL or a value between any two of them.

[0017] Preferably, in S1, the organic solvent is dichloromethane (DCM), ethyl acetate (EA), or chloroform.

[0018] Preferably, in S1, the solvent of the aqueous phase is water or a buffer solution, and the buffer solution can be PBS.

[0019] Preferably, the stirring rate in the S2 mixing process is 6000-10000 rpm. Exemplarily, the stirring rate is any one of 6000 rpm, 8000 rpm, 10000 rpm or a value between any two of them.

[0020] Preferably, in S3, the surfactant is PVA (polyvinyl alcohol) or Tween80.

[0021] In some embodiments of the present invention, the mass-volume concentration of the surfactant in S3 is selected from any one of 0.5%, 1%, 2% or a value between any two of them.

[0022] Preferably, the stirring rate in S3 is 3000-5000 rpm. Exemplarily, the stirring rate in S3 is any one of 3000 rpm, 4000 rpm, 5000 rpm or a value between any two of them.

[0023] Preferably, the stirring in S3 lasts for 3-10 minutes.

[0024] Preferably, the process of collecting microspheres in S4 is to collect the microspheres from the suspension by centrifugation or filtration.

[0025] Preferably, the centrifugal force for centrifugation is 5000 - 8000 rpm. Exemplarily, the centrifugal force is any one of 5000 rpm, 7000 rpm, 8000 rpm or a value between the two.

[0026] Preferably, the drying in S4 is freeze-drying or spray-drying.

[0027] Preferably, the freezing temperature is -20°C to -80°C.

[0028] In a second aspect, the present invention provides a polylactic acid microsphere prepared by the above preparation method.

[0029] In a third aspect, the present invention provides an application of the polylactic acid microsphere, and the application includes a long-acting drug release system or the field of rapid drug release.

[0030] Preferably, the application includes fields such as bone tissue engineering, bone repair, tissue scaffolds, cell culture, wound dressings, antibacterial coatings, etc.

[0031] Preferably, the molecular weight of the polylactic acid is 150 - 200 kDa and is applied to a long-acting drug release system.

[0032] Preferably, the dopant is chitosan and is applied to the field of rapid drug release.

[0033] Preferably, the dopant is hydroxyapatite or nano-hydroxyapatite and is applied to a long-acting drug release system.

[0034] The beneficial effects of the present invention are as follows:

[0035] The present invention realizes efficient drug encapsulation through a double-emulsion method of first forming a W / O primary emulsion and then forming a W / O / W system, avoiding the premature release of drugs. By adjusting the PLA molecular weight and the concentration of the surfactant, the microsphere particle size is further regulated, and the drug release rate is precisely controlled, producing high-quality PLA microspheres with controllable degradation performance and drug release performance to meet different biomedical application requirements.

[0036] When preparing the polylactic acid microspheres, the present invention adds a dopant, which is mainly used to improve the mechanical properties, toughness and degradation rate of PLA, ensuring reliability in drug release and implantation applications. These materials not only regulate the degradation rate but also increase the biological activity, can further regulate the degradation rate of the microspheres, and enhance their interaction with cells, and are particularly suitable for scaffolds and bone repair in tissue engineering, etc. Description of the Drawings

[0037] Figure 1 SEM image of PLA microspheres without doping. Detailed implementation manners

[0038] To enable those skilled in the art to better understand the technical solutions of the invention, the following further details the present invention in conjunction with specific implementation manners.

[0039] Example 1

[0040] This example provides a preparation method for a series of polylactic acid microspheres (PLA) doped with hydroxyapatite or chitosan. By adjusting the molecular weight of PLA, the types and concentrations of dopants, and key process parameters, the effects of these factors on the particle size, drug loading efficiency, and degradation performance of the microspheres are explored to ensure that the microspheres meet specific requirements in different application scenarios.

[0041] The experimental steps are as follows:

[0042] 1. Matrix preparation

[0043] (1) Preparation of the oil phase: Dissolve PLA with different molecular weights in dichloromethane (DCM) to form a 6% (w / v) PLA solution; add the dopant hydroxyapatite (HAP) to the PLA solution.

[0044] (3) Preparation of the aqueous phase: Dissolve the drug (amoxicillin is used in this example) in deionized water.

[0045] 2. Preparation of the primary emulsion:

[0046] Slowly add the aqueous phase to the oil phase at different stirring rates to form a W / O primary emulsion.

[0047] 3. Secondary emulsification:

[0048] Slowly drop the prepared primary emulsion into the polyvinyl alcohol (PVA) solution and form a W / O / W system by high-speed stirring for 3 - 10 minutes.

[0049] 4. Solvent evaporation:

[0050] Continue stirring at room temperature for 24 - 36 hours to completely evaporate the organic solvent.

[0051] 5. Collection and washing of microspheres

[0052] Collect the microspheres from the suspension by centrifugation for 10 minutes or filtration.

[0053] Wash with deionized water or PBS multiple times to remove residual emulsifiers and unloaded drugs.

[0054] 6. Freeze-drying

[0055] The microspheres were frozen at -20 °C and then freeze-dried to obtain polylactic acid microspheres containing drugs.

[0056] Degradation test method:

[0057] 1) The prepared PLA / nHAP microspheres were placed in simulated body fluid (SBF, pH 7.4) and cultured in a constant temperature environment at 37 °C.

[0058] 2) Samples were taken every 7 days, and the electronic balance was used to record the mass change of the microspheres, and a degradation curve was plotted.

[0059] 3) Measure the time of 90% mass loss and analyze the influence of different parameters on the degradation rate.

[0060] Result analysis:

[0061] 1. Influence of PLA molecular weight on the particle size, drug loading and degradation of polylactic acid microspheres

[0062] Table 1

[0063]

[0064] As can be seen from Table 1, under the same preparation conditions, the larger the molecular weight of PLA, the larger the particle size of the prepared microsphere product, and the slower the degradation rate. When the molecular weight of PLA is 150 - 200 kDa, the prepared microspheres are more suitable for long-acting drug delivery systems.

[0065] 2. Influence of dopants on particle size and degradation performance

[0066] It was determined that the molecular weight of PLA was 100 kDa, the drug concentration in the aqueous phase was 5 mg / mL, the stirring rate during the preparation of the primary emulsion in step 2 was 8000 rpm, the concentration of PVA during the secondary emulsification in step 3 was 1%, the stirring rate during the secondary emulsification in step 3 was 4000 rpm, and the centrifugal force in step 5 was 7000 rpm. The influence of a single variable of the dopant on the particle size and degradation performance was investigated.

[0067] Table 2

[0068] Type of dopant Doping ratio (%) Particle size (μm) Drug loading efficiency (%) Time for 80% mass loss Undoped 0 0.8±0.2 75±3 6 weeks Hydroxyapatite 10 1.0±0.2 78±2 8 weeks Hydroxyapatite 20 1.2±0.2 80±2 10 weeks Chitosan 10 1.2±0.2 77±2 6 weeks Chitosan 20 1.4±0.2 79±2 4 weeks

[0069] As can be seen from Table 2, compared with the product obtained without dopants, the microsphere product doped with hydroxyapatite has an increased particle size and a delayed degradation rate, which is suitable for applications in the field of bone repair; while the microsphere product doped with chitosan has an accelerated degradation rate and is suitable for the field of rapid drug release.

[0070] Among them, under these preparation conditions, the SEM image of the product obtained without dopants can be seen in Figure 1 , and it can be seen from Figure 1 that the microsphere morphology is regular and the surface is relatively smooth.

[0071] Example 2

[0072] This example provides a method for preparing doped nano-hydroxyapatite poly(lactic acid) microspheres (PLA). By adjusting the PLA molecular weight, nano-hydroxyapatite (nHAP) doping ratio, and process parameters, the effects of these factors on the degradation performance, particle size, drug loading efficiency, and mechanical properties of the microspheres are explored to provide a controllable long-acting scaffold material for bone tissue regeneration.

[0073] The experimental steps are as follows:

[0074] 1. Matrix preparation

[0075] (1) Oil phase preparation: Dissolve PLA with different molecular weights in dichloromethane (DCM) to form a 6% (w / v) PLA solution; add the dopant nano-hydroxyapatite (nHAP) to the PLA solution and disperse it with an ultrasonic device for 10 minutes to ensure uniform dispersion.

[0076] (2) Aqueous phase preparation: Dissolve the drug (amoxicillin is used in this example) in deionized water.

[0077] 2. Primary emulsion preparation:

[0078] Slowly add the aqueous phase to the oil phase at different stirring rates and stir to form a W / O primary emulsion.

[0079] 3. Secondary emulsification:

[0080] Slowly drop the prepared primary emulsion into a polyvinyl alcohol (PVA) solution and form a W / O / W system by high-speed stirring for 3 - 10 minutes.

[0081] 4. Solvent evaporation:

[0082] Evaporate the organic solvent by reduced pressure evaporation at room temperature.

[0083] 5. Collection and washing of microspheres

[0084] Collect the microspheres from the suspension by centrifugation for 10 minutes or filtration.

[0085] Wash with deionized water or PBS multiple times to remove residual emulsifier and unloaded drug.

[0086] 6. Freeze-drying

[0087] Freeze the microspheres at -20 °C and then perform freeze-drying to obtain poly(lactic acid) microspheres containing the drug.

[0088] Degradation test method:

[0089] 1) Place the prepared PLA / nHAP microspheres in simulated body fluid (SBF, pH 7.4) and culture them in a constant temperature environment at 37°C.

[0090] 2) Sample every 7 days, record the mass change of the microspheres using an electronic balance, and plot the degradation curve.

[0091] 3) Measure the time of 90% mass loss and analyze the influence of different parameters on the degradation rate.

[0092] Result analysis:

[0093] 1. Influence of PLA molecular weight on the degradation rate of polylactic acid microspheres

[0094] Table 3

[0095]

[0096]

[0097] As can be seen from Table 3, under the same preparation conditions, the larger the molecular weight of PLA, the slower the degradation rate of the prepared microsphere product. When the molecular weight of PLA is 150 - 200 kDa, the prepared microspheres are more suitable for long-acting drug delivery systems, such as long-acting bone tissue scaffolds.

[0098] 2. Influence of the doping ratio on the particle size and degradation performance

[0099] Determine that the molecular weight of PLA is 100 kDa, the drug concentration in the aqueous phase is 1 mg / mL, the stirring rate during the preparation of the primary emulsion in step 2 is 8000 rpm, the concentration of PVA during the secondary emulsification in step 3 is 1%, the stirring rate during the secondary emulsification in step 3 is 4000 rpm, and the centrifugal force in step 5 is 7000 rpm. Investigate the influence of the single variable of the doping ratio on the particle size and degradation performance.

[0100] Table 4

[0101] nHAP ratio (w / w%) Particle size (μm) Time for 50% mass loss Time for 80% mass loss 0 0.5～2.0 4 weeks 8 weeks 10 0.8～2.5 6 weeks 12 weeks 20 1.0～3.0 8 weeks 14 weeks 30 1.2～3.5 10 weeks N / A 40 1.5～4.0 12 weeks N / A

[0102] As can be seen from Table 4, as the doping ratio of nHAP increases, the particle size of the microspheres increases and the degradation rate significantly slows down, which is suitable for bone repair materials that require long-term support.

[0103] 3. Influence of PVA concentration on the particle size

[0104] Determine that the molecular weight of PLA is 100 kDa, the nHAP content is 10%, the drug concentration in the aqueous phase is 5 mg / mL, the stirring rate during the preparation of the primary emulsion in step 2 is 8000 rpm, the stirring rate during the secondary emulsification in step 3 is 4000 rpm, and the centrifugal force in step 5 is 7000 rpm. Investigate the influence of PVA concentration on the particle size.

[0105] Table 5

[0106] Concentration of emulsifier (PVA) (w / v%) Particle size (μm) 0.5 0.5～1.0 1.0 0.3～0.8 2.0 0.1～0.5

[0107] As can be seen from Table 5, the microspheres generated at a high emulsifier concentration have a smaller particle size, which is beneficial to improving the drug release efficiency.

[0108] 4. Mechanical Property Test

[0109] It was determined that the molecular weight of PLA (kDa) was 100, the drug concentration in the aqueous phase was 5 mg / mL, the stirring rate during the preparation of the primary emulsion in Step 2 was 8000 rpm, the concentration of PVA during the secondary emulsification in Step 3 was 1%, the stirring rate during the secondary emulsification in Step 3 was 4000 rpm, and the centrifugal force in Step 5 was 7000 rpm. The influence of a single variable of the dopant on the compressive strength was investigated.

[0110] Table 6

[0111] nHAP ratio (w / w%) Compressive strength (MPa) 0 1.5±0.2 10 2.5±0.3 20 3.5±0.2 30 4.0±0.1 40 4.5±0.1

[0112] As can be seen from Table 6, the addition of nHAP improves the compressive strength of the microspheres, making them more suitable for bone tissue repair.

[0113] As can be seen above, by adjusting the molecular weight of PLA and the proportion of nHAP, the degradation time can be extended from 8 weeks to more than 16 weeks. By regulating the concentration of the emulsifier, the particle size can be flexibly adjusted within the range of 100 nm to 1 μm. The addition of nHAP increases the compressive strength to 4.5 MPa, meeting the requirements of bone repair materials. The PLA 150 kDa + 20% nHAP microspheres are degraded within 12 weeks, and at the same time have excellent mechanical properties and drug release control. Through the optimization of multi-dimensional parameters, the PLA / nHAP composite microspheres exhibit good biocompatibility, mechanical properties and degradation control. Such microspheres are suitable for long-term bone repair scaffolds and can meet the requirements of different tissue engineering applications by adjusting the molecular weight of PLA and the proportion of nHAP.

[0114] The above is only the preferred embodiment of the present invention. It should be noted that the above preferred embodiment should not be regarded as a limitation of the present invention, and the protection scope of the present invention should be subject to the scope defined by the claims. For those of ordinary skill in the art, without departing from the spirit and scope of the present invention, several improvements and modifications can also be made, and these improvements and modifications should also be regarded as the protection scope of the present invention.

Claims

1. A method for preparing polylactic acid microspheres with controllable degradation performance, characterized in that, It includes the following steps: S1. Dissolve polylactic acid with a molecular weight of 50 - 200 kDa in an organic solvent to obtain an oil phase, and dissolve the drug in a solvent to obtain an aqueous phase; S2. Add the aqueous phase to the oil phase to form a W / O primary emulsion; S3. Add the W / O primary emulsion to a solution containing a surfactant with a mass - volume concentration of 0.5% - 2%, and stir to form a W / O / W system; S4. Volatilize the solvent of the W / O / W system; S5. Collect the microspheres and dry them to obtain the product.

2. The preparation method according to claim 1, characterized in that, In S1, a dopant is further added to the oil phase, and the dopant is selected from any one or more of hydroxyapatite, chitosan, nano - hydroxyapatite, silicon dioxide nanoparticles, calcium carbonate, and gelatin.

3. The preparation method according to claim 2, characterized in that, The mass concentration of the dopant is 10% - 40%.

4. According to the preparation method described in any one of claims 1 to 3, it is characterized in that In S1, the mass - volume concentration of polylactic acid is 6%.

5. According to the preparation method described in any one of claims 1 to 3, characterized in that, In S1, the concentration of the drug in the aqueous phase is 1 mg / mL - 10 mg / mL.

6. According to the preparation method described in any one of claims 1 to 3, it is characterized in that The stirring rate during the mixing process of S2 is 6000 - 10000 rpm.

7. According to the preparation method described in any one of claims 1 to 3, it is characterized in that In S3, the surfactant is polyvinyl alcohol or Tween80.

8. A polylactic acid microsphere prepared by the preparation method according to any one of claims 1 - 7.

9. An application of poly(lactic acid) microspheres, characterized in that, The polylactic acid microsphere is the polylactic acid microsphere according to claim 8, and the applications include long - acting drug release systems or rapid drug release fields.

10. The application according to claim 9, wherein The applications include fields such as bone tissue engineering, bone repair, tissue scaffolds, cell culture, wound dressings, antibacterial coatings, etc.

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