Magnesium metal / PLGA-TCP composite porous microsphere bone repair material and preparation method thereof

Abstract

The invention relates to the field of oral alveolar bone repair materials, provides a magnesium metal / PLGA-TCP composite porous microsphere bone repair material and a preparation method thereof, and aims to solve the problems that in the prior art, magnesium ion release is uncontrollable, corrosion is accelerated due to the fact that PLGA is degraded to produce acid, and a microsphere hole structure is single. According to the technical scheme, the preparation method comprises the following steps: dispersing metal magnesium microspheres and beta-tricalcium phosphate in dichloromethane, then adding PLGA and ethyl cellulose, stirring and dissolving to form an oil phase solution, taking a polyvinyl alcohol solution as an outer water phase, dissolving gelatin in part of the polyvinyl alcohol solution as an inner water phase, dropwise adding the inner water phase into the oil phase, and carrying out dual-power ultrasonic emulsification to form a primary emulsion; magnesium metal / PLGA-TCP composite microspheres are prepared through a microfluidic device, the microspheres are solidified and then subjected to water bath to remove gelatin, and then freeze drying is conducted to obtain the multistage through hole microspheres which are used for preparing an oral cavity alveolar bone repair material.

Description

Technical Field

[0001] This invention relates to the field of alveolar bone repair materials, and particularly to a magnesium / PLGA-TCP composite porous microsphere bone repair material and its preparation method. Background Technology

[0002] Bone repair materials are a class of functional biomaterials used to fill, repair, or reconstruct bone defects. In the field of oral medicine, ideal alveolar bone repair materials need to possess characteristics such as good biocompatibility, biodegradability, osteogenic induction, and injectability.

[0003] Currently, biodegradable polyester materials, represented by polylactic-co-glycolic acid copolymer (PLGA), are widely used due to their adjustable degradation cycle and good processing performance. To enhance their bioactivity, bioceramic components such as tricalcium phosphate (TCP) are often introduced to neutralize the acidic products generated during PLGA degradation and release calcium and phosphorus ions. Furthermore, magnesium ions, as an important osteogenic regulator, are introduced primarily through methods such as directly blending magnesium oxide (MgO) and magnesium carbonate (MgCO3) powders into the PLGA matrix, or surface coating of metallic magnesium. Preparation processes often employ traditional emulsification-solvent evaporation methods and spray drying methods.

[0004] However, existing technologies still have significant drawbacks:

[0005] Firstly, the magnesium source introduced by the blending method is not matched with the degradation rate of PLGA, resulting in uncontrollable magnesium ion release behavior. The initial burst release is significant, while the later release is insufficient, which cannot meet the needs of the bone regeneration cycle.

[0006] Secondly, the acidic microenvironment generated by PLGA degradation will accelerate the corrosion of metallic magnesium, not only causing premature release of magnesium ions, but also potentially triggering sudden changes in local pH and hydrogen accumulation, leading to inflammatory reactions.

[0007] Third, microspheres prepared by traditional methods have a uniform pore size distribution and lack a multi-level interconnected pore structure, making it difficult to simultaneously support early cell adhesion and later blood vessel ingrowth, and their particle size uniformity is poor. These defects severely restrict the effectiveness of the materials in clinical applications.

[0008] Therefore, developing a composite microsphere material that can achieve controlled release of magnesium ions, maintain microenvironmental stability, and has a multi-level porous structure that promotes osteovascularization has become a key problem that urgently needs to be solved in this field. Summary of the Invention

[0009] This invention provides a magnesium / PLGA-TCP composite porous microsphere bone repair material and its preparation method, in order to solve the above-mentioned technical problems.

[0010] To achieve the above-mentioned objectives, the technical solution adopted by this invention is as follows:

[0011] In a first aspect, a method for preparing a magnesium / PLGA-TCP composite porous microsphere bone repair material is characterized by...

[0012] Step 1: Add magnesium microspheres and β-tricalcium phosphate to dichloromethane and disperse by ultrasonication; then add PLGA and EC and stir magnetically for 24 hours to obtain the oil phase solution.

[0013] Step 2: Add polyvinyl alcohol (PVA) to deionized water, heat and stir to dissolve, then filter through a 0.22μm filter to obtain the external aqueous phase;

[0014] Step 3: Dissolve gelatin in a portion of the PVA solution and heat in a water bath to dissolve, obtaining the inner aqueous phase; specifically, add gelatin to the PVA solution and dissolve it in a 40°C water bath to obtain the inner aqueous phase.

[0015] Step 4: Add the aqueous phase to the oil phase solution and mix. Divide the mixture into two parts and emulsify and disperse them separately using a cell ultrasonic pulverizer at different power levels. Then mix the two emulsions evenly under magnetic stirring to form a primary emulsion.

[0016] Step 5: Using the primary emulsion as the oil phase and the external aqueous phase as the aqueous phase, microspheres are formed using a coaxial needle of a microfluidic device and collected in a PVA solution for static solidification.

[0017] Step 6: After washing the cured microspheres with water, remove the gelatin in a water bath, and then freeze-dry to obtain porous microspheres.

[0018] Furthermore, in step 1, the ratio of PLGA, magnesium microspheres, β-TCP, and EC is 7:1:2:0.1, and the concentration of the polymer solution as the oil phase is 10 wt%.

[0019] Furthermore, in step 2, the PVA solution concentration is 2 w / v.

[0020] Furthermore, in step 4, the amount of the internal aqueous phase added accounts for 10-20% of the oil phase, and dispersion is carried out under ice bath conditions with different ultrasonic powers of 80W and 160W, respectively, for a working time of 15 minutes.

[0021] Furthermore, in step 3, the amount of gelatin added to the internal aqueous phase is 10 w / v.

[0022] Furthermore, in step 5, the pressure value of the oil phase tube is 400 mbar, the pressure value of the water phase tube is 60 mbar, and the specification of the coaxial needle is 19G / 32G.

[0023] Further, in specific step 6, the microspheres after chemical treatment are washed with deionized water and then dispersed again in deionized water. They are placed in a 40°C water bath for 2 hours to remove gelatin and form porous microspheres. They are then centrifuged and washed three times with deionized water, frozen at -80°C overnight, and then freeze-dried in a freeze dryer for 48 hours.

[0024] Secondly, the magnesium / PLGA-TCP composite porous microsphere bone repair material is characterized by...

[0025] Includes PLGA, magnesium microspheres, β-TCP, and EC;

[0026] The PLGA contains lactic acid (LA) to glycolic acid (GA) monomers in a ratio of (70:30) to (80:20), with a molecular weight of 30-50 kDa; the magnesium microspheres have a particle size of 20-50 μm.

[0027] Thirdly, the application of magnesium / PLGA-TCP composite porous microsphere bone repair material in the preparation of oral alveolar bone repair materials.

[0028] The beneficial effects of this invention are as follows:

[0029] 1. It achieves controllable and linear release of magnesium ions, adapting to the bone tissue regeneration cycle.

[0030] This invention utilizes a PLGA-TCP composite layer to encapsulate magnesium microspheres, effectively preventing direct contact between magnesium and body fluids and avoiding problems such as initial burst release and insufficient release in the later stages. The TCP component continuously neutralizes the acidic products generated by PLGA degradation, maintaining a stable local microenvironment pH, thereby regulating the magnesium degradation rate. This ensures that the magnesium release curve closely matches the 21–28-day cycle required for bone regeneration, with a cumulative release of over 80% in 28 days and a burst release rate of less than 8%, significantly superior to existing blend systems.

[0031] 2. High-porosity microspheres with multi-level interconnected pore structures were constructed, which simultaneously support cell adhesion and blood vessel ingrowth.

[0032] By employing a "gradient pore formation" strategy, which utilizes gelatin as a pore-forming agent and combines it with treatment at different ultrasonic powers (80W and 160W), interconnected hierarchical pores of varying sizes are formed within the microspheres. This structure not only provides a porosity of over 85%, meeting the dual requirements of early cell adhesion (>20μm pore size) and later blood vessel ingrowth (>100μm interconnected pores), but also overcomes the limitations of traditional microspheres with a single pore size, significantly improving osteogenic and angiogenic properties.

[0033] 3. Through material composites and process innovation, the vicious cycle between PLGA degradation and acid production and magnesium corrosion has been effectively solved.

[0034] This invention ingeniously introduces β-TCP into a PLGA matrix, utilizing its alkaline degradation products to neutralize the acidic substances generated by PLGA hydrolysis. This avoids accelerated corrosion of magnesium microspheres due to sudden local pH drops and also prevents inflammatory reactions caused by sudden hydrogen release. Simultaneously, the addition of EC improves oil phase stability, slows down the sedimentation rate of magnesium microspheres and TCP, and maintains the uniformity of magnesium microspheres and TCP within the microspheres, thus achieving a beneficial balance between degradation and release. Attached Figure Description

[0035] Figure 1 This is a flowchart of the application;

[0036] Figure 2 Image of Mg / PLGA-TCP porous microspheres;

[0037] Figure 3 From left to right, these are electron micrographs of pure PLGA microspheres, PLGA-TCP microspheres, and Mg / PLGA-TCP microspheres. Detailed Implementation

[0038] To make the content of this invention easier to understand, the technical solutions in the embodiments of this invention will be clearly and completely described below with reference to the accompanying drawings.

[0039] like Figures 1 to 3 As shown, the method for preparing a magnesium / PLGA-TCP composite porous microsphere bone repair material is characterized by,

[0040] Step 1: Preparation of oil phase solution: Add magnesium microspheres and β-tricalcium phosphate (β-TCP) to dichloromethane and disperse by ultrasonication (40Hz, 30min); then add PLGA and EC and stir magnetically for 24h to obtain the oil phase solution.

[0041] The purpose of this step is to form a homogeneous oil-phase dispersion system. Magnesium microspheres serve as a magnesium ion source, β-TCP is used to neutralize the acidic products generated from PLGA degradation, EC acts as a suspension stabilizer to delay the sedimentation of the magnesium microspheres and β-TCP, and PLGA serves as the microsphere matrix. Ultrasonic dispersion ensures that the magnesium microspheres and β-TCP are uniformly distributed in the organic solvent, while magnetic stirring ensures that the PLGA and EC are fully dissolved, forming a stable oil-phase solution, laying the foundation for subsequent emulsion preparation.

[0042] Step 2, Preparation of external aqueous phase: Polyvinyl alcohol (PVA) is added to deionized water, heated and stirred to dissolve, and then filtered through a 0.22μm filter to obtain the external aqueous phase; specifically, polyvinyl alcohol (PVA) is added to deionized water, magnetically stirred at 80℃ for 4h, and after the solution cools naturally, it is filtered through a 0.22μm filter to obtain the PVA solution as the external aqueous phase.

[0043] Step 3: Preparation of the inner aqueous phase: Dissolve gelatin in a portion of the PVA solution and heat in a water bath to obtain the inner aqueous phase. Specifically, add gelatin to the PVA solution and dissolve it in a 40°C water bath to obtain the inner aqueous phase.

[0044] Gelatin in the aqueous phase acts as a pore-forming agent; after dissolving in the aqueous phase, it forms droplets in the oil phase. The porous structure is subsequently formed by removing the gelatin. The addition of PVA helps stabilize the droplets in the aqueous phase. Water bath heating ensures complete dissolution of the gelatin, forming a homogeneous aqueous phase, which provides the necessary conditions for subsequent primary emulsion preparation.

[0045] Step 4: Preparation of the primary emulsion: The aqueous phase is added dropwise to the oil phase solution and mixed. The mixture is divided into two portions, and each portion is emulsified and dispersed using a cell ultrasonic disruptor at different power levels. The two emulsions are then mixed evenly under magnetic stirring to form the primary emulsion. Specifically, the amount of aqueous phase added is 10-20% of the oil phase (V / V%). The amount of aqueous phase added determines the porosity of the microspheres, and the ultrasonic power determines the droplet size formed by the aqueous phase in the oil phase, thereby controlling the microsphere pore size. The ultrasonic powers of the two emulsions are 80W and 160W, respectively, and the working time for each is 15 minutes (5 seconds on, 5 seconds off).

[0046] Treatment with different ultrasonic powers (80W and 160W) can form internal aqueous phase droplets of different sizes in the oil phase, thereby creating a hierarchical pore structure in the final microspheres. High power forms small pores, low power forms large pores, and mixing achieves a through-hole hierarchical pore structure.

[0047] Step 5: Microfluidic preparation of microspheres: Using the primary emulsion as the oil phase and the external aqueous phase as the aqueous phase, microspheres are formed through a coaxial needle in a microfluidic device and collected in a PVA solution for static solidification. Specifically, the primary emulsion is connected to the oil phase tube of the microfluidic device, and the external aqueous phase is connected to the aqueous phase tube of the microfluidic device. Microspheres are formed through a coaxial needle; the microspheres are collected in a glass beaker containing 2% PVA solution and allowed to stand at room temperature for 48 hours to allow the solvent to evaporate and the microspheres to solidify.

[0048] The coaxial needle structure allows the primary emulsion (oil phase) and the external aqueous phase (water phase) to form uniform microspheres under the action of interfacial tension. These microspheres are collected in a PVA solution and allowed to stand for 48 hours, allowing the dichloromethane to slowly evaporate and the PLGA to solidify, thus preventing deformation or breakage of the microspheres.

[0049] Step 6: Removal of pore-forming agent: After washing the cured microspheres with water, the gelatin is removed by water bath, and then the microspheres are freeze-dried to obtain porous microspheres. Specifically, the cured microspheres are washed with deionized water and then dispersed again in deionized water, and placed in a 40°C water bath for 2 hours to remove gelatin and form porous microspheres; they are then centrifuged and washed three times with deionized water, frozen at -80°C overnight, and then freeze-dried in a freeze dryer for 48 hours.

[0050] Water bath treatment (40℃) dissolves the gelatin and washes it out of the microspheres, forming a through-pore structure. Centrifugal washing removes residual gelatin and PVA, and freeze-drying prevents the pore structure from collapsing, maintaining high porosity (>85%), ultimately yielding injectable porous microspheres with multi-level pore sizes, suitable for bone repair applications.

[0051] Furthermore, in step 1, the ratio of PLGA, magnesium microspheres, β-TCP, and EC is 7:1:2:0.1, and the concentration of the polymer solution as the oil phase is 10 wt%.

[0052] Furthermore, in step 2, the PVA solution concentration is 2 w / v.

[0053] Furthermore, in step 3, the amount of gelatin added to the internal aqueous phase is 10 w / v.

[0054] Furthermore, in step (5), the pressure value of the oil phase tube is 400 mbar, the pressure value of the water phase tube is 60 mbar, and the specification of the coaxial needle is 19G / 32G.

[0055] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for preparing a magnesium / PLGA-TCP composite porous microsphere bone repair material, characterized in that, Step 1: Add magnesium microspheres and β-tricalcium phosphate to dichloromethane and disperse by ultrasonication; then add PLGA and EC and stir magnetically for 24 hours to obtain an oil phase solution. Step 2: Add polyvinyl alcohol (PVA) to deionized water, heat and stir to dissolve, then filter through a 0.22μm filter to obtain the external aqueous phase; Step 3: Dissolve gelatin in a portion of the PVA solution, heat in a water bath to dissolve, and obtain the internal aqueous phase; Step 4: Add the aqueous phase to the oil phase solution and mix. Divide the mixture into two parts and emulsify and disperse them separately using a cell ultrasonic pulverizer at different power levels. Then mix the two emulsions evenly under magnetic stirring to form a primary emulsion. Step 5: Using the primary emulsion as the oil phase and the external aqueous phase as the aqueous phase, microspheres are formed using a coaxial needle of a microfluidic device and collected in a PVA solution for static solidification. Step 6: After washing the cured microspheres with water, remove the gelatin in a water bath, and then freeze-dry to obtain porous microspheres.

2. The method for preparing the magnesium / PLGA-TCP composite porous microsphere bone repair material according to claim 1, characterized in that, In step 1, the ratio of PLGA, magnesium microspheres, β-TCP, and EC is 7:1:2:0.1, and the concentration of the polymer solution as the oil phase is 10wt%.

3. The method for preparing the magnesium / PLGA-TCP composite porous microsphere bone repair material according to claim 1, characterized in that, In step 2, the PVA solution concentration is 2 w / v.

4. The method for preparing the magnesium / PLGA-TCP composite porous microsphere bone repair material according to claim 1, characterized in that, In step 4, the amount of the internal aqueous phase added accounts for 10-20% of the oil phase, and dispersion is carried out under ice bath conditions with different ultrasonic powers of 80W and 160W, respectively, for a working time of 15 minutes.

5. The method for preparing the magnesium / PLGA-TCP composite porous microsphere bone repair material according to claim 1, characterized in that, In step 3, the amount of gelatin added to the internal aqueous phase is 10 w / v.

6. The method for preparing the magnesium / PLGA-TCP composite porous microsphere bone repair material according to claim 1, characterized in that, In step 5, the pressure value of the oil phase tube is 400 mbar, the pressure value of the water phase tube is 60 mbar, and the specification of the coaxial needle is 19G / 32G.

7. The method for preparing the magnesium / PLGA-TCP composite porous microsphere bone repair material according to claim 1, characterized in that, In specific step 6, the cured microspheres are washed with deionized water and then dispersed again in deionized water. They are placed in a 40°C water bath for 2 hours to remove gelatin and form porous microspheres. They are then centrifuged and washed three times with deionized water, frozen at -80°C overnight, and then freeze-dried in a freeze dryer for 48 hours.

8. A metallic magnesium / PLGA-TCP composite porous microsphere bone repair material prepared by the preparation method according to any one of claims 1 to 7, characterized in that, Includes PLGA, magnesium microspheres, β-TCP, and EC; The PLGA contains lactic acid (LA) to glycolic acid (GA) monomers in a ratio of (50:50) to (75:25), with a molecular weight of 30-50 kDa; the magnesium microspheres have a particle size of 20-50 μm.

9. The application of the magnesium / PLGA-TCP composite porous microsphere bone repair material according to claim 8 in the preparation of oral alveolar bone repair materials.

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