Polylactic acid microsphere / hydrogel composite material as well as preparation method and application thereof

Abstract

The invention relates to the technical field of alveolar bone repair materials, and discloses a polylactic acid microsphere / hydrogel composite material as well as a preparation method and application thereof. Wherein the stereopolylactic acid microspheres are dispersed and distributed in the hydrogel, and the stereopolylactic acid comprises poly-L-lactic acid and poly-D-lactic acid. The polylactic acid microsphere / hydrogel composite material disclosed by the invention has good piezoelectricity, degradability and biocompatibility. The composite material has potential application prospects in the field of alveolar bone repair and is expected to replace existing bone meal.

Description

Technical Field

[0001] This invention relates to the field of alveolar bone repair materials, specifically to a polylactic acid microsphere / hydrogel composite material, its preparation method, and its application. Background Technology

[0002] The rate and number of people losing teeth are increasing year by year, leading to a growing demand for dental implants. Implant placement places strict requirements on the quality and volume of alveolar bone. However, after tooth loss, normal occlusal forces can no longer provide physiological stimulation to the alveolar bone, causing a continuous decline in bone quality and volume, making it unsuitable for dental implantation. To broaden the indications for dental implants, alveolar bone implant materials are widely used in implant surgery. Currently, the most common method is to guide alveolar bone regeneration by filling with bone powder. Clinically, it has been found that using bone powder for alveolar bone repair has two major problems: first, although bone powder can guide bone repair, it lacks osteoinductive activity; second, bone powder is difficult for newly formed bone tissue to absorb and replace, ultimately leading to a mismatch between the quality of the new bone and the original bone. Therefore, finding a material with high osteoinductive activity that can be absorbed and replaced by tissue is key to solving this problem.

[0003] With the discovery of the bone piezoelectric effect, natural bone tissue has been shown to possess piezoelectric properties; mechanical stimulation can induce microcurrents in bone, thereby triggering calcium... 2+ Influx of piezoelectric materials upregulates osteogenic gene expression and promotes bone tissue regeneration. Piezoelectric materials can generate microcurrents under stress without external electromagnetic stimulation, thus possessing great application potential in alveolar bone filling. Currently, the main piezoelectric materials include ceramics and polymers. Strong piezoelectric materials, primarily ferroelectric ceramics, are non-degradable and biocompatible, while weak piezoelectric materials, mainly natural polymers, have low electroactivity and insufficient tissue regeneration capacity. Therefore, there is an urgent need to develop a bone-inducing regeneration material that combines strong piezoelectricity, biodegradability, and biocompatibility. Summary of the Invention

[0004] The purpose of this invention is to overcome the aforementioned problems in the prior art and to provide a polylactic acid microsphere / hydrogel composite material, its preparation method, and its application.

[0005] To achieve the above objectives, a first aspect of the present invention provides a polylactic acid microsphere / hydrogel composite material, the composite material comprising stereopolylactic acid microspheres and hydrogel; wherein the stereopolylactic acid microspheres are dispersed in the hydrogel, and the stereopolylactic acid comprises L-polylactic acid and D-polylactic acid.

[0006] A second aspect of the present invention provides a method for preparing polylactic acid microspheres / hydrogel composite materials, the method comprising the following steps:

[0007] (1) A water-soluble polymer, L-polylactic acid and D-polylactic acid are first mixed in a molten state, and then the water-soluble polymer is removed to obtain porous stereopolylactic acid microspheres.

[0008] (2) A solution containing hydrophilic polymers is mixed with the porous stereopolylactic acid microspheres obtained in step (1) for a second time; then the mixture obtained from the second mixing is contacted with a solution containing polyvalent cations to obtain a polylactic acid microsphere / hydrogel composite material.

[0009] A third aspect of the present invention provides a polylactic acid microsphere / hydrogel composite material prepared by the method described above.

[0010] The fourth aspect of this invention provides the application of the polylactic acid microsphere / hydrogel composite material described above in alveolar bone repair.

[0011] Through the above technical solution, the present invention achieves the following beneficial effects:

[0012] (1) The polylactic acid microsphere / hydrogel composite material of the present invention has good piezoelectricity, biodegradability, and biocompatibility. This composite material has potential applications in alveolar bone repair and is expected to replace existing bone powder. Simultaneously, the composite material of the present invention solves the problem of powder splashing in stereolithographic polylactic acid microspheres. Preferably, the composite material of the present invention can also solve the problem of excessively high local acidity caused by polylactic acid degradation.

[0013] (2) This invention improves the piezoelectricity and biocompatibility of conventional polylactic acid by preparing porous stereochemical polylactic acid microspheres using water-soluble polymers, L-polylactic acid, and D-polylactic acid, and then preparing the porous stereochemical polylactic acid microspheres into hydrogel composite materials. Preferably, when a solution containing calcium ions is used to prepare the hydrogel composite material, it can further promote bone repair. Attached Figure Description

[0014] Figure 1 This is a photograph of the hydrogel prepared using the method in step (2) of Example 1;

[0015] Figure 2 This is a photograph of the stereopolylactic acid microsphere / hydrogel composite material prepared in Example 1. Detailed Implementation

[0016] The endpoints and any values ​​of the ranges disclosed herein are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of the various ranges, the endpoint values ​​of the various ranges and individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed herein.

[0017] The first aspect of the present invention provides a polylactic acid microsphere / hydrogel composite material, the composite material comprising stereopolylactic acid microspheres and hydrogel; wherein the stereopolylactic acid microspheres are dispersed in the hydrogel, and the stereopolylactic acid comprises L-polylactic acid and D-polylactic acid.

[0018] According to the present invention, preferably, the stereopolylactic acid microspheres are uniformly dispersed in the hydrogel. The average particle size of the stereopolylactic acid microspheres in the present invention is 0.2-50 μm.

[0019] According to the present invention, preferably, the stereopolylactic acid microspheres are porous stereopolylactic acid microspheres, and more preferably, the porosity of the porous stereopolylactic acid microspheres is 10-50%.

[0020] According to the present invention, preferably, the weight ratio of L-polylactic acid to D-polylactic acid is 1:0.5-2. In the present invention, the weight ratio of L-polylactic acid to D-polylactic acid in the polylactic acid microsphere / hydrogel composite material is calculated based on the amount of material fed.

[0021] According to the present invention, preferably, the weight-average molecular weight of the L-polylactic acid and the D-polylactic acid is greater than 20,000 g / mol; more preferably, the weight-average molecular weight of the L-polylactic acid and the D-polylactic acid is independently 50,000-300,000 g / mol; and even more preferably, 200,000-250,000 g / mol.

[0022] According to the present invention, the hydrogel contains a hydrophilic polymer; the hydrophilic polymer includes natural hydrophilic polymers and / or synthetic hydrophilic polymers, preferably at least one of sodium alginate, gelatin, chitosan and its derivatives, cellulose and its derivatives, polyethylene glycol, polyvinyl alcohol, and polyvinylpyrrolidone, and more preferably sodium alginate.

[0023] A second aspect of the present invention provides a method for preparing polylactic acid microspheres / hydrogel composite materials, the method comprising the following steps:

[0024] (1) A water-soluble polymer, L-polylactic acid and D-polylactic acid are first mixed in a molten state, and then the water-soluble polymer is removed to obtain porous stereopolylactic acid microspheres.

[0025] (2) The solution containing hydrophilic polymers is mixed with the porous stereopolylactic acid microspheres obtained in step (1) for a second time; then the mixture obtained from the second mixing is contacted with a crosslinking agent to obtain a polylactic acid microsphere / hydrogel composite material.

[0026] The inventors of this invention have discovered that when porous stereopolylactic acid (PLA) microspheres are prepared from L- and D-polylactic acid using water-soluble polymers, and then these porous PLA microspheres are used to prepare PLA microsphere / hydrogel composite materials, not only can the problems of non-degradability and poor biocompatibility of traditional piezoelectric materials be solved, but also the problem of PLA microsphere powder splashing can be solved, and the piezoelectric properties of PLA can be improved.

[0027] According to the present invention, preferably, the weight-average molecular weight of the water-soluble polymer is 1000-20000 g / mol.

[0028] According to the present invention, preferably, the water-soluble polymer includes natural water-soluble polymers and / or synthetic water-soluble polymers, more preferably at least one selected from polyethylene glycol (PEG), polyvinylpyrrolidone (PVP), and carboxymethyl cellulose. The polylactic acid / hydrogel composite material prepared using carboxymethyl cellulose as the water-soluble polymer exhibits almost equivalent performance compared to that prepared using polyethylene glycol.

[0029] According to the present invention, in order to further improve the piezoelectricity, biodegradability, and biocompatibility of the polylactic acid microsphere / hydrogel composite material, preferably, the weight ratio of L-polylactic acid to D-polylactic acid is 1:0.5-2. The weight ratio of L-polylactic acid to D-polylactic acid can be 1:0.5, 1:0.7, 1:0.9, 1:1.1, 1:1.3, 1:1.5, 1:1.7, 1:1.9, 1:2, or any two of the above ratios.

[0030] According to the present invention, preferably, the weight-average molecular weight of the L-polylactic acid and the D-polylactic acid is greater than 20,000 g / mol; more preferably, the weight-average molecular weight of the L-polylactic acid and the D-polylactic acid is independently 50,000-300,000 g / mol; and even more preferably, 200,000-250,000 g / mol.

[0031] According to the present invention, preferably, the content of the water-soluble polymer is 10-50% by weight, based on the total weight of the water-soluble polymer, L-polylactic acid and D-polylactic acid, for example, it can be 10% by weight, 20% by weight, 30% by weight, 40% by weight, 50% by weight, and any two of the above.

[0032] According to the present invention, preferably, the conditions for the first mixing include: a temperature of 180-200°C, more preferably 185-195°C; and a time of 1-10 min.

[0033] According to the present invention, preferably, the method for removing water-soluble polymers is to wash the powder obtained from the first mixture with water. The number of washes is typically 3-6.

[0034] According to the present invention, preferably, the method further includes: drying the water-washed powder at a temperature of 50-80°C. The drying time can be 6-24 hours.

[0035] According to the present invention, the hydrophilic polymer includes natural hydrophilic polymers and / or synthetic hydrophilic polymers, preferably at least one of sodium alginate, gelatin, chitosan and its derivatives, cellulose and its derivatives, polyethylene glycol, polyvinyl alcohol, and polyvinylpyrrolidone, more preferably sodium alginate.

[0036] According to the present invention, the concentration of the solution containing hydrophilic polymers can be selected within a wide range, as long as it can form a hydrogel. Preferably, the content of hydrophilic polymers in the solution containing hydrophilic polymers is 2-10% by weight.

[0037] According to the present invention, the solvent in the solution containing the hydrophilic polymer is independently selected from at least one of water, physiological saline, phosphate buffer solution, and cell culture medium. The phosphate buffer solution and cell culture medium can be commonly used phosphate buffer solutions and commonly used cell culture media. The phosphate buffer solution mainly contains water and also contains substances such as dihydrogen phosphate, disodium hydrogen phosphate, sodium chloride, and potassium chloride. The concentration of sodium chloride is 100-137 mmol / L, the concentration of potassium chloride is 0.1-2.7 mmol / L, the concentration of disodium hydrogen phosphate is 1-10 mmol / L, and the concentration of potassium dihydrogen phosphate is 0.1-1.8 mmol / L.

[0038] According to the present invention, preferably, the volume of the solution containing the hydrophilic polymer is 3-10 mL relative to each gram of porous stereopolylactic acid microspheres. When the ratio of the porous stereopolylactic acid microspheres to the solution containing the hydrophilic polymer is limited to the above range, the porous stereopolylactic acid microspheres can be uniformly dispersed in the hydrogel while maintaining their high piezoelectricity.

[0039] According to the present invention, the crosslinking agent is preferably at least one of a polyvalent cation solution, an acid crosslinking agent, a base crosslinking agent, an aldehyde crosslinking agent, an epoxide, and a dianhydride, and more preferably a polyvalent cation solution.

[0040] Preferably, the multivalent cation includes Ca. 2+ Mn 2+ Mg 2+ and Fe 3+ At least one of them; more preferably Ca 2+ Although, Mn 2+ Mg 2+ and Fe 3+When used as a multivalent cation, it can also improve the piezoelectricity, biodegradability, and biocompatibility of polylactic acid microspheres / hydrogel composites. However, the inventors of this invention further discovered that when Ca is used... 2+ When acting as a multivalent cation, it can further promote bone repair. The solvent in the solution containing the multivalent cation can be water. The anion in the solution containing the multivalent cation can be Cl-. - NO3 - SO4 2- At least one of them.

[0041] According to the present invention, the concentration of the solution containing polyvalent cations can be selected within a wide range, as long as it enables the aqueous solution containing hydrophilic polymers to form a hydrogel. Preferably, the concentration of the solution containing polyvalent cations is 100-500 mmol / L.

[0042] According to the present invention, the contact time is not particularly limited, as long as it is sufficient to form a hydrogel; preferably, the contact time is greater than 20 seconds; more preferably, it is 30-120 seconds. Generally, excessively long contact times will lead to excessive cation residue, thereby affecting the biocompatibility of the composite material.

[0043] A third aspect of the present invention provides a polylactic acid microsphere / hydrogel composite material prepared by the method described above.

[0044] The fourth aspect of this invention provides the application of the polylactic acid microsphere / hydrogel composite material described above in alveolar bone repair.

[0045] The present invention will be described in detail below through embodiments. In the following embodiments,

[0046] The L-polylactic acid is a commercially available product from Corbion under the brand name Luminy PLA L175, with a weight-average molecular weight of 200,000 g / mol.

[0047] The dextrorotatory polylactic acid is a commercially available product from Corbion under the brand name Luminy PLA D120, with a weight-average molecular weight of 200,000 g / mol;

[0048] Sodium alginate is a commercially available product from Sigma-Aldrich, with a weight-average molecular weight of 100,000 g / mol.

[0049] Phosphate buffer contains dihydrogen phosphate, dihydrogen phosphate, sodium chloride, potassium chloride, and water; the concentration of sodium chloride is 137 mmol / L, the concentration of potassium chloride is 2.7 mmol / L, the concentration of disodium hydrogen phosphate is 10 mmol / L, the concentration of potassium dihydrogen phosphate is 1.8 mmol / L, and the remainder is water.

[0050] Example 1

[0051] (1) 24g of water-soluble polymer (polyethylene glycol, PEG, molecular weight 10000g / mol) was mixed with 18g of L-polylactic acid and 18g of D-polylactic acid, and then melt-mixed using a mixer at a temperature of 190℃ for 5min. After the melt mixing was completed, the mixture was cooled to room temperature and the resulting solid was ground into powder. The powder was then washed 5 times in water to remove PEG, and then dried in an oven at 80℃ for 12h to obtain porous stereochemical polylactic acid powder.

[0052] (2) Sodium alginate was mixed with phosphate buffer to prepare a 6wt% sodium alginate solution. 0.2g of the porous stereopolylactic acid powder obtained in step (1) was mixed evenly with 1mL of the 6wt% sodium alginate solution, and then placed in a CaCl2 aqueous solution (concentration of 300mmol / L) for 1min to stabilize, thus obtaining a stereopolylactic acid microsphere / hydrogel composite material.

[0053] A photograph of a hydrogel (i.e., a hydrogel that does not contain porous stereopolylactic acid powder) prepared solely using step (2) of Example 1 is shown below. Figure 1 As shown. A photograph of the stereopolymer polylactic acid microsphere / hydrogel composite material prepared in Example 1 is shown. Figure 2 As shown. Figure 2 and Figure 1 The comparison shows that in the composite material prepared by the method of the present invention, the stereopolylactic acid microspheres are uniformly dispersed in the hydrogel.

[0054] Example 2

[0055] The method was carried out according to Example 1, except that step (1) was performed as follows: 12g of water-soluble polymer (polyethylene glycol, PEG, molecular weight 10000g / mol) was mixed with 24g of L-polylactic acid and 24g of D-polylactic acid, and then melt-mixed using a mixer at a temperature of 190°C for 5 minutes. After the melt mixing was completed, the mixture was cooled to room temperature and the resulting solid was ground into powder. The powder was then washed five times in water to remove PEG, and then dried in an oven at 80°C for 12 hours to obtain porous stereochemical polylactic acid powder.

[0056] Example 3

[0057] The method of Example 1 was followed, except that step (2) was performed as follows: 0.1g of the porous stereopolylactic acid powder obtained in step (1) was mixed evenly with 1mL of 6wt% sodium alginate solution, and then placed in CaCl2 aqueous solution (concentration of 300mmol / L) for 1min to stabilize, so as to obtain stereopolylactic acid microsphere / hydrogel composite material.

[0058] Example 4

[0059] The method of Example 1 was followed, except that in step (1), the melting and mixing temperature was 180°C and the mixing time was 5 min.

[0060] Example 5

[0061] The procedure was carried out according to Example 1, except that in step (2), the concentration of the CaCl2 aqueous solution was 100 mmol / L and the soaking time was 1 min.

[0062] Example 6

[0063] The procedure was carried out according to Example 1, except that the phosphate buffer was replaced with water.

[0064] Example 7

[0065] The procedure was carried out according to Example 1, except that "polyethylene glycol" was replaced with an equal weight of "polyvinylpyrrolidone".

[0066] Example 8

[0067] The procedure was carried out according to Example 1, except that the amount of L-polylactic acid used was 24g and the amount of D-polylactic acid used was 12g.

[0068] Comparative Example 1

[0069] The procedure was carried out according to Example 1, except that PEG was not added, and 30g of L-polylactic acid and 30g of D-polylactic acid were used.

[0070] Comparative Example 2

[0071] The procedure was carried out according to Example 1, except that dextrorotatory polylactic acid was replaced with an equal weight of levorotatory polylactic acid.

[0072] Test case

[0073] The properties of the stereopolylactic acid microspheres / hydrogel composites prepared in the above examples and comparative examples were tested, and the test structures are shown in Table 1.

[0074] (1) The porosity of the stereopolylactic acid microspheres was obtained by density packing test, and the calculation formula is as follows:

[0075]

[0076] (2) The mechanical properties of the stereopolylactic acid microsphere / hydrogel composite material were tested by rotational rheometer;

[0077] (3) The piezoelectricity of the stereopolylactic acid microsphere / hydrogel composite material was tested by a self-made piezoelectric measuring instrument. The composite material was fixed on the substrate, and copper electrodes were attached to the surface. The electrodes were connected to a voltage amplifier. The composite material was pulsed with a constant pressure and frequency using an iron sheet. At the same time, the voltage change was recorded by the voltage amplifier to obtain the open circuit voltage of the composite material.

[0078] (4) The cell compatibility of the stereopolylactic acid microsphere / hydrogel composite material was obtained by CCK8 test on its extract.

[0079] Table 1

[0080]

[0081] As can be seen from the results in Table 1, the stereopolymer polylactic acid microspheres / hydrogel composite material prepared by the method of the present invention has a high open-circuit voltage, thus exhibiting strong piezoelectric properties; at the same time, the cell viability of the composite material of the present invention is higher than 95%, demonstrating good biocompatibility. Particularly preferred are Examples 1 and Examples 5-8 of the present invention, which have even higher open-circuit voltages.

[0082] The preferred embodiments of the present invention have been described in detail above; however, the present invention is not limited thereto. Within the scope of the inventive concept, various simple modifications can be made to the technical solutions of the present invention, including combinations of various technical features in any other suitable manner. These simple modifications and combinations should also be considered as the content disclosed in the present invention and are all within the protection scope of the present invention.

Claims

1. A polylactic acid microsphere / hydrogel composite material, characterized in that, The composite material comprises stereopolylactic acid microspheres and hydrogel; wherein the stereopolylactic acid microspheres are dispersed in the hydrogel, and the stereopolylactic acid includes L-polylactic acid and D-polylactic acid.

2. The composite material according to claim 1, wherein, The weight ratio of L-polylactic acid to D-polylactic acid is 1:0.5-2; And / or, the weight-average molecular weight of the L-polylactic acid and the D-polylactic acid is greater than 20,000 g / mol; And / or, the hydrogel contains a hydrophilic polymer; preferably, the hydrophilic polymer includes natural hydrophilic polymers and / or synthetic hydrophilic polymers, more preferably at least one of sodium alginate, gelatin, chitosan and its derivatives, cellulose and its derivatives, polyethylene glycol, polyvinyl alcohol and polyvinylpyrrolidone, and even more preferably sodium alginate.

3. A method for preparing polylactic acid microspheres / hydrogel composite materials, characterized in that, The method includes the following steps: (1) A water-soluble polymer, L-polylactic acid and D-polylactic acid are first mixed in a molten state, and then the water-soluble polymer is removed to obtain porous stereopolylactic acid microspheres. (2) The solution containing hydrophilic polymers is mixed with the porous stereopolylactic acid microspheres obtained in step (1) for a second time; then the mixture obtained from the second mixing is contacted with a crosslinking agent to obtain a polylactic acid microsphere / hydrogel composite material.

4. The method according to claim 3, wherein, The water-soluble polymer includes natural water-soluble polymers and / or synthetic water-soluble polymers, preferably at least one of polyethylene glycol, polyvinylpyrrolidone and carboxymethyl cellulose; And / or, the weight ratio of L-polylactic acid to D-polylactic acid is 1:0.5-2; And / or, the weight-average molecular weight of the L-polylactic acid and the D-polylactic acid is greater than 20,000 g / mol.

5. The method according to claim 3, wherein, Based on the total weight of the water-soluble polymer, L-polylactic acid, and D-polylactic acid, the content of the water-soluble polymer is 10-50% by weight.

6. The method according to claim 3, wherein, The conditions for the first mixing include: a temperature of 180-200℃ and a time of 1-10 min; And / or, the method of removing water-soluble polymers is to wash the powder obtained from the first mixture with water; Preferably, the method further includes drying the washed powder at a temperature of 50-80°C.

7. The method according to claim 3, wherein, The hydrophilic polymer includes natural hydrophilic polymers and / or synthetic hydrophilic polymers, preferably at least one of sodium alginate, gelatin, chitosan and its derivatives, cellulose and its derivatives, polyethylene glycol, polyvinyl alcohol and polyvinylpyrrolidone, more preferably sodium alginate; And / or, the hydrophilic polymer content in the solution containing the hydrophilic polymer is 2-10% by weight; And / or, the solvent in the solution containing the hydrophilic polymer is independently selected from at least one of water, physiological saline, phosphate buffer, and cell culture medium; And / or, relative to the volume of the solution containing the hydrophilic polymer per gram of porous stereopolylactic acid microspheres, the volume of the solution is 3-10 mL.

8. The method according to claim 3, wherein, The crosslinking agent is at least one of a polyvalent cation solution, an acid crosslinking agent, a base crosslinking agent, an aldehyde crosslinking agent, an epoxide, and a dianhydride, preferably a polyvalent cation solution; The multivalent cations include Ca 2+ Mn 2+ Mg 2+ and Fe 3+ At least one of them; And / or, the concentration of the solution containing the polyvalent cation is 100-500 mmol / L; And / or, the contact time is greater than 20 seconds.

9. The polylactic acid microsphere / hydrogel composite material prepared by the method according to any one of claims 3-7.

10. The application of the polylactic acid microsphere / hydrogel composite material according to any one of claims 1-2 and 9 in alveolar bone repair.

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