A method for preparing a beta cyclodextrin / polycaprolactone-polylactic acid polycaprolactone copolymer inclusion complex microsphere

Abstract

The application relates to a preparation method of a cyclodextrin / polycaprolactone-polylactic acid polycaprolactone copolymer inclusion complex microsphere, which comprises the following steps: (1) polycaprolactone, lactide and caprolactone are polymerized under the catalysis of stannous octoate to obtain polycaprolactone-polylactic acid polycaprolactone copolymer; (2) the polycaprolactone-polylactic acid polycaprolactone copolymer is preliminarily dissolved in an acetone solution, and cyclodextrin is dissolved in water; (3) the aqueous solution of cyclodextrin is added dropwise into the acetone solution of the polycaprolactone-polylactic acid polycaprolactone copolymer, and stirring is performed intensively; (4) the mixed solution obtained in the step (3) is continuously stirred at room temperature, washed through acetone and water, and dried to obtain an inclusion complex; and (5) the inclusion complex obtained in the step (4) is dispersed in a solvent to obtain an inclusion complex microsphere. The microsphere prepared by the application has biocompatibility, can be dispersed in various solvents, can be used as a carrier of various drugs, and can also be used as a reinforcing filler of polylactic acid.

Description

Technical Field

[0001] This invention belongs to the field of biomedical materials technology, specifically relating to a method for preparing microspheres of β-cyclodextrin / polycaprolactone-polylactic acid polycaprolactone copolymer inclusion complex. Background Technology

[0002] Polylactic acid (PLA) and polycaprolactone (PCL) are highly suitable for use as biomedical materials due to their excellent biocompatibility and biodegradability. However, both PLA and PCL are highly hydrophobic, lacking bioactive and cell-specific recognition sites on their surfaces, making them prone to inducing non-infectious inflammatory responses. Furthermore, they lack active functional groups that can interact with drugs, resulting in low loading rates for hydrophilic drugs. These performance defects limit the application of PLA microspheres as drug carriers in tissue engineering. Encapsulation with cyclodextrin can effectively solve these problems. Due to its hydrophilic outer wall and hydrophobic inner cavity, cyclodextrin possesses the ability to encapsulate guest molecules. "Encapsulation" refers to the process by which cyclodextrin molecules and guest molecules recognize each other through intermolecular interactions, ultimately resulting in the guest molecule being partially or completely embedded within the host. It can form inclusion complexes not only with small organic molecules and inorganic ions but also with most long-chain polymers through self-encapsulation. Whether cyclodextrin can form inclusion complexes with guest polymers is mainly influenced by the following two factors: (1) Due to the hydrophobicity of the cyclodextrin cavity, the stronger the hydrophobicity of the guest polymer, the easier it is for it to enter the cyclodextrin cavity; (2) The size between the cyclodextrin cavity and the guest polymer should be similar: if the guest polymer is too large, it cannot penetrate the cavity; if the guest polymer is too small, the resulting inclusion complex is very unstable and the inclusion process is slow. The crystal structure of cyclodextrin inclusion complexes includes cage-like structures and tunnel-like structures. The long chain structure of the polymer determines that the crystal structure of its inclusion complex with cyclodextrin is generally tunnel-like, in which case the cyclodextrin molecules are stacked together and arranged coaxially in the cavity of the central cylinder.

[0003] Conventional inclusion complexes of polymers and cyclodextrins are often in a state that is poorly soluble in both water and organic solvents, meaning they are difficult to disperse in solvents and tend to form aggregates. The strong intramolecular hydrogen bonds formed by the coaxial arrangement of cyclodextrins in the tunnel structure, coupled with the inherent hydrophilicity of the cyclodextrin outer wall, greatly limit the application potential of inclusion complexes of cyclodextrins with biodegradable polymers. Summary of the Invention

[0004] The purpose of this invention is to overcome the shortcomings of existing cyclodextrin, polylactic acid, polycaprolactone and their inclusion complexes, and to provide a method for preparing β-cyclodextrin / polycaprolactone-polylactic acid-polycaprolactone copolymer inclusion complex microspheres using a selective host-guest complexation mechanism. This inclusion complex can be simultaneously dispersed into micron-sized microspheres in conventional polar and non-polar solvents, has the potential to simultaneously load hydrophilic and hydrophobic drugs, and can be used as a reinforcing filler for polylactic acid, thus broadening the application range of cyclodextrin and polymer inclusion complexes.

[0005] A method for preparing β-cyclodextrin / polycaprolactone-polylactic acid polycaprolactone copolymer inclusion complex microspheres includes the following steps:

[0006] (1) Polycaprolactone, lactide and caprolactone were dissolved in toluene. Using polycaprolactone as a macromolecular initiator, ring-opening polymerization was carried out under nitrogen atmosphere with the catalysis of stannous octoate. After precipitation with diethyl ether, centrifugation and washing were performed to obtain polycaprolactone-polylactic acid polycaprolactone copolymer.

[0007] (2) Dissolve the polycaprolactone-polylactic acid polycaprolactone copolymer in acetone solution and heat it to the target temperature to obtain an acetone solution of polycaprolactone-polylactic acid polycaprolactone copolymer.

[0008] (3) Add the aqueous solution of β-cyclodextrin dropwise to the acetone solution of polycaprolactone-polylactic acid polycaprolactone copolymer and stir vigorously to obtain a mixed solution;

[0009] (4) The mixture was stirred at room temperature for a predetermined time, and then washed by centrifugation with acetone and water to obtain the β-cyclodextrin / polycaprolactone-polylactic acid polycaprolactone copolymer inclusion complex.

[0010] (5) The inclusion complex of β-cyclodextrin / polycaprolactone-polylactic acid polycaprolactone was ultrasonically dispersed in a solvent to obtain inclusion complex microspheres.

[0011] As a preferred embodiment, in step (1), the mass ratio of polycaprolactone, lactide, and caprolactone is 2:(2-4):(3-6).

[0012] As a preferred embodiment, in step (1), the parameters for ring-opening polymerization include: a temperature of 100–120°C and a polymerization reaction time of 17–24 h.

[0013] As a preferred embodiment, in step (1), the number average molecular weight of polycaprolactone is 8000-15000 g / mol.

[0014] As a preferred embodiment, in step (2), the mass percentage of the acetone solution of polycaprolactone-polylactic acid polycaprolactone copolymer is 1-2%.

[0015] As a preferred embodiment, in step (2), the target temperature is 50-70°C.

[0016] As a preferred embodiment, in step (3), the mass ratio of polycaprolactone-polylactic acid polycaprolactone copolymer to β-cyclodextrin is 1:(0.5-2.5), and the vigorous stirring time is 2-4 hours.

[0017] As a preferred embodiment, in step (3), the mass percentage of the aqueous solution of β-cyclodextrin is 5-10%.

[0018] As a preferred option, in step (4), the predetermined duration is not less than 20 hours.

[0019] As a preferred embodiment, in step (5), the mass percentage of the dispersion of the β-cyclodextrin / polycaprolactone-polylactic acid polycaprolactone copolymer inclusion complex in the solvent is 0.2-1%.

[0020] As a preferred embodiment, the solvent is water or a non-polar solvent.

[0021] Compared with the prior art, the beneficial effects of this invention are:

[0022] This invention utilizes the size mismatch between the β-cyclodextrin cavity and the polylactic acid monomer to selectively include β-cyclodextrin with the polycaprolactone block molecular chains of the polycaprolactone-polylactic acid-polycaprolactone copolymer, resulting in a high molecular weight cyclodextrin inclusion complex with one hydrophilic end and one hydrophobic end. This complex can be dispersed in various solvents into micron-sized microspheres, which can be used as both drug carriers and reinforcing fillers for polylactic acid. Attached Figure Description

[0023] Figure 1 The particle size distribution of the inclusion complex microspheres in chloroform solvent as measured by a dynamic light scattering instrument in Example 1 of the present invention;

[0024] Figure 2 This is the X-ray diffraction pattern of the inclusion compound microspheres of Example 1 of the present invention;

[0025] Figure 3 This is a polarized light microscope image of the polylactic acid composite material of Example 1 of the present invention during isothermal crystallization at 130°C for 5 minutes. Detailed Implementation

[0026] The technical solution of the present invention will be further explained and illustrated below through specific embodiments.

[0027] Example 1:

[0028] The preparation method of the β-cyclodextrin / polycaprolactone-polylactic acid polycaprolactone copolymer inclusion complex microspheres in this embodiment includes the following steps:

[0029] (1) 4g of dried polycaprolactone (Mn = 12500 kg / mol), 6g of recrystallized lactide, and 10g of caprolactone were dissolved in 150mL of anhydrous toluene. The reaction was carried out at 110℃ for 20h under a nitrogen atmosphere with the catalysis of 0.2g of stannous octoate. After the reaction was completed, the solution was added dropwise to anhydrous diethyl ether to precipitate. After centrifugation and washing three times, a white precipitate was obtained, which is polycaprolactone-polylactic acid polycaprolactone copolymer. After drying in a vacuum drying oven for 48h, pure polycaprolactone-polylactic acid polycaprolactone copolymer was obtained. Polycaprolactone is one block and the random copolymer of polylactic acid and polycaprolactone is another block.

[0030] (2) Dissolve the polycaprolactone-polylactic acid polycaprolactone copolymer in (1) in acetone at 60°C at a mass percentage of 1.5% to obtain an acetone solution;

[0031] β-cyclodextrin was dissolved in deionized water at a mass percentage of 8% to obtain an aqueous solution of β-cyclodextrin.

[0032] (3) The aqueous solution of β-cyclodextrin in (2) was added dropwise to the acetone solution in (2) at a mass ratio of polycaprolactone-polylactic acid polycaprolactone copolymer:β-cyclodextrin of 1:1.5, and stirred vigorously at 1200 rpm for 3 h.

[0033] (4) Continue stirring the mixed solution obtained in step (3) at 300 rpm for 24 hours at room temperature, remove the free polycaprolactone-polylactic acid polycaprolactone copolymer by centrifugation with acetone, and remove the unencapsulated cyclodextrin by centrifugation with deionized water.

[0034] (5) The β-cyclodextrin / polycaprolactone-polylactic acid polycaprolactone copolymer inclusion complex obtained in step (4) is ultrasonically dispersed in chloroform at a mass percentage of 0.5% to obtain inclusion complex microspheres.

[0035] The dynamic light-scattering particle size distribution of the inclusion complex microspheres dispersed in chloroform in this embodiment is as follows: Figure 1 As shown, the X-ray diffraction pattern of the inclusion microspheres is as follows: Figure 2 As shown, we can see:

[0036] The inclusion complex microspheres exhibited a uniform size distribution, around 1000 nm. In the X-ray diffraction pattern, a distinct diffraction peak for the cyclodextrin tunnel-type inclusion complex appeared at 2θ = 20°, while no crystallization diffraction peak for polycaprolactone was observed, indicating that β-cyclodextrin selectively included polycaprolactone blocks. Therefore, the prepared inclusion complex microspheres possess both hydrophilic and hydrophobic properties.

[0037] In addition, commercially available polylactic acid (PLA) was premixed with inclusion complex microspheres at a mass ratio of 20:1 via co-precipitation, and then hot-pressed using a flat vulcanizing machine to obtain a PLA composite material. For example... Figure 3As shown, observation using a polarizing microscope revealed that the microspheres were uniformly distributed in the polylactic acid matrix and increased the polylactic acid crystallization rate.

[0038] Example 2:

[0039] The preparation method of the β-cyclodextrin / polycaprolactone-polylactic acid polycaprolactone copolymer inclusion complex microspheres in this embodiment includes the following steps:

[0040] (1) The polycaprolactone-polylactic acid polycaprolactone copolymer in Example 1 was dissolved in acetone at 60°C at 1.5% by mass, and β-cyclodextrin was dissolved in deionized water at 8% by mass.

[0041] (2) The aqueous solution of β-cyclodextrin in (1) was added dropwise to the acetone solution in Example 1 at a mass ratio of polycaprolactone-polylactic acid polycaprolactone copolymer:β-cyclodextrin of 1:1, and stirred vigorously for 3 hours.

[0042] (3) Continue stirring the mixed solution obtained in step (2) at room temperature for 24 hours. Remove the free polycaprolactone-polylactic acid polycaprolactone copolymer by centrifugation with acetone, and remove the unencapsulated cyclodextrin by centrifugation with deionized water;

[0043] (4) The β-cyclodextrin / polycaprolactone-polylactic acid polycaprolactone copolymer inclusion complex obtained in step (3) was ultrasonically dispersed in chloroform at a mass percentage of 0.5% to obtain inclusion complex microspheres.

[0044] Commercially available polylactic acid (PLA) was premixed with inclusion complex microspheres at a mass ratio of 20:1 via co-precipitation, and then hot-pressed using a flat vulcanizing machine to obtain the composite material. Cooling curves obtained using differential scanning calorimetry (DSC) showed that this improved the crystallinity of the PLA.

[0045] Example 3:

[0046] The preparation method of the β-cyclodextrin / polycaprolactone-polylactic acid polycaprolactone copolymer inclusion complex microspheres in this embodiment includes the following steps:

[0047] (1) The polycaprolactone-polylactic acid polycaprolactone copolymer in Example 1 was dissolved in acetone at 60°C at 1.5% by mass, and β-cyclodextrin was dissolved in deionized water at 8% by mass.

[0048] (2) The aqueous solution of β-cyclodextrin in (1) was added dropwise to the acetone solution described in Example 1 at a mass ratio of polycaprolactone-polylactic acid polycaprolactone copolymer:β-cyclodextrin of 1:2, and stirred vigorously for 3 hours.

[0049] (3) Continue stirring the mixed solution obtained in step (2) at room temperature for 24 hours. Remove the free polycaprolactone-polylactic acid polycaprolactone copolymer by centrifugation with acetone, and remove the unencapsulated cyclodextrin by centrifugation with deionized water;

[0050] (4) The β-cyclodextrin / polycaprolactone-polylactic acid polycaprolactone copolymer inclusion complex obtained in step (3) was ultrasonically dispersed in tetrahydrofuran at a mass percentage of 0.5% to obtain inclusion complex microspheres. Commercially available polylactic acid was premixed by co-precipitation at a polylactic acid:inclusion complex microsphere mass ratio of 20:1, and then hot-pressed in a flat vulcanizing machine to obtain the composite material.

[0051] Example 4:

[0052] The preparation method of the β-cyclodextrin / polycaprolactone-polylactic acid polycaprolactone copolymer inclusion complex microspheres in this embodiment includes the following steps:

[0053] (1) The polycaprolactone-polylactic acid polycaprolactone copolymer in Example 1 was dissolved in acetone at 60°C at 1.5% by mass, and β-cyclodextrin was dissolved in deionized water at 8% by mass.

[0054] (2) The aqueous solution of β-cyclodextrin in (1) was added dropwise to the acetone solution described in Example 1 at a mass ratio of polycaprolactone-polylactic acid polycaprolactone copolymer:β-cyclodextrin of 1:1.5, and stirred vigorously for 3 hours.

[0055] (3) Continue stirring the mixed solution obtained in step (2) at room temperature for 24 hours. Remove the free polycaprolactone-polylactic acid polycaprolactone copolymer by centrifugation with acetone, and remove the unencapsulated cyclodextrin by centrifugation with deionized water;

[0056] (4) The β-cyclodextrin / polycaprolactone-polylactic acid polycaprolactone copolymer inclusion complex obtained in step (3) was ultrasonically dispersed in tetrahydrofuran at a mass percentage of 0.8% to obtain inclusion complex microspheres.

[0057] Example 5:

[0058] The preparation method of the β-cyclodextrin / polycaprolactone-polylactic acid polycaprolactone copolymer inclusion complex microspheres in this embodiment includes the following steps:

[0059] (1) The polycaprolactone-polylactic acid polycaprolactone copolymer in Example 1 was dissolved in acetone at 60°C at 1.5% by mass, and β-cyclodextrin was dissolved in deionized water at 8% by mass.

[0060] (2) The aqueous solution of β-cyclodextrin in (1) was added dropwise to the acetone solution described in Example 1 at a mass ratio of polycaprolactone-polylactic acid polycaprolactone copolymer:β-cyclodextrin of 1:2, and stirred vigorously for 3 hours.

[0061] (3) Continue stirring the mixed solution obtained in step (2) at room temperature for 24 hours. Remove the free polycaprolactone-polylactic acid polycaprolactone copolymer by centrifugation with acetone, and remove the unencapsulated cyclodextrin by centrifugation with deionized water;

[0062] (4) The β-cyclodextrin / polycaprolactone-polylactic acid polycaprolactone copolymer inclusion complex obtained in step (3) was ultrasonically dispersed in acetone at a mass percentage of 0.5% to obtain inclusion complex microspheres.

[0063] Example 6:

[0064] The preparation method of the β-cyclodextrin / polycaprolactone-polylactic acid polycaprolactone copolymer inclusion complex microspheres in this embodiment includes the following steps:

[0065] (1) Dissolve 2% by mass of polycaprolactone-polylactic acid polycaprolactone copolymer with a number average molecular weight of 9000 g / mol in acetone at 60°C, and dissolve 8% by mass of β-cyclodextrin in deionized water.

[0066] (2) The aqueous solution of β-cyclodextrin in (1) was added dropwise to the acetone solution described in Example 1 at a mass ratio of polycaprolactone-polylactic acid polycaprolactone copolymer:β-cyclodextrin of 1:0.5, and stirred vigorously for 3 hours.

[0067] (3) Continue stirring the mixed solution obtained in step (2) at room temperature for 24 hours. Remove the free polycaprolactone-polylactic acid polycaprolactone copolymer by centrifugation with acetone, and remove the unencapsulated cyclodextrin by centrifugation with deionized water;

[0068] (4) The β-cyclodextrin / polycaprolactone-polylactic acid polycaprolactone copolymer inclusion complex obtained in step (3) was ultrasonically dispersed in dimethyl sulfoxide at a mass percentage of 0.5% to obtain inclusion complex microspheres.

[0069] Example 7:

[0070] The preparation method of the β-cyclodextrin / polycaprolactone-polylactic acid polycaprolactone copolymer inclusion complex microspheres in this embodiment includes the following steps:

[0071] (1) The polycaprolactone-polylactic acid polycaprolactone copolymer in Example 6 was dissolved in acetone at 60°C at 1.5% by mass, and β-cyclodextrin was dissolved in deionized water at 8% by mass.

[0072] (2) The aqueous solution of β-cyclodextrin in (1) was added dropwise to the acetone solution in Example 1 at a mass ratio of polycaprolactone-polylactic acid polycaprolactone copolymer:β-cyclodextrin of 1:1, and stirred vigorously for 3 hours.

[0073] (3) Continue stirring the mixed solution obtained in step (2) at room temperature for 24 hours. Remove the free polycaprolactone-polylactic acid polycaprolactone copolymer by centrifugation with acetone, and remove the unencapsulated cyclodextrin by centrifugation with deionized water;

[0074] (4) The β-cyclodextrin / polycaprolactone-polylactic acid polycaprolactone copolymer inclusion complex obtained in step (3) was ultrasonically dispersed in acetone at a mass percentage of 0.5% to obtain inclusion complex microspheres.

[0075] Because there are numerous embodiments of the present invention and a large amount of experimental data for each embodiment, it is not suitable to list and describe them one by one here. However, the content to be verified and the final conclusions obtained in each embodiment are similar. Therefore, the verification content of each embodiment will not be described one by one here, but only embodiments 1-7 are used as representatives to illustrate the advantages of the present invention.

[0076] The above description is merely a detailed explanation of preferred embodiments and principles of the present invention. For those skilled in the art, there may be changes in specific implementation methods based on the ideas provided by the present invention, and these changes should also be considered within the scope of protection of the present invention.

Claims

1. A method for preparing microspheres of a β-cyclodextrin / polycaprolactone-polylactic acid polycaprolactone copolymer inclusion complex, characterized in that, Includes the following steps: (1) Polycaprolactone, lactide, and caprolactone are dissolved in toluene. Using polycaprolactone as a macromolecular initiator, ring-opening polymerization is carried out under nitrogen atmosphere with the catalysis of stannous octoate. After precipitation with diethyl ether, centrifugation, and washing, polycaprolactone-polylactic acid-polycaprolactone copolymer is obtained. Polycaprolactone is one block, and the random copolymer of polylactic acid and polycaprolactone is another block. The mass ratio of polycaprolactone, lactide, and caprolactone is 2:(2-4):(3-6), and the number average molecular weight of polycaprolactone is 8000-15000 g / mol. (2) Dissolve the polycaprolactone-polylactic acid polycaprolactone copolymer in acetone solution and heat it to the target temperature to obtain an acetone solution of polycaprolactone-polylactic acid polycaprolactone copolymer; (3) Add the aqueous solution of β-cyclodextrin dropwise to the acetone solution of polycaprolactone-polylactic acid polycaprolactone copolymer and stir vigorously to obtain a mixed solution; wherein the mass ratio of polycaprolactone-polylactic acid polycaprolactone copolymer to β-cyclodextrin is 1:(0.5~2.5). (4) The mixed solution was stirred at room temperature for a predetermined time, and then washed by centrifugation with acetone and water to obtain the β-cyclodextrin / polycaprolactone-polylactic acid polycaprolactone copolymer inclusion complex; wherein, β-cyclodextrin selectively includes the polycaprolactone block molecular chain of the polycaprolactone-polylactic acid polycaprolactone copolymer to obtain a high molecular weight cyclodextrin inclusion complex with one end hydrophilic and the other end hydrophobic. (5) The inclusion complex of β-cyclodextrin / polycaprolactone-polylactic acid polycaprolactone was ultrasonically dispersed in a solvent to obtain inclusion complex microspheres.

2. The preparation method according to claim 1, characterized in that, In step (1), the parameters for ring-opening polymerization include: temperature of 100-120℃ and polymerization reaction time of 17-24h.

3. The preparation method according to claim 1, characterized in that, In step (2), the mass percentage of the acetone solution of polycaprolactone-polylactic acid polycaprolactone copolymer is 1-2%.

4. The preparation method according to claim 1, characterized in that, In step (2), the target temperature is 50-70℃.

5. The preparation method according to claim 1, characterized in that, In step (3), the vigorous stirring time is 2 to 4 hours.

6. The preparation method according to claim 1, characterized in that, In step (3), the mass percentage of the aqueous solution of β-cyclodextrin is 5-10%.

7. The preparation method according to claim 1, characterized in that, In step (4), the predetermined duration is not less than 20 hours.

8. The preparation method according to claim 1, characterized in that, In step (5), the mass percentage of the dispersion of the β-cyclodextrin / polycaprolactone-polylactic acid polycaprolactone copolymer inclusion complex in the solvent is 0.2-1%.

9. The preparation method according to claim 1, characterized in that, In step (5), the solvent is either a polar or non-polar solvent.

Images