A polylactic acid-gelatin composite modified material, a preparation method and application thereof

Abstract

This invention belongs to the field of biomedical polymer materials technology, and discloses a polylactic acid-gelatin composite modified material and its preparation method and application. The preparation method includes the following steps: (1) dissolving polylactic acid to obtain a polylactic acid solution; dissolving gelatin to obtain a gelatin solution; (2) adding the gelatin solution to the polylactic acid solution to obtain a mixture; (3) adding a crosslinking agent to the mixture, reacting to obtain a blend; (4) injecting the blend into a mold and freeze-drying to obtain the polylactic acid-gelatin composite modified material; the gelatin is selected from type A gelatin or type B gelatin; the crosslinking agent is 1-ethyl-(3-dimethylaminopropyl)carbodiimide hydrochloride and / or N-hydroxysuccinimide; the mass ratio of polylactic acid to gelatin in the mixture is 60-95:(5-40). The obtained polylactic acid-gelatin composite modified material simultaneously meets the requirements of good mechanical properties and degradation performance, and the degradation performance can be controlled.

Description

Technical Field

[0001] This invention belongs to the field of biomedical polymer materials technology, specifically relating to a polylactic acid-gelatin composite modified material, its preparation method, and its application. Background Technology

[0002] Polylactic acid (PLA) is an aliphatic polyester derived from renewable resources. It possesses good biodegradability, biocompatibility, and a certain degree of mechanical strength, and has been approved for use in various human implant materials. PLA has shown great application potential in orthopedic internal fixation devices, tissue engineering scaffolds, surgical sutures, and dental guided tissue regeneration membranes.

[0003] However, the application of single PLA materials in the medical field has the following inherent drawbacks: (1) Strong hydrophobicity leads to poor cell adhesion and easily triggers aseptic inflammatory response; (2) The degradation cycle is long and cannot be adjusted. The degradation of PLA usually takes more than 2 years, which is not matched with the growth rate of new tissue. (3) It lacks bioactive sites and does not have the ability to induce tissue regeneration; (4) Insufficient mechanical properties.

[0004] To address these shortcomings, researchers have attempted to blend PLA with natural polymers to obtain modified materials. However, the resulting modified materials still suffer from poor mechanical properties or complex preparation processes. Furthermore, these modified materials are primarily used as drug carriers or hemostatic materials, making them unsuitable for human implantation. Moreover, existing PLA-modified materials are prone to using toxic reagents, such as hexafluoroisopropanol (HFIP), during preparation, posing biosafety risks and hindering the fabrication of thick-walled three-dimensional scaffolds.

[0005] Therefore, there is an urgent need to develop a PLA modified material that is easy to process and can simultaneously meet the requirements of good mechanical properties and degradation performance. Summary of the Invention

[0006] This invention aims to solve at least one of the technical problems existing in the prior art. To this end, this invention proposes a polylactic acid-gelatin composite modified material, its preparation method, and its application. The polylactic acid-gelatin composite modified material prepared by the method of this invention simultaneously satisfies good mechanical properties and degradation performance, and the degradation performance can be controlled. Furthermore, the polylactic acid-gelatin composite modified material of this invention also exhibits good biocompatibility.

[0007] The preparation method described in this invention is based on solution blending-crosslinking-freeze drying to obtain polylactic acid-gelatin composite modified materials. By precisely controlling the specific selection of gelatin ratio, gelatin type and crosslinking agent type, medical implant materials with good mechanical properties, controllable degradation rate and excellent cell compatibility can be obtained, solving the problems of strong hydrophobicity, untunable degradation and complex processing of PLA in the prior art.

[0008] The first aspect of the present invention provides a method for preparing a polylactic acid-gelatin composite modified material.

[0009] Specifically, a method for preparing a polylactic acid-gelatin composite modified material includes the following steps: (1) Dissolve polylactic acid to obtain a polylactic acid solution; dissolve gelatin to obtain a gelatin solution; (2) Add the gelatin solution to the polylactic acid solution to obtain a mixture; (3) Add a crosslinking agent to the mixture and react to obtain a blend; (4) The blend liquid is injected into a mold and freeze-dried to obtain the polylactic acid-gelatin composite modified material; The gelatin is selected from type A gelatin or type B gelatin; The crosslinking agent is 1-ethyl-(3-dimethylaminopropyl)carbodiimide hydrochloride (EDC) and / or N-hydroxysuccinimide (NHS). The mass ratio of polylactic acid to gelatin in the mixture is 60-95:(5-40).

[0010] Preferably, the isoelectric point pH of the type A gelatin is 7.0-9.0.

[0011] Preferably, the isoelectric point pH of the type B gelatin is 4.8-5.2.

[0012] Preferably, the gel strength of the gelatin is 200~300 Bloom (Bloom is a unit of gel strength of gelatin).

[0013] Preferably, in the mixture, based on the total mass of polylactic acid and gelatin, the mass fraction of polylactic acid is 60-95% and the mass fraction of gelatin is 5-40%.

[0014] Preferably, in step (1), the polylactic acid is L-polylactic acid (PLLA) or racemic polylactic acid (PDLLA).

[0015] Preferably, in step (1), the polylactic acid has a weight-average molecular weight of 50,000 to 200,000.

[0016] Preferably, in step (1), the solvent used in the dissolution process includes 1,4-dioxane and / or deionized water. For example, it is a mixed solvent of 1,4-dioxane and deionized water, and the volume ratio of 1,4-dioxane to deionized water in the mixed solvent is 70-90:(10-30). This solvent is environmentally friendly and non-toxic.

[0017] Preferably, in step (1), the mass concentration of the gelatin solution is 5-15%. For example, it is 5%, 10%, or 15%.

[0018] Preferably, in step (3), the mass of the crosslinking agent is 1-20% of the mass of the gelatin in the mixed solution. For example, it is 5-20%.

[0019] Preferably, in step (3), the crosslinking agent is composed of 1-ethyl-(3-dimethylaminopropyl)carbodiimide hydrochloride (EDC) and N-hydroxysuccinimide (NHS) in a molar ratio of 1:(0.5-1.5).

[0020] Preferably, in step (3), the reaction temperature is 0-5℃ and the reaction time is 10-12 hours.

[0021] Preferably, in step (4), the freeze-drying process is as follows: first freeze at -20°C to -30°C for 8-12 hours, and then freeze at -50°C to -40°C for 30-48 hours.

[0022] Preferably, in step (4), after the freeze-drying is completed, the polylactic acid-gelatin composite modified material is soaked in deionized water to remove residual crosslinking agent and solvent, and then the freeze-drying is repeated. This process can remove impurities.

[0023] Preferably, in step (4), the mold is a support, rod, or prosthesis. It can be designed into various shapes according to the shape requirements of the medical implant material.

[0024] Preferably, in step (4), the blend liquid is vacuum dried by casting to obtain a thin film of polylactic acid-gelatin composite modified material.

[0025] The preparation method described in this invention can achieve cost control and performance adjustment, and can achieve precise matching of mechanical properties and degradation rate by adjusting the gelatin content and crosslinking degree.

[0026] A second aspect of the present invention provides a polylactic acid-gelatin composite modified material.

[0027] Specifically, a polylactic acid-gelatin composite modified material is prepared by the above preparation method.

[0028] A third aspect of the present invention provides an application of a polylactic acid-gelatin composite modified material.

[0029] The application of polylactic acid-gelatin composite modified material prepared by the above method in the preparation of medical devices.

[0030] Compared with the prior art, the beneficial effects of the present invention are as follows: (1) The preparation method of the present invention obtains a medical implant material with good mechanical properties, controllable degradation rate and excellent cell compatibility by precisely controlling the gelatin ratio, gelatin type and crosslinking agent type, thereby solving the problems of strong hydrophobicity, unadjustable degradation and complex processing of PLA in the prior art.

[0031] (2) In the polylactic acid-gelatin composite modified material of the present invention, when the gelatin content is 20% to 30% of the total mass of gelatin and polylactic acid, the elastic structure of gelatin forms a microscopic semi-interpenetrating network with PLA, and the tensile strength is increased by 15% to 30% compared with pure PLA, thus overcoming the technical bias of the mechanical properties of natural polymer / PLA blended materials in the prior art.

[0032] (3) The hydrophilicity of the polylactic acid-gelatin composite modified material described in this invention is significantly improved: the water contact angle is reduced from 125° of pure PLA to 0° to 50°, the water absorption rate is increased by 3 to 5 times, and the initial cell adhesion rate is increased by more than 2 times.

[0033] (4) The degradation rate of the polylactic acid-gelatin composite modified material described in this invention is adjustable: by controlling the gelatin content and cross-linking degree, the degradation half-life can be precisely adjusted within the range of 4 weeks to 12 months, thus achieving the matching between the degradation rate of PLA-based materials and the soft / hard tissue repair cycle.

[0034] (5) The polylactic acid-gelatin composite modified material of the present invention has excellent cell compatibility: the cytotoxicity rating is 0, and the proliferation rate of L929 and MC3T3-E1 cells is >110%, which is significantly better than that of the pure PLA group (<90%).

[0035] (6) The preparation method described in this invention is a green process: no fluorine-containing toxic solvents are used throughout the process, the production cost is reduced by more than 40%, and it is feasible for industrialization. Detailed Implementation

[0036] To enable those skilled in the art to more clearly understand the technical solutions described in this invention, the following embodiments are provided for illustration. It should be noted that the following embodiments do not constitute a limitation on the scope of protection claimed by this invention.

[0037] Unless otherwise specified, the raw materials, reagents or devices used in the following examples are available from conventional commercial sources or can be obtained by existing known methods.

[0038] The polylactic acid used in the following examples is L-polylactic acid (PLLA), with a weight-average molecular weight of 95,000-100,000 g / mol.

[0039] The gelatin used in the following examples is type A gelatin with an isoelectric point pH of 8.0 and a gel strength of 250 Bloom. Example 1

[0040] A method for preparing a polylactic acid-gelatin composite modified material includes the following steps: (1) Dissolve polylactic acid in a mixed solvent (the mixed solvent is composed of 1,4-dioxane and deionized water in a volume ratio of 90:10), stir magnetically for 2 hours to obtain a polylactic acid solution; dissolve type A gelatin in deionized water (50℃ water bath) to obtain a 10% mass fraction gelatin solution; (2) Blending: Add the gelatin solution dropwise to the polylactic acid solution and stir at 40°C for 30 minutes to obtain a mixture (the mass ratio of gelatin to polylactic acid in the mixture is 5:95). (3) Crosslinking: Add a crosslinking agent (the crosslinking agent is composed of EDC and NHS in a molar ratio of 1:1, and the mass of EDC is 5% of the mass of gelatin in the mixture) to the mixture, react at 4°C for 12 hours to obtain a blend; (4) Molding and freeze-drying: The blend liquid is injected into the scaffold mold, frozen at -20℃ for 12 hours, and then frozen at -50℃ for 48 hours to obtain a three-dimensional porous scaffold. It is then soaked in deionized water for 10 hours, frozen at -20℃ for 12 hours, and then frozen at -50℃ for 48 hours to obtain polylactic acid-gelatin composite modified material. Example 2

[0041] A method for preparing a polylactic acid-gelatin composite modified material includes the following steps: (1) Dissolve polylactic acid in a mixed solvent (the mixed solvent is composed of 1,4-dioxane and deionized water in a volume ratio of 90:10), stir magnetically for 2 hours to obtain a polylactic acid solution; dissolve type A gelatin in deionized water (50℃ water bath) to obtain a 10% mass fraction gelatin solution; (2) Blending: Add the gelatin solution dropwise to the polylactic acid solution and stir at 40°C for 30 minutes to obtain a mixture (the mass ratio of gelatin to polylactic acid in the mixture is 30:70). (3) Crosslinking: Add a crosslinking agent (the crosslinking agent is composed of EDC and NHS in a molar ratio of 1:1, and the mass of EDC is 10% of the mass of gelatin in the mixture) to the mixture, react at 4°C for 12 hours to obtain a blend; (4) Molding and freeze-drying: The blend liquid is injected into the scaffold mold, frozen at -20℃ for 12 hours, and then frozen at -50℃ for 48 hours to obtain a three-dimensional porous scaffold. It is then soaked in deionized water for 10 hours, frozen at -20℃ for 12 hours, and then frozen at -50℃ for 48 hours to obtain polylactic acid-gelatin composite modified material. Example 3

[0042] A method for preparing a polylactic acid-gelatin composite modified material includes the following steps: (1) Dissolve polylactic acid in a mixed solvent (the mixed solvent is composed of 1,4-dioxane and deionized water in a volume ratio of 90:10), stir magnetically for 2 hours to obtain a polylactic acid solution; dissolve type A gelatin in deionized water (50℃ water bath) to obtain a 10% mass fraction gelatin solution; (2) Blending: Add the gelatin solution dropwise to the polylactic acid solution and stir at 40°C for 30 minutes to obtain a mixture (the mass ratio of gelatin to polylactic acid in the mixture is 40:60). (3) Crosslinking: Add a crosslinking agent (the crosslinking agent is composed of EDC and NHS in a molar ratio of 1:1, and the mass of EDC is 15% of the mass of gelatin in the mixture) to the mixture, react at 4°C for 12 hours to obtain a blend; (4) Molding and freeze-drying: The blend liquid is injected into the scaffold mold, frozen at -20℃ for 12 hours, and then frozen at -50℃ for 48 hours to obtain a three-dimensional porous scaffold. It is then soaked in deionized water for 10 hours, frozen at -20℃ for 12 hours, and then frozen at -50℃ for 48 hours to obtain polylactic acid-gelatin composite modified material. Example 4

[0043] A method for preparing a polylactic acid-gelatin composite modified material includes the following steps: (1) Dissolve polylactic acid in a mixed solvent (the mixed solvent is composed of 1,4-dioxane and deionized water in a volume ratio of 90:10), stir magnetically for 2 hours to obtain a polylactic acid solution; dissolve type A gelatin in deionized water (50℃ water bath) to obtain a 10% mass fraction gelatin solution; (2) Blending: Add the gelatin solution dropwise to the polylactic acid solution and stir at 40°C for 30 minutes to obtain a mixture (the mass ratio of gelatin to polylactic acid in the mixture is 30:70). (3) Crosslinking: Add a crosslinking agent (the crosslinking agent is composed of EDC and NHS in a molar ratio of 1:1, and the mass of EDC is 20% of the mass of gelatin in the mixture) to the mixture, react at 4°C for 12 hours to obtain a blend; (4) Molding and freeze-drying: The blend liquid is injected into the scaffold mold, frozen at -20℃ for 12 hours, and then frozen at -50℃ for 48 hours to obtain a three-dimensional porous scaffold. It is then soaked in deionized water for 10 hours, frozen at -20℃ for 12 hours, and then frozen at -50℃ for 48 hours to obtain polylactic acid-gelatin composite modified material. Comparative Example 1

[0044] A method for preparing pure polylactic acid material includes the following steps: (1) Dissolve polylactic acid in a mixed solvent (the mixed solvent is composed of 1,4-dioxane and deionized water in a volume ratio of 90:10), and stir magnetically for 2 hours to obtain a polylactic acid solution; (2) Molding and freeze drying: The polylactic acid solution was injected into the scaffold mold, frozen at -20°C for 12 hours, and then frozen at -50°C for 48 hours to obtain a three-dimensional porous scaffold. It was then soaked in deionized water for 10 hours, frozen at -20°C for 12 hours, and then frozen at -50°C for 48 hours to obtain pure polylactic acid material.

[0045] Compared to Example 1, Comparative Example 1 did not contain gelatin or crosslinking agent. Comparative Example 2

[0046] Compared with Example 2, the only difference in Comparative Example 2 is that pigskin gelatin (isoelectric point pH 5.5) was used instead of type A gelatin in Example 2. The other processes were the same as in Example 2. Comparative Example 3

[0047] Compared with Example 2, the only difference in Comparative Example 3 is that glutaraldehyde is used instead of the crosslinking agent in Example 2, and the mass of glutaraldehyde is 1.5% of the mass of gelatin in the mixture. The other processes are the same as in Example 2. Comparative Example 4

[0048] Compared with Example 2, the only difference in Comparative Example 4 is that the mass ratio of gelatin to polylactic acid in the mixed solution in step (2) is 50:50. The other processes are the same as in Example 2.

[0049] Product effectiveness test The polylactic acid-gelatin composite modified material and pure polylactic acid material prepared in the above examples and comparative examples were tested for tensile strength, elongation at break, water contact angle, 2-week degradation weight loss rate, and cell activity. The results are shown in Table 1.

[0050] Tensile strength and elongation at break: Tested using a universal testing machine in accordance with GB / T 1040.1-2018 "Determination of tensile properties of plastics".

[0051] Water contact angle: The seated drop method was used to test the water contact angle using a contact angle measuring instrument at room temperature. Five different points were measured for each sample and the average value was calculated.

[0052] 2-week degradation weight loss: The sample was immersed in phosphate-buffered saline (PBS) at pH 7.4 and incubated in a 37°C constant temperature shaking incubator. The PBS was replaced weekly. At the predetermined time point (2 weeks), the sample was removed, freeze-dried, and weighed. The 2-week degradation weight loss was calculated using the formula (initial mass - dried mass) / initial mass × 100%.

[0053] Cell viability: Referring to GB / T 16886.5-2017 "Biological evaluation of medical devices - Part 5: In vitro cytotoxicity test", the proliferation of L929 mouse fibroblasts after culturing in the material extract for 24 h, 48 h and 72 h was detected by CCK-8 method. The cell viability of the blank control group was normalized to 100%.

[0054] Table 1 Tensile strength (MPa) Elongation at break (%) Water contact angle (°) Degradation weight loss rate (%) over 2 weeks Cell viability (%) Example 1 11.2 2.8 95 2.1 96 Example 2 13.5 2.1 22 9.8 129 Example 3 11.8 2.4 0 18.5 135 Example 4 14.2 2.0 25 4.5 118 Comparative Example 1 9.1 3.0 127 0.5 82 Comparative Example 2 10.8 1.5 58 14.2 103 Comparative Example 3 12.1 1.8 30 6.5 88 Comparative Example 4 8.5 0.8 0 28.5 142 As can be seen from Table 1, the polylactic acid-gelatin composite modified material prepared in the examples has better mechanical properties and more suitable and controllable degradation properties compared with the material prepared in the comparative example.

[0055] In particular, the polylactic acid-gelatin composite modified material prepared in Example 2 combines mechanical, hydrophilic, and bioactivity properties, while the polylactic acid-gelatin composite modified material prepared in Example 3 exhibits a rapid degradation rate, making it suitable for short-term soft tissue repair. The polylactic acid-gelatin composite modified material prepared in Example 4 is suitable for bone repair requiring long-term mechanical stability.

[0056] Compared to Example 2, Comparative Example 2 used gelatin of an undefined type, which resulted in a significant decrease in the tensile strength and cell activity of the prepared material. This demonstrates that the type A or type B gelatin selected in the present invention with a specific isoelectric point range is crucial for achieving excellent overall performance.

[0057] Compared to Example 2, Comparative Example 3, while achieving a certain crosslinking effect using glutaraldehyde, produced a material exhibiting significant cytotoxicity and low cell activity. This demonstrates that the EDC / NHS zero-length crosslinking agent system of the present invention has an irreplaceable advantage in ensuring good biocompatibility.

[0058] The material prepared in Comparative Example 4 was brittle, difficult to mold, and exhibited a weight loss of 28.5% after two weeks of degradation, resulting in structural collapse. Compared to Example 2, in Comparative Example 4, when the gelatin content exceeded 40%, the structure of polylactic acid as a continuous phase was disrupted, leading to a sharp decline in the material's mechanical properties, failing to meet the basic mechanical requirements for implantation. This demonstrates the critical significance of the gelatin content range defined in this invention.

[0059] In summary, this invention successfully prepared a material with significantly improved mechanical properties, degradation performance, and biocompatibility by precisely controlling the type, content, and crosslinking agent of gelatin. Comparative experiments further confirm that the specific type of gelatin, EDC / NHS crosslinking agent, and gelatin content range of 5%–40% selected in this invention are key technical characteristics for obtaining a material that combines high strength, controllable degradation, and excellent cell compatibility.

[0060] The above description outlines the basic principles, main technical features, and advantages of this invention. Those skilled in the art should understand that the scope of protection of this invention is not limited to the above embodiments. Various changes and modifications can be made to this invention without departing from its spirit and scope, and all such changes and modifications fall within the scope of the invention as claimed.

Claims

1. A method for preparing a polylactic acid-gelatin composite modified material, characterized in that, Includes the following steps: (1) Dissolve polylactic acid to obtain a polylactic acid solution; Dissolve the gelatin to obtain a gelatin solution; (2) Add the gelatin solution to the polylactic acid solution to obtain a mixture; (3) Add a crosslinking agent to the mixture and react to obtain a blend; (4) The blend liquid is injected into a mold and freeze-dried to obtain the polylactic acid-gelatin composite modified material; The gelatin is selected from type A gelatin or type B gelatin; The crosslinking agent is 1-ethyl-(3-dimethylaminopropyl)carbodiimide hydrochloride and / or N-hydroxysuccinimide; The mass ratio of polylactic acid to gelatin in the mixture is 60-95:(5-40).

2. The preparation method according to claim 1, characterized in that, The isoelectric point pH of the type A gelatin is 7.0-9.0; and / or the isoelectric point pH of the type B gelatin is 4.8-5.

2.

3. The preparation method according to claim 1, characterized in that, In step (1), the polylactic acid is L-polylactic acid or racemic polylactic acid.

4. The preparation method according to claim 1, characterized in that, In step (1), the solvent used in the dissolution process includes 1,4-dioxane and / or deionized water.

5. The preparation method according to claim 1, characterized in that, In step (1), the mass concentration of the gelatin solution is 5-15%.

6. The preparation method according to claim 1, characterized in that, In step (3), the mass of the crosslinking agent is 1-20% of the mass of gelatin in the mixed solution.

7. The preparation method according to claim 1, characterized in that, In step (3), the crosslinking agent is composed of 1-ethyl-(3-dimethylaminopropyl)carbodiimide hydrochloride and N-hydroxysuccinimide in a molar ratio of 1:(0.5-1.5); and / or, in step (3), the reaction temperature is 0-5°C and the reaction time is 10-12 hours.

8. The preparation method according to claim 1, characterized in that, In step (4), the freeze-drying process is as follows: first freeze at -20℃ to -30℃ for 8-12 hours, and then freeze at -50℃ to -40℃ for 30-48 hours.

9. A polylactic acid-gelatin composite modified material, characterized in that, It is prepared by the preparation method according to any one of claims 1-8.

10. The application of the polylactic acid-gelatin composite modified material prepared by the preparation method according to any one of claims 1-8 in the preparation of medical devices.