Stress-responsive adaptive expanding bone repair scaffold and preparation method and application thereof

Abstract

This invention belongs to the field of medical implant materials and devices, and discloses a method for preparing a stress-responsive adaptive expandable bone repair scaffold. The method includes: preparing a polymer solution of polylactic acid-glycolic acid copolymer (PLGA); preparing a PLGA raw material with a molecular chain orientation structure using electrospinning technology; preparing a scaffold with a three-dimensional interconnected porous structure using the PLGA raw material; applying cyclic compressive stress to the porous scaffold to activate its stress-responsive expansion characteristics, thereby obtaining a stress-responsive adaptive expandable bone repair scaffold. This invention also discloses the scaffold prepared according to the above method and its applications, solving the technical problems of morphological mismatch, interface voids, and inability to respond to stress environments in existing passively filled scaffolds.

Description

Technical Field

[0001] This invention belongs to the field of medical implant materials and devices, specifically relating to stress-responsive adaptive expandable bone repair scaffolds. This invention also relates to the preparation method and application of the above-mentioned scaffolds. Background Technology

[0002] Bone defect repair is one of the core challenges in orthopedic clinical practice, commonly seen in surgeries such as traumatic fractures, bone tumor resection, joint revision surgery, and spinal fusion. Currently, there are three main types of bone defect filling methods used clinically, but all have inherent limitations: 1. Autologous bone grafting: It is considered the "gold standard", but problems such as donor site damage, limited sources, and postoperative pain limit its widespread application.

[0003] 2. Allogeneic bone: The sources are relatively wide, but there are risks such as immune rejection, disease transmission, and low bone induction activity.

[0004] 3. Synthetic bone repair materials, such as calcium phosphate bone cement, calcium sulfate granules, and polylactic acid scaffolds, are currently the most commonly used clinical solutions. However, these materials are all passive fillers, and they have the following unresolved technical problems: Shape mismatch: The fixed shape of the scaffold cannot adapt to irregular bone defect cavities, and temporary trimming and reshaping are often required during surgery, which prolongs the operation time and makes it difficult to achieve a perfect match.

[0005] Interface voids: Unpredictable microvoids exist between the scaffold and the host bone wall, hindering bone ingrowth and leading to delayed or failed bone healing.

[0006] Unresponsive to stress environments: Existing scaffolds cannot respond to postoperative physiological stress environments, cannot actively guide bone regeneration, and cannot adjust their own degradation rate according to the bone healing process.

[0007] Therefore, there is an urgent need for a bone repair scaffold that can actively adapt to the shape of bone defects and intelligently adjust its behavior according to the physiological stress environment. Summary of the Invention

[0008] The first objective of this invention is to provide a stress-responsive adaptive expandable bone repair scaffold, which solves the technical problems of morphological mismatch, interface voids and inability to respond to stress environments in existing passive filling scaffolds.

[0009] A second objective of this invention is to provide a method for preparing the aforementioned stent.

[0010] A third object of the present invention is to provide the use of the above-described scaffold in the preparation of a medical device for the treatment and repair of bone defects.

[0011] The first technical solution adopted in this invention is: a method for preparing a stress-responsive adaptive expandable bone repair scaffold, comprising: preparing a polymer solution of polylactic acid-glycolic acid copolymer (PLGA); preparing a PLGA raw material with a molecular chain orientation structure using electrospinning technology; preparing a scaffold with a three-dimensional interconnected porous structure using the PLGA raw material; applying cyclic compressive stress to the porous scaffold to activate the stress-responsive expansion characteristics of the scaffold, thereby obtaining a stress-responsive adaptive expandable bone repair scaffold.

[0012] The first technical solution adopted in this invention is further characterized by: The above preparation method is implemented according to the following steps: Step 1: Preparation of PLGA raw materials with molecular chain orientation structure: Polylactic acid-glycolic acid copolymer is dissolved in dichloromethane or trichloromethane to prepare a polymer solution with a mass fraction of 10%-20%. The polymer solution is electrospun under a high voltage electric field to obtain oriented PLGA fibers. After drying, the collected oriented PLGA fibers become PLGA raw materials with molecular chain orientation structure. Step 2: Fabrication of a scaffold with a three-dimensional interconnected porous structure: The oriented PLGA fibers obtained in step 1 are cut into short fibers, mixed evenly with the pore-forming agent, filled into a mold, hot-pressed, cooled and demolded, and the molded body is immersed in deionized water to fully dissolve the sodium chloride pore-forming agent. Finally, drying yields a porous scaffold with a three-dimensional interconnected porous structure, but whose stress response characteristics have not yet been activated; Step 3: Activate the stress response expansion characteristics of the stent: Cyclic compressive stress is applied to the porous scaffold obtained in step 2 to activate its stress response capability. After processing, it is vacuum dried and stored to obtain a stress-responsive adaptive expansion bone repair scaffold.

[0013] In step 1, the polylactic acid-glycolic acid copolymer (PLGA) is of medical grade, the molar ratio of lactic acid to glycolic acid is 50:50 to 85:15, the preferred ratio is 75:25, and the molecular weight is 50,000 to 200,000 Daltons, preferably 100,000 to 150,000 Daltons. The high-voltage electric field is 15-25kV; The electrospinning receiving device is a rotating drum with a rotation speed of 1000-3000 rpm to further enhance the orientation of the molecular chains; The collected oriented PLGA fibers are dried in a vacuum oven at 40-60℃ for 12-48 hours to remove residual solvent. The dried fibers are PLGA raw materials with molecular chain orientation structure.

[0014] Step 2 is as follows: Cut the oriented PLGA fibers obtained in step 1 into short fibers with a length of 1-5 mm, and mix them evenly with the pore-forming agent at a mass ratio of 1:10-1:5. Fill the mixture into the mold and hot press it at a temperature of 60-80℃ and a pressure of 5-10MPa for 30-60 minutes. After cooling and demolding, the molded body is immersed in deionized water and continuously shaken in a constant temperature shaker at 37°C for 48-72 hours, with the deionized water replaced every 12 hours to fully dissolve the pore-forming agent; finally, it is dried in a vacuum oven at 40-60°C for 12-48 hours to obtain a porous scaffold with a three-dimensional interconnected porous structure, but whose stress response characteristics have not yet been activated.

[0015] In step 2, the pore-forming agent is sodium chloride particles with a particle size of 300-500 μm.

[0016] Step 3 is as follows: The porous scaffold obtained in Step 2 is placed in an environment of 37°C and 80%-90% relative humidity, and cyclic compressive stress is applied with a stress amplitude of 0.1-0.5MPa and a frequency of 1-5Hz for 24-48 hours. This process allows the oriented molecular chains in the scaffold to undergo pre-adaptation under simulated physiological stress conditions, thereby activating its stress response capability. After processing, the scaffold is vacuum dried and stored at room temperature to obtain a stress-responsive adaptive expansion bone repair scaffold.

[0017] The second technical solution adopted in this invention is: a stress-responsive adaptive expandable bone repair scaffold obtained according to the above method. The scaffold has a three-dimensional interconnected porous structure, and the whole has an arbitrary regular or irregular three-dimensional shape. The surface has a porous texture, the porosity is 70%-85%, and the pore size ranges from 300-500μm.

[0018] The initial volume of the aforementioned scaffold is 80%-95% of the bone defect area; The aforementioned stent automatically stops expanding when it encounters resistance from the host bone wall. After new bone forms and bears stress, the aforementioned scaffold triggers a degradation process, with the degradation rate matching the bone healing process. The porous structure of the aforementioned scaffold is loaded with bioactive substances.

[0019] The third technical solution adopted in this invention is: the application of the above-mentioned bone repair scaffold in the preparation of a medical device for treating bone defects.

[0020] The beneficial effects of this invention are: 1. Stress-driven directional expansion: The bone repair scaffold of the present invention is the first to utilize physiological stress to drive the bone repair scaffold to actively fill the bone defect area and achieve directional expansion in the direction of least resistance.

[0021] 2. Adaptive morphological adjustment: The bone repair scaffold of the present invention can automatically adjust its volume and shape according to the actual irregular shape of the bone defect area to form a perfect gapless fit.

[0022] 3. Mechano-biological closed-loop feedback: The entire process of "expansion-stopping-guided osteoogenesis-degradation" of the bone repair scaffold of the present invention is automatically regulated by the physiological stress environment, forming a closed-loop intelligent response system. Attached Figure Description

[0023] Figure 1 This is a schematic diagram of the overall appearance of the bracket of the present invention; Figure 2 This is a schematic diagram of the internal cross-sectional structure of the bracket of the present invention; Figure 3 This is an enlarged schematic diagram of the microstructure of the support surface of the present invention; Figure 4 This is a comparative schematic diagram of the bracket of the present invention and existing materials; Figure 5 This is a schematic diagram of the initial state of stent implantation according to the present invention; Figure 6 This is a schematic diagram of the expansion process of the stent according to the present invention; Figure 7 This is a schematic diagram of the complete expansion state of the stent according to the present invention; Figure 8 This is a schematic diagram of bone ingrowth and degradation after the scaffold of the present invention has been implanted. Detailed Implementation

[0024] The present invention will now be described in detail with reference to the accompanying drawings and specific embodiments.

[0025] This invention provides a stress-responsive adaptive expandable bone repair scaffold made of a stress-responsive biodegradable polymer. When subjected to continuous physiological stress, the internal molecular chains of the polymer align in a specific direction, causing the material to expand slowly along the direction of the stress. When the expansion encounters resistance, the expansion behavior automatically stops.

[0026] The support is a three-dimensional interconnected porous structure, with an overall shape that can be either regular or irregular. It can be designed into any shape best suited to the specific defects. For example, a cylinder can be used as an illustration. Figure 1 As shown, the surface has a porous texture, such as Figure 2 As shown, the porosity is 70%-85%, and the pore size ranges from 300-500 μm, which facilitates osteoblast migration, blood vessel ingrowth, and nutrient delivery. Figure 3 As shown, the rough surface of the pore walls facilitates cell adhesion, and the pores are interconnected through channels, which facilitates nutrient delivery and blood vessel ingrowth.

[0027] The initial volume of the scaffold is 80%-95% of the bone defect area, slightly smaller than the defect area, so that it can adaptively fill the defect area through self-expansion after implantation.

[0028] The stress-responsive biodegradable polymer is selected from one or more of polylactic acid-glycolic acid copolymer (PLGA), polycaprolactone (PCL), and polylactic acid (PLA), and is endowed with stress-responsive expansion properties after specific modification treatment.

[0029] The scaffold can load bioactive substances such as bone morphogenetic proteins, antibiotics, and growth factors into its porous structure to enhance its bone induction and anti-infection capabilities.

[0030] The preparation method of the above-mentioned stress-responsive adaptive expandable bone repair scaffold is as follows: I. Raw Material Selection Medical-grade polylactic acid-glycolic acid copolymer (PLGA) is selected, with a molar ratio of lactic acid to glycolic acid of 50:50 to 85:15, preferably 75:25, and a molecular weight of 50,000 to 200,000 Daltons, preferably 100,000 to 150,000 Daltons. This material has been approved by the FDA for use in various implants and has good biocompatibility and a controllable degradation rate.

[0031] II. Preparation of PLGA raw materials with molecular chain orientation structure PLGA is dissolved in dichloromethane or trichloromethane to prepare a polymer solution with a mass fraction of 10%-20% (preferably 15%). The solution is injected into an electrospinning device, and electrospinning is performed under a high voltage electric field of 15-25kV. During the spinning process, the polymer molecular chains are highly oriented along the fiber axis under the action of the electric field force. The receiving device is a rotating drum with a rotation speed of 1000-3000rpm to further enhance the orientation of the molecular chains. The collected oriented PLGA fibers are dried in a vacuum oven at 40-60℃ for 12-48 hours, preferably 24 hours, to remove residual solvent. The dried fibers are the PLGA raw material with molecular chain orientation structure.

[0032] III. Fabrication of scaffolds with three-dimensional interconnected porous structures The oriented PLGA fibers obtained in step one are cut into short fibers (1-5 mm in length) and mixed evenly with a pore-forming agent (sodium chloride particles, particle size 300-500 μm) at a mass ratio of 1:10-1:5.

[0033] The mixture is filled into a mold and hot-pressed at a temperature of 60-80℃ and a pressure of 5-10MPa for 30-60 minutes.

[0034] After cooling and demolding, the molded body is immersed in deionized water and continuously shaken in a constant temperature shaker at 37°C for 48-72 hours, with the deionized water replaced every 12 hours to fully dissolve the sodium chloride pore-forming agent. After removal, it is dried in a vacuum oven at 40-60°C for 12-48 hours, preferably 24 hours, to obtain a scaffold with a three-dimensional interconnected porous structure but whose stress response characteristics have not yet been activated.

[0035] IV. Stress Response Expansion Characteristics of Activated Stent The porous scaffold obtained in step two is placed in an environment of 37°C and 80%-90% relative humidity, and cyclic compressive stress (stress amplitude 0.1-0.5MPa, frequency 1-5Hz) is applied for 24-48 hours. This process allows the oriented molecular chains in the scaffold to undergo pre-adaptation under simulated physiological stress conditions, thereby activating its stress response capability.

[0036] After processing, the support was vacuum dried and stored at room temperature.

[0037] The final scaffold is the final product – a stress-responsive adaptive expandable bone repair scaffold.

[0038] V. Support Characteristic Parameters Table 1

[0039] VI. Mechanism of Stress-Response Expansion After the above treatment, the PLGA molecular chains inside the stent are oriented. When implanted in the body, the cyclic stress generated by the patient's physiological activities (muscle traction, weight-bearing, etc.) acts on the stent. Under the stress stimulation, the oriented molecular chains are further stretched, driving the stent to expand in the direction of the gap with the least resistance in the bone defect area.

[0040] When the scaffold expands to contact the host bone wall, the expansion behavior encounters resistance, and the stress state changes from "free expansion" to "restrained expansion". The driving force of molecular chain extension and the resistance of the bone wall reach a balance, and the expansion stops automatically.

[0041] The porous structure of the scaffold provides a crawling framework for osteoblasts, guiding new bone ingrowth. As the amount of new bone increases, the stress state of the scaffold changes, triggering a degradation process, and eventually leading to complete degradation and absorption.

[0042] The core advantages of the stent of the present invention are shown in Table 2: Table 2

[0043] The differences between the stent of the present invention and the prior art are shown in Table 3: Table 3

[0044] Comparison of the present invention's support structure with existing materials Figure 4 As shown, existing metals are non-degradable and non-expandable, ceramics are degradable but not expandable, and ordinary polymers are degradable but not expandable; the stent of the present invention simultaneously possesses the three characteristics of being degradable, expandable, and self-adaptive.

[0045] The technical solution of the present invention will be further illustrated below through embodiments.

[0046] Example 1 A method for preparing a stress-responsive adaptive expandable bone repair scaffold includes: preparing a polymer solution of polylactic acid-glycolic acid copolymer (PLGA); preparing a PLGA raw material with a molecular chain orientation structure using electrospinning technology; preparing a scaffold with a three-dimensional interconnected porous structure using the PLGA raw material; applying cyclic compressive stress to the porous scaffold to activate the stress-responsive expansion characteristics of the scaffold, thereby obtaining a stress-responsive adaptive expandable bone repair scaffold.

[0047] Example 2 The method for preparing a stress-responsive adaptive expandable bone repair scaffold is implemented according to the following steps: Step 1: Preparation of PLGA raw materials with molecular chain orientation structure: Polylactic acid-glycolic acid copolymer was dissolved in dichloromethane or trichloromethane to prepare a polymer solution with a mass fraction of 10%. The polymer solution was electrospun under a high voltage electric field to obtain oriented PLGA fibers. After drying, the collected oriented PLGA fibers become PLGA raw materials with molecular chain orientation structure. The polylactic acid-glycolic acid copolymer (PLGA) is of medical grade, with a molar ratio of lactic acid to glycolic acid of 50:50 and a molecular weight of 50,000 Daltons. The high-voltage electric field is 15kV; The electrospinning receiving device is a rotating drum with a rotation speed of 1000 rpm to further enhance the orientation of the molecular chains; The collected oriented PLGA fibers were dried in a vacuum oven at 40°C for 12 hours to remove residual solvent. The dried fibers are PLGA raw materials with molecular chain orientation structure.

[0048] Step 2: Fabrication of a scaffold with a three-dimensional interconnected porous structure: The oriented PLGA fibers obtained in step 1 are cut into short fibers, mixed evenly with the pore-forming agent, filled into a mold, hot-pressed, cooled and demolded, and the molded body is immersed in deionized water to fully dissolve the sodium chloride pore-forming agent. Finally, drying yields a porous scaffold with a three-dimensional interconnected porous structure, but whose stress response characteristics have not yet been activated; The oriented PLGA fibers obtained in step 1 are cut into short fibers with a length of 1 mm and mixed with the pore-forming agent at a mass ratio of 1:5. The mixture is filled into a mold and hot-pressed at a temperature of 60°C and a pressure of 5MPa for 30 minutes. After cooling and demolding, the molded body is immersed in deionized water and continuously shaken in a constant temperature shaker at 37°C for 48 hours, with the deionized water replaced every 12 hours to fully dissolve the pore-forming agent; finally, it is dried in a vacuum oven at 40°C for 12 hours to obtain a porous scaffold with a three-dimensional interconnected porous structure, but whose stress response characteristics have not yet been activated.

[0049] In step 2, the pore-forming agent is sodium chloride particles with a particle size of 300 μm.

[0050] Step 3: Activate the stress response expansion characteristics of the stent: The porous scaffold obtained in step 2 was placed in an environment of 37°C and 80% relative humidity, and cyclic compressive stress was applied with a stress amplitude of 0.1 MPa and a frequency of 1 Hz for 24 hours. This process caused the oriented molecular chains in the scaffold to undergo pre-adaptation under simulated physiological stress conditions, thereby activating its stress response capability. After processing, the scaffold is vacuum dried and stored at room temperature to obtain a stress-responsive adaptive expansion bone repair scaffold.

[0051] Example 3 The method for preparing a stress-responsive adaptive expandable bone repair scaffold is implemented according to the following steps: Step 1: Preparation of PLGA raw materials with molecular chain orientation structure: Polylactic acid-glycolic acid copolymer was dissolved in dichloromethane or trichloromethane to prepare a polymer solution with a mass fraction of 20%. The polymer solution was electrospun under a high voltage electric field to obtain oriented PLGA fibers. After drying, the collected oriented PLGA fibers become PLGA raw materials with molecular chain orientation structure. The polylactic acid-glycolic acid copolymer (PLGA) is of medical grade, with a molar ratio of lactic acid to glycolic acid of 85:15 and a molecular weight of 200,000 Daltons. The high-voltage electric field is 25kV; The electrospinning receiving device is a rotating drum with a rotation speed of 3000 rpm to further enhance the orientation of the molecular chains; The collected oriented PLGA fibers were dried in a vacuum oven at 60°C for 48 hours to remove residual solvent. The dried fibers are PLGA raw materials with molecular chain orientation structure.

[0052] Step 2: Fabrication of a scaffold with a three-dimensional interconnected porous structure: The oriented PLGA fibers obtained in step 1 are cut into short fibers, mixed evenly with the pore-forming agent, filled into a mold, hot-pressed, cooled and demolded, and the molded body is immersed in deionized water to fully dissolve the sodium chloride pore-forming agent. Finally, drying yields a porous scaffold with a three-dimensional interconnected porous structure, but whose stress response characteristics have not yet been activated; The oriented PLGA fibers obtained in step 1 were cut into short fibers with a length of 5 mm, and mixed with the pore-forming agent at a mass ratio of 1:10. The mixture is filled into a mold and hot-pressed at a temperature of 80℃ and a pressure of 10MPa for 60 minutes. After cooling, demold the molded body and immerse it in deionized water. Shake it continuously in a constant temperature shaker at 37°C for 72 hours, changing the deionized water every 12 hours to fully dissolve the pore-forming agent. Finally, the sample was dried in a vacuum oven at 60°C for 48 hours to obtain a porous scaffold with a three-dimensional interconnected porous structure but whose stress response characteristics have not yet been activated.

[0053] In step 2, the pore-forming agent is sodium chloride particles with a particle size of 500 μm.

[0054] Step 3: Activate the stress response expansion characteristics of the stent: The porous scaffold obtained in step 2 was placed in an environment of 37°C and 90% relative humidity, and cyclic compressive stress was applied with a stress amplitude of 0.5 MPa and a frequency of 5 Hz for 48 hours. This process caused the oriented molecular chains in the scaffold to undergo pre-adaptation under simulated physiological stress conditions, thereby activating its stress response capability. After processing, the scaffold is vacuum dried and stored at room temperature to obtain a stress-responsive adaptive expansion bone repair scaffold.

[0055] Example 4 The method for preparing a stress-responsive adaptive expandable bone repair scaffold is implemented according to the following steps: Step 1: Preparation of PLGA raw materials with molecular chain orientation structure: Polylactic acid-glycolic acid copolymer was dissolved in dichloromethane or trichloromethane to prepare a polymer solution with a mass fraction of 15%. The polymer solution was electrospun under a high voltage electric field to obtain oriented PLGA fibers. After drying, the collected oriented PLGA fibers become PLGA raw materials with molecular chain orientation structure. The polylactic acid-glycolic acid copolymer (PLGA) is of medical grade, with a molar ratio of lactic acid to glycolic acid of 75:25 and a molecular weight of 150,000 Daltons. The high-voltage electric field is 20kV; The electrospinning receiving device is a rotating drum with a rotation speed of 2000 rpm to further enhance the orientation of the molecular chains. The collected oriented PLGA fibers are dried in a vacuum oven at 50°C for 24 hours to remove residual solvents. The dried fibers are PLGA raw materials with molecular chain orientation structure.

[0056] Step 2: Fabrication of a scaffold with a three-dimensional interconnected porous structure: The oriented PLGA fibers obtained in step 1 are cut into short fibers, mixed evenly with the pore-forming agent, filled into a mold, hot-pressed, cooled and demolded, and the molded body is immersed in deionized water to fully dissolve the sodium chloride pore-forming agent. Finally, drying yields a porous scaffold with a three-dimensional interconnected porous structure, but whose stress response characteristics have not yet been activated; The oriented PLGA fibers obtained in step 1 were cut into short fibers with a length of 3 mm, and mixed with the pore-forming agent at a mass ratio of 1:8. The mixture is filled into a mold and hot-pressed at a temperature of 70°C and a pressure of 8MPa for 50 minutes. After cooling and demolding, the molded body is immersed in deionized water and continuously shaken in a constant temperature shaker at 37°C for 64 hours, with the deionized water replaced every 12 hours to fully dissolve the pore-forming agent; finally, it is dried in a vacuum oven at 40-60°C for 24 hours to obtain a porous scaffold with a three-dimensional interconnected porous structure, but whose stress response characteristics have not yet been activated.

[0057] In step 2, the pore-forming agent is sodium chloride particles with a particle size of 400 μm.

[0058] Step 3: Activate the stress response expansion characteristics of the stent: The porous scaffold obtained in step 2 was placed in an environment of 37°C and 85% relative humidity, and cyclic compressive stress was applied with a stress amplitude of 0.3 MPa and a frequency of 3 Hz for 32 hours. This process caused the oriented molecular chains in the scaffold to undergo pre-adaptation under simulated physiological stress conditions, thereby activating its stress response capability. After processing, the scaffold is vacuum dried and stored at room temperature to obtain a stress-responsive adaptive expansion bone repair scaffold.

[0059] Example 5 The above-mentioned method of using the bone repair scaffold includes the following steps: Step 1: Implant the bone repair scaffold into the bone defect area. The initial volume of the scaffold should be slightly smaller than the defect area. Step 2: The scaffold expands in a directional manner through the stress generated by the patient's physiological activities, automatically filling the bone defect area; Step 3: The scaffold automatically stops expanding after filling the defect and contacting the host bone wall; Step 4: New bone grows along the porous structure of the scaffold; Step 5: The scaffold gradually degrades and is absorbed as new bone forms.

[0060] Example 6 like Figure 5 As shown, the stress-responsive adaptive expandable bone repair scaffold of the present invention is implanted into the bone defect area. The initial volume of the scaffold is 80-95% of the defect area, and there are tiny irregular gaps between the scaffold and the host bone wall.

[0061] Post-surgery, when patients engage in normal physiological activities (such as walking and weight-bearing), the cyclic stress generated by muscle traction and body weight is transmitted to the bone defect area and acts on the implanted scaffold.

[0062] like Figure 6 As shown, when the polymer inside the scaffold senses continuous physiological stress stimulation, its molecular chains align in a direction along the force, driving the material to expand in a directional manner toward the region of least resistance—that is, the unfilled voids in the bone defect.

[0063] like Figure 7 As shown, when the scaffold expands to completely fill the bone defect area and comes into contact with the host bone wall, the expansion encounters resistance. After the material senses the resistance, its molecular chains stop oriented and the expansion automatically terminates. At this point, a perfect gapless fit is formed between the scaffold and the host bone wall.

[0064] like Figure 8 As shown, the three-dimensional interconnected porous structure of the scaffold provides an ideal crawling scaffold for osteoblasts and osteoprogenitors, while also providing a channel for blood vessel ingrowth. New bone gradually grows in along the porous structure of the scaffold and secretes new bone matrix.

[0065] As the amount of newly formed bone increases, the new bone gradually takes on the physiological stress that was originally borne by the scaffold. The stress state of the scaffold changes, and this stress change signal is sensed by the scaffold material, triggering its degradation process. The scaffold gradually degrades, and the degradation products are safe and metabolizable small molecules (such as lactic acid and glycolic acid), which are eventually excreted from the body through normal metabolic pathways. The scaffold is completely absorbed, and the bone defect area is completely repaired by the new bone itself.

Claims

1. A method for preparing a stress-responsive adaptive expandable bone repair scaffold, characterized in that, include: A polymer solution of polylactic acid-glycolic acid copolymer (PLGA) was prepared. The solution was then used to prepare PLGA raw material with a molecular chain orientation structure using electrospinning technology. A scaffold with a three-dimensional interconnected porous structure was prepared using the PLGA raw material. Cyclic compressive stress was applied to the porous scaffold to activate the stress-response expansion characteristics of the scaffold, thereby obtaining the stress-response adaptive expansion bone repair scaffold.

2. The preparation method according to claim 1, characterized in that, The preparation method is specifically implemented according to the following steps: Step 1: Preparation of PLGA raw materials with molecular chain orientation structure: Polylactic acid-glycolic acid copolymer is dissolved in dichloromethane or trichloromethane to prepare a polymer solution with a mass fraction of 10%-20%. The polymer solution is electrospun under a high voltage electric field to obtain oriented PLGA fibers. After drying, the collected oriented PLGA fibers become PLGA raw materials with molecular chain orientation structure. Step 2: Fabrication of a scaffold with a three-dimensional interconnected porous structure: The oriented PLGA fibers obtained in step 1 are cut into short fibers, mixed evenly with the pore-forming agent, filled into a mold, hot-pressed, cooled and demolded, and the molded body is immersed in deionized water to fully dissolve the sodium chloride pore-forming agent. Finally, drying yields a porous scaffold with a three-dimensional interconnected porous structure, but whose stress response characteristics have not yet been activated; Step 3: Activate the stress response expansion characteristics of the stent: Cyclic compressive stress is applied to the porous scaffold obtained in step 2 to activate its stress response capability. After processing, it is vacuum dried and stored to obtain the stress-responsive adaptive expansion bone repair scaffold.

3. The preparation method according to claim 2, characterized in that, In step 1, the polylactic acid-glycolic acid copolymer (PLGA) is of medical grade, with a molar ratio of lactic acid to glycolic acid of 50:50 to 85:15 and a molecular weight of 50,000 to 200,000 Daltons. The high-voltage electric field is 15-25kV; The electrospinning receiving device is a rotating drum with a rotation speed of 1000-3000 rpm to further enhance the orientation of the molecular chains; The collected oriented PLGA fibers are dried in a vacuum oven at 40-60℃ for 12-48 hours to remove residual solvent. The dried fibers are PLGA raw materials with molecular chain orientation structure.

4. The preparation method according to claim 3, characterized in that, The molar ratio of lactic acid to glycolic acid is 75:25, and the molecular weight is 100,000-150,000 Daltons.

5. The preparation method according to claim 2, characterized in that, Step 2 is as follows: the oriented PLGA fibers obtained in step 1 are cut into short fibers with a length of 1-5 mm, and mixed with a pore-forming agent at a mass ratio of 1:10-1:

5. The mixture is filled into a mold and hot-pressed at a temperature of 60-80℃ and a pressure of 5-10MPa for 30-60 minutes. After cooling and demolding, the molded body is immersed in deionized water and continuously shaken in a constant temperature shaker at 37°C for 48-72 hours, with the deionized water replaced every 12 hours to fully dissolve the pore-forming agent; finally, it is dried in a vacuum oven at 40-60°C for 12-48 hours to obtain a porous scaffold with a three-dimensional interconnected porous structure, but whose stress response characteristics have not yet been activated.

6. The preparation method according to claim 5, characterized in that, In step 2, the pore-forming agent is sodium chloride particles with a particle size of 300-500 μm.

7. The preparation method according to claim 2, characterized in that, Step 3 is as follows: The porous scaffold obtained in step 2 is placed in an environment of 37°C and 80%-90% relative humidity, and cyclic compressive stress is applied with a stress amplitude of 0.1-0.5MPa and a frequency of 1-5Hz for 24-48 hours. This process allows the oriented molecular chains in the scaffold to undergo pre-adaptation under simulated physiological stress conditions, thereby activating its stress response capability. After processing, the scaffold is vacuum dried and stored at room temperature to obtain a stress-responsive adaptive expansion bone repair scaffold.

8. The stress-responsive adaptive expandable bone repair scaffold obtained by the method according to any one of claims 1-7, characterized in that, The support has a three-dimensional interconnected porous structure, with an overall shape that is either regular or irregular. The surface has a porous texture, a porosity of 70%-85%, and a pore size range of 300-500μm.

9. The bone repair scaffold according to claim 8, characterized in that, The initial volume of the scaffold is 80%-95% of the bone defect area; The stent automatically stops expanding when it encounters resistance from the host bone wall. The scaffold triggers a degradation process after new bone forms and bears stress, with the degradation rate matching the bone healing process. The porous structure of the scaffold is loaded with bioactive substances.

10. The use of the bone repair scaffold according to claim 8 in the preparation of a medical device for treating the repair of bone defects.

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