A bionic double-gradient rotator cuff patch and its preparation method

Abstract

The present invention belongs to the field of biomedical engineering technology, and in particular, relates to a biological rotator cuff patch with a dual gradient structure and a preparation method thereof. The preparation method is: electrospinning a spinning solution, controlling the rotation speed of a receiving drum to increase at a constant rate during the electrospinning process, and obtaining a nanofiber membrane after electrospinning; L-polylactic acid and D-polylactic acid are dissolved in the spinning solution at the same time; the minimum rotation speed of the receiving drum is 100-500rpm and the maximum is 3000-4000rpm. The biological rotator cuff patch with a dual gradient structure finally obtained presents an orientation gradient and a piezoelectric effect gradient on a thickness scale at the same time, and has both mechanical support capability and biocompatibility, realizing the bionic healing of the gradient structure patch.

Description

Technical Field

[0001] The present invention belongs to the technical field of biomedical engineering, and relates to a bionic double-gradient rotator cuff patch and a preparation method thereof. Background Art

[0002] As a dynamic stabilizing structure of the shoulder joint, the rotator cuff is a tendon complex formed by the tendons of the supraspinatus, infraspinatus, subscapularis, and teres minor muscles attaching to the joint capsule. The connection between the tendon and the bone is called the tendon-bone interface (TBI), which is the location where the stress is most concentrated and has limited regenerative ability. Acute overload injuries or degenerative aging processes often lead to rotator cuff tears. Despite the continuous development of clinical intervention methods, the postoperative failure rate is still as high as 20-90%, mainly due to poor tendon-bone interface healing and the formation of fibrovascular scar tissue.

[0003] Traditional repair materials face many limitations: The existing acellular tissue scaffolds are limited in their application due to strict processing requirements and secondary wound problems. New tissue engineering materials mostly use synthetic or natural polymers, but the former has low bioactivity and acidic degradation products, while the latter has insufficient mechanical properties. From the tendon to the bone tissue at the tendon-bone interface, the arrangement of collagen fibers shows a gradient change in the degree of orientation from highly ordered to gradually disordered. This gradient change in the degree of orientation achieves a smooth transition in mechanical properties, enhances the structural toughness, can promote tissue integration to ensure a firm connection, and at the same time guides the migration, proliferation, and differentiation of fibroblasts, osteoblasts, etc. along the fiber arrangement direction, promoting tissue regeneration and integration. It can also form an efficient mass transport network through the cooperation of the inter-fiber channels in the ordered region and the porous structure in the disordered region, regulate nutrient transport, balance the metabolic microenvironment, and maintain the good structure and function of the tissue. The existing patches have a single structure and cannot guide the gradient reconstruction of the degree of orientation of the tendon-bone interface tissue, resulting in the formation of scar tissue with poor mechanical properties at the repair site, which is prone to micro-injury and even fracture in the long term. These limitations affect the effectiveness and long-term stability of the patch. For example, patent application CN118542975A discloses a rotator cuff patch based on the layer-by-layer assembly of collagen and nanofiber membranes and a preparation method thereof. A rotator cuff patch is made of natural biomaterials and synthetic polymer materials through electrospinning and collagen coating techniques, improving the biocompatibility, but the structural design does not solve the problem of the gradient arrangement of collagen orientation in the tendon-bone interface and is difficult to provide sufficient topographical cues for the regeneration of interface tissue.

[0004] Studies have shown that tendons, bones, and their main component, type I collagen, have piezoelectricity. In the natural tendon-bone interface, the arrangement of collagen fibers gradually transitions from the ordered parallel arrangement of tendons to the loose and disordered structure of bones, forming not only a gradient change in the degree of orientation but also a gradient change in the piezoelectric effect. The piezoelectric effect gradient is manifested as follows: highly oriented collagen fibers generate directional charges under mechanical stress, and these charges can guide tendon cells (TCs) to migrate directionally to the stressed area, promote collagen synthesis, and help tendons maintain structural and functional stability under mechanical stimulation; as the transition to bone tissue occurs, the charges generated by the disordered collagen fibers under stress are more complexly distributed, but they can effectively regulate the ion concentration in the microenvironment around bone cells, activate the signal pathways related to bone remodeling, stimulate the activity of osteoblasts, and promote bone matrix mineralization, ensuring that bone tissue maintains strength and integrity under diverse mechanical states, and achieving the coordinated optimization of cell behavior, tissue repair, and mechanical properties from tendons to bones under the drive of the piezoelectric effect. The piezoelectric effect of the hydroxyapatite (HA)-collagen complex is weak, but the piezoelectric potential in the local stress concentration area can stimulate osteoblast differentiation and mineralization, which provides new ideas for the application of bioelectricity in tissue regeneration. Patent CN116370708A discloses a rotator cuff patch with piezoelectric effect and its preparation method. By compounding a variety of materials, such as polylactic acid-polyglycolic acid, natural polymer gelatin, bone-conducting inorganic biomaterial nano-hydroxyapatite, and piezoelectric material nano-barium titanate, a bionic piezoelectric rotator cuff scaffold is prepared, which improves biocompatibility and constructs the structure and topographical cues for promoting bone regeneration. However, there are certain risks in aspects such as the short release period, poor controllability of inorganic piezoelectric materials, and the potential harmfulness of components to the human body during the piezoelectric promotion of healing.

[0005] In view of this, it is necessary to design a biological rotator cuff patch that presents a gradient of orientation degree and a gradient of piezoelectric effect on the thickness scale. Summary of the Invention

[0006] The purpose of the present invention is to solve the problems existing in the prior art and provide a bionic double-gradient rotator cuff patch and its preparation method.

[0007] To achieve the above purpose, the present invention adopts the following technical solutions:

[0008] A preparation method of a bionic double-gradient rotator cuff patch, electrospinning a spinning solution, and controlling the rotation speed of the receiving drum to increase at a constant rate during the electrospinning process, and obtaining a nanofiber membrane after electrospinning;

[0009] Both L-polylactic acid (PLLA) and D-polylactic acid (PDLA) are dissolved in the spinning solution;

[0010] The minimum rotation speed of the receiving drum is 100 - 500 rpm, and the maximum rotation speed is 3000 - 4000 rpm.

[0011] The rotator cuff patch of the present invention presents a gradient of orientation degree in the thickness dimension to simulate the arrangement and distribution of collagen fibers in the four tissues at the tendon-bone interface. The gradient of orientation degree is formed by controlling the rotation speed of the receiving roller to increase at a constant rate during the electrospinning process. Specifically, the arrangement of collagen fibers from tendon to bone at the tendon-bone interface is highly oriented (tendon, inducing cell differentiation into tendon)-moderately oriented (unmineralized fibrocartilage and mineralized fibrocartilage, inducing cell differentiation into cartilage tissue)-random distribution (bone, promoting cell differentiation into bone). The increase in the rotation speed of the roller is intuitively manifested as the superposition of the orientation degree of micro-nano fibers under the stretching of centripetal force, which conforms to the distribution of collagen fibers in the interfacial tissue. The accumulation over a certain period enables effective bonding between the transitional interfaces, making it more suitable for the sequential ingrowth and repair of the four tissues at the tendon-bone interface.

[0012] The rotation speed of the receiving roller increases at a constant rate, which not only considers the surface layer structure in direct contact with the tendon tissue and bone tissue, but also focuses more on the biomimicry of the orientation distribution of collagen fibers in the four different tissues within the interfacial tissue, as well as the fusion and transitional regeneration situation between tissues. This is directly related to the repair effect after tissue regeneration and can effectively inhibit the risk of retear caused by poor healing of the intermediate layer fibrocartilage tissue.

[0013] In addition to presenting a gradient of orientation degree in the thickness dimension, the rotator cuff patch of the present invention also presents a gradient of piezoelectric effect, because in the electrospinning process of the present invention, the rotation speed of the receiving roller is controlled to increase at a constant rate. The minimum rotation speed of the receiving roller is 100 - 500 rpm, and the maximum is 3000 - 4000 rpm. The specific reasons are as follows:

[0014] The piezoelectric effect of fibers is closely related to the crystallinity of fibers and the crystal forms in fibers. The higher the crystallinity of fibers, the more obvious the piezoelectric effect of fibers. The crystal forms in fibers include the HC crystal form (homogeneous crystalline form of a single isomer) and the SC crystal form (stereocomplex crystalline form). The piezoelectric effect of the SC crystal form is more obvious than that of the HC crystal form. When the rotation speed of the roller is small (100 - 500 rpm), the orientation degree of fibers is low, which in turn makes the crystallinity of fibers low. At the same time, the crystal form in fibers is mainly the HC crystal form, and the piezoelectric effect of fibers is weak. As the rotation speed of the roller increases, the orientation degree of fibers also increases, which in turn makes the crystallinity of fibers increase. At the same time, the HC crystal form in fibers gradually decreases, and the SC crystal form gradually increases, and the piezoelectric effect of fibers becomes stronger. When the rotation speed of the roller is large (3000 - 4000 rpm), the orientation degree of fibers is high, making the crystallinity of fibers high. At the same time, the crystal form in fibers is mainly the SC crystal form, and the piezoelectric effect of fibers is strong.

[0015] As a preferred technical solution:

[0016] A preparation method of the bionic double-gradient rotator cuff patch as described above, the mass ratio of L-polylactic acid to D-polylactic acid in the spinning solution is 1:1. At the same roller rotation speed, the closer the mass ratio of L-polylactic acid to D-polylactic acid is to 1:1, the more the number of SC crystal forms formed.

[0017] A preparation method of the bionic double-gradient rotator cuff patch as described above, in the spinning solution, the total mass fraction of L-polylactic acid and D-polylactic acid is 6-10%, and the solvent is one or more of dichloromethane (DCM), N,N-dimethylformamide (DMF), hexafluoroisopropanol (HFIP), and chloroform (CF). The weight-average molecular weight range of L-polylactic acid and D-polylactic acid is 16-50Wg / mol (i.e., 1.6×10 5 -5×10 5 g / mol).

[0018] A preparation method of the bionic double-gradient rotator cuff patch as described above, the value range of the constant rate is 300-1000 rpm / h.

[0019] A preparation method of the bionic double-gradient rotator cuff patch as described above, during electrospinning, the spinning solution is injected into a syringe and pushed at a speed of 0.8-1.5 mL / h. The surface of the receiving roller is wrapped with aluminum foil. The receiving distance between the receiving roller and the spinning needle is 12-16 cm, and the receiving voltage is 15-21 kV.

[0020] A preparation method of the bionic double-gradient rotator cuff patch as described above, the nanofiber membrane is also immersed in the polymer solution, so that the polymer in the polymer solution recrystallizes on the nanofiber membrane to form a shish-kebab crystal, and then the nanofiber membrane is taken out. Among them, both L-polylactic acid and D-polylactic acid are dissolved in the polymer solution.

[0021] Recrystallization can make the gradient of the piezoelectric effect of the rotator cuff patch more obvious on the thickness scale. During the recrystallization process, due to the principle of isomorphous attraction of transcrystals, transcrystals of the HC crystal form will grow at the sites of the HC crystal form on the fiber, and transcrystals of the SC crystal form will grow at the sites of the SC crystal form on the fiber. Since the sites of the SC crystal form have a stronger ability to adsorb free molecular chains than the sites of the HC crystal form, the structure of the transcrystals of the SC crystal form is more stable than that of the transcrystals of the HC crystal form, making the piezoelectric effect of the transcrystals of the SC crystal form more obvious than that of the transcrystals of the HC crystal form. Since the crystal forms in the fibers of the rotator cuff patch show a change trend of "more HC crystal forms and fewer SC crystal forms → fewer HC crystal forms and more SC crystal forms → all SC crystal forms" on the thickness scale, the transcrystals of the rotator cuff patch accordingly show a change trend of "more transcrystals of the HC crystal form and fewer transcrystals of the SC crystal form → fewer transcrystals of the HC crystal form and more transcrystals of the SC crystal form → all transcrystals of the SC crystal form" on the thickness scale. The increase in the piezoelectric effect caused by the growth of transcrystals is more obvious closer to the surface layer of the rotator cuff patch.

[0022] In addition, transcrystals can also promote macrophage polarization anti-inflammation and bone tissue mineralization. The microporous structure formed by transcrystals on the fiber (as shown in Figure 5 Figure 5 or 6) is more likely to generate charge separation under external force, thereby enhancing the piezoelectric effect.

[0023] For the preparation method of a bionic double-gradient rotator cuff patch as described above, the mass ratio of L-polylactic acid to D-polylactic acid in the polymer solution is the same as that in the spinning solution.

[0024] For the preparation method of a bionic double-gradient rotator cuff patch as described above, the polymer solution is obtained by dissolving L-polylactic acid and D-polylactic acid in a solvent at 120 - 140 °C; in the polymer solution, the total mass fraction of L-polylactic acid and D-polylactic acid is 0.01 - 0.05%, the solvent is p-xylene, and the weight-average molecular weight range of both L-polylactic acid and D-polylactic acid is 1 - 3Wg / mol (i.e., 1×10 4 -3×10 4 g / mol). A smaller weight-average molecular weight of L-polylactic acid and D-polylactic acid in the polymer solution is beneficial to forming a transcrystalline structure at a lower recrystallization temperature.

[0025] For the preparation method of a bionic double-gradient rotator cuff patch as described above, the recrystallization temperature is 80 - 87 °C and the time is 6 - 15 h.

[0026] For the preparation method of a bionic double-gradient rotator cuff patch as described above, before immersing the nanofiber membrane in the polymer solution, the nanofiber membrane is also left standing in a vacuum oven at 25 - 37 °C for 12 - 36 h.

[0027] A preparation method of a bionic double-gradient rotator cuff patch as described above. Before immersing the nanofiber membrane in the polymer solution, the nanofiber membrane is also cut, and the size after cutting is 5-8 cm, and the shape is rectangular, square or circular.

[0028] A preparation method of a bionic double-gradient rotator cuff patch as described above. After immersing the nanofiber membrane in the polymer solution, the nanofiber membrane is also rinsed with p-xylene 3-5 times, and after rinsing, the nanofiber membrane is left standing at room temperature for 24 h.

[0029] The present invention also provides a bionic double-gradient rotator cuff patch, which is prepared by using the preparation method of a bionic double-gradient rotator cuff patch described in any one of the above.

[0030] The bionic double-gradient rotator cuff patch of the present invention presents an orientation gradient and a piezoelectric effect gradient on the thickness scale, and can provide a bionic tendon-bone structure and corresponding mechanical properties. On this basis, the regulation effect of external mechanical stress on the fiber piezoelectric effect can promote the bionic double-gradient rotator cuff patch to generate a gradient piezoelectric effect suitable for the corresponding tissue, thereby effectively promoting the healing and regeneration of the tendon-bone interface, and thus obtaining a bionic double-gradient rotator cuff patch with both mechanical support ability and good biocompatibility.

[0031] Beneficial effects:

[0032] The present invention uses biodegradable polylactic acid as a raw material for electrospinning. By controlling the rotation speed of the receiving roller to increase at a constant rate during the electrospinning process, the bionic double-gradient rotator cuff patch presents an orientation gradient and a piezoelectric effect gradient on the thickness scale at the same time, and has both mechanical support ability and biocompatibility, realizing the bionic promotion of healing of the gradient structure patch.

[0033] The preparation method of the bionic double-gradient rotator cuff patch of the present invention has strong controllability. On the one hand, it can regulate the growth and differentiation of different tissue cells by regulating the fiber orientation degree, fiber diameter, porosity and multiple crystal forms, and can be applied to the repair and regeneration of various tissues such as tendons, cartilage and bones. On the other hand, by regulating the crystallinity, crystal form structure and stress degree of the fiber, the promotion effect of the biological rotator cuff patch is controlled, and a corresponding biological rotator cuff patch is provided for different degrees of damage and different individuals to meet the actual application needs, which has high application value.

[0034] The preparation method of the bionic double-gradient rotator cuff patch of the present invention has a simple process and low cost, and can meet the needs of industrial large-scale production. Description of the drawings

[0035] Figure 1 It is the SEM microtopography and fiber orientation degree distribution diagram of the rotator cuff patch 1; among them, a1 is the SEM microtopography diagram, and a2 is the fiber orientation degree distribution diagram;

[0036] Figure 2 SEM microtopography and fiber orientation distribution diagrams of the rotator cuff patch 2; among them, b1 is the SEM microtopography diagram, and b2 is the fiber orientation distribution diagram;

[0037] Figure 3 SEM microtopography and fiber orientation distribution diagrams of the rotator cuff patch 3; among them, c1 is the SEM microtopography diagram, and c2 is the fiber orientation distribution diagram;

[0038] Figure 4 SEM microtopography and fiber orientation distribution diagrams of the rotator cuff patch 4; among them, d1 is the SEM microtopography diagram, and d2 is the fiber orientation distribution diagram;

[0039] Figure 5 SEM microtopography diagram of the rotator cuff patch 5; compared with the rotator cuff patch 3, the only difference is that the rotator cuff patch 5 has undergone recrystallization to form shish-kebab crystals, which does not affect the orientation degree of the rotator cuff patch 5. Therefore, the orientation degree of the rotator cuff patch 5 is not shown;

[0040] Figure 6 SEM microtopography diagram of the rotator cuff patch 6; compared with the rotator cuff patch 4, the only difference is that the rotator cuff patch 6 has undergone recrystallization to form shish-kebab crystals, which does not affect the orientation degree of the rotator cuff patch 6. Therefore, the orientation degree of the rotator cuff patch 6 is not shown;

[0041] Figure 7 DSC comparison diagrams of the rotator cuff patches 1-8;

[0042] Figure 8 Output voltage comparison diagrams of the rotator cuff patches 1-6 after being stressed. Specific Embodiments

[0043] The present invention will be further described below in conjunction with specific embodiments. It should be understood that these embodiments are only used to illustrate the present invention and not to limit the scope of the present invention. In addition, it should be understood that after reading the content taught by the present invention, those skilled in the art can make various changes or modifications to the present invention, and these equivalent forms also fall within the scope defined by the appended claims of this application.

[0044] The detection methods for relevant performance indicators in the following examples and comparative examples are as follows:

[0045] Tensile strength and elastic modulus: Referring to the standard test method for the tensile properties of plastics ASTM-D638-2022, specimens were prepared using the sample preparation parameters of Type V splines, and tensile tests were performed using a universal testing machine (model CTM2050). The test conditions were set as follows: gauge length 10 mm, tensile speed 0.5 mm / min.

[0046] Orientation degree: Import the scanning electron microscope (SEM) image into Image J software. Use the straight line tool to draw the known length scale in the image. After setting the actual length and unit, manually select the fibers in the SEM image. After measuring ≥60 fiber samples, statistically analyze the measurement option angle, and then perform frequency analysis on the data to finally obtain the orientation degree distribution range of the fibers in the SEM image.

[0047] Output voltage after force application (characterizing piezoelectric properties): Cut the rotator cuff patch into a test sample of 2.5×2.5 cm. Paste copper sheets on the upper and lower surfaces of the test sample as electrodes, and lead out copper bars from the two electrodes as wires. Then use a polyimide film to cover the electrode surface to complete the assembly of the piezoelectric sensor. Subsequently, fix the piezoelectric sensor at the right end of a calibrated electrometer (KEITHLEY 6514), and connect the wires to the positive and negative poles of the electrometer. After setting the parameter frequency to 1 Hz, apply a dynamic force of 6 - 10 N (Linmot linear motor) at the left end. The potential difference generated by the piezoelectric sensor under force is collected and calculated by the electrometer to obtain the output voltage after force application.

[0048] Example 1

[0049] A preparation method of a bionic double-gradient rotator cuff patch, the specific steps are as follows:

[0050] (1) Prepare raw materials:

[0051] Spinning solution: The solvent is a mixed solution of dichloromethane and N,N-dimethylformamide with a mass ratio of 1:1. The mass ratio of L-polylactic acid to D-polylactic acid in the spinning solution is 1:1, the total mass fraction of L-polylactic acid and D-polylactic acid is 6%, the weight-average molecular weight of L-polylactic acid is 16W g / mol, and the weight-average molecular weight of D-polylactic acid is 16W g / mol;

[0052] Polymer solution: Dissolve L-polylactic acid and D-polylactic acid in p-xylene at 120°C. Among them, the mass ratio of L-polylactic acid to D-polylactic acid is 1:1, the total mass fraction of L-polylactic acid and D-polylactic acid is 0.03%, the weight-average molecular weight of L-polylactic acid is 1W g / mol, and the weight-average molecular weight of D-polylactic acid is 1W g / mol;

[0053] p-xylene;

[0054] (2) Electrospinning:

[0055] Inject the spinning solution into a syringe for electrospinning. The syringe injection speed is 0.8 mL / h. During the electrospinning process, control the rotation speed of the receiving drum to increase from 500 rpm to 4000 rpm at a constant rate of 1000 rpm / h. After electrospinning, a nanofiber membrane is obtained;

[0056] Among them, the surface of the receiving roller is wrapped with aluminum foil, the receiving distance between the receiving roller and the spinning needle is 13 cm, and the receiving voltage is 15 kV;

[0057] (3) Recrystallization:

[0058] (3.1) After the nanofiber membrane is left standing in a vacuum oven at 25 °C for 12 h, the nanofiber membrane is then cut into a square with a side length of 8 cm;

[0059] (3.2) The cut nanofiber membrane is placed in a polymer solution and soaked at 80 °C for 6 h (to form a sheaf crystal), then the nanofiber membrane is taken out, and the nanofiber membrane is rinsed 3 times with p-xylene. After rinsing, the nanofiber membrane is left standing at room temperature for 24 h to obtain the bionic double-gradient rotator cuff patch.

[0060] In order to confirm that the above rotator cuff patch presents an orientation gradient and a piezoelectric effect gradient in the thickness scale, the following experiments were carried out:

[0061] Rotator cuff patch 1: The preparation method is basically the same as that of Example 1, except that during the electrospinning process, the rotation speed of the receiving roller is kept constant at 500 rpm and no recrystallization is carried out.

[0062] Rotator cuff patch 2: The preparation method is basically the same as that of the nanofiber membrane of Example 1, except that during the electrospinning process, the rotation speed of the receiving roller is kept constant at 1000 rpm and no recrystallization is carried out.

[0063] Rotator cuff patch 3: The preparation method is basically the same as that of the nanofiber membrane of Example 1, except that during the electrospinning process, the rotation speed of the receiving roller is kept constant at 2000 rpm and no recrystallization is carried out.

[0064] Rotator cuff patch 4: The preparation method is basically the same as that of the nanofiber membrane of Example 1, except that during the electrospinning process, the rotation speed of the receiving roller is kept constant at 4000 rpm and no recrystallization is carried out.

[0065] Rotator cuff patch 5: The preparation method is basically the same as that of the nanofiber membrane of Example 1, except that during the electrospinning process, the rotation speed of the receiving roller is kept constant at 2000 rpm.

[0066] Rotator cuff patch 6: The preparation method is basically the same as that of the nanofiber membrane of Example 1, except that during the electrospinning process, the rotation speed of the receiving roller is kept constant at 4000 rpm.

[0067] Rotator cuff patch 7: The preparation method is basically the same as that of rotator cuff patch 4, except that in the spinning solution, the same mass of L-polylactic acid is used instead of D-polylactic acid (i.e., all is L-polylactic acid).

[0068] Rotator cuff patch 8: The preparation method is basically the same as that of rotator cuff patch 4, except that the same mass of dextrorotatory polylactic acid is used instead of levorotatory polylactic acid in the spinning solution (i.e., all dextrorotatory polylactic acid).

[0069] From the SEM micrographs of rotator cuff patches 1 - 4 (as Figures 1 - 4 shown), it can be seen that as the rotational speed of the receiving drum increases, the fibers on the rotator cuff patch gradually distribute in the vertical direction, and the degree of fiber orientation also increases accordingly.

[0070] From the output voltages of rotator cuff patches 1 - 4 after being stressed (as Figure 8 shown), it can be seen that as the rotational speed of the receiving drum increases, the output voltage of the rotator cuff patch after being stressed also increases accordingly.

[0071] From the DSC comparison diagrams of rotator cuff patches 1 - 8, it can be seen that: ① For rotator cuff patches 7 and 8, no melting peak appears near the melting point of 220 - 230 °C, indicating that the SC crystal form is not formed in these two rotator cuff patches, while obvious melting peaks appear near 220 - 230 °C for rotator cuff patches 1 - 6, indicating that these rotator cuff patches have successfully formed the SC crystal form; ② The crystallinity of rotator cuff patches 1 - 4 shows an increasing trend, indicating that on the premise of the same other conditions, as the rotational speed of the receiving drum increases, the crystallinity of the rotator cuff patch shows an increasing trend; ③ By comparing rotator cuff patch 5 with rotator cuff patch 3, it can be seen that the recrystallization treatment significantly improves the crystallinity of the rotator cuff patch. By comparing rotator cuff patch 6 with rotator cuff patch 4, it can also be seen that the recrystallization treatment significantly improves the crystallinity of the rotator cuff patch.

[0072] From the SEM micrographs of rotator cuff patches 3 and 5 (as Figure 3 and Figure 5 shown), it can be seen that new string-like crystal structures grow around the fibers of rotator cuff patch 5, indicating that rotator cuff patch 5 has formed shish-kebab crystals on the fiber surface through recrystallization.

[0073] From the comparison of the output voltages of rotator cuff patches 3 and 5 after being stressed (as Figure 8 shown), it can be seen that the formation of shish-kebab crystals increases the output voltage of the rotator cuff patch after being stressed, that is, the piezoelectric effect is improved.

[0074] From the SEM micrographs of rotator cuff patches 4 and 6 (as Figure 4 and Figure 6 shown), it can be seen that new string-like crystal structures grow around the fibers of rotator cuff patch 6, indicating that rotator cuff patch 6 has formed shish-kebab crystals on the fiber surface through recrystallization.

[0075] From the comparison of the output voltages of rotator cuff patches 4 and 6 after being stressed (asFigure 8 As can be seen from the comparison (as shown), the formation of the shish-kebab crystals causes the output voltage of the rotator cuff patch to increase after being stressed, that is, the piezoelectric effect is enhanced.

[0076] By comparing the change values of the output voltages of the rotator cuff patch 3 and the rotator cuff patch 5 after being stressed, and the change values of the output voltages of the rotator cuff patch 4 and the rotator cuff patch 6 after being stressed, it can be seen that the change value of the output voltage of the rotator cuff patch 4 and the rotator cuff patch 6 after being stressed is significantly higher than that of the rotator cuff patch 3 and the rotator cuff patch 5 after being stressed, indicating that the greater the rotational speed of the receiving roller, the more obvious the improvement effect of recrystallization on the piezoelectric effect of the rotator cuff patch.

[0077] Example 2

[0078] A preparation method of a bionic double-gradient rotator cuff patch is as follows:

[0079] (1) Prepare raw materials:

[0080] Spinning solution: The solvent is a mixed solution of dichloromethane and N,N-dimethylformamide with a mass ratio of 1:1. The mass ratio of L-polylactic acid to D-polylactic acid in the spinning solution is 1:1, the total mass fraction of L-polylactic acid and D-polylactic acid is 8%, the weight-average molecular weight of L-polylactic acid is 20W g / mol, and the weight-average molecular weight of D-polylactic acid is 20W g / mol;

[0081] Polymer solution: Prepared by dissolving L-polylactic acid and D-polylactic acid in p-xylene at 120 °C. Among them, the mass ratio of L-polylactic acid to D-polylactic acid is 1:1, the total mass fraction of L-polylactic acid and D-polylactic acid is 0.01%, the weight-average molecular weight of L-polylactic acid is 3W g / mol, and the weight-average molecular weight of D-polylactic acid is 3W g / mol;

[0082] p-xylene;

[0083] (2) Electrospinning:

[0084] Inject the spinning solution into a syringe for electrospinning. The syringe injection speed is 0.8 mL / h. During the electrospinning process, control the rotational speed of the receiving roller to increase from 200 rpm to 3500 rpm at a constant rate of 800 rpm / h. After electrospinning, a nanofiber membrane is obtained;

[0085] Among them, the surface of the receiving roller is wrapped with aluminum foil, the receiving distance between the receiving roller and the spinning needle is 12 cm, and the receiving voltage is 15 kV;

[0086] (3) Recrystallization:

[0087] (3.1) After allowing the nanofiber membrane to stand in a vacuum oven at 30 °C for 24 h, then cut the nanofiber membrane into a square with a side length of 8 cm;

[0088] (3.2) Place the cut nanofiber membrane in the polymer solution, soak it at 80 °C for 8 h (to form shish-kebab crystals), take out the nanofiber membrane, rinse the nanofiber membrane 4 times with p-xylene, and let the nanofiber membrane stand at room temperature for 24 h to obtain the bionic double-gradient rotator cuff patch.

[0089] Example 3

[0090] A preparation method of a bionic double-gradient rotator cuff patch comprises the following specific steps:

[0091] (1) Prepare raw materials:

[0092] Spinning solution: The solvent is a mixed solution of dichloromethane and N,N-dimethylformamide with a mass ratio of 2:1. The mass ratio of L-polylactic acid to D-polylactic acid in the spinning solution is 1:1. The total mass fraction of L-polylactic acid and D-polylactic acid is 8%. The weight-average molecular weight of L-polylactic acid is 200,000 g / mol, and the weight-average molecular weight of D-polylactic acid is 200,000 g / mol;

[0093] Polymer solution: It is obtained by dissolving L-polylactic acid and D-polylactic acid in p-xylene at 130 °C. Among them, the mass ratio of L-polylactic acid to D-polylactic acid is 1:1. The total mass fraction of L-polylactic acid and D-polylactic acid is 0.01%. The weight-average molecular weight of L-polylactic acid is 30,000 g / mol, and the weight-average molecular weight of D-polylactic acid is 30,000 g / mol;

[0094] p-xylene;

[0095] (2) Electrospinning:

[0096] Inject the spinning solution into a syringe for electrospinning. The syringe injection speed is 1 mL / h. During the electrospinning process, control the rotation speed of the receiving drum to increase from 100 rpm to 3500 rpm at a constant rate of 800 rpm / h. After electrospinning, a nanofiber membrane is obtained;

[0097] Among them, the surface of the receiving drum is wrapped with aluminum foil. The receiving distance between the receiving drum and the spinning needle is 15 cm, and the receiving voltage is 18 kV;

[0098] (3) Recrystallization:

[0099] (3.1) After the nanofiber membrane is left standing in a vacuum oven at 30 °C for 24 h, then cut the nanofiber membrane into a square with a side length of 7 cm;

[0100] (3.2) Place the cut nanofiber membrane in the polymer solution, soak it at 85 °C for 8 h (to form a shish-kebab crystal), take out the nanofiber membrane, rinse the nanofiber membrane three times with p-xylene, and let the nanofiber membrane stand at room temperature for 24 h to obtain the bionic double-gradient rotator cuff patch.

[0101] Example 4

[0102] A preparation method of a bionic double-gradient rotator cuff patch, the specific steps are as follows:

[0103] (1) Prepare raw materials:

[0104] Spinning solution: The solvent is a mixed solution of dichloromethane and hexafluoroisopropanol with a mass ratio of 2:1. The mass ratio of L-polylactic acid to D-polylactic acid in the spinning solution is 1:1. The total mass fraction of L-polylactic acid and D-polylactic acid is 8%. The weight-average molecular weight of L-polylactic acid is 200,000 g / mol, and the weight-average molecular weight of D-polylactic acid is 200,000 g / mol;

[0105] Polymer solution: Prepared by dissolving L-polylactic acid and D-polylactic acid in p-xylene at 130 °C. Among them, the mass ratio of L-polylactic acid to D-polylactic acid is 1:1. The total mass fraction of L-polylactic acid and D-polylactic acid is 0.02%. The weight-average molecular weight of L-polylactic acid is 20,000 g / mol, and the weight-average molecular weight of D-polylactic acid is 20,000 g / mol;

[0106] p-xylene;

[0107] (2) Electrospinning:

[0108] Inject the spinning solution into a syringe for electrospinning. The syringe injection speed is 1 mL / h. During the electrospinning process, control the rotation speed of the receiving drum to increase from 200 rpm to 3500 rpm at a constant rate of 800 rpm / h. After electrospinning, a nanofiber membrane is obtained;

[0109] Among them, the surface of the receiving drum is wrapped with aluminum foil. The receiving distance between the receiving drum and the spinning needle is 15 cm, and the receiving voltage is 18 kV;

[0110] (3) Recrystallization:

[0111] (3.1) Place the nanofiber membrane in a vacuum oven and let it stand at 35 °C for 24 h, and then cut the nanofiber membrane into a square with a side length of 6 cm;

[0112] (3.2) Place the cut nanofiber membrane in the polymer solution, soak it at 85 °C for 10 h (to form a shish-kebab crystal), take out the nanofiber membrane, rinse the nanofiber membrane three times with p-xylene, and let the nanofiber membrane stand at room temperature for 24 h to obtain the bionic double-gradient rotator cuff patch.

[0113] Example 5

[0114] A preparation method of a bionic double-gradient rotator cuff patch, the specific steps are as follows:

[0115] (1) Prepare raw materials:

[0116] Spinning solution: The solvent is a mixed solution of dichloromethane and chloroform with a mass ratio of 3:1. The mass ratio of L-polylactic acid to D-polylactic acid in the spinning solution is 1:1. The total mass fraction of L-polylactic acid and D-polylactic acid is 10%. The weight-average molecular weight of L-polylactic acid is 30W g / mol, and the weight-average molecular weight of D-polylactic acid is 30W g / mol;

[0117] Polymer solution: Prepared by dissolving L-polylactic acid and D-polylactic acid in p-xylene at 140°C. Among them, the mass ratio of L-polylactic acid to D-polylactic acid is 1:1. The total mass fraction of L-polylactic acid and D-polylactic acid is 0.04%. The weight-average molecular weight of L-polylactic acid is 2W g / mol, and the weight-average molecular weight of D-polylactic acid is 2W g / mol;

[0118] p-xylene;

[0119] (2) Electrospinning:

[0120] Inject the spinning solution into a syringe for electrospinning. The syringe injection speed is 1.2 mL / h. During the electrospinning process, control the rotation speed of the receiving drum to increase from 500 rpm to 3000 rpm at a constant rate of 500 rpm / h. After electrospinning, a nanofiber membrane is obtained;

[0121] Among them, the surface of the receiving drum is wrapped with aluminum foil. The receiving distance between the receiving drum and the spinning needle is 16 cm, and the receiving voltage is 20 kV;

[0122] (3) Recrystallization:

[0123] (3.1) After standing the nanofiber membrane in a vacuum oven at 37°C for 36 h, then cut the nanofiber membrane into a circle with a diameter of 6 cm;

[0124] (3.2) Place the cut nanofiber membrane in the polymer solution and soak it at 87°C for 12 h (to form a shish-kebab crystal), take out the nanofiber membrane, rinse the nanofiber membrane 5 times with p-xylene, and then let the nanofiber membrane stand at room temperature for 24 h to obtain the bionic double-gradient rotator cuff patch.

[0125] Example 6

[0126] A preparation method of a bionic double-gradient rotator cuff patch, the specific steps are as follows:

[0127] (1) Prepare raw materials:

[0128] Spinning solution: The solvent is a mixed solution of dichloromethane and chloroform with a mass ratio of 4:1. The mass ratio of L-polylactic acid to D-polylactic acid in the spinning solution is 1:1. The total mass fraction of L-polylactic acid and D-polylactic acid is 10%. The weight-average molecular weight of L-polylactic acid is 50W g / mol, and the weight-average molecular weight of D-polylactic acid is 50W g / mol;

[0129] Polymer solution: Prepared by dissolving L-polylactic acid and D-polylactic acid in p-xylene at 140 °C. Among them, the mass ratio of L-polylactic acid to D-polylactic acid is 1:1. The total mass fraction of L-polylactic acid and D-polylactic acid is 0.05%. The weight-average molecular weight of L-polylactic acid is 1W g / mol, and the weight-average molecular weight of D-polylactic acid is 1W g / mol;

[0130] p-xylene;

[0131] (2)Electrospinning:

[0132] Inject the spinning solution into a syringe for electrospinning. The syringe injection speed is 1.5 mL / h. During the electrospinning process, control the rotation speed of the receiving drum to increase from 500 rpm to 3000 rpm at a constant rate of 300 rpm / h. After electrospinning, a nanofiber membrane is obtained;

[0133] Among them, the surface of the receiving drum is wrapped with aluminum foil. The receiving distance between the receiving drum and the spinning needle is 16 cm, and the receiving voltage is 21 kV;

[0134] (3)Recrystallization:

[0135] (3.1)Let the nanofiber membrane stand in a vacuum oven at 37 °C for 36 h, and then cut the nanofiber membrane into a circle with a diameter of 5 cm;

[0136] (3.2)Place the cut nanofiber membrane in the polymer solution and soak it at 87 °C for 15 h (to form a sheaf crystal), take out the nanofiber membrane, rinse the nanofiber membrane 5 times with p-xylene, and let the nanofiber membrane stand at room temperature for 24 h after rinsing, then the bionic double-gradient rotator cuff patch is obtained.

[0137] Example 7

[0138] A preparation method of a bionic double-gradient rotator cuff patch is basically the same as that in Example 6, except that: in this example, the mass ratio of L-polylactic acid to D-polylactic acid in the spinning solution is 2:1.

[0139] Example 8

[0140] A preparation method of a bionic double-gradient rotator cuff patch is basically the same as that in Example 6, except that: this example does not have step (3), that is, the nanofiber membrane obtained after electrospinning is used as the bionic double-gradient rotator cuff patch.

[0141] Comparative Example 1

[0142] A preparation method of a bionic rotator cuff patch is basically the same as that in Example 1, except that: during the electrospinning process, the initial rotation speed of the receiving roller is 50 rpm.

[0143] Comparative Example 2

[0144] A preparation method of a bionic rotator cuff patch is basically the same as that in Example 5, except that: during the electrospinning process, the initial rotation speed of the receiving roller is 800 rpm.

[0145] Comparative Example 3

[0146] A preparation method of a bionic rotator cuff patch is basically the same as that in Example 5, except that: during the electrospinning process, the final rotation speed of the receiving roller is 2800 rpm.

[0147] Comparative Example 4

[0148] A preparation method of a bionic rotator cuff patch is basically the same as that in Example 1, except that: during the electrospinning process, the final rotation speed of the receiving roller is 4500 rpm.

[0149] The mechanical property indexes of the rotator cuff patches prepared in the examples and comparative examples are shown in Table 1 below:

[0150] Table 1 Mechanical property indexes of the rotator cuff patches prepared in the examples and comparative examples

[0151] Item Tensile Strength (MPa) Elastic Modulus (MPa) Example 1 7.516 124.384 Example 2 7.067 119.291 Example 3 6.510 112.140 Example 4 6.673 108.540 Example 5 7.235 114.245 Example 6 6.957 110.759 Example 7 5.790 87.660 Example 8 5.361 83.108 Comparative Example 1 3.148 45.265 Comparative Example 2 3.588 60.392 Comparative Example 3 4.269 73.328 Comparative Example 4 4.957 82.819

[0152] It can be seen from the data in Table 1 that the mechanical properties of the bionic rotator cuff patches prepared in Comparative Examples 1-4 become worse. The specific reasons for this phenomenon are analyzed as follows:

[0153] In Comparative Example 1, when preparing the bionic rotator cuff patch, the initial rotation speed of the receiving roller is 50 rpm; the lower initial rotation speed causes the fibers to be collected before being fully stretched, which in turn reduces the overall crystallinity of the fiber membrane and its mechanical properties, resulting in poor mechanical properties when used as a rotator cuff patch.

[0154] In Comparative Example 2, when preparing the bionic rotator cuff patch, the initial rotation speed of the receiving roller is 800 rpm; the higher initial rotation speed affects the initial fiber receiving efficiency, resulting in insufficient adhesion between the fiber membrane and the collecting device, affecting the subsequent deposition of the fiber membrane, and causing insufficient mechanical properties between the layers of the fiber membrane, resulting in poor mechanical properties when used as a rotator cuff patch.

[0155] In Comparative Example 3, when preparing the bionic rotator cuff patch, the final rotation speed of the receiving roller was 2800 rpm; the relatively low final rotation speed prevented the crystallinity of the oriented fibers from being fully enhanced. Since some fibers were not fully drawn, the crystallinity of the overall fiber membrane decreased, resulting in reduced mechanical properties and poor mechanical properties when used as a rotator cuff patch.

[0156] In Comparative Example 4, when preparing the bionic rotator cuff patch, the final rotation speed of the receiving roller was 4500 rpm; the relatively high final rotation speed increased the difficulty of collecting fibers at a higher rotation speed on the surface of the fiber membrane with a certain deposited thickness. Moreover, the excessively high rotation speed reduced the collection efficiency and increased the possibility of fibers being blown away, resulting in insufficient mechanical properties of the fiber membrane and poor mechanical properties when used as a rotator cuff patch.

Claims

1. A preparation method of a bionic double-gradient rotator cuff patch, characterized in that, Electrospinning is carried out on the spinning solution, and during the electrospinning process, the rotation speed of the receiving roller is controlled to increase at a constant rate. After electrospinning, a nanofiber membrane is obtained. Then, the nanofiber membrane is immersed in a polymer solution, so that the polymer in the polymer solution recrystallizes on the nanofiber membrane to form a shish-kebab crystal, and then the nanofiber membrane is taken out; Both L-polylactic acid and D-polylactic acid are dissolved in the spinning solution; The minimum rotation speed of the receiving roller is 100 - 500 rpm, and the maximum rotation speed is 3000 - 4000 rpm; Both L-polylactic acid and D-polylactic acid are dissolved in the polymer solution.

2. The preparation method of a bionic double-gradient rotator cuff patch according to claim 1, characterized in that, The mass ratio of L-polylactic acid to D-polylactic acid in the spinning solution is 1:

1.

3. The preparation method of a bionic double-gradient rotator cuff patch according to claim 2, characterized in that In the spinning solution, the total mass fraction of L-polylactic acid and D-polylactic acid is 6 - 10%, and the range of the weight-average molecular weight of L-polylactic acid and D-polylactic acid is 16 - 50 Wg / mol.

4. The preparation method of a bionic double-gradient rotator cuff patch according to claim 1, characterized in that, The range of the value of the constant rate is 300 - 1000 rpm / h.

5. The preparation method of a bionic double-gradient rotator cuff patch according to claim 1, characterized in that, During electrospinning, the spinning solution is injected into a syringe and pushed at a speed of 0.8 - 1.5 mL / h. The surface of the receiving roller is wrapped with aluminum foil, the receiving distance between the receiving roller and the spinning needle is 12 - 16 cm, and the receiving voltage is 15 - 21 kV.

6. The preparation method of a bionic double-gradient rotator cuff patch according to claim 1, characterized in that, The mass ratio of L-polylactic acid to D-polylactic acid in the polymer solution is the same as that of L-polylactic acid to D-polylactic acid in the spinning solution.

7. The preparation method of a bionic double-gradient rotator cuff patch according to claim 6, characterized in that, In the polymer solution, the total mass fraction of L-polylactic acid and D-polylactic acid is 0.01 - 0.05%, and the range of the weight-average molecular weight of L-polylactic acid and D-polylactic acid is 1 - 3 Wg / mol.

8. The preparation method of a bionic double-gradient rotator cuff patch according to claim 1, characterized in that, The temperature of recrystallization is 80 - 87 °C, and the time is 6 - 15 h.

9. A bionic double-gradient rotator cuff patch, characterized in that, It is prepared by using the preparation method of a bionic double-gradient rotator cuff patch according to any one of claims 1 - 8.

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