Modified gelatin liquid metal biomedical nerve adhesive and preparation method thereof

Abstract

The invention discloses a modified gelatin liquid metal biomedical nerve adhesive and a preparation method thereof, belongs to the technical field of biomedical materials, and aims at solving the technical problems that an existing nerve tissue adhesive is low in adhesion strength, lack of conductivity and the like. According to the method, gelatin is used as a biocompatible matrix, and the reaction activity of the gelatin is improved through amination modification; lipoic acid is used as a main cross-linking component, a controllable polymer network structure is constructed by using the thermal initiation ring-opening polymerization characteristic of the lipoic acid, and tannic acid is used as a cross-linking agent to assist in regulating and controlling the pre-reaction degree; meanwhile, by adopting a mode of coating the liquid metal nanoparticles with tannic acid, the material is endowed with good conductivity, and the combination of the liquid metal and the organic matrix is enhanced at the same time. By accurately controlling the pre-reaction and deep polymerization process, the obtained adhesive has good histocompatibility and neural signal transduction capability, and has potential application value in the fields of nervous tissue repair and regeneration.

Description

Technical Field

[0001] The invention belongs to the technical field of biomedical adhesives, and in particular relates to a modified gelatin liquid metal biomedical nerve adhesive and a preparation method thereof. Background Art

[0002] As an emerging method of neural tissue repair, biomedical adhesives have attracted more and more attention due to their advantages such as simple operation, little tissue damage and good biocompatibility, and are considered to be a highly promising alternative.

[0003] Existing biomedical adhesives still face many challenges in the application of nerve tissue repair. On the one hand, the adhesion strength of existing adhesives is insufficient, making it difficult to achieve firm tissue adhesion in a complex physiological environment, which can easily lead to adhesion failure; on the other hand, nerve tissue has high electrophysiological activity, while most existing adhesives lack conductivity, making it difficult to promote nerve signal transmission and regeneration.

[0004] Therefore, developing a new type of neural tissue adhesive that has both high adhesion strength and excellent conductivity while also taking into account good biocompatibility is a key technical problem that needs to be urgently solved in this field. Summary of the invention

[0005] The invention overcomes the shortcomings of the prior art and provides a modified gelatin liquid metal biomedical nerve adhesive and a preparation method thereof.

[0006] To achieve the above object, the technical solution adopted by the present invention is: a method for preparing a modified gelatin liquid metal biomedical nerve adhesive, comprising the following steps:

[0007] S1, subjecting gelatin to an amination reaction in a buffer system to obtain amino gelatin;

[0008] S2, dissolving the amino gelatin and tannic acid in a buffer solution to obtain a precursor solution;

[0009] S3, adding lipoic acid to the precursor solution to form an intermediate solution;

[0010] S4, preparing tannic acid-coated liquid metal nanoparticles;

[0011] S5. Adding tannic acid-coated liquid metal nanoparticles into the intermediate solution to carry out polymerization reaction to obtain modified gelatin liquid metal biomedical nerve adhesive.

[0012] Furthermore, in step S1, the buffer system is a phosphate solution with a concentration of 0.01-1 mol / L and a pH value of 4-6, and the solute is sodium dihydrogen phosphate or potassium dihydrogen phosphate.

[0013] Further, in step S1, the amidation reaction includes:

[0014] (i) Add an ethylenediamine solution to the buffer system;

[0015] (ii) Adjust the pH of the system to 5 - 6, add a carboxyl activator to initiate the amidation reaction, maintain the reaction temperature at 37 - 40 °C, and the reaction time is 4 - 8 h.

[0016] Further, in step (i), the molar ratio of the carboxyl group of gelatin to ethylenediamine is 1:1 - 1:100; in step (ii), the molar ratio of the carboxyl group of gelatin to the carboxyl activator is 1:1 - 1:5, and the carboxyl activator is 1-ethyl-(3-dimethylaminopropyl)carbodiimide hydrochloride or a composition of one or more of 1-ethyl-(3-dimethylaminopropyl)carbodiimide hydrochloride, N-hydroxysuccinimide, N-hydroxy thiosuccinimide, and 1-hydroxybenzotriazole hydrate.

[0017] Further, step S1 also includes dialysis purification and freeze-drying of the amidation reaction product: Load the amidation reaction product into a dialysis bag with a molecular weight cut-off of 3000 - 14000 and dialyze for 3 - 5 days. Place the remaining product at -50 to -90 °C for 4 - 6 h and then lyophilize for 24 - 48 h.

[0018] Further, in step S2, the buffer solution is one of a tris(hydroxymethyl)aminomethane hydrochloride buffer solution, a phosphate buffer solution prepared from sodium dihydrogen phosphate and potassium dihydrogen phosphate, and a glycine buffer solution.

[0019] Further, the method for preparing tannic acid-coated liquid metal nanoparticles in step S4 includes: Add liquid metal to the tannic acid solution, perform ultrasonic treatment, and obtain tannic acid-coated liquid metal nanoparticles through centrifugation and washing with water.

[0020] Further, the liquid metal is a liquid gallium-indium alloy or a liquid gallium-indium-tin alloy, and the mass ratio to tannic acid is 1:5 - 1:50; the tannic acid solution is one of a tannic acid-aqueous solution, a tannic acid-ethanol solution, and a tannic acid-ethylene glycol solution, with a concentration of 50 - 300 mg / mL; the ultrasonic power for ultrasonic treatment is set at 600 - 900 W, and the ultrasonic time is 0.5 - 2 h.

[0021] Further, in step S2, the mass ratio of amidated gelatin to tannic acid is 1:0.1 - 1:5; in step S3, the mass ratio of lipoic acid to amidated gelatin is 1:5 - 1:20.

[0022] Further, the dissolution temperature in step S2 is 40 - 60 °C, the dissolution temperature in step S3 is 40 - 60 °C, and the polymerization reaction temperature in step S5 is 70 - 80 °C.

[0023] Another technical solution provided by the present invention: A modified gelatin liquid metal biomedical nerve adhesive, prepared by the above method.

[0024] The present invention solves the defects existing in the background technology and has the following beneficial effects:

[0025] (1) The present invention provides a biomedical nerve adhesive and its preparation method, which can realize the synergistic optimization of biocompatibility, tissue adhesiveness and conductivity, thereby providing a material selection with excellent performance for the fields of tissue engineering and nerve repair.

[0026] (2) The present invention uses gelatin, lipoic acid, tannic acid and liquid metal as the main components of the adhesive. Among them, gelatin serves as a biocompatible matrix, providing good cell affinity; lipoic acid provides mechanical strength through ring-opening polymerization, and its disulfide bonds can participate in cross-linking reactions; tannic acid, as a polyphenolic compound, has multiple functions such as cross-linking, adhesion and antioxidant; liquid metal nanoparticles serve as conductive fillers, endowing the material with excellent electrical conductivity. In addition, the present invention effectively improves the dispersion and biocompatibility of liquid metal by coating liquid metal nanoparticles with tannic acid. The phenolic hydroxyl groups in tannic acid molecules can coordinate with metal ions to form a protective layer on the surface of liquid metal, preventing its aggregation, reducing its cytotoxicity, and at the same time enhancing its binding force with the organic matrix. Compared with the single-component biomedical adhesives in the prior art, the present invention can better meet the comprehensive requirements of nerve tissue repair and regeneration for material properties, has a wider application range, realizes the multiple improvements of the biocompatibility, tissue adhesiveness, conductivity and mechanical properties of the adhesive, overcomes the shortcomings of traditional biomedical adhesives such as single function and insufficient performance, improves the nerve tissue adhesion and repair efficiency, and is expected to promote the effective transmission of nerve signals.

[0027] (3) The present invention adopts a stepwise polymerization strategy to control the structure and properties of the intermediate solution through pre-reaction, creating favorable conditions for subsequent deep polymerization. In the pre-reaction stage, lipoic acid undergoes partial polymerization under specific conditions to form an intermediate network with a certain degree of cross-linking and reaction activity, and initially combines with amino-gelatin and tannic acid. The present invention uses liquid metal nanoparticles coated with tannic acid as the active component for deep polymerization to enhance the interaction between the organic matrix and the conductive filler. The tannic acid on the surface of the nanoparticles can react with the components in the intermediate solution to promote the formation of an interpenetrating network structure. Compared with the traditional one-step polymerization method, the stepwise polymerization strategy of the present invention can better control the reaction process, avoid problems such as over-polymerization or insufficient reaction, thereby obtaining a material with more uniform and stable properties, and preparing a biomedical nerve adhesive with excellent tissue adhesiveness, conductivity and mechanical properties, providing a convenient and feasible new technology for in vivo application and clinical detection.

[0028] (4) Tannic acid not only acts as a crosslinking agent to enhance adhesion but also is used to coat liquid metal nanoparticles. By controlling the degree of pre-reaction and the depth of polymerization, an interpenetrating network with specific structures and properties is constructed, ensuring that each component can fully play its role and work synergistically. The multiple functions of tannic acid and the stepwise polymerization strategy enable tannic acid to better exert its crosslinking and coating effects. In the pre-reaction stage, tannic acid forms an intermediate network with amino-gelatin and lipoic acid; in the deep polymerization stage, the liquid metal nanoparticles coated with tannic acid can react fully with the intermediate network, thereby firmly binding the liquid metal nanoparticles to the organic matrix, improving the conductivity and mechanical properties of the material, and achieving the unity of simplicity in material preparation and excellent performance. This multifunctional nerve adhesive helps to simultaneously achieve the purposes of effective tissue adhesion, long-term stability, and promotion of nerve regeneration. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required for use in the description of the embodiments or the prior art. Obviously, the drawings in the following description are only some embodiments recorded in the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained based on these drawings;

[0030] Figure 1 is a flowchart of a preparation method of a modified gelatin liquid metal biomedical nerve adhesive;

[0031] Figure 2 is a schematic diagram of the preparation principle of amino-gelatin;

[0032] Figure 3 is a schematic diagram of the reaction principle of amino-gelatin - lipoic acid - tannic acid;

[0033] Figure 4 is a schematic diagram of the preparation principle of liquid metal nanoparticles coated with tannic acid;

[0034] Figure 5 is a schematic diagram of the preparation principle of a modified gelatin liquid metal biomedical nerve adhesive. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0035] The following will clearly and completely describe the technical solutions in the embodiments of the present invention with reference to the drawings in the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, rather than all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts belong to the scope of protection of the present invention.

[0036] In the following description, numerous specific details are set forth in order to provide a thorough understanding of the present invention. However, the present invention may be practiced in other ways than those specifically described herein. Therefore, the scope of the present invention is not limited by the specific embodiments disclosed below.

[0037] In the description of the present application, it should be understood that the orientation or positional relationships indicated by the terms "center", "longitudinal", "transverse", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", etc. are based on the orientation or positional relationships shown in the drawings. These are only for the convenience of describing the present application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation. Therefore, they should not be construed as limiting the scope of protection of the present application. In addition, the terms "first", "second", etc. are only used for descriptive purposes and cannot be construed as indicating or implying relative importance or implicitly specifying the quantity of the indicated technical features. Therefore, features defined with "first", "second", etc. may explicitly or implicitly include one or more of such features. In the description of the present invention, unless otherwise stated, the meaning of "a plurality" is two or more.

[0038] In the description of the present application, it should be noted that unless otherwise clearly specified and limited, the terms "mounted", "connected", and "connected" should be understood in a broad sense. For example, it may be a fixed connection, a detachable connection, or an integral connection; it may be a mechanical connection or an electrical connection; it may be directly connected or indirectly connected through an intermediate medium, and it may be the communication inside two elements. For those of ordinary skill in the art, the specific meanings of the above terms in the present application can be understood through specific circumstances.

[0039] Exemplary method:

[0040] As Figure 1 shown, a preparation method of a modified gelatin liquid metal biomedical nerve adhesive includes the following steps:

[0041] S1. Perform an amination reaction on gelatin in a buffer system to obtain aminated gelatin;

[0042] S2. Dissolve the aminated gelatin and tannic acid in a buffer solution to obtain a precursor solution;

[0043] S3. Add lipoic acid to the precursor solution to form an intermediate solution;

[0044] S4. Prepare tannic acid-coated liquid metal nanoparticles;

[0045] S5. Add the tannic acid-coated liquid metal nanoparticles into the intermediate solution and carry out a polymerization reaction to obtain a modified gelatin liquid metal biomedical nerve adhesive.

[0046] In the above preparation method, gelatin serves as a biocompatible matrix, lipoic acid serves as the main cross-linking component and provides mechanical strength, tannic acid serves as a cross-linking agent to enhance adhesion while coating the liquid metal nanoparticles, and the liquid metal nanoparticles serve as a conductive material to provide conductivity. By first performing a pre-reaction of amino-gelatin, lipoic acid, and tannic acid, and then adding the tannic acid-coated liquid metal nanoparticles into the intermediate solution for deep polymerization, all components are thus connected into an interpenetrating network structure to obtain a biomedical nerve adhesive with excellent comprehensive properties.

[0047] Next, each step will be described in detail.

[0048] In step S1, since the amidation reaction is very sensitive to the pH value. Using a buffer system can effectively maintain the pH value stability of the reaction system and prevent the pH value fluctuation from affecting the reaction efficiency and product quality.

[0049] Specifically, the buffer system is a phosphate solution with a concentration of 0.01 - 1 mol / L and a pH value of 4 - 6, and the solute is sodium dihydrogen phosphate or potassium dihydrogen phosphate. The phosphate buffer solution is a commonly used buffer system with good buffering capacity and good biocompatibility. After adding gelatin, the buffer system is heated to 40 - 60 °C and stirred to dissolve the gelatin.

[0050] As Figure 2 shown, the amidation reaction specifically includes:

[0051] (i) Add an ethylenediamine solution to the buffer system. Among them, the molar ratio of the carboxyl group of gelatin to ethylenediamine is 1:1 - 1:100.

[0052] (ii) Adjust the system pH to 5 - 6, add a carboxyl activator to initiate the amidation reaction, keep the reaction temperature at 37 - 40 °C, and the reaction time is 4 - 8 h. Among them, the molar ratio of the carboxyl group of gelatin to the carboxyl activator is 1:1 - 1:5, and the carboxyl activator is 1-ethyl-(3-dimethylaminopropyl)carbodiimide hydrochloride (EDC) or a combination of 1-ethyl-(3-dimethylaminopropyl)carbodiimide hydrochloride (EDC) and one or more of 1-ethyl-(3-dimethylaminopropyl)carbodiimide hydrochloride, N-hydroxysuccinimide, N-hydroxy thiosuccinimide, and 1-hydroxybenzotriazole hydrate.

[0053] Ethylenediamine is an organic small molecule containing two amino groups (-NH2), which can undergo an amidation reaction with the carboxyl groups on gelatin, connect the amino groups to the gelatin molecules, and improve the reaction activity of gelatin. A carboxyl activator (such as EDC) can convert the carboxyl groups (-COOH) on gelatin into active ester intermediates, making them more easily attacked by amines. The reaction rate between carboxyl groups and amines themselves is very slow, and an activator is needed to accelerate the reaction. It should be noted that pH 5-6 ensures that ethylenediamine has a certain nucleophilicity, which is beneficial for the carboxyl activator to play a role and at the same time avoids gelatin denaturation.

[0054] After the amidation reaction, the product contains small molecule impurities such as unreacted ethylenediamine, carboxyl activator and its by-products, and salt ions in the phosphate buffer solution. These impurities will affect the subsequent reactions and the performance of the final product, so they need to be removed. In addition, amidated gelatin is prone to degradation in the solution state, which is not conducive to preservation. By freeze-drying, the moisture in the product is removed to obtain solid amidated gelatin.

[0055] Small molecule impurities in the product, including unreacted ethylenediamine, carboxyl activator and its by-products, and salt ions in the phosphate buffer solution, are removed by dialysis, and the remaining product is freeze-dried to obtain amidated gelatin.

[0056] Specifically, the dialysis method is as follows: The product is loaded into a dialysis bag with a molecular weight cut-off of 3000-14000 and dialyzed for 3-5 days, during which the water is changed every 4-8 h. The freeze-drying method is as follows: The product is frozen at -50 to -90 °C for 4-6 h and then transferred to a vacuum freeze-dryer for freeze-drying for 24-48 h.

[0057] In step S2, the amidated gelatin is dissolved in a buffer solution with a concentration of 0.1-0.5 g / mL, tannic acid is added, and they are mixed at 40-60 °C to obtain a precursor solution. Preliminary binding occurs between the amidated gelatin and tannic acid molecules through forces such as hydrogen bonds, forming a complex, which provides more reaction sites for the subsequent lipoic acid polymerization reaction.

[0058] The buffer solution is one of tris(hydroxymethyl)aminomethane hydrochloride buffer (Tris-HCl), phosphate buffer solution (PBS) prepared from sodium dihydrogen phosphate and potassium dihydrogen phosphate, and glycine buffer solution.

[0059] Tannic acid is a natural polyphenolic compound with multiple phenolic hydroxyl groups (-OH). These phenolic hydroxyl groups can form hydrogen bonds with the amino and hydroxyl groups on the amidated gelatin, thereby connecting the amidated gelatin molecules to form a cross-linked network. In addition, tannic acid has good adhesion performance, antioxidant effect, anti-inflammatory and antibacterial activities.

[0060] As Figure 3As shown, in step S3, lipoic acid is added to the precursor solution and continuously stirred at 40 - 60 °C to form an intermediate solution.

[0061] Lipoic acid (LA) is an organic compound containing a disulfide bond (-S-S-), and its molecule contains a five-membered ring disulfide bond. Under heating conditions, the disulfide bond in the lipoic acid molecule is prone to breakage, forming free radicals and initiating a ring-opening polymerization reaction. Through the polymerization reaction, lipoic acid molecules are connected together to form a polymer network. During the polymerization of lipoic acid, tannic acid participates in the reaction as a cross-linking agent and combines with the lipoic acid polymer chains to form a more complex and stable interpenetrating network structure.

[0062] It should be noted that the purpose of this step is to initiate a partial polymerization reaction to form some short-chain lipoic acid polymers or oligomers. These short-chain polymers or oligomers undergo preliminary binding with amino-gelatin and tannic acid to form an intermediate network structure. There are still a large number of unreacted functional groups in this intermediate network (such as the disulfide bond of lipoic acid, the phenolic hydroxyl group of tannic acid, the amino group and carboxyl group of amino-gelatin), and these functional groups will undergo deep polymerization with tannic acid-coated liquid metal nanoparticles in step S5.

[0063] As Figure 4 shown, in step S4, the method for preparing tannic acid-coated liquid metal nanoparticles includes: adding liquid metal to the tannic acid solution, performing ultrasonic treatment, and obtaining tannic acid-coated liquid metal nanoparticles through centrifugation and washing with water.

[0064] Among them, the tannic acid solution is one of tannic acid - aqueous solution, tannic acid - ethanol solution, and tannic acid - ethylene glycol solution, with a concentration of 50 - 300 mg / mL. The liquid metal is liquid gallium indium alloy or liquid gallium indium tin alloy, and the mass ratio of the liquid metal to tannic acid is 1:5 - 1:50. The ultrasonic power of the ultrasonic treatment is set to 600 - 900 W, and the ultrasonic time is 0.5 - 2 h.

[0065] Both gallium indium alloy and gallium indium tin alloy have excellent electrical conductivity, which can endow the material with good electrical conductivity and meet the requirements of applications such as nerve repair. However, due to the relatively high surface tension of liquid metal, it is prone to agglomeration, forming larger particles, resulting in poor dispersibility and affecting the performance of the material.

[0066] Tannic acid is a polyphenolic compound containing a large number of phenolic hydroxyl groups (-OH). These phenolic hydroxyl groups form coordination bonds with metal ions on the surface of the liquid metal, thereby firmly binding tannic acid to the surface of the liquid metal. The ultrasonic wave generates a cavitation effect, dispersing the liquid metal into tiny droplets, and then coating with tannic acid, effectively reducing the surface tension of the liquid metal and preventing the agglomeration of liquid metal particles, thereby obtaining nanoparticles with uniform particle size.

[0067] It should be noted that the tannic acid-coated liquid metal nanoparticles are not only conductive fillers but also active components for the deep polymerization occurring in step S5. The tannic acid on the surface of the nanoparticles reacts with the aminoated gelatin and lipoic acid in the intermediate solution, promoting the formation of a network, thereby firmly binding the liquid metal nanoparticles to the organic matrix.

[0068] As Figure 3 、 Figure 5 shown, in step S5, the polymerization reaction temperature is 70 - 80 °C, and the reaction time is 2 - 6 h to obtain a viscous solution. The viscous solution is placed in a freezer at -20 to -40 °C for freezing for 0.5 - 3 h and thawed at room temperature for 0.5 - 3 h to finally obtain the modified gelatin liquid metal biomedical nerve adhesive.

[0069] At 70 - 80 °C, the disulfide bond on the five-membered ring of lipoic acid is completely cleaved, further initiating the polymerization reaction, i.e., deep polymerization. Deep polymerization refers to the full reaction of the intermediate solution (aminoated gelatin, lipoic acid, and tannic acid) obtained in step S3 with the tannic acid-coated liquid metal nanoparticles prepared in step S4 to form an interpenetrating network structure.

[0070] In this network structure, lipoic acid forms polymer chains through ring-opening polymerization, tannic acid serves as a cross-linking agent to connect the polymer chains and aminoated gelatin, and the liquid metal nanoparticles are uniformly dispersed in the network and interact with each component in the network.

[0071] Deep polymerization significantly improves the properties of the material such as mechanical strength, adhesion, conductivity, and biocompatibility. Through deep polymerization, the advantages of each component are combined to achieve synergistic effects.

[0072] The freeze-thaw cycle is a commonly used physical treatment method that can further promote the polymerization and cross-linking reaction of lipoic acid and increase the cross-linking density of the material.

[0073] Exemplary adhesive:

[0074] A modified gelatin liquid metal biomedical nerve adhesive is prepared based on the above exemplary method.

[0075] Example 1

[0076] S1: Add 5 parts of gelatin into 280 parts of sodium dihydrogen phosphate solution with a concentration of 1 mol / L and a pH value of 6, heat and stir at 40 °C until the gelatin is completely dissolved; add 0.9 parts of ethylenediamine solution, and the molar ratio of carboxyl groups on the gelatin to ethylenediamine is 1:50; adjust the pH of the solution to 5.0, add 3.6 parts of carboxyl activator to initiate the amidation reaction, where the carboxyl activator is 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride and N-hydroxysuccinimide with a molar ratio of 1:2, and the molar ratio of carboxyl groups on the gelatin to the carboxyl activator is 1:2. Keep the amidation reaction temperature at 37 °C. After the reaction for 5 h, put the reaction product into a dialysis bag with a molecular weight cut-off of 3500, and dialyze with deionized water for 3 days, changing the water every 4 hours; transfer the dialyzed solution to a freeze-drying bottle, freeze at -80 °C for 4 hours and lyophilize in a vacuum freeze dryer for 48 hours to obtain solid amidated gelatin.

[0077] S2: Add 1 part of amidated gelatin into a tris(hydroxymethyl)aminomethane hydrochloride buffer solution with a concentration of 0.2 g / mL, add 0.4 part of tannic acid, and stir magnetically at 50 °C until completely dissolved to obtain a precursor solution.

[0078] S3: Add 1 part of lipoic acid into the precursor solution, and continuously stir at 50 °C until the lipoic acid is completely dissolved to form an intermediate solution.

[0079] S4: Add liquid gallium-indium alloy into an aqueous tannic acid solution with a concentration of 50 mg / mL, and the mass ratio of the liquid metal to tannic acid is 1:5. Use an ultrasonic cell disruptor for ultrasonic treatment with an ultrasonic power of 900 W and an ultrasonic time of 2 h; centrifuge the ultrasonically treated solution to obtain tannic acid-coated liquid metal nanoparticles.

[0080] S5: Add 0.002 part of tannic acid-coated liquid metal nanoparticles into the intermediate solution and mix evenly; heat the mixture to 70 °C, keep warm for 2 hours for deep polymerization; after the reaction, cool the reaction system to room temperature, put the cooled solution into a -20 °C freezer and freeze for 0.5 h and then thaw at room temperature for 0.5 h to obtain a modified gelatin liquid metal biomedical nerve adhesive.

[0081] Example 2

[0082] S1: Add 5 parts of gelatin into 280 parts of sodium dihydrogen phosphate solution with a concentration of 0.01 mol / L and a pH value of 5, heat and stir at 60 °C until the gelatin is completely dissolved; add 36 parts of ethylenediamine solution, and the molar ratio of carboxyl groups on gelatin to ethylenediamine is 1:20; adjust the pH of the solution to 5.0, add 3.6 parts of carboxyl activator to initiate the amidation reaction, where the carboxyl activator is 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride and N-hydroxysulfosuccinimide with a molar ratio of 1:2.5, and the molar ratio of carboxyl groups on gelatin to carboxyl activator is 1:3. Keep the amidation reaction temperature at 40 °C. After 8 h of reaction, put the reaction product into a dialysis bag with a molecular weight cut-off of 3500, and dialyze with deionized water for 3 days, changing the water every 4 hours; transfer the dialyzed solution to a freeze-drying bottle, freeze at -80 °C for 4 hours and lyophilize in a vacuum freeze dryer for 48 hours to obtain solid amidated gelatin.

[0083] S2: Add 1 part of amidated gelatin into a tris(hydroxymethyl)aminomethane hydrochloride buffer solution with a concentration of 0.3 g / mL, add 0.6 part of tannic acid, and stir magnetically at 50 °C until completely dissolved to obtain a precursor solution.

[0084] S3: Add 8 parts of lipoic acid into the precursor solution, continuously stir at 60 °C until the lipoic acid is completely dissolved to form an intermediate solution.

[0085] S4: Add liquid gallium-indium-tin alloy into an aqueous tannic acid solution with a concentration of 300 mg / mL, and the mass ratio of liquid metal to tannic acid is 1:25. Use an ultrasonic cell disruptor for ultrasonic treatment with an ultrasonic power of 800 W and an ultrasonic time of 1 h; centrifuge the ultrasonically treated solution to obtain tannic acid-coated liquid metal nanoparticles.

[0086] S5: Add 0.2 part of tannic acid-coated liquid metal nanoparticles into the intermediate solution and mix evenly; heat the mixture to 70 °C, keep it warm for 2 hours for deep polymerization; after the reaction ends, cool the reaction system to room temperature, put the cooled solution into a -20 °C freezer and freeze for 1 h and then thaw at room temperature for 1 h to obtain a modified gelatin liquid metal biomedical nerve adhesive.

[0087] Example 3

[0088] S1: Add 5 parts of gelatin to 280 parts of sodium dihydrogen phosphate solution with a concentration of 0.25 mol / L and a pH value of 5, heat and stir at 50 °C until the gelatin is completely dissolved; add 12.5 parts of ethylenediamine solution, and the molar ratio of carboxyl groups on the gelatin to ethylenediamine is 1:50; adjust the solution pH to 5.0, add 4.2 parts of carboxyl activator to initiate the amidation reaction, where the carboxyl activator is 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride and 1-hydroxybenzotriazole hydrate with a molar ratio of 1:1, and the molar ratio of carboxyl groups on the gelatin to the carboxyl activator is 1:1.5. Keep the amidation reaction temperature at 37 °C. After 6 h of reaction, put the reaction product into a dialysis bag with a molecular weight cut-off of 3500 and dialyze with deionized water for 3 days, changing the water every 4 hours; transfer the dialyzed solution to a freeze-drying bottle, freeze at -80 °C for 4 hours and lyophilize in a vacuum freeze dryer for 48 hours to obtain solid amidated gelatin.

[0089] S2: Add 2 parts of amidated gelatin to a 0.5 g / mL glycine buffer solution, add 0.3 part of tannic acid, and stir magnetically at 50 °C until completely dissolved to obtain a precursor solution.

[0090] S3: Add 6 parts of lipoic acid to the precursor solution and continuously stir at 50 °C until the lipoic acid is completely dissolved to form an intermediate solution.

[0091] S4: Add liquid gallium-indium alloy to a tannic acid ethanol solution with a concentration of 150 mg / mL, and the mass ratio of the liquid metal to tannic acid is 1:30. Use an ultrasonic cell disruptor for ultrasonic treatment with an ultrasonic power of 700 W and an ultrasonic time of 1.5 h; centrifuge the ultrasonically treated solution to obtain tannic acid-coated liquid metal nanoparticles.

[0092] S5: Add 0.3 part of tannic acid-coated liquid metal nanoparticles to the intermediate solution and mix evenly; heat the mixture to 70 °C, keep warm for 2 hours for deep polymerization; after the reaction ends, cool the reaction system to room temperature, put the cooled solution into a -20 °C freezer and freeze for 3 h and thaw at room temperature for 3 h to obtain a modified gelatin liquid metal biomedical nerve adhesive.

[0093] Example 4

[0094] S1: Add 5 parts of gelatin into 280 parts of sodium dihydrogen phosphate solution with a concentration of 0.2 mol / L and a pH value of 4, heat and stir at 50 °C until the gelatin is completely dissolved; add 7.2 parts of ethylenediamine solution, and the molar ratio of carboxyl groups on the gelatin to ethylenediamine is 1:20; adjust the pH of the solution to 5.0, add 2.3 parts of carboxyl activator to initiate the amidation reaction, where the carboxyl activator is 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride, and the molar ratio of carboxyl groups on the gelatin to the carboxyl activator is 1:1.5. Keep the amidation reaction temperature at 37 °C. After 6 hours of reaction, put the reaction product into a dialysis bag with a molecular weight cut-off of 3500, and dialyze with deionized water for 3 days, changing the water every 4 hours; transfer the dialyzed solution to a freeze-drying bottle, freeze at -80 °C for 4 hours and lyophilize in a vacuum freeze dryer for 48 hours to obtain solid amidated gelatin.

[0095] S2: Add 1 part of amidated gelatin into a tris(hydroxymethyl)aminomethane hydrochloride buffer solution with a concentration of 0.4 g / mL, add 0.5 part of tannic acid, and stir magnetically at 60 °C until completely dissolved to obtain a precursor solution.

[0096] S3: Add 5 parts of lipoic acid into the precursor solution, and continuously stir at 50 °C until the lipoic acid is completely dissolved to form an intermediate solution.

[0097] S4: Add liquid gallium-indium-tin alloy into a tannic acid ethanol solution with a concentration of 250 mg / mL, and the mass ratio of the liquid metal to tannic acid is 1:30. Use an ultrasonic cell disruptor for ultrasonic treatment, with an ultrasonic power of 900 W and an ultrasonic time of 2 h; centrifuge the ultrasonically treated solution to obtain tannic acid-coated liquid metal nanoparticles.

[0098] S5: Add 0.005 part of tannic acid-coated liquid metal nanoparticles into the intermediate solution and mix evenly; heat the mixture to 70 °C and keep it warm for 2 hours for deep polymerization; after the reaction is completed, cool the reaction system to room temperature, put the cooled solution into a -20 °C freezer and freeze for 3 h and thaw at room temperature for 3 h to obtain a modified gelatin liquid metal biomedical nerve adhesive.

[0099] Example 5

[0100] S1: Add 5 parts of gelatin to 280 parts of sodium dihydrogen phosphate solution with a concentration of 0.1 mol / L and a pH value of 5, heat and stir at 50 °C until the gelatin is completely dissolved; add 7.2 parts of ethylenediamine solution, and the molar ratio of carboxyl groups on the gelatin to ethylenediamine is 1:50; adjust the pH of the solution to 5.0, add 3.7 parts of carboxyl activator to initiate the amidation reaction, where the carboxyl activator is 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride, and the molar ratio of carboxyl groups on the gelatin to the carboxyl activator is 1:2. Keep the amidation reaction temperature at 37 °C. After 6 hours of reaction, put the reaction product into a dialysis bag with a molecular weight cut-off of 3500, and dialyze with deionized water for 3 days, changing the water every 4 hours; transfer the dialyzed solution to a freeze-drying bottle, freeze at -80 °C for 4 hours and lyophilize in a vacuum freeze dryer for 48 hours to obtain solid amidated gelatin.

[0101] S2: Add 1.5 parts of amidated gelatin to a tris(hydroxymethyl)aminomethane hydrochloride buffer solution with a concentration of 0.5 g / mL, add 0.7 part of tannic acid, and stir magnetically at 60 °C until completely dissolved to obtain a precursor solution.

[0102] S3: Add 4.8 parts of lipoic acid to the precursor solution, and continuously stir at 50 °C until the lipoic acid is completely dissolved to form an intermediate solution.

[0103] S4: Add liquid gallium-indium alloy to a tannic acid ethylene glycol solution with a concentration of 300 mg / mL, and the mass ratio of the liquid metal to tannic acid is 1:50. Use an ultrasonic cell disruptor for ultrasonic treatment, with an ultrasonic power of 900 W and an ultrasonic time of 1.5 h; centrifuge the ultrasonically treated solution to obtain tannic acid-coated liquid metal nanoparticles.

[0104] S5: Add 0.5 part of tannic acid-coated liquid metal nanoparticles to the intermediate solution and mix evenly; heat the mixture to 70 °C, keep it warm for 2 hours for deep polymerization; after the reaction is completed, cool the reaction system to room temperature, put the cooled solution into a -20 °C freezer and freeze for 2 h and thaw at room temperature for 2 h to obtain a modified gelatin liquid metal biomedical nerve adhesive.

[0105] Example 6

[0106] S1: Add 5 parts of gelatin into 280 parts of sodium dihydrogen phosphate solution with a concentration of 1 mol / L and a pH value of 5, heat and stir at 60 °C until the gelatin is completely dissolved; add 7.2 parts of ethylenediamine solution, and the molar ratio of carboxyl groups on the gelatin to ethylenediamine is 1:30; adjust the pH of the solution to 5.0, add 2.3 parts of carboxyl activator to initiate the amidation reaction, where the carboxyl activator is 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride, and the molar ratio of carboxyl groups on the gelatin to the carboxyl activator is 1:2.5. Keep the amidation reaction temperature at 37 °C. After 7 h of reaction, put the reaction product into a dialysis bag with a molecular weight cut-off of 3500, and dialyze with deionized water for 3 days, changing the water every 4 hours; transfer the dialyzed solution to a freeze-drying bottle, freeze at -80 °C for 4 hours and lyophilize in a vacuum freeze dryer for 48 hours to obtain solid amidated gelatin.

[0107] S2: Add 1.5 parts of amidated gelatin into a tris(hydroxymethyl)aminomethane hydrochloride buffer solution with a concentration of 0.15 g / mL, add 0.5 part of tannic acid, and stir magnetically at 50 °C until completely dissolved to obtain a precursor solution.

[0108] S3: Add 5.5 parts of lipoic acid to the precursor solution, and continuously stir at 50 °C until the lipoic acid is completely dissolved to form an intermediate solution.

[0109] S4: Add liquid gallium-indium-tin alloy into a tannic acid ethylene glycol solution with a concentration of 100 mg / mL, and the mass ratio of liquid metal to tannic acid is 1:25. Use an ultrasonic cell disruptor for ultrasonic treatment, with an ultrasonic power of 750 W and an ultrasonic time of 1.5 h; centrifuge the ultrasonically treated solution to obtain tannic acid-coated liquid metal nanoparticles.

[0110] S5: Add 0.020 part of tannic acid-coated liquid metal nanoparticles to the intermediate solution and mix evenly; heat the mixture to 70 °C, keep it warm for 2 hours for deep polymerization; after the reaction ends, cool the reaction system to room temperature, put the cooled solution into a -20 °C freezer for 2 h and thaw at room temperature for 2 h to obtain a modified gelatin liquid metal biomedical nerve adhesive.

[0111] Experimental Example 1

[0112] (1) Refer to ISO 17190 (Test for Water Absorbency of Absorbent Hygiene Products), take 3 samples of the adhesives from Examples 1-6 each, cut them into thin slices with a size of 1 cm × 1 cm × 0.1 cm, and dry them to a constant weight (m0); immerse the samples in a phosphate buffer solution (PBS, pH = 7.4) at 37 °C, take out the samples every 1 h, dry the surface moisture with filter paper and then weigh (m t) until the mass change rate is less than 1%, which is regarded as the swelling equilibrium; the swelling rate calculation formula is

[0113] (2) Referring to ASTM E96 (Test Method for Water Vapor Transmission of Materials), the desiccant method (weighing method) is adopted. The adhesive sample (diameter 3 cm) is sealed at the mouth of a moisture permeation cup (inner diameter 2.5 cm) containing 5 g of anhydrous calcium chloride to ensure there is no gap between the sample and the cup mouth; the moisture permeation cup is placed in a constant temperature and humidity chamber (temperature 37 °C, relative humidity 90%); the moisture permeation cup is taken out and weighed every 24 h (accurate to 0.1 mg), and the mass increase (Δm) of the moisture permeation cup is recorded; the water vapor transmission rate (WVTR) calculation formula is where A is the sample area (cm 2 ), and t is the time (h).

[0114] (3) Referring to ASTM F2255 (Test Method for Shear Strength of Tissue Adhesives), the adhesives of Examples 1 - 6 are coated on the surface of a standard substrate polytetrafluoroethylene plate, with a coating area of 1 cm 2 , a thickness of 0.5 mm. After curing, it is bonded to another identical substrate, and a constant pressure (10 kPa) is applied and maintained for 5 min; a universal material testing machine (such as Instron 5565) is used to apply a shear force to the bonding area at a rate of 10 mm / min, and the maximum breaking force is recorded; the shear adhesion force calculation formula is shear adhesion force where A is the bonding area (cm 2 ).

[0115] According to the experimental methods of (1)-(3) above, the results are shown in Table 1 below:

[0116] Table 1 Summary of the properties of the adhesives of Examples 1 - 6

[0117]

[0118] Comparative Example 1

[0119] In this comparative example, steps S1, S2, S4, and S5 are exactly the same as those in Example 3. The difference is that in step S3 of this comparative example, 5.6 parts of lipoic acid are added to the precursor solution, and continuous stirring is carried out at 50 °C until the lipoic acid is completely dissolved to form an intermediate solution.

[0120] Comparative Example 2

[0121] In this comparative example, steps S1, S2, S4, and S5 are exactly the same as those in Example 3. The difference is that in step S3 of this example, 5.2 parts of lipoic acid are added to the precursor solution, and continuous stirring is carried out at 50 °C until the lipoic acid is completely dissolved to form an intermediate solution.

[0122] Comparative Example 3

[0123] In this comparative example, steps S1, S2, S4, and S5 are exactly the same as those in Example 3. The difference is that in step S3 of this example, 6.4 parts of lipoic acid are added to the precursor solution, and continuous stirring is carried out at 50 °C until the lipoic acid is completely dissolved to form an intermediate solution.

[0124] Comparative Example 4

[0125] In this comparative example, steps S1, S2, S4, and S5 are exactly the same as those in Example 3. The difference is that in step S3 of this example, 6.8 parts of lipoic acid are added to the precursor solution, and continuous stirring is carried out at 50 °C until the lipoic acid is completely dissolved to form an intermediate solution.

[0126] Experimental Example 2

[0127] (1) Referring to ISO 17190 (Test for Water Absorbency of Absorbent Hygiene Products), take 3 samples of the adhesives of Example 3 and Comparative Examples 1-4 respectively, cut them into thin slices with a size of 1 cm × 1 cm × 0.1 cm, and dry them to a constant weight (m0); immerse the samples in phosphate buffer solution (PBS, pH = 7.4) at 37 °C, take out the samples every 1 h, dry the surface moisture with filter paper and then weigh (m t ), and consider it as swelling equilibrium until the mass change rate is less than 1%; the swelling rate calculation formula is

[0128] (2) Referring to ASTM E96 (Test for Water Vapor Transmission of Materials), using the desiccant method (weighing method), seal the adhesive sample (diameter 3 cm) at the mouth of a moisture permeation cup (inner diameter 2.5 cm) containing 5 g of anhydrous calcium chloride to ensure that there is no gap between the sample and the cup mouth; place the moisture permeation cup in a constant temperature and humidity chamber (temperature 37 °C, relative humidity 90%); take out the moisture permeation cup every 24 h and weigh it (accurate to 0.1 mg), and record the mass increase amount (Δm) of the moisture permeation cup; the water vapor transmission rate (WVTR) calculation formula is Wherein, A is the sample area (cm 2 ), and t is the time (h).

[0129] (3) Referring to ASTM F2255 (Test for Shear Strength of Tissue Adhesives), coat the adhesives of Example 3 and Comparative Examples 1-4 on the surface of a standard substrate polytetrafluoroethylene plate, with a coating area of 1 cm 2 , a thickness of 0.5 mm, and after curing, bond it to another same substrate, apply a constant pressure (10 kPa) and maintain it for 5 min; use a universal material testing machine (Instron 5565) to apply a shear force to the bonding area at a rate of 10 mm / min, and record the maximum breaking force; the shear adhesion force calculation formula is shear adhesion force Wherein, A is the bonding area (cm 2)。

[0130] (4) Refer to ASTM F390 (Conductivity Test of Thin Film Materials). The adhesives of Example 3 and Comparative Examples 1-4 were made into wafers with a diameter of 1 cm and a thickness of 1 mm, and silver paste electrodes (spacing 5 mm) were coated at both ends. The volume conductivity (σ) was measured using a four-probe conductivity tester (Keithley 2400) at a constant temperature (25 °C). The calculation formula is where I is the current (A), V is the voltage (V), L is the electrode spacing (m), and A is the cross-sectional area of the sample (m 2 )。

[0131] According to the experimental methods of (1)-(4) above, the results are shown in Table 2 below:

[0132] Table 2 Summary of Adhesive Properties of Example 3 and Comparative Examples 1-4

[0133]

[0134] It can be seen from the data in Table 2 that overall, with the change of the amount of lipoic acid used, each performance parameter does not show a simple linear relationship, but shows a trend of first improving and then deteriorating, indicating that there is an optimal range of lipoic acid usage. Specifically, the swelling rate and water vapor transmission rate show a trend of first decreasing and then increasing with the increase of the amount of lipoic acid used, and reach the lowest value when the amount of lipoic acid is 6.8 parts; while the shear adhesion force and conductivity show a trend of first increasing and then decreasing, and reach the highest value when the amount of lipoic acid is 6.8 parts. These data indicate that an appropriate degree of pre-reaction can optimize the comprehensive performance of the material, but too high or too low a degree of pre-reaction will lead to a decline in performance.

[0135] This is because, from the perspective of the crosslinking mechanism of the material, lipoic acid mainly acts as a crosslinking agent in the system, promoting the formation of an interpenetrating network structure between the components. When the amount of lipoic acid used is too low, the degree of pre-reaction is insufficient, the crosslinking density of the material is low, resulting in a high swelling rate and water vapor transmission rate, poor mechanical strength and adhesion. At the same time, the electron transport path is reduced and the conductivity is also weak. When the amount of lipoic acid used is too high, the degree of pre-reaction is too high, resulting in excessive self-polymerization of lipoic acid, which will instead hinder its effective crosslinking with other components, forming an overly dense network structure, reducing the flexibility of the material, and at the same time affecting the dispersion of liquid metal nanoparticles in the system, resulting in a decrease in adhesion and conductivity. Only when the amount of lipoic acid is appropriate can an appropriate network structure be formed in the pre-reaction stage, providing the best conditions for the subsequent deep polymerization with liquid metal nanoparticles, so as to obtain a material with the optimal comprehensive performance.

[0136] Based on the inspiration of the ideal embodiments of the present invention, through the above description, relevant personnel can completely make various changes and modifications without departing from the technical idea of this invention. The technical scope of this invention is not limited to the content in the specification, and the technical scope must be determined according to the scope of the claims.

Claims

1. A preparation method of a modified gelatin liquid metal biomedical nerve adhesive, characterized in that, It includes the following steps: S1. Aminate gelatin in a buffer system to obtain aminated gelatin. S2. Dissolve the aminated gelatin and tannic acid in a buffer solution to obtain a precursor solution. S3. Add lipoic acid to the precursor solution to form an intermediate solution. S4. Prepare tannic acid-coated liquid metal nanoparticles. S5. Add the tannic acid-coated liquid metal nanoparticles to the intermediate solution and carry out a polymerization reaction to obtain a modified gelatin liquid metal biomedical nerve adhesive.

2. The preparation method according to claim 1, characterized in that, In step S1, the buffer system is a phosphate solution with a concentration of 0.01 - 1 mol / L and a pH value of 4 - 6, and the solute is sodium dihydrogen phosphate or potassium dihydrogen phosphate.

3. The preparation method according to claim 1, characterized in that, In step S1, the amination reaction includes: (i) Add an ethylenediamine solution to the buffer system. (ii) Adjust the pH of the system to 5 - 6, add a carboxyl activator to initiate the amination reaction, keep the reaction temperature at 37 - 40 °C, and the reaction time is 4 - 8 h.

4. The preparation method according to claim 3, characterized in that, In step (i), the molar ratio of the carboxyl group of gelatin to ethylenediamine is 1:1 - 1:100; in step (ii), the molar ratio of the carboxyl group of gelatin to the carboxyl activator is 1:1 - 1:5, and the carboxyl activator is 1-ethyl-(3-dimethylaminopropyl)carbodiimide hydrochloride or a composition of it and one or more of 1-ethyl-(3-dimethylaminopropyl)carbodiimide hydrochloride, N-hydroxysuccinimide, N-hydroxy thiosuccinimide, and 1-hydroxybenzotriazole hydrate.

5. The preparation method according to claim 1, wherein, In step S2, the buffer solution is one of a tris(hydroxymethyl)aminomethane hydrochloride buffer solution, a phosphate buffer solution prepared from sodium dihydrogen phosphate and potassium dihydrogen phosphate, and a glycine buffer solution.

6. The preparation method according to claim 1, wherein The method for preparing the tannic acid-coated liquid metal nanoparticles in step S4 includes: adding liquid metal to a tannic acid solution, carrying out ultrasonic treatment, and obtaining the tannic acid-coated liquid metal nanoparticles through centrifugation and washing with water.

7. The preparation method according to claim 6, characterized in that, The liquid metal is a liquid gallium-indium alloy or a liquid gallium-indium-tin alloy, and the mass ratio to tannic acid is 1:5 - 1:50; the tannic acid solution is one of a tannic acid-aqueous solution, a tannic acid-ethanol solution, and a tannic acid-ethylene glycol solution, with a concentration of 50 - 300 mg / mL; the ultrasonic power of the ultrasonic treatment is set at 600 - 900 W, and the ultrasonic time is 0.5 - 2 h.

8. The preparation method according to claim 1, characterized in that In step S2, the mass ratio of aminated gelatin to tannic acid is 1:0.1 - 1:5; in step S3, the mass ratio of lipoic acid to aminated gelatin is 1:5 - 1:

20.

9. The preparation method according to claim 1, wherein The dissolution temperature in step S2 is 40 - 60 °C, the dissolution temperature in step S3 is 40 - 60 °C, and the polymerization reaction temperature in step S5 is 70 - 80 °C.

10. A modified gelatin liquid metal biomedical nerve adhesive, characterized in that, Prepared by the method according to any one of claims 1 - 9.

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