A protein-based tubular hydrogel, and a preparation method and application thereof

Abstract

This invention relates to the field of biomaterials technology, and more particularly to a protein-based tubular hydrogel, its preparation method, and its applications. The hydrogel is prepared from the following raw materials: a skin layer solution and a core layer solution; the skin layer solution comprises a 5-20 wt% aqueous protein solution; and the core layer solution comprises a 20-30 wt% aqueous hydrophilic salt solution. The hydrogel preparation steps include: mixing the skin layer solution and the core layer solution in a receiving bath via coaxial extrusion, followed by solidification to form the hydrogel. This method uses a high-concentration salt solution to induce protein salting out, constructing a tubular hydrogel structure. The addition of polysaccharides or shaping agents enhances the gel's plasticity and stability, preventing deformation and collapse. The resulting tubular material exhibits excellent biocompatibility and mechanical properties, making it suitable for biomedical scaffolds and other applications. Furthermore, the preparation process is simple and inexpensive, indicating broad prospects for industrialization.

Description

Technical Field

[0001] This invention relates to the field of biomaterials technology, and in particular to a protein-based tubular hydrogel, its preparation method, and its applications. Background Technology

[0002] Protein-based hydrogels are a class of high-water-content three-dimensional network structure materials constructed using natural proteins (such as collagen, fibroin, gelatin, etc.) as substrates. Due to their ability to mimic the structural characteristics of natural tubular tissues, as well as their excellent biocompatibility, biodegradability, and structural tunability, they have shown great application value in multiple fields, especially in the biomedical field where their application potential has attracted much attention.

[0003] Protein-based tubular hydrogels (such as gelatin tubing) have wide applications in tissue engineering, drug delivery, and vascular simulation. In vascular repair, protein-based tubular hydrogels can be used to construct vascular substitutes, addressing the key issues of thrombosis and restenosis that are easily induced by traditional synthetic materials. For example, silk fibroin (SF) and fibroin-based tubular hydrogels have demonstrated good blood compatibility and suitable mechanical properties in animal experiments, providing an effective direction for the development of vascular substitutes. In respiratory system repair, they can be used for tracheal and bronchial reconstruction. The methacrylated silk fibroin multilayer biomimetic tracheal scaffold developed by the Central South University team has been shown in rabbit models to significantly promote cartilage regeneration, reduce the incidence of airway stenosis, and effectively improve respiratory function in experimental animals. In nerve repair, this material can serve as a nerve conduit, providing guidance and support for axonal regeneration. For example, chitosan-tube pre-filled oriented fibrin nanofiber hydrogels have shown excellent performance in facial nerve repair research. Their unique fiber structure can promote the oriented alignment of cells, thereby accelerating the nerve regeneration process. In urinary system reconstruction, they can be used for the repair and functional reconstruction of the ureter and urethra. For instance, silk fibroin-based drug-release ureteral stents can effectively prevent postoperative ureteral stenosis through drug release while providing stent support. In addition, this material can also serve as a core component of bioreactors or in vitro models for large-scale cell culture and tissue modeling. For example, 3D cell culture systems constructed from collagen hydrogel microtubes can provide an experimental platform that closely resembles the in vivo physiological environment for drug screening and disease mechanism research, thus assisting in research in related fields.

[0004] Currently, the mainstream preparation routes for tubular hydrogels include template-assisted methods, 3D printing, self-curing / film transfer, phase separation / foaming, and coaxial extrusion. Template-assisted methods often use polytetrafluoroethylene, glass tubes, or soluble salts / sugars as templates, and are suitable for preparing natural polymer hydrogels such as collagen and silk fibroin. They offer the advantage of rapid prototyping in the laboratory, but the tube wall is prone to collapse during template removal, affecting product integrity. 3D printing methods mostly employ coaxial extrusion printing, enabling one-step molding of hydrogel tubes. However, this method requires high equipment precision and material compatibility, and the shaping process often relies on photopolymerization technology, which can lead to the risk of crosslinking agent residue, thus affecting the material's biocompatibility. Self-curing / film transfer methods involve gradient crosslinking of the film or solvent placement... The core advantage of induced self-rolling to form hollow tubes lies in the absence of templates and the simplicity of the process. However, it also suffers from poor structural stability and difficulty in precisely controlling the uniformity of the tube diameter. Coaxial extrusion utilizes the coaxial co-extrusion of inner and outer fluids to gel the outer layer to form the tube wall, while the inner layer is supported by a sacrificial liquid or gas. It has outstanding advantages such as continuous preparation, adjustable tube diameter, and the ability to achieve multi-layer composites. However, this method has a technical bottleneck in that it is difficult to precisely match the flow rate of the inner and outer layers with the viscosity of the materials. Therefore, previous studies have mostly applied it to the preparation of microspheres or the molding of solid columnar gels. Currently, there are no reports on the preparation of hollow hydrogel tubes using this method.

[0005] The difficulty in preparing protein-based tubular hydrogels stems primarily from the fact that the rheological properties of protein solutions are easily affected by both concentration and ambient temperature, and the sudden increase in viscosity during preparation often leads to processing challenges. Therefore, these materials are currently mostly prepared using traditional methods such as mold casting. However, these methods have significant drawbacks: low molding precision, resulting in products prone to deformation or collapse; difficult demolding processes that easily damage the tube walls; and significant limitations in the dimensions and length of the prepared tubular materials, making it difficult to flexibly adjust them according to actual application requirements.

[0006] The core mechanism of salting-out for protein hydrogels is the Hofmeister effect, which uses Kosmotropic salts to compete for the hydration layer on the surface of protein molecules, strengthening hydrophobic association and chain entanglement between protein molecules, thereby achieving physical cross-linking and improved mechanical properties of the material. However, the application scenarios of existing salting-out methods are relatively limited, mainly focusing on protein purification and bulk gel preparation. Targeted optimization designs for tubular structure formation have not yet been developed, failing to meet the requirements for efficient and stable preparation of protein-based tubular hydrogels.

[0007] Chinese invention patent CN110402281A discloses a 3D printing method for gel networks. This method involves forming multiple gel objects within one or more microfluidic channels, distributing these gel objects from the channels to regions used for network generation, and constructing a multi-layered network with different properties to mimic human tissue or optical devices. Chinese invention patent application CN115894968A prepares hydrogel shell-core tubes by injecting and photocuring a gel solution using a double-layered coaxial needle. This solves the problems of reproducing three-dimensional structures and controlling cell regionalization in traditional cell culture, achieving effective cell partitioning and promoting metabolism. The hydrogel prepared by this technology is essentially a solid columnar structure. Existing technologies cannot obtain structurally stable, biocompatible hollow tubular hydrogel structures.

[0008] In view of this, the present invention aims to solve the above-mentioned problems of the prior art and provide a method for preparing protein-based tubular hydrogels that is simple to operate, stable in molding, and flexibly controllable. Summary of the Invention

[0009] The first aspect of the present invention provides a protein-based tubular hydrogel, wherein the raw materials for preparing the hydrogel include: a skin layer solution and a core layer solution; The cortical solution comprises an aqueous protein solution with a concentration of 5-20 wt%; examples include 5 wt%, 6 wt%, 7 wt%, 8 wt%, 9 wt%, 10 wt%, 11 wt%, 12 wt%, 13 wt%, 14 wt%, 15 wt%, 16 wt%, 17 wt%, 18 wt%, 19 wt%, and 20 wt%.

[0010] The core solution comprises an aqueous solution of a kosmotropic salt at a concentration of 20-30 wt%; examples include 20 wt%, 21 wt%, 22 wt%, 23 wt%, 24 wt%, 25 wt%, 26 wt%, 27 wt%, 28 wt%, 29 wt%, and 30 wt%.

[0011] To address the shortcomings of traditional mold casting methods in the preparation of tubular protein hydrogels, which suffer from low molding precision, easy deformation and collapse, easy damage to the tube wall during demolding, and limited length specifications, existing coaxial extrusion technology is limited to the preparation of microspheres or solid columnar gels due to the difficulty in coordinating the flow rate of the inner and outer layers with the material viscosity, and salting out methods are only suitable for protein purification and block gel preparation, lacking optimized design for tubular structures, this invention adopts a two-layer system of "high-concentration salt solution as the core layer + protein aqueous solution as the skin layer". Combining coaxial extrusion technology with salting out curing process, it achieves the continuous preparation of high-precision, high-stability protein-based tubular hydrogel materials with good biocompatibility, controllable mechanical properties, low cost, and high customization. The reason is that the high-concentration salt solution competes for the protein hydration layer through the Hofmeister effect, strengthens hydrophobic association and chain entanglement, realizes rapid protein salting out and gelation, effectively avoids structural collapse in traditional molding, and realizes the preparation of tubular hydrogel materials.

[0012] It should be noted that the tubular structure prepared by this invention refers to a three-dimensional structure with a clearly defined hollow cavity (hollow in the middle) and a continuous tube wall surrounding the cavity. Its core feature is the organic combination of "hollow" and "tube wall"—the tube wall serves as the main structural support, giving the material morphological stability and mechanical load-bearing capacity, while the hollow cavity provides space for material transport, cell colonization, or loading of functional carriers. This structure is fundamentally different from a solid column structure: a solid column has no internal hollow cavity and is a homogeneous, dense, or porous filled form, lacking the unique "cavity-wall" binary configuration and functional adaptability brought by the hollow space of a tubular structure. This is also the essential difference and advantage of this invention over existing non-tubular products.

[0013] Optionally, the concentration of the protein aqueous solution in the cortical solution is 11-20 wt%.

[0014] The proteins mentioned may include gelatin, collagen, fibroin, silk fibroin, bovine serum albumin, soy protein isolate, etc.

[0015] Optionally, the protein includes at least one of gelatin, collagen, fibroin, and silk fibroin.

[0016] Examples of lyophilic salts include magnesium sulfate (MgSO4), ammonium sulfate, sodium citrate, disodium hydrogen phosphate, sodium sulfate, sodium tartrate, potassium citrate, dipotassium hydrogen phosphate, potassium sulfate, and potassium tartrate.

[0017] To optimize the salting-out rate of the hydrogel and ensure rapid gelation of the tubular material, the hydrophilic salt includes at least one of MgSO4, ammonium sulfate, and sodium citrate; most preferably, MgSO4.

[0018] The cortex solution also includes polysaccharides; examples of polysaccharides include natural polysaccharides such as carboxymethyl cellulose, alginate, chitosan, agarose, hyaluronic acid, pectin, and xanthan gum.

[0019] Optionally, the polysaccharide includes at least one of carboxymethyl cellulose, sodium alginate, chitosan, and agarose.

[0020] Optionally, the amount of polysaccharide added is 0.1-10% of the protein mass; examples include 0.1%, 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, and 10%.

[0021] To further control the viscosity of the solution and improve the stability of the hydrogel, the skin solution also includes a plasticizer, which may include glycerin, polyvinyl alcohol, hydroxypropyl methylcellulose, polyethylene glycol, sorbitol, gum arabic, etc.

[0022] Optionally, the shaping agent includes at least one of glycerol, polyvinyl alcohol, and hydroxypropyl methylcellulose.

[0023] In addition, polysaccharides or plasticizers can be selectively added to the cortex solution of the present invention to further enhance the cross-linking density of the gel network and improve the material's plasticity and resistance to deformation.

[0024] In some embodiments, the temperature can be appropriately increased to accelerate dissolution when preparing the protein aqueous solution; for example, warm water at 40-60°C can be used to dissolve the protein; the present invention does not impose a special limitation on the dissolution temperature, but can determine it according to the actual dissolution situation.

[0025] The core mechanism of this invention for preparing tubular (especially hollow tubular) hydrogels is as follows: using a high-concentration salt solution as the core layer, the salting-out effect competitively binds to the hydration layer of protein molecules, reducing their water solubility and driving rapid hydrophobic association and chain entanglement of proteins, thus achieving rapid gelation of the cortex protein solution; while the polysaccharides or plasticizers compounded in the cortex can form a synergistic cross-linking network with the protein chains through intermolecular hydrogen bonds and electrostatic interactions, effectively increasing the cross-linking density of the gel and enhancing the material's plasticity and deformation resistance. At the same time, a specific coaxial extrusion process is used to achieve continuous and stable molding of the tubular structure, fundamentally avoiding the defects such as structural collapse and uneven wall thickness that are prone to occur in traditional mold methods or single-fluid extrusion methods. Moreover, this preparation strategy has good universality and can be extended to the construction of tubular hydrogels of various protein-based biomaterials such as gelatin, collagen, and fibrin.

[0026] A second aspect of the present invention provides a method for preparing the protein-based tubular hydrogel as described above, wherein the preparation steps of the hydrogel include: The skin layer solution and core layer solution are mixed in a receiving bath by coaxial extrusion and solidified to form a hydrogel.

[0027] Optionally, the preparation steps of the hydrogel include: Prepare the dermal layer solution by placing it into syringe A; Prepare the core layer solution and place it into syringe B; Syringe A and Syringe B are connected with a coaxial needle. The skin layer solution and the core layer solution are extruded from the outlet of the coaxial needle. The extruded mixture enters the receiving bath and solidifies to form a hollow tubular hydrogel.

[0028] Optionally, the coaxial needle is formed by at least two needles nested coaxially.

[0029] The coaxial needle is a type of needle that is slender and cylindrical, consisting of two core components, an "outer needle" and an "inner needle", with their axes completely overlapping, forming a double-layer channel structure of "outer tube wrapping inner tube".

[0030] The coaxial needle is formed by two needles, one and two, nested coaxially. The diameter of the first needle is 0.1–10 mm (corresponding to a fine needle); the diameter of the second needle is 0.3–30 mm (corresponding to a coarse needle); and the diameter of the first needle is smaller than the diameter of the second needle.

[0031] In some embodiments, needle one is connected to syringe B, and needle two is connected to syringe A.

[0032] Optionally, the diameter of the first needle is 0.1–2 mm, and can be listed as 0.1 mm, 0.2 mm, 0.3 mm, 0.4 mm, 0.5 mm, 0.6 mm, 0.7 mm, 0.8 mm, 0.9 mm, 1 mm, 1.5 mm, 2 mm; the diameter of the second needle is 0.3–3 mm, and can be listed as 0.3 mm, 0.4 mm, 0.5 mm, 0.6 mm, 0.7 mm, 0.8 mm, 0.9 mm, 1 mm, 1.5 mm, 2 mm, 2.5 mm, 3 mm.

[0033] Optionally, the diameter difference between the first needle and the second needle is 0.1-1 mm (corresponding to the wall thickness of the generated hollow tubular hydrogel).

[0034] Optionally, the extrusion flow rate of the cortical solution is 1-20 mL / min; more preferably 1-5 mL / min; examples include 1 mL / min, 2 mL / min, 3 mL / min, 4 mL / min, and 5 mL / min.

[0035] Optionally, the extrusion flow rate of the core layer solution is 1-20 mL / min; more preferably 1-5 mL / min; examples include 1 mL / min, 2 mL / min, 3 mL / min, 4 mL / min, and 5 mL / min.

[0036] Optionally, the ratio of the extrusion flow rates of the skin layer solution and the core layer solution is (1-3):1; examples include 1:1, 2:1, and 3:1.

[0037] Optionally, the hollow tubular hydrogel has a wall thickness of 0.01-4 mm and a hollow inner diameter of 0.2-8 mm.

[0038] This invention utilizes a coaxial needle consisting of a first needle with a diameter of 0.1–10 mm and a second needle with a diameter of 0.3–30 mm. The skin layer solution and the core layer solution are simultaneously extruded through this coaxial needle at a flow rate of 1–20 m / min, forming a tubular flow structure. The extrusion process allows for continuous production. By further controlling the flow rate ratio of the skin layer solution to the core layer solution to (1–3):1, hollow tubular hydrogels with a wall thickness of 0.1–1 mm and a hollow inner diameter of 0.2–2 mm can be precisely obtained, thereby achieving high-precision molding of the skin-core layer composite structure.

[0039] Optionally, the receiving bath is a salt solution or an alcohol.

[0040] Optionally, the concentration of the salt solution is 20-30 wt%; examples include 20 wt%, 21 wt%, 22 wt%, 23 wt%, 24 wt%, 25 wt%, 26 wt%, 27 wt%, 28 wt%, 29 wt%, and 30 wt%.

[0041] Optionally, the salt is the same as the hydrophilic salt in the core solution.

[0042] The salts mentioned can be listed as magnesium sulfate (MgSO4), ammonium sulfate, sodium citrate, disodium hydrogen phosphate, sodium sulfate, potassium sodium tartrate, potassium citrate, dipotassium hydrogen phosphate, potassium sulfate, potassium tartrate, etc.

[0043] The alcohol solution may include ethanol, isopropanol, propylene glycol, etc.

[0044] Optionally, the temperature of the coagulation bath is 20-40℃; examples include 20℃, 21℃, 22℃, 23℃, 24℃, 25℃, 26℃, 27℃, 28℃, 29℃, 30℃, 31℃, 32℃, 33℃, 34℃, 35℃, 36℃, 37℃, 38℃, 39℃, and 40℃.

[0045] Optionally, the curing time is 1-60s; examples include 1s, 2s, 3s, 4s, 5s, 6s, 7s, 8s, 9s, 10s, 20s, 30s, 40s, 50s, and 60s.

[0046] This invention uses the same salt or alcohol solution as the core layer solution as the receiving bath to receive the extruded tubular flow structure. Rapid protein gelation is induced through salting-out or a salting-out-dehydration synergistic effect, forming a stable tubular hydrogel material. Further adjusting the receiving bath temperature to 20-40℃ can further optimize gelation efficiency, reducing the gelation time to less than 1 minute and preventing deformation of the tubular structure.

[0047] In some embodiments, the hydrogel can be post-processed for purification.

[0048] Optionally, the post-processing method is washing, which can be done by multiple water washes or dialysis to remove residual excess salt ions; the hydrogel can also be dried after washing, and the drying method includes freeze drying or air drying.

[0049] Optionally, the post-treatment can also be chemical cross-linking, such as by glutaraldehyde cross-linking or EDC / NHS (EDC: 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide hydrochloride; NHS: N-hydroxysuccinimide) cross-linking, to further enhance the mechanical properties of the material and achieve precise control of its biodegradation rate.

[0050] In some embodiments, the preparation method of the present invention can be combined with 3D printing technology to assist needle movement, thereby realizing the preparation of tubular hydrogels with complex geometries.

[0051] The coaxial extrusion technology of this invention achieves continuous forming of tubular structures and precise control of wall thickness and inner diameter by accurately controlling the needle size and the flow rate ratio between the inner and outer layers, thus solving the problem of coordinating flow rate and viscosity. Optional washing, drying, or cross-linking post-treatment steps can further remove residual salt ions, optimize the mechanical properties and degradation characteristics of the material, and ultimately enable the prepared tubular material to meet the application requirements of biomedical scaffolds, vascular substitutes, and other scenarios. A third aspect of the present invention provides an application of the protein-based tubular hydrogel described above, wherein the hydrogel is used in the fields of tissue engineering, drug delivery, or biomimetic organ construction; for example, biomedical scaffolds, vascular substitutes, nerve conduits, or drug delivery systems.

[0052] Beneficial effects: This invention provides a protein-based tubular hydrogel, its preparation method, and its applications, which have the following advantages: (1) The present invention designs a core layer and a skin layer solution to form a tubular hydrogel by coaxial extrusion. The core layer uses a 20-30 wt% high-concentration hydrophilic salt solution, which is mixed with the skin layer protein solution by coaxial needle extrusion. Under the salting-out effect, the solubility of the protein is efficiently reduced, which promotes the rapid gelation of the skin layer solution (curing time <1 min). The tubular hydrogel prepared by this method can take into account both the processing fluidity and the molding stability, and effectively avoid the structural deformation problem that is easy to occur in the curing stage of the tubular hydrogel. (2) The present invention uses natural proteins such as gelatin, collagen, and fibrin as the base material, and combines them with biocompatible polysaccharides or plasticizers such as carboxymethyl cellulose and sodium alginate. The raw materials are widely available and have high biocompatibility. They can not only synergistically improve the material performance, but also meet the core requirements of biocompatibility of materials in the biomedical field. (3) This invention uses coaxial extrusion technology to achieve simultaneous extrusion of core layer and skin layer solutions. The core layer salt solution provides dynamic support. With precise flow rate ratio (1-3):1 and needle size control, it can achieve continuous forming of tubular structure and ensure uniform tube wall and smooth inner wall. It fundamentally solves the defects of traditional methods such as easy collapse and uneven wall thickness. It can also be extended to multi-layer biomimetic structure. (4) The preparation process of the present invention does not require complex equipment and harsh reaction conditions. The steps of dissolution, extrusion, curing and post-processing are simple and controllable. Customized production of products of different specifications can be achieved by adjusting the process parameters. Demolding is convenient and without damage. The production efficiency can reach several meters / minute, which has the feasibility of large-scale industrial production. (5) The tubular hydrogel products provided by the present invention have good biocompatibility, mechanical stability and conductivity, and can be widely used in core scenarios such as biomedical scaffolds, vascular substitutes and nerve conduits. They can also be extended to emerging fields such as flexible sensors and electrically stimulating tissue engineering, which meet the development needs of the biomaterials industry and have great potential for industrialization. Attached Figure Description

[0053] Figure 1 Example 1: Schematic diagram of the preparation of protein-based tubular hydrogels; Figure 2 Example 1: Extrusion stage of protein-based tubular hydrogel and finished hydrogel image; Figure 2 The left image shows the actual product during the extrusion stage, and the right image shows the finished hydrogel product. Figure 3 Example 1: Microscopic photograph of a protein-based tubular hydrogel; Figure 2 The left image is a magnified cross-sectional view under a microscope, and the right image is a magnified longitudinal cross-sectional view under a microscope. Figure 4 Example 2: Actual image of the extrusion stage of the protein-based tubular hydrogel and magnified microscopic photograph of the hydrogel; Figure 4The left image is a picture of the actual object during the extrusion stage; the middle image is a magnified cross-sectional view under a microscope; and the right image is a magnified longitudinal cross-sectional view under a microscope. Figure 5 Comparative Example 1: A physical image of a protein-based tubular hydrogel; Figure 6 Comparative Example 2: A physical image of a protein-based tubular hydrogel; Figure 7 Comparative Example 3: A physical image of a protein-based tubular hydrogel; Figure 8 Comparative Example 4: A physical image of a protein-based tubular hydrogel; Figure 9 Comparative Example 5: A physical image of a protein-based tubular hydrogel; Figure 10 Comparative Example 6: A physical image of a protein-based tubular hydrogel; Figure 11 Example 2: Conductivity test diagram of protein-based tubular hydrogel; Figure 12 Example 2: Mechanical property test results of protein-based tubular hydrogels. Detailed Implementation

[0054] Unless otherwise specified, the solvents used in the solutions involved in this invention are all water; the concentrations involved are all mass concentrations; the room temperature is 25°C; and the raw materials, equipment and other consumables used are all commercially available.

[0055] Example 1 This embodiment provides a protein-based tubular hydrogel and its preparation method. The raw materials for preparing the hydrogel include: a skin layer solution and a core layer solution; The skin layer solution is a 15wt% gelatin aqueous solution; the preparation method is as follows: dissolve 7.5g of gelatin in 50mL of water (50℃), stir until dissolved, and obtain a gelatin aqueous solution.

[0056] The core layer solution is a 25wt% aqueous solution of MgSO4.

[0057] The preparation steps of the hydrogel include: S1. Prepare the dermal layer solution by placing it into syringe A; S2. Prepare the core layer solution and place it in syringe B; S3. Connect syringe A and syringe B with a coaxial needle. Extrude the skin layer solution and core layer solution from the outlet of the coaxial needle. The extruded mixture enters the receiving bath and solidifies for 10 seconds to form a hollow tubular hydrogel (extrusion length approximately 2.6 cm, see...). Figure 2 ); S4. Post-treatment: The hydrogel is washed with deionized water to remove salt ions and dried at room temperature to obtain the finished product.

[0058] The coaxial needle is composed of two needles, needle one and needle two, which are nested coaxially. The diameter of needle one is 0.5 mm and the diameter of needle two is 1 mm. Needle one is connected to syringe B and needle two is connected to syringe A.

[0059] The extrusion flow rate of both the skin layer solution and the core layer solution is 3 mL / min.

[0060] The coagulation bath is a 25wt% MgSO4 aqueous solution, and the temperature of the coagulation bath is 20℃.

[0061] The hollow tubular hydrogel has a wall thickness of 0.1 mm and a hollow inner diameter of 0.53 mm.

[0062] A schematic diagram of the preparation of the hydrogel is shown below. Figure 1 Photos of the extrusion stage and the finished hydrogel product are available in [link / reference]. Figure 2 Microscopic images of the hydrogel can be found here. Figure 3 .

[0063] Figure 2 The results show that the tubular hydrogel obtained in Example 1 has a uniform diameter and no obvious deformation; Figure 3 The results show that the prepared hydrogel has a regular hollow tubular structure with uniform tube walls and smooth skin and inner walls.

[0064] Example 2 This embodiment provides a protein-based tubular hydrogel and its preparation method. The raw materials for preparing the hydrogel include: a skin layer solution and a core layer solution; The skin layer solution is a mixed aqueous solution of 10.3 wt% gelatin and 4.7% sodium alginate. The core layer solution is a 25wt% aqueous solution of MgSO4.

[0065] The preparation steps of the hydrogel include: S1. Prepare the dermal layer solution by placing it into syringe A; S2. Prepare the core layer solution and place it in syringe B; S3. Connect syringe A and syringe B with a coaxial needle, and squeeze the skin layer solution and core layer solution from the outlet of the coaxial needle. The squeezed mixture enters the receiving bath and solidifies for 10 seconds to form a hollow tubular hydrogel. S4. Post-treatment: The hydrogel is washed with deionized water to remove salt ions and dried at room temperature to obtain the finished product.

[0066] The coaxial needle is composed of two needles, one and two, nested coaxially. The diameter of the first needle is 1 mm and the diameter of the second needle is 2 mm. The first needle is connected to syringe B and the second needle is connected to syringe A.

[0067] The extrusion flow rate of both the skin layer solution and the core layer solution is 9 mL / min.

[0068] The coagulation bath is ethanol, and the temperature of the coagulation bath is 20°C.

[0069] The hollow tubular hydrogel has a wall thickness of 0.03 mm and a hollow inner diameter of 0.3 mm.

[0070] The actual image of the hydrogel during the extrusion stage and the magnified microscope photograph of the hydrogel are shown below. Figure 4 .

[0071] Figure 4 The results show that the prepared hydrogel has a regular hollow tubular structure with uniform tube walls and smooth skin and inner walls.

[0072] Comparative Example 1 This comparative example provides a protein-based tubular hydrogel, the preparation steps of which include: S1. Prepare a mixture by mixing and dissolving 20.6 wt% gelatin aqueous solution and 9.4 wt% CMCS (carboxymethyl chitosan) aqueous solution at a volume ratio of 1:1. S2. Extrude the mixture into a rigid polycarbonate straight tube (2 mm inner diameter) and insert a stainless steel core layer (1 mm diameter). S3. Allow to cure in a cool place at 5±3℃ for 1 hour. After curing, demold to obtain hollow tubular hydrogel.

[0073] See the physical image of the obtained hydrogel. Figure 5 .

[0074] Figure 5 The results showed that the obtained hydrogel tubes were partially broken, and there were multiple break points or defects inside the tubular hydrogel, which could not meet the usage requirements.

[0075] Comparative Example 2 This comparative example provides a protein-based tubular hydrogel, the raw materials for which the hydrogel is prepared include: a skin layer solution and a core layer solution; The skin layer solution is a mixed aqueous solution with a gelatin concentration of 10.3 wt% and a CMC concentration of 4.7%. The core layer solution is a 25wt% aqueous solution of MgSO4.

[0076] The preparation steps of the hydrogel are as follows: using a coaxial spinning device, the skin layer solution and the core layer solution are extruded synchronously at a rate of 9 mm / min, and solidified in a 25 wt% MgSO4 aqueous solution (temperature 20℃).

[0077] See the physical image of the obtained hydrogel. Figure 6 .

[0078] Figure 6 The results show that the prepared hydrogel has a continuous tubular structure with uniform tube walls and smooth skin and inner walls.

[0079] Comparative Example 3 This comparative example provides a protein-based tubular hydrogel, with the same implementation method as Example 2; the difference is that sodium alginate is replaced with CMCS.

[0080] See the physical image of the obtained hydrogel. Figure 7 .

[0081] Figure 7 The results showed that the prepared hydrogel had a continuous tubular structure, but the overall structure was not uniform and there were many irregular swellings, which could not meet the requirements for use.

[0082] Comparative Example 4 This comparative example provides a hydrogel, with the same implementation method as Example 2; the difference is that sodium alginate is replaced with hydroxypropyltrimethylammonium chloride chitosan (Macklin, catalog number 850126, degree of substitution 98%).

[0083] See the physical image of the obtained hydrogel. Figure 8 .

[0084] Figure 8 The results showed that the mixture collapsed after extrusion, forming a blocky gel that could not form a tubular structure.

[0085] Comparative Example 5 This comparative example provides a hydrogel, specifically Example 2; the difference is that the chitosan quaternary ammonium salt is replaced with polyethylene oxide (Sigma-Aldrich, catalog number 189464). See the physical image of the obtained hydrogel. Figure 9 .

[0086] Figure 9 The results showed that the mixture collapsed after extrusion, forming a blocky gel that could not form a tubular structure.

[0087] Comparative Example 6 This comparative example provides a hydrogel, specifically Example 2; the difference lies in that the skin layer solution is a 10.3 wt% gelatin aqueous solution. A photograph of the resulting hydrogel is shown below. Figure 10.

[0088] Figure 10 The results showed that the mixture collapsed after extrusion, forming a blocky gel that could not form a tubular structure.

[0089] Performance testing 1. Electrical conductivity The resistance of the hydrogel in Example 2 was tested using a digital multimeter. The test results are shown below. Figure 11 .

[0090] Figure 11 The results show that the hydrogel prepared in Example 2 has a resistance value of 37.6 MΩ, proving that the hydrogel has a certain conductivity.

[0091] 2. Mechanical properties The mechanical properties of the hydrogel from Example 2 were tested using a universal testing machine. The test results are shown in [Figure number missing]. Figure 12 .

[0092] Figure 12 The results show that the hydrogel prepared in Example 2 has reliable mechanical strength and a certain degree of toughness, which can meet the needs of use in biomedical scenarios.

Claims

1. A protein-based tubular hydrogel, characterized in that, The raw materials for preparing the hydrogel include: a skin layer solution and a core layer solution; The cortical solution comprises a protein aqueous solution with a concentration of 5-20 wt%; The core layer solution comprises a hydrophilic salt aqueous solution with a concentration of 20-30 wt%.

2. The hydrogel according to claim 1, characterized in that, The protein includes at least one of gelatin, collagen, fibroin, silk fibroin, bovine serum albumin, and soy protein isolate; Preferably, the hydrophilic salt includes at least one of magnesium sulfate, ammonium sulfate, sodium citrate, disodium hydrogen phosphate, sodium sulfate, sodium tartrate, potassium citrate, dipotassium hydrogen phosphate, potassium sulfate, and potassium tartrate. Preferably, the cortex solution further includes polysaccharides; Preferably, the polysaccharide includes at least one of carboxymethyl cellulose, alginate, chitosan, agarose, hyaluronic acid, pectin, and xanthan gum; Preferably, the amount of polysaccharide added is 0.1-10% of the protein mass; Preferably, the skin solution further includes a plasticizer; Preferably, the shaping agent includes at least one of glycerin, polyvinyl alcohol, hydroxypropyl methylcellulose, polyethylene glycol, sorbitol, and gum arabic.

3. A method for preparing a protein-based tubular hydrogel according to claim 1 or 2, characterized in that, The preparation steps of the hydrogel include: The skin layer solution and core layer solution are mixed in a receiving bath by coaxial extrusion and solidified to form a hydrogel.

4. The preparation method according to claim 3, characterized in that, The preparation steps of the hydrogel include: Prepare the dermal layer solution by placing it into syringe A; Prepare the core layer solution and place it into syringe B; Syringe A and Syringe B are connected with a coaxial needle. The skin layer solution and the core layer solution are extruded from the outlet of the coaxial needle. The extruded mixture enters the receiving bath and solidifies to form a hollow tubular hydrogel. The coaxial needle is composed of at least two needles nested coaxially.

5. The preparation method according to claim 4, characterized in that, The coaxial needle is formed by coaxially nesting needle one and needle two; the diameter of needle one is 0.1–10 mm, and the diameter of needle two is 0.3–30 mm; and the diameter of needle one is smaller than the diameter of needle two.

6. The preparation method according to claim 4, characterized in that, The extrusion flow rate of the cortex solution is 1-20 mL / min; the extrusion flow rate of the core solution is 1-20 mL / min. Preferably, the ratio of the extrusion flow rates of the skin layer solution and the core layer solution is (1-3):

1.

7. The preparation method according to claim 4, characterized in that, The hollow tubular hydrogel has a wall thickness of 0.01-4 mm and a hollow inner diameter of 0.2-8 mm.

8. The preparation method according to claim 5, characterized in that, The receiving bath is a salt solution or an alcohol.

9. The preparation method according to claim 5, characterized in that, The temperature of the coagulation bath is 20-40℃; the curing time is 1-60s.

10. The application of the hydrogel according to claim 1 or 2 or the preparation method according to any one of claims 3-9, characterized in that, It has applications in tissue engineering, drug delivery, or biomimetic organ construction.

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