Preparation method of bionic multilevel network bean dreg cellulose-guar gum composite hydrogel

Abstract

The invention discloses a preparation method of bionic multilevel network bean dreg cellulose-guar gum composite hydrogel, which comprises the following steps: guiding bean dreg cellulose to be directionally arranged by an alternating rotating magnetic field to form a parallel skeleton (primary network); mg < 2 + > induces guar gum to be spirally wound on a parallel framework (a secondary network), a multi-layer bionic annual ring structure (a three-level network) is formed in combination with temperature oscillation circulation, and finally Ca < 2 + > anchors cross-linking points (a four-level network). Or the bean dreg cellulose is guided by an alternating rotating magnetic field to be directionally arranged to form a parallel framework (a first-stage network), Mg < 2 + > is canceled to induce guar gum spiral winding, a multi-layer bionic annual ring structure (a second-stage network) is formed by direct low-temperature rapid forming (low-temperature and rapid temperature oscillation circulation), and finally Ca < 2 + > is anchored to form a cross-linking point (a third-stage network). The networks cooperate with one another to form a multi-stage network structure of the composite hydrogel, so that the composite hydrogel is endowed with better mechanical properties, stability and functionality.

Description

Technical Field

[0001] The present invention relates to the technical field of hydrogels, and particularly relates to a preparation method of a bionic multi-level network okara cellulose-guar gum composite hydrogel. Background Art

[0002] As a kind of polymer material with a three-dimensional network structure, hydrogels have shown great application potential in many fields such as biomedicine, food, and agriculture. Traditional hydrogel preparation methods often have some limitations. For example, the use of toxic chemical cross-linking agents not only pollutes the environment but may also pose potential hazards to human health in applications. Or the preparation process has high energy consumption and harsh conditions, which limits large-scale production and application.

[0003] In the preparation of composite hydrogels, how to effectively utilize natural polymer materials to form a stable network system with special structures and properties has always been a research focus and difficulty. Okara cellulose and guar gum, as natural polymers with wide sources, low prices, and good biocompatibility, have certain limitations in performance when used alone. Preparing a composite hydrogel by combining the two is expected to integrate the advantages of both and obtain materials with more excellent properties. However, there is still a lack of effective methods for precisely controlling the structure formation during the compounding process of the two and for achieving efficient compounding under mild conditions.

[0004] In addition, in terms of the microstructural design of materials, mimicking the unique structures of biological materials in nature, such as the tree ring structure, to endow materials with special properties is also an important research direction in the current field of materials science. However, existing preparation technologies are difficult to accurately construct similar bionic structures in hydrogels, which limits the further improvement of hydrogel properties.

[0005] Based on the above background, it is urgent to develop a preparation method of a composite hydrogel that is green, mild, and can precisely control the structure formation. Summary of the Invention

[0006] The purpose of the present invention is to provide a preparation method of a bionic multi-level network okara cellulose-guar gum composite hydrogel to solve the deficiencies of the prior art.

[0007] To achieve the above purpose, the technical solution adopted by the present invention is: A preparation method of a bionic multi-level network okara cellulose-guar gum composite hydrogel, comprising the following steps: (1), crushing the sepiolite-palygorskite composite mineral, and then subjecting it to supercritical CO2 activation treatment to obtain an activated sepiolite-palygorskite composite mineral; (2) Mix the activated sepiolite-palygorskite composite mineral and deionized water, and perform cold soaking in an oscillator. The soaking solution is filtered through a filter membrane to obtain a clear ion slow-release solution. (3) Freeze-dry fresh soybean dregs, then grind them, and subsequently obtain soybean dreg fibers through high-pressure homogenization treatment; sieve food-grade guar gum to remove lumps; add the soybean dreg fibers and guar gum to the ion slow-release solution in step (2), and mix well to obtain a mixed solution. (4) Pour the mixed solution obtained in step (3) into a flexible silicone mold and then transfer it to a magnetic field-temperature control coupling reactor. First, start the alternating rotating magnetic field, and at the same time cool down to a certain temperature and maintain it for a certain period of time to make the soybean dreg cellulose arrange along the magnetic field direction to form a parallel skeleton; then turn off the magnetic field, heat up to a certain temperature and let it stand for a certain period of time. During this period, Mg 2+ induces the helical winding of guar gum on the parallel skeleton formed by soybean dreg cellulose; then turn on the alternating rotating magnetic field, and within a certain temperature range, perform multiple temperature oscillation cycles, and each temperature oscillation cycle forms 1 layer of bionic annual ring structure; after the bionic annual ring structure is formed, the magnetic field of the magnetic field-temperature control coupling reactor is not turned off, cool down, and Ca 2+ anchors cross-linking points under this temperature condition; finally, turn off the magnetic field, let the formed gel stand under this temperature condition, and demold it through the flexible silicone mold to obtain the composite hydrogel. Or pour the mixed solution obtained in step (3) into a flexible silicone mold and then transfer it to a magnetic field-temperature control coupling reactor. First, start the alternating rotating magnetic field, and at the same time cool down to a certain temperature and maintain it for a certain period of time to make the soybean dreg cellulose arrange along the magnetic field direction to form a parallel skeleton; then turn off the magnetic field, heat up to a certain temperature, and within a certain temperature range, perform multiple temperature oscillation cycles, and each temperature oscillation cycle forms 1 layer of bionic annual ring structure; after the bionic annual ring structure is formed, the magnetic field-temperature control coupling reactor maintains this temperature, and Ca 2+ anchors cross-linking points under this temperature condition; finally, let the formed gel stand under this temperature condition, and demold it through the flexible silicone mold to obtain the composite hydrogel.

[0008] Further, in step (1): Crush the sepiolite-palygorskite composite mineral to 200-400 mesh. The temperature of the supercritical CO2 activation treatment of the crushed sepiolite-palygorskite composite mineral is 35-45 °C, the pressure is 12-18 MPa, and the time is 1-3 h.

[0009] Even further, in step (1): The Ca 2+ :Mg 2+ :K + molar ratio of the activated sepiolite-palygorskite composite mineral is (1.2-1.5):(0.8-1.2):(0.3-0.5), and the specific surface area is 300-400 m 2 / g.

[0010] Further, in step (2): the solid-liquid ratio of the activated sepiolite-palygorskite composite mineral to deionized water is 1 g: 30 mL - 40 mL; cold soak for 8 - 16 h at 3 - 8 °C and 60 - 150 rpm in an oscillator; the leaching solution is filtered through a 0.22 μm nylon filter membrane to obtain a clear ion slow-release solution.

[0011] Even further, in step (2): in the ion slow-release solution, Ca 2+ is 10 - 16 mM, Mg 2+ is 8 - 12 mM, and K + is 3 - 6 mM.

[0012] Further, in step (3): the soybean residue fiber is 50 - 100 nm soybean residue cellulose; the food-grade guar gum is sieved through a 200 - 400 mesh sieve to remove lumps; the soybean residue fiber and guar gum are added to the ion slow-release solution in step (2) at a mass ratio of 2 - 4:1, and the total mass of the soybean residue fiber and guar gum to the volume of the ion slow-release solution is 6 - 10 mg: 100 mL, and stirred at 4 ± 1 °C at 300 - 600 rpm for 20 - 60 min to mix evenly to obtain a mixed solution.

[0013] Even further, in step (4): in the magnetic field-temperature control coupled reactor, the magnetic field uses a three-axis Helmholtz coil to construct a magnetic field generating device, and the magnetic field direction is switched in a clockwise spiral in turn along the X, Y, and Z axes; the temperature control is a semiconductor temperature control device.

[0014] Even further, in step (4): the mixed solution obtained in step (3) is poured into a flexible silicone mold and then transferred to the magnetic field-temperature control coupled reactor. First, start the alternating rotating magnetic field with parameters of magnetic field intensity 65 mT, switching frequency 10.48 Hz, and inclination angle 40°. At the same time, cool down from 8 °C to 3 °C at a rate of 0.5 °C / min and maintain for 20 min, so that the soybean residue cellulose is arranged along the magnetic field direction to form a parallel skeleton; then turn off the magnetic field, heat up from 3 °C to 6 °C at a rate of 0.3 °C / min, and let it stand for 15 min. During this period, Mg 2+ induces the guar gum to helically wind around the parallel skeleton formed by the soybean residue cellulose; then turn on the alternating rotating magnetic field with a magnetic field intensity of 80 mT, a switching frequency of 14.31 Hz, and an inclination angle of 35°. In the range of 2 - 6 °C, perform 3 - 5 temperature oscillation cycles at a rate of 0.2 - 0.3 °C / min. Among them, one temperature oscillation cycle is: start from 6 °C and cool down to 2 °C at a rate of 0.2 - 0.3 °C / min, and then heat up to 6 °C at a rate of 0.2 - 0.3 °C / min. Each temperature oscillation cycle forms 1 layer of biomimetic annual ring structure, with a total of 3 - 5 layers; after the biomimetic annual ring structure is formed, the magnetic field in the magnetic field-temperature control coupled reactor is not turned off, and continue to cool down to 2 °C at a rate of 0.2 - 0.3 °C / min, Ca 2+The cross-linking points were anchored at 2°C; finally, the magnetic field was turned off, and the molded gel was left to stand at 2°C for 2-6 h, and then demolded through a flexible silicone mold to obtain a composite hydrogel.

[0015] Further, in step (4): or the mixed solution obtained in step (3) is poured into a flexible silicone mold and then transferred to a magnetic field-temperature control coupled reactor, firstly, an alternating rotating magnetic field is started, and the parameters are a magnetic field intensity of 65 mT, a switching frequency of 10.48 Hz, and an inclination angle of 40°, and at the same time, the temperature is reduced from 2°C to 0.5°C at a rate of 0.6°C / min and maintained for 20 min, so that the okara cellulose is arranged along the magnetic field direction to form a parallel skeleton; then the magnetic field is turned off, and the temperature is increased from 0.5°C to 2°C at a rate of 0.4°C / min, and within the range of 0.5-2°C, 8 temperature oscillation cycles are performed at a rate of 0.4°C / min, wherein 1 temperature oscillation cycle is: starting from 2°C, the temperature is reduced to 0.5°C at a rate of 0.4°C / min, and then the temperature is increased to 2°C at a rate of 0.4°C / min, and each temperature oscillation cycle forms 1 layer of bionic annual ring structure, with a total of 8 layers; after the bionic annual ring structure is formed, the magnetic field-temperature control coupled reactor is maintained at 2°C, and Ca 2+ The cross-linking points were anchored at 2°C; finally, the molded gel was allowed to stand at 2°C for 2-6 h, and demolded through a flexible silicone mold to obtain a composite hydrogel.

[0016] Furthermore, in step (4): the interlayer spacing D of the bionic annual ring structure is regulated by the temperature oscillation number n, satisfying the following relationship: .

[0017] Beneficial effects of the present invention: 1. The present invention relies on natural mineral ions (Ca 2+ Mg 2+ , K + ) to construct the stable structure of the composite hydrogel. In the preparation process, the natural mineral sepiolite-attapulgite composite mineral is innovatively used as the ion source. After supercritical CO2 activation treatment, the natural mineral ion gradient is slowly released to provide the required ions for the formation of the composite hydrogel. No harmful chemicals are introduced in the whole process, avoiding the potential harm to the environment and human health caused by the chemical cross-linking agent residues in the traditional preparation method.

[0018] 2. The present invention is the first to create a magnetic-temperature coordinated control system, which guides the directional arrangement of biological macromolecules through an alternating rotating magnetic field and combines temperature oscillation to form a bionic tree ring structure, laying the foundation for the multi-level network construction process of composite hydrogels.

[0019] 3. The present invention develops a process for constructing a multi-level network of composite hydrogels, which can form a multi-level network structure, endowing the composite hydrogel with better mechanical properties, stability and functionality, and can be applied to fields such as tissue engineering scaffolds, drug delivery, wound dressings, food thickeners, food moisturizers, etc. An alternating rotating magnetic field guides the directional alignment of soybean dregs cellulose to form a parallel skeleton (primary network). During the stage of heating and standing still with the magnetic field turned off, Mg 2+ induces the helical winding of guar gum around the parallel skeleton (secondary network) and combines with temperature oscillation cycles to form a multi-layer (3 - 5 layers) biomimetic annual ring structure (tertiary network). Finally, Ca 2+ anchors cross-linking points (quaternary network: Ca 2+ chelates with relevant groups in soybean dregs cellulose and guar gum molecules to form an ion chelation network). Or an alternating rotating magnetic field guides the directional alignment of soybean dregs cellulose to form a parallel skeleton (primary network), cancels the induction of Mg 2+ for the helical winding of guar gum, and directly forms a multi-layer (8 layers) biomimetic annual ring structure (secondary network) by low-temperature rapid prototyping (low temperature, rapid temperature oscillation cycles). Finally, Ca 2+ anchors cross-linking points (tertiary network: Ca 2+ chelates with relevant groups in soybean dregs cellulose and guar gum molecules to form an ion chelation network). These networks cooperate with each other to jointly constitute the multi-level network structure of the composite hydrogel. K + can change the ionic strength of the system, affect the internal osmotic pressure of the hydrogel, and appropriate ionic strength and osmotic pressure help to maintain the swelling balance of the hydrogel and ensure its effective absorption and retention of moisture.

[0020] 4. The preparation method of the present invention has a green, environmentally friendly, mild and low-energy consumption process, is easy to operate, and is suitable for large-scale production and application. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 are scanning electron microscope images of the composite hydrogels of each example and comparative example.

[0022] Figure 2 are graphs of the hardness results of the composite hydrogels of each example and comparative example.

[0023] Figure 3 are graphs of the adhesiveness and resilience results of the composite hydrogels of each example and comparative example.

[0024] Figure 4 are graphs of the elasticity and cohesiveness results of the composite hydrogels of each example and comparative example.

[0025] Figure 5 are graphs of the water holding capacity results of the composite hydrogels of each example and comparative example.

[0026] Figure 6Storage modulus result graphs of the composite hydrogels for each example and comparative example. Detailed implementation mode

[0027] The present invention will be further described below in conjunction with specific examples and the accompanying drawings, but the present invention is not limited by the examples and the drawings.

[0028] Example 1

[0029] Step 1: Grind the sepiolite-palygorskite composite mineral (purchased from Lianyungang Rongbai New Materials Co., Ltd.) to 200 mesh, place it in a supercritical CO2 reactor (Nantong Yichuang Experimental Instrument Co., Ltd., model: CFY-3; 40 °C, 15 MPa) and treat it for 2 h. The Ca 2+ :Mg 2+ :K + molar concentration ratio of the activated sepiolite-palygorskite composite mineral (i.e., activated mineral) obtained after supercritical CO2 activation treatment is 1.3:1.0:0.4, and the specific surface area reaches 320 m 2 / g.

[0030] Step 2: Take 5 g of the activated mineral and mix it with 200 mL of deionized water, and cold soak it in an oscillator at 4 ± 0.5 °C and 120 rpm for 12 h. The soaking solution is filtered through a 0.22 μm nylon filter membrane to obtain a clear ion release solution (the ion concentration detected by ICP-OES is: Ca 2+ 12 mM, Mg 2+ 9 mM, K + 5 mM).

[0031] Step 3: Freeze-dry fresh soybean dregs (without obvious mildew and peculiar smell, water content 70 wt%–80 wt%) (vacuum degree 10-20 Pa, freezing temperature of fresh soybean dregs -50 °C, cold trap temperature -55 °C) for 24 h, then grind it with a planetary ball mill (zirconia balls, diameter 3 mm) at 300 r / min for 2 h, and then obtain 50-100 nm soybean dreg cellulose (Zeta potential about -35 mV) through high-pressure homogenization treatment (pressure 120 MPa, cycle 3 times, 2 min each time; temperature controlled at 20-40 °C); Select food-grade guar gum (purchased from Anhui Cool Biological Engineering Co., Ltd., CAS: 9000-30-0, viscosity 5500 ± 200 cps, pH6.5-7.0) and pass it through a 200-mesh sieve to remove lumps. Then mix the soybean dreg cellulose and guar gum at a mass ratio of 3:1 (12 g of soybean dreg cellulose, 4 g of guar gum) and add them to the ion release solution obtained in Step 2, and stir at 500 rpm at 4 ± 1 °C for 30 min to obtain a mixed solution.

[0032] Step 4: Pour the mixture obtained in Step 3 into a flexible silicone mold and then transfer it to a magnetic field-temperature control (using a three-axis Helmholtz coil to construct a magnetic field generating device, and the magnetic field direction is switched clockwise in a spiral manner along the X, Y, and Z axes in sequence)-coupled reactor. First, start the alternating rotating magnetic field with parameters of magnetic field strength 65 mT, switching frequency 10.48 Hz (the switching frequency and magnetic field strength satisfy the following relationship: , where f is the switching frequency (Hz) and B is the magnetic field strength (mT); the same applies hereinafter), inclination angle (the angle between the magnetic field direction and the temperature gradient direction (cooling / heating direction); the same applies hereinafter) 40°. At the same time, cool from 8°C (pre-cooled to 8°C in advance) to 3°C at a rate of 0.5°C / min and maintain for 20 min, so that the soybean residue cellulose is arranged along the magnetic field direction to form a parallel skeleton. Then turn off the magnetic field, heat from 3°C to 6°C at a rate of 0.3°C / min, and let it stand for 15 min. During this period, Mg 2+ induces guar gum to helically wind around the parallel skeleton formed by soybean residue cellulose. Then turn on the alternating rotating magnetic field with a magnetic field strength of 80 mT, a switching frequency of 14.31 Hz, and an inclination angle of 35°. In the range of 2-6°C, perform 3 temperature oscillation cycles at a rate of 0.2°C / min (1 temperature oscillation cycle is: start from 6°C and cool to 2°C at a rate of 0.2°C / min, and then heat to 6°C at a rate of 0.2°C / min). Each temperature oscillation cycle forms 1 layer of biomimetic annual ring structure (layer spacing 55±5 nm, the layer spacing D of the biomimetic annual ring structure is regulated by the number of temperature oscillation times n (n is 3 in this example), and satisfies the following relationship: , a total of 3 layers; after the biomimetic annual ring structure is formed, the magnetic field-temperature control coupled reactor (the magnetic field is not turned off) continues to cool to 2°C at a rate of 0.2°C / min, and Ca 2+ anchors cross-linking points under low temperature (2°C) conditions. Finally, turn off the magnetic field, let the formed gel stand at 2°C for 2 h, and demold through the flexible silicone mold to obtain a cylindrical composite hydrogel with a diameter of 5 cm and a height of 3 cm.

[0033] Example 2

[0034] Step 1: Crush the sepiolite-palygorskite composite mineral (purchased from Lianyungang Rongbai New Materials Co., Ltd.) to 200 meshes, place it in a supercritical CO2 reactor (Nantong Yichuang Experimental Instrument Co., Ltd., model: CFY-3; 40°C, 15 MPa) and treat it for 3 h. The Ca 2+ :Mg 2+ :K + molar concentration ratio of the activated sepiolite-palygorskite composite mineral (i.e., the activated mineral) obtained after supercritical CO2 activation treatment is 1.5:0.8:0.3, and the specific surface area reaches 369 m 2 / g.

[0035] Step 2: Mix 5 g of activated mineral with 200 mL of deionized water, and perform cold soaking at 4 ± 0.5 °C and 120 rpm for 14 h in an oscillator. The soaking solution is filtered through a 0.22 μm nylon filter membrane to obtain a clear ion slow-release solution (the ion concentrations detected by ICP-OES are: Ca 2+ 14.5 mM, Mg 2+ 9 mM, K + 5 mM).

[0036] Step 3: Freeze-dry fresh soybean dregs (without obvious mildew and odor, water content 70 wt%-80 wt%) (vacuum degree 10-20 Pa, freezing temperature of fresh soybean dregs -50 °C, cold trap temperature -55 °C) for 24 h, then grind with a planetary ball mill (zirconia balls, diameter 3 mm) at 300 r / min for 2 h, and then obtain 50-100 nm soybean dreg cellulose (Zeta potential about -35 mV) through high-pressure homogenization treatment (pressure 120 MPa, circulating 3 times, 2 min each time; temperature controlled at 20-40 °C); select food-grade guar gum (purchased from Anhui Cool Biological Engineering Co., Ltd., CAS: 9000-30-0, viscosity 5500 ± 200 cps, pH 6.5-7.0), and pass it through a 200-mesh sieve to remove lumps. Then mix soybean dreg cellulose and guar gum at a mass ratio of 3:1 (12 g of soybean dreg cellulose, 4 g of guar gum), add them to the ion slow-release solution obtained in Step 2, and stir at 500 rpm for 30 min at 4 ± 1 °C to obtain a mixed solution.

[0037] Step 4: Pour the mixed solution obtained in Step 3 into a flexible silicone mold and then transfer it to a magnetic field - temperature control (semiconductor temperature control device) coupled reactor. First, start the alternating rotating magnetic field, with parameters of magnetic field strength 65 mT, switching frequency 10.48 Hz (the switching frequency and magnetic field strength satisfy the following relationship: , where f is the switching frequency (Hz), B is the magnetic field strength (mT); the same below), inclination angle (the angle between the magnetic field direction and the temperature gradient direction (cooling / heating direction); the same below) 40°, and at the same time cool from 8 °C (pre-cooled to 8 °C in advance) to 3 °C at a rate of 0.5 °C / min and maintain for 20 min, so that the soybean dreg cellulose is arranged along the magnetic field direction to form a parallel framework. Then turn off the magnetic field, heat from 3 °C to 6 °C at a rate of 0.3 °C / min, and let it stand for 15 min. During this period, Mg 2+Induce guar gum to helically wind around the parallel framework formed by soybean dregs cellulose. Then, turn on an alternating rotating magnetic field with a magnetic field strength of 80 mT, a switching frequency of 14.31 Hz, and an inclination angle of 35°. In the temperature range of 2 - 6 °C, perform 5 temperature oscillation cycles at a rate of 0.3 °C / min (one temperature oscillation cycle is: starting from 6 °C, cooling to 2 °C at a rate of 0.3 °C / min, and then heating to 6 °C at a rate of 0.3 °C / min). Each temperature oscillation cycle forms 1 layer of the biomimetic annual ring structure (the layer spacing is 65 ± 5 nm, and the layer spacing D of the biomimetic annual ring structure is regulated by the number of temperature oscillation times n (n is 5 in this example), and satisfies the following relationship: , a total of 5 layers; after the formation of the biomimetic annual ring structure, the magnetic field-thermostat coupling reactor (the magnetic field is not turned off) continues to cool to 2 °C at a rate of 0.3 °C / min, and Ca 2+ anchors cross-linking points under low temperature (2 °C) conditions. Finally, turn off the magnetic field, let the formed gel stand at 2 °C for 6 h, and demold it through a flexible silicone mold to obtain a cylindrical composite hydrogel with a diameter of 5 cm and a height of 3 cm.

[0038] Example 3

[0039] Step 1: Crush the sepiolite-palygorskite composite mineral (purchased from Lianyungang Rongbai New Materials Co., Ltd.) to 200 mesh, place it in a supercritical CO2 reaction kettle (Nantong Yichuang Experimental Instrument Co., Ltd., model: CFY-3; 40 °C, 15 MPa) and process it for 2 h. The activated sepiolite-palygorskite composite mineral (i.e., the activated mineral) obtained after supercritical CO2 activation treatment has a Ca 2 + :Mg 2+ :K + molar concentration ratio of 1.3:1.0:0.4 and a specific surface area of 320 m 2 / g.

[0040] Step 2: Take 5 g of the activated mineral and mix it with 200 mL of deionized water, and cold soak it in an oscillator at 4 ± 0.5 °C and 120 rpm for 12 h. The immersion liquid is filtered through a 0.22 μm nylon filter membrane to obtain a clear ion slow-release solution (the ion concentration detected by ICP-OES is: Ca 2+ 12 mM, Mg 2+ 9 mM, K + 5 mM).

[0041] Step 3: Freeze-dry the fresh soybean dregs (without obvious mildew and odor, and the moisture content is 70 wt%-80 wt %) (the vacuum degree is 10-20 Pa, the freezing temperature of the fresh soybean dregs is -50 °C, and the cold trap temperature is -55 °C) for 24 h, then grind it with a planetary ball mill (zirconia balls, diameter 3 mm) at 300 r / min for 2 h, and then obtain soybean dreg cellulose with a particle size of 50-100 nm (Zeta potential is about -35 mV) through high-pressure homogenization treatment (pressure 120 MPa, circulating 3 times, 2 min each time; the temperature is controlled at 20-40 °C); select food-grade guar gum (purchased from Anhui Cool Biological Engineering Co., Ltd., CAS: 9000-30-0, viscosity 5500±200 cps, pH 6.5-7.0), and pass it through a 200-mesh sieve to remove lumps. Then, mix the soybean dreg cellulose and guar gum according to a mass ratio of 3:1 (12 g of soybean dreg cellulose and 4 g of guar gum), add them to the ion sustained-release solution obtained in Step 2, and stir at 500 rpm for 30 min at 4±1 °C to obtain a mixed solution.

[0042] Step 4: Pour the mixed solution obtained in Step 3 into a flexible silicone mold and then transfer it to a magnetic field-temperature control (using a three-axis Helmholtz coil to construct a magnetic field generating device, and the magnetic field direction is switched clockwise in a spiral manner along the X, Y, and Z axes in sequence)-temperature control (semiconductor temperature control device) coupled reactor. First, start the alternating rotating magnetic field, with parameters of magnetic field strength 65 mT, switching frequency 10.48 Hz (the switching frequency and magnetic field strength satisfy the following relationship: , where f is the switching frequency (Hz), B is the magnetic field strength (mT); the same below), inclination angle (the angle between the magnetic field direction and the temperature gradient direction (cooling / heating direction); the same below) 40°, and at the same time cool from 2 °C (pre-cooled to 2 °C in advance) to 0.5 °C at a rate of 0.6 °C / min and maintain for 20 min, so that the soybean dreg cellulose is arranged along the magnetic field direction to form a parallel skeleton. Then turn off the magnetic field, heat from 0.5 °C to 2 °C at a rate of 0.4 °C / min, and in the range of 0.5-2 °C, perform 8 temperature oscillation cycles at a rate of 0.4 °C / min (1 temperature oscillation cycle is: start from 2 °C and cool to 0.5 °C at a rate of 0.4 °C / min, and then heat to 2 °C at a rate of 0.4 °C / min). Each temperature oscillation cycle forms 1 layer of biomimetic annual ring structure (the layer spacing is 80±5 nm, and the layer spacing D of the biomimetic annual ring structure is regulated by the number of temperature oscillation times n (n is 8 in this embodiment), and satisfies the following relationship: , a total of 8 layers; after the biomimetic annual ring structure is formed, the magnetic field-temperature control coupled reactor is maintained at 2 °C, and Ca 2+ anchors cross-linking points under low temperature (2 °C) conditions. Finally, let the formed gel stand at 2 °C for 2 h, demold it through the flexible silicone mold, and obtain a cylindrical composite hydrogel with a diameter of 5 cm and a height of 3 cm.

[0043] Comparative Example Step 1: Fresh soybean dregs (without obvious mildew and peculiar smell, water content 70 wt%-80 wt%) were freeze-dried (vacuum degree 10-20 Pa, freezing temperature of fresh soybean dregs -50°C, cold trap temperature -55°C) for 24 h, then ground with a planetary ball mill (zirconia balls, diameter 3 mm) at 300 r / min for 2 h, and then obtained 50-100 nm soybean dreg cellulose (Zeta potential -35 mV) through high-pressure homogenization treatment (pressure 120 MPa, circulating 3 times, 2 min each time; temperature controlled at 20-40°C); Food-grade guar gum (purchased from Anhui Cool Biological Engineering Co., Ltd., CAS: 9000-30-0, viscosity 5500±200 cps, pH 6.5-7.0) was sieved through a 200-mesh sieve to remove lumps. Then, soybean dreg cellulose and guar gum were mixed in a mass ratio of 3:1 (12 g of soybean dreg cellulose and 4 g of guar gum) and added to 200 mL of deionized water, and magnetically stirred at 500 rpm for 30 min at 4±1°C to obtain a mixed solution.

[0044] Step 2: A 6% (w / v) CaCl2 solution was prepared with deionized water as a cross-linking solution. 30 mL was taken and added to the mixed solution of soybean dreg nanocellulose and guar gum in Step 1 and mixed evenly, then poured into a flexible silicone mold and left to stand at room temperature for 2 h, and demolded through the flexible silicone mold to obtain a cylindrical composite hydrogel with a diameter of 5 cm and a height of 3 cm.

[0045] The following analyses were performed on the composite hydrogels obtained in each example and comparative example: Test Method 1. Scanning electron microscopy (SEM) analysis The morphological structure of the freeze-dried composite hydrogel sample (a thin slice with a diameter of 10-20 mm and a thickness of 1-5 mm) was observed by a scanning electron microscope (SU3800, Shanghai Xinu Optoelectronic Technology Co., Ltd.) at a magnification of 2000 times.

[0046] 2. Texture analysis The texture properties of the composite hydrogel samples were analyzed using a texture analyzer (TA.GEL, Suzhou Baoman Precision Instrument Co., Ltd.). Each composite hydrogel sample was cut into a rectangle (4 cm×4 cm×1 cm), and then fixed on the test platform to ensure sufficient contact between the sample and the probe. The test parameters used were as follows: test speed: 60 mm / s, post-test speed: 200 mm / s, probe lift height: 15 mm, extrusion distance: 5 mm, test interval: 3 s, initial force: 0.4 N. Each sample was analyzed 10 times, and the average value of these 10 measurements was calculated and used as the final result of each sample.

[0047] 3. Water holding capacity (WHC) analysis Mix 1 g (M0) of the freeze-dried and pulverized composite hydrogel sample with 70 mL of distilled water, stir well at 20 °C for 2 h, then centrifuge at 5000 r / min for 10 min. After discarding the supernatant, weigh the mass of the residual solid (M1). The formula for calculating the water holding capacity is as follows:

[0048] 4. Rheological property analysis The rheological properties of the composite hydrogel sample were measured using a rotational shear rheometer (SmartPave 92, Anton Paar (Shanghai) Trading Co., Ltd.). Add 0.5 g of the freeze-dried and pulverized composite hydrogel sample to 40 mL of distilled water to prepare a suspension, and then measure the apparent shear viscosity of the suspension using a gap distance of 1 mm, a temperature of 25 °C, and a shear rate of 1 - 100 s -1 . The dynamic shear modulus was obtained by arranging parallel plates with a gap of 1 mm under the condition of 0.1 - 6 Hz (25 °C).

[0049] Test results: As Figure 1 shown, under room temperature conditions, the composite hydrogel formed by cross-linking only with 6% (w / v) CaCl2 solution in the comparative example presented a relatively loose and irregular microstructure. The pore sizes inside were uneven and the distribution was non-uniform. This was because the simple cross-linking method failed to effectively guide the orderly aggregation of molecules, resulting in a loose and disordered overall structure lacking stability and regularity. In Example 1, an ordered fibrous or layered arrangement was observed in its structure, and the pore distribution was relatively uniform. In Example 2, the biomimetic annual ring structure was clearer, and compared with Example 1, the pore size was further reduced and the distribution was more uniform. This structural change was attributed to the stronger ionic bonding between Ca 2+ and the active groups on the molecules of soy residue nanocellulose and guar gum, which strengthened the intermolecular interaction and thus optimized the microstructure of the composite hydrogel. In Example 3, the low-temperature rapid prototyping resulted in a multi-layer stacked structure of the composite hydrogel, where the biomimetic annual ring structures were intertwined and the interlayer distance was enlarged.

[0050] As Figure 2 shown, the hardness of Examples 1 - 3 was higher than that of the comparative example. In Example 1, a stable three-dimensional network structure was formed, giving it a certain hardness; in Example 2, more Ca 2+ further enhanced the cross-linking effect, thus increasing the hardness; the multi-layer structure of Example 3 also provided good support for it, but the removal of Mg 2+ induced the helical winding of guar gum, resulting in an imperfect cross-linking network formed, making it difficult for soy residue cellulose and guar gum to form a firm connection, thus causing insufficient support force for the overall structure and a decrease in hardness.

[0051] As Figure 3 shown, the adhesiveness of the comparative example is 46.23, while the adhesiveness of Examples 1, 2, and 3 are 99.49, 108.69, and 78.79 respectively, all significantly higher than that of the comparative example. The comparative example forms a composite hydrogel by simply standing still at room temperature, with relatively weak intermolecular interactions. In Example 1, the magnetic field-thermostatic coupling is used to arrange the okara cellulose in an orderly manner, Mg 2+ induces the helical winding of guar gum, and Ca 2+ anchors the crosslinking points, enhancing the intermolecular interaction and improving the adhesiveness; in Example 2, more Ca 2+ strengthens the crosslinking, further enhancing the adhesiveness; although Example 3 adopts a low-temperature rapid prototyping process, the 8-layer bionic annual ring structure also increases the internal interaction points, and the adhesiveness is still higher than that of the comparative example.

[0052] The resilience of the comparative example is 0.41, and the resilience of Examples 1, 2, and 3 are 0.34, 0.22, and 0.38 respectively. The resilience of the comparative example is relatively high, which may be because the composite hydrogel formed by simple standing still has a relatively loose structure and is easier to return to its original state after being subjected to external forces. The resilience of Examples 1 and 2 is lower than that of the comparative example. Although an ordered structure is formed in Example 1, the relatively tight crosslinked network may limit its elastic recovery to a certain extent; in Example 2, more Ca 2+ strengthens the crosslinking, making the structure more rigid and reducing the resilience. The resilience of Example 3 is comparable to that of the comparative example. Its multi-layer structure has a certain elastic buffer space, compensating for the possible lack of resilience caused by the low-temperature rapid prototyping.

[0053] As Figure 4 shown, the elasticity value of the comparative example is 0.42, and the elasticity values of Examples 1, 2, and 3 are 0.8, 0.88, and 0.69 respectively, all significantly higher than that of the comparative example. The comparative example forms a composite hydrogel by simply standing still at room temperature. Its internal structure is loose and the intermolecular interaction is weak, so the elasticity is poor. In Example 1, through the magnetic field-thermostatic coupling reaction, the okara cellulose is arranged along the magnetic field direction to form a parallel skeleton, and subsequent ion-induced crosslinking constructs a relatively ordered three-dimensional network structure, improving the elasticity; in Example 2, more Ca 2+ enhances the crosslinking degree, further strengthening the structural stability, so the elasticity performance is better; the low-temperature rapid prototyping process of Example 3 forms an 8-layer bionic annual ring structure. Although the structure is unique, the perfection degree of crosslinking may be inferior to that of Example 2 and Example 1, so the elasticity is slightly lower, but still higher than that of the comparative example.

[0054] The cohesiveness of the comparative example was 0.26, and the cohesiveness of Examples 1, 2, and 3 were 0.73, 0.79, and 0.57 respectively. The cohesiveness of each example was higher than that of the comparative example. The preparation method of simply standing still under room temperature conditions for the comparative example made the cohesion between molecules weaker. In Example 1, the ordered structure and ion-induced cross-linking enhanced the mutual attraction between molecules and improved the cohesiveness; Example 2 had more Ca 2+ enhanced the cross-linking effect and further improved the cohesiveness; the multi-layer structure of Example 3 also increased the internal cohesion to a certain extent. Although its rapid prototyping process at low temperature might have affected part of the cross-linking effect, the cohesiveness was still higher than that of the comparative example.

[0055] As Figure 5 shown, the water retention capacity of the comparative example was 92.3%, and the water retention capacities of Examples 1, 2, and 3 were 98.7%, 97.1%, and 94.6% respectively. The water retention capacities of the three examples were all higher than that of the comparative example. The comparative example formed a composite hydrogel by simply standing still at room temperature, with a relatively loose internal structure, and water molecules were easy to escape, resulting in a low water retention capacity. In Example 1, the magnetic field-thermostatic coupling made the soybean residue cellulose arrange orderly, and the subsequent three-dimensional network structure formed by ion induction could effectively bind water molecules and improve the water retention capacity; Example 2 had more Ca 2+ enhanced the cross-linking effect, making the network structure more compact, but this might have made some pores smaller and affected the accommodation of water molecules to a certain extent, so the water retention capacity was slightly lower than that of Example 1; although Example 3 adopted the rapid prototyping process at low temperature, the unique 8-layer bionic annual ring structure also increased the storage space for water molecules, so the water retention capacity was also higher than that of the comparative example.

[0056] As Figure 6 shown, under the same frequency conditions, the storage modulus of the comparative example was significantly lower than that of Examples 1, 2, and 3. The comparative example formed a composite hydrogel by simply standing still at room temperature, with a loose structure and weak intermolecular interactions, so its ability to resist deformation and store energy was poor and the storage modulus was low. In Example 1, through magnetic field-thermostatic coupling and ion-induced cross-linking, an ordered three-dimensional network structure was formed, enhancing the ability to resist deformation and resulting in a higher storage modulus; Example 2 had more Ca 2+ further strengthened the cross-linking, with a more stable structure and the highest storage modulus; although Example 3 had a unique multi-layer structure of rapid prototyping at low temperature, compared with the former two, the cross-linking perfection or structural stability was slightly inferior, but it was still higher than that of the comparative example.

[0057] Although the present invention has been disclosed above with preferred embodiments, it is not intended to limit the present invention. Any person familiar with this technology can make various changes and modifications without departing from the spirit and scope of the present invention. Therefore, the protection scope of the present invention should be defined by the claims.

Claims

1. A preparation method of a bionic multi-level network okara cellulose-guar gum composite hydrogel, characterized in that, It includes the following steps: (1) Crush the sepiolite-palygorskite composite mineral, and then perform supercritical CO2 activation treatment to obtain the activated sepiolite-palygorskite composite mineral; (2) Mix the activated sepiolite-palygorskite composite mineral with deionized water, and perform cold soaking in an oscillator. The soaking solution is filtered through a filter membrane to obtain a clear ion sustained-release solution; (3) Freeze-dry fresh soybean dregs, then grind them, and subsequently obtain soybean dreg fibers through high-pressure homogenization treatment; Sieve food-grade guar gum to remove lumps; Add the soybean dreg fibers and guar gum to the ion sustained-release solution in step (2), and mix evenly to obtain a mixed solution; (4) Pour the mixture obtained in step (3) into a flexible silicone mold and then transfer it to a magnetic field-thermostatic coupling reactor. First, start the alternating rotating magnetic field, while cooling to a certain temperature and maintaining for a certain time, so that the soybean residue cellulose is arranged along the magnetic field direction to form a parallel skeleton; then turn off the magnetic field, heat up to a certain temperature and let it stand for a certain time. During this period, Mg 2+ induces guar gum to helically wind around the parallel skeleton formed by soybean residue cellulose; then turn on the alternating rotating magnetic field, within a certain temperature range, perform multiple temperature oscillation cycles, and each temperature oscillation cycle forms 1 layer of bionic annual ring structure; after the bionic annual ring structure is formed, the magnetic field of the magnetic field-thermostatic coupling reactor is not turned off, cool down, and Ca 2+ anchors crosslinking points under this temperature condition; finally, turn off the magnetic field, let the formed gel stand under this temperature condition, and demold through the flexible silicone mold to obtain the composite hydrogel. Alternatively, pour the mixture obtained in step (3) into a flexible silicone mold and then transfer it to a magnetic field-thermostatic coupling reactor. First, start the alternating rotating magnetic field, while cooling to a certain temperature and maintaining for a certain period of time, so that the soybean dregs cellulose arranges along the magnetic field direction to form a parallel skeleton; then turn off the magnetic field, heat up to a certain temperature, and within a certain temperature range, perform multiple temperature oscillation cycles, and each temperature oscillation cycle forms 1 layer of bionic annual ring structure; after the bionic annual ring structure is formed, the magnetic field-thermostatic coupling reactor maintains this temperature, and Ca 2+ Anchors crosslinking points under this temperature condition; finally, let the formed gel stand under this temperature condition, demold through the flexible silicone mold, and obtain the composite hydrogel.

2. The preparation method of a bionic multi-stage network okara cellulose-guar gum composite hydrogel according to claim 1, characterized in that In step (1): Crush the sepiolite-palygorskite composite mineral to 200-400 mesh. The temperature of the supercritical CO2 activation treatment of the crushed sepiolite-palygorskite composite mineral is 35-45 °C, the pressure is 12-18 MPa, and the time is 1-3 h.

3. The preparation method of a bionic multi-level network okara cellulose-guar gum composite hydrogel according to claim 2, characterized in that, In step (1): The Ca 2+ :Mg 2+ :K + molar ratio of the activated sepiolite-palygorskite composite mineral is (1.2 - 1.5):(0.8 - 1.2):(0.3 - 0.5), and the specific surface area is 300 - 400 m 2 / g.

4. The preparation method of a bionic multi-level network okara cellulose-guar gum composite hydrogel according to claim 1, characterized in that, In step (2): The solid-liquid ratio of the activated sepiolite-palygorskite composite mineral to deionized water is 1 g: 30 mL - 40 mL; Perform cold soaking in an oscillator at 3-8 °C and 60-150 rpm for 8-16 h; The soaking solution is filtered through a 0.22 μm nylon filter membrane to obtain a clear ion sustained-release solution.

5. The preparation method of a bionic multi-level network okara cellulose-guar gum composite hydrogel according to claim 4, characterized in that, In step (2): Ca in the ion sustained-release solution 2+ 10 - 16 mM, Mg 2+ 8 - 12 mM, K + 3 - 6 mM.

6. The preparation method of a bionic multi-level network okara cellulose-guar gum composite hydrogel according to claim 1, characterized in that, In step (3): The soybean dreg fibers are 50-100 nm soybean dreg cellulose; Sieve food-grade guar gum through a 200-400 mesh sieve to remove lumps; Add the soybean dreg fibers and guar gum to the ion sustained-release solution in step (2) at a mass ratio of 2-4:

1. The total mass ratio of the soybean dreg fibers and guar gum to the volume of the ion sustained-release solution is 6-10 mg: 100 mL. Stir at 4 ± 1 °C at 300-600 rpm for 20-60 min and mix evenly to obtain a mixed solution.

7. The preparation method of a bionic multi-level network okara cellulose-guar gum composite hydrogel according to claim 1, characterized in that, In step (4): In the magnetic field-temperature control coupling reactor, the magnetic field uses a three-axis Helmholtz coil to construct a magnetic field generating device, and the magnetic field direction is sequentially switched clockwise in a spiral along the X, Y, and Z axes; The temperature control is a semiconductor temperature control device.

8. The preparation method of a bionic multi-level network okara cellulose-guar gum composite hydrogel according to claim 1, characterized in that, In step (4): Pour the mixture obtained in step (3) into a flexible silicone mold and then transfer it to a magnetic field-temperature coupling reactor. First, start an alternating rotating magnetic field with parameters of magnetic field strength 65 mT, switching frequency 10.48 Hz, and inclination angle 40°. At the same time, cool from 8 °C to 3 °C at a rate of 0.5 °C / min and maintain for 20 min, so that the soybean residue cellulose is arranged along the magnetic field direction to form a parallel skeleton; then turn off the magnetic field, heat from 3 °C to 6 °C at a rate of 0.3 °C / min, and let it stand for 15 min. During this period, Mg 2+ induces guar gum to helically wind around the parallel skeleton formed by soybean residue cellulose; then turn on an alternating rotating magnetic field with a magnetic field strength of 80 mT, a switching frequency of 14.31 Hz, and an inclination angle of 35°. In the temperature range of 2-6 °C, perform 3-5 temperature oscillation cycles at a rate of 0.2-0.3 °C / min. Among them, one temperature oscillation cycle is: start from 6 °C and cool to 2 °C at a rate of 0.2-0.3 °C / min, and then heat to 6 °C at a rate of 0.2-0.3 °C / min. Each temperature oscillation cycle forms 1 layer of biomimetic annual ring structure, with a total of 3-5 layers; after the biomimetic annual ring structure is formed, the magnetic field of the magnetic field-temperature coupling reactor is not turned off, and continue to cool to 2 °C at a rate of 0.2-0.3 °C / min, Ca 2+ anchor cross-linking points at 2 °C; finally, turn off the magnetic field, let the formed gel stand at 2 °C for 2-6 h, and demold through the flexible silicone mold to obtain a composite hydrogel.

9. The preparation method of a bionic multi-level network okara cellulose-guar gum composite hydrogel according to claim 1, characterized in that, In step (4): alternatively, pour the mixture obtained in step (3) into a flexible silicone mold and then transfer it to a magnetic field-thermostatic coupling reactor. First, start the alternating rotating magnetic field with parameters of magnetic field strength 65 mT, switching frequency 10.48 Hz, and inclination angle 40°. At the same time, cool from 2°C to 0.5°C at a rate of 0.6°C / min and maintain for 20 min to make the soybean dregs cellulose align along the magnetic field direction to form a parallel skeleton. Then turn off the magnetic field and heat from 0.5°C to 2°C at a rate of 0.4°C / min. In the range of 0.5 - 2°C, perform 8 temperature oscillation cycles at a rate of 0.4°C / min. Among them, 1 temperature oscillation cycle is: start from 2°C and cool to 0.5°C at a rate of 0.4°C / min, and then heat to 2°C at a rate of 0.4°C / min. Each temperature oscillation cycle forms 1 layer of biomimetic annual ring structure, with a total of 8 layers. After the biomimetic annual ring structure is formed, the magnetic field-thermostatic coupling reactor is maintained at 2°C, and Ca 2+ anchor cross-linking points under the condition of 2°C; finally, let the formed gel stand at 2°C for 2 - 6 h, demold through the flexible silicone mold to obtain the composite hydrogel.

10. The preparation method of a bionic multi-level network okara cellulose-guar gum composite hydrogel according to claim 8 or 9, characterized in that, In step (4), the layer spacing D of the bionic annual ring structure is regulated by the number of temperature oscillations n, and satisfies the following relationship: .

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