Alginate-based aerogel, method for preparing the same, and use thereof

Abstract

The application provides a alginate-based aerogel, a preparation method and application thereof. The alginate-based aerogel has parallelly arranged large pores and oriented channels at an angle with the large pores, and the angle ranges from 0 to 180 degrees. The large pores are distributed in the same direction inside the alginate-based aerogel, and the oriented channels improve the interconnectivity between the large pores. The existence of the large pores and the oriented channels makes the alginate-based aerogel have the characteristics of anisotropy and a multi-scale pore structure, and the size of the large pores and the oriented channels is suitable for inducing vascularization and osteogenesis. Therefore, the aerogel can be used as a bone scaffold material. Tests show that the aerogel has the characteristics of light weight and high strength. In addition, other components beneficial to osteogenesis can be added in the alginate system, and the size of the pores can be adjusted without affecting the formation of the pore structure.

Description

Technical Field

[0001] This invention belongs to the field of bio-tissue engineering materials technology, specifically relating to an alginate-based aerogel, its preparation method, and its application. Background Technology

[0002] Aerogels, as porous materials, can serve as tissue engineering scaffolds, replacing artificial bone materials to improve osteogenic outcomes in animals. Alginate, a biodegradable natural polymer derived from the unbranched anionic hydrophilic polysaccharide stems of brown algae, possesses high water absorption capacity, promoting cell growth, and is currently widely used in wound dressings, drug delivery, and tissue regeneration and repair. Furthermore, due to its excellent biocompatibility, scaffold-forming properties, biodegradability, and low cost, it is considered one of the best candidates for bone regeneration scaffolds. However, alginate aerogels lack good mechanical properties; therefore, there is an urgent need to improve their mechanical properties through microstructural design to better facilitate their application in the field of bone tissue regeneration scaffolds.

[0003] Although aerogels are generally porous, there is currently no unified standard for the optimal pore size range suitable for bone regeneration. However, some studies have shown that large pore size and high pore interconnectivity of aerogels are beneficial to bone regeneration, and micropores are beneficial for improving porosity, pore interconnectivity, and cell adhesion. In addition, some studies have reported that the orientation of pores also has an important influence on bone regeneration; isotropic, randomly arranged pore channel structures are not conducive to vascular infiltration, mineralized extracellular matrix deposition, and substance transport.

[0004] While the pore size of aerogels is easily adjustable, current research on aerogels generally suffers from isotropy and uniform pore size, thus limiting the achievable performance control and significantly restricting their effectiveness in promoting bone repair. Therefore, developing an aerogel material that can overcome these problems is of great practical significance. Summary of the Invention

[0005] In view of this, the purpose of this invention is to provide an alginate-based aerogel, its preparation method, and its applications. The alginate-based aerogel has an anisotropic, multi-scale porous structure, which, when used to prepare bone scaffold materials, can greatly improve the effect of promoting bone repair.

[0006] To achieve this objective, the present invention adopts the following technical solution:

[0007] In a first aspect, the present invention provides an alginate-based aerogel having parallel macropores and oriented channels at an angle to the macropores;

[0008] The angle ranges from 0 to 180°.

[0009] The macropores are distributed along the same direction inside the alginate-based aerogel, wherein the same direction is the length direction of the macropores.

[0010] Preferably, the average pore diameter of the macropore is 380–420 μm.

[0011] Preferably, the average diameter of the orientation channel is 80–100 μm.

[0012] Secondly, the present invention also provides a method for preparing the above-mentioned alginate-based aerogel, comprising the following steps:

[0013] S1: Provides an alginate-based gel with parallel-arranged macropores;

[0014] S2: After flipping the alginate-based gel in S1 at a certain angle, it is oriented and frozen until the upper surface of the gel is solid. The frozen sample is then dried to obtain alginate-based aerogel.

[0015] The angle ranges from 0 to 180°.

[0016] Preferably, step S1 specifically involves: adding an alginate solution to a mold with an alginate film coated on its inner wall, and spraying a metal salt solution onto the surface of the alginate solution. After the film is formed, the metal salt solution is added, and the mixture is allowed to stand and react to obtain an alginate-based gel with parallel-arranged macropores.

[0017] Preferably, the metal salt solution is selected from any one or more of calcium chloride, copper chloride, copper sulfate, strontium chloride, zinc chloride, barium chloride, or ferric chloride.

[0018] Preferably, the solute in the alginate solution is sodium alginate.

[0019] Preferably, the concentration of the alginate solution is 2–100 g / L.

[0020] Preferably, the concentration of the metal salt solution is 0.2–2 mol / L.

[0021] Preferably, the volume ratio of the alginate solution to the metal salt solution is 20:(5-15).

[0022] Preferably, the alginate solution also includes additives.

[0023] Preferably, the additive is selected from any one or more of hydroxyapatite, calcium carbonate, calcium phosphate, chitin fiber, carbon nanotubes, graphene oxide, montmorillonite, polyvinyl alcohol, gelatin, silk protein, or collagen fiber.

[0024] Preferably, the mass ratio of alginate to additive in the alginate solution is (70-99.9):(0.1-30).

[0025] Preferably, the settling time is 6 to 72 hours.

[0026] Thirdly, the present invention provides a bone scaffold material, which includes the alginate-based aerogel involved in the above-mentioned technical solutions.

[0027] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0028] (1) This invention provides an anisotropic, multi-scale alginate-based aerogel. By rotating an alginate-based aerogel with parallel-arranged macropores at a certain angle and then subjecting it to orientation freezing, oriented channels at an angle to the macropores are obtained. The presence of these oriented channels enables interconnection between the macropores. Using the alginate-based aerogel as a bone scaffold material is beneficial for cell attachment, migration, substance transport, and vascular infiltration. Testing showed that the average pore size of the macropores is 380–420 μm, and the average diameter of the oriented channels is 80–100 μm. The dimensions of the macropores and oriented channels, as well as the structural design of the gel, are conducive to osteogenic formation. Furthermore, the alginate-based aerogel possesses excellent mechanical properties (a Young's modulus of approximately 100 kPa, capable of withstanding compressive forces 10,000 times its own weight without deformation). When used to prepare bone scaffold materials, it meets the mechanical strength requirements of bone scaffold materials, and the prepared bone scaffold materials exhibit good biocompatibility, making it suitable for use in the field of bio-tissue engineering materials.

[0029] (2) This invention can also be further improved by adding additives to the alginate system. These additives can be one or more organic or inorganic nano-components that promote osteogenic processes. Studies have shown that the introduction of organic or inorganic nano-components does not affect the pore size formation in the alginate-based aerogel; that is, suitable other components that promote osteogenic processes can be added to the alginate system. This invention can also control the pore size by adjusting the content of the additives, facilitating the production of alginate-based aerogels of different sizes. This provides strong scalability and makes practical applications more convenient. Attached Figure Description

[0030] Figure 1 This is a photograph of the alginate-based aerogel prepared in Example 1 of the present invention.

[0031] Figure 2 This is a schematic diagram of the macroporous structure of the alginate-based aerogel prepared in Example 1 of the present invention;

[0032] Figure 3 This is a schematic diagram of the macroporous cross-section of the alginate-based aerogel prepared in Example 1 of the present invention;

[0033] Figure 4 This is a photograph of the alginate-graphene oxide aerogel prepared in Example 2 of the present invention.

[0034] Figure 5 This is a schematic diagram of the macroporous structure of the alginate-graphene oxide aerogel prepared in Example 2 of the present invention;

[0035] Figure 6 This is a schematic diagram of the macroporous cross-section of the alginate-graphene oxide aerogel prepared in Example 2 of the present invention;

[0036] Figure 7 This is a photograph of the alginate-polyvinyl alcohol aerogel prepared in Example 3 of the present invention.

[0037] Figure 8 This is a schematic diagram of the macroporous structure of the alginate-polyvinyl alcohol aerogel prepared in Example 3 of the present invention;

[0038] Figure 9 This is a schematic diagram of the macroporous cross-section of the alginate-polyvinyl alcohol aerogel prepared in Example 3 of the present invention;

[0039] Figure 10 This is a photograph of the alginate-montmorillonite aerogel prepared in Example 4 of the present invention.

[0040] Figure 11 This is a schematic diagram of the macroporous structure of the alginate-montmorillonite aerogel prepared in Example 4 of the present invention;

[0041] Figure 12 This is a schematic diagram of the macroporous cross-section of the alginate-montmorillonite aerogel prepared in Example 4 of the present invention;

[0042] Figure 13 The images show actual alginate-graphene oxide aerogels containing different concentrations of graphene oxide, along with schematic diagrams of their corresponding macropores and cross-sections.

[0043] Figure 14 This is a physical image of the alginate-based aerogel prepared in Comparative Example 1 of the present invention;

[0044] Figure 15 This is a schematic diagram of the macroporous structure of the alginate-based aerogel prepared in Comparative Example 1 of the present invention;

[0045] Figure 16 This is a schematic diagram of the macroporous cross-section of the alginate-based aerogel prepared in Comparative Example 1 of the present invention;

[0046] Figure 17This is a photograph of the alginate-based aerogel prepared in Example 1 of the present invention subjected to a pressure of 10,000 times its own mass.

[0047] Figure 18 Comparison of stress-strain curves obtained from compression mechanics tests of the aerogels prepared in Examples 1-4 of this invention. Detailed Implementation

[0048] The technical solution of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0049] Existing aerogels generally suffer from isotropy and uniform pore size. In recent years, researchers have shown increasing interest in hierarchical assembly techniques to prepare materials with complex structures and properties. The inspiration for hierarchical assembly techniques comes from nature. From tiny DNA, proteins, and cells to macroscopic life forms like shells, bones, and bamboo, all are materials with complex structures and properties obtained through hierarchical assembly of nanoscale molecular units. A 2011 article published in *Science* magazine pointed out that self-assembly has entered the design era (see *Science* magazine, 2011, issue 334, page 183). Therefore, this invention aims to obtain aerogels with anisotropic, multi-level pore structures through hierarchical assembly techniques, thereby preparing high-performance bone scaffold materials.

[0050] However, while alginate, as a biodegradable natural polymer, possesses advantages such as good biocompatibility, scaffold-forming properties, biodegradability, and low cost, alginate aerogels lack good mechanical properties. Therefore, there is an urgent need to improve the mechanical properties of alginate aerogels through microstructure design to better apply them in the field of bone tissue regeneration scaffolds. This invention discovers that alginate has the ability to crosslink with multivalent cations to form gels with anisotropic pores, offering unique advantages in the manufacture of porous aerogel materials. Based on the above discussion, this invention considers combining multi-level assembly technology to obtain alginate-based aerogels with ordered multi-scale porous structures and good mechanical properties, representing an effective strategy for preparing high-performance bone scaffold materials.

[0051] Based on the above considerations, the present invention provides an alginate-based aerogel having parallel macropores and oriented channels at an angle to the macropores. The angle ranges from 0 to 180°, and is not 0°; specifically, it can be 1°, 5°, 10°, 30°, 50°, 60°, 90°, 120°, 150°, or 180°, preferably 90°, i.e., the oriented channels are perpendicular to the macropores.

[0052] The macropores are distributed along the same direction within the alginate-based aerogel, which is the length direction of the macropores, and the macropores can be through-hole. In this invention, the macropores are preferably distributed in a "top-to-bottom" direction along the alginate-based aerogel, i.e., longitudinally. Additionally, oriented pores at a certain angle to the macropores can be referred to as "micropores" and are distributed in layers.

[0053] In this invention, the macropores and oriented pores present in the alginate-based aerogel give it anisotropic and multi-scale porous structure. When used as a bone scaffold material, the aligned, parallel macropores facilitate the deposition of mineralized extracellular matrix and vascular infiltration. The presence of oriented pores enables interconnection between the parallel macropores, thereby improving pore interconnectivity and promoting cell attachment, migration, substance transport, and vascular infiltration.

[0054] In some embodiments of the present invention, the average pore diameter of the macropores is 380–420 μm, and can be 380 μm, 390 μm, 395 μm, 400 μm, 405 μm, 410 μm, 415 μm, or 420 μm, etc.; the average diameter of the oriented channels is 80–100 μm, and can be 80 μm, 82 μm, 84 μm, 86 μm, 88 μm, 90 μm, 92 μm, 94 μm, 96 μm, 98 μm, or 100 μm, etc. The above-mentioned sizes of macropores and oriented channels are the most suitable size range for inducing vascularized osteogenic formation, and the structural design of macropores and oriented channels is beneficial to osteogenic formation.

[0055] Tests have shown that the alginate-based aerogel has excellent mechanical properties (Young's modulus of approximately 100 kPa, capable of withstanding compressive forces 10,000 times its own weight without deformation). When used to prepare bone scaffold materials, it can meet the mechanical strength requirements of bone scaffold materials, and the prepared bone scaffold materials have good biocompatibility and can be used in the field of bio-tissue engineering materials technology.

[0056] The present invention also provides a method for preparing the above-mentioned alginate-based aerogel, comprising the following steps:

[0057] S1: Provides an alginate-based gel with parallel-arranged macropores;

[0058] S2: After flipping the alginate-based gel in S1 at a certain angle, it is oriented and frozen until the upper surface of the gel is solid. The frozen sample is then dried to obtain alginate-based aerogel.

[0059] The angle ranges from 0 to 180°.

[0060] According to the present invention, an alginate-based gel with parallel-arranged macropores is first provided, which can be prepared using conventional techniques well known to those skilled in the art, such as ionogel technology. In some embodiments of the present invention, the alginate-based gel with parallel-arranged macropores is preferably prepared by the following method:

[0061] An alginate solution was added to a mold whose inner wall was coated with an alginate film, and a metal salt solution was sprayed onto the surface of the alginate solution. After the film was formed, the metal salt solution was added and allowed to stand for reaction to obtain an alginate-based gel with parallel macropores.

[0062] According to this invention, a mold with an inner wall coated with an alginate film is first provided. This invention does not impose any particular limitations on the mold; conventional laboratory equipment can be used, such as a beaker or a polytetrafluoroethylene container. Before coating the mold with the alginate solution, it is preferably cleaned in a plasma cleaner for 2–10 minutes, preferably 5 minutes. In this invention, alginate is first mixed with a solvent, preferably under stirring conditions, to obtain an alginate solution. The alginate is preferably sodium alginate (commercially available products are generally acceptable), and the solvent is preferably water, which can be deionized water or ultrapure water. The concentration of the alginate solution is preferably 2–100 g / L, and can be 2 g / L, 5 g / L, 8 g / L, 10 g / L, 20 g / L, 30 g / L, 40 g / L, 50 g / L, 60 g / L, 70 g / L, 80 g / L, 90 g / L, or 100 g / L, etc. The obtained alginate solution is coated onto the inner wall of the mold and dried, forming an alginate film on the inner wall. The presence of this film facilitates the subsequent formation of a film from the added alginate solution when a metal salt solution is sprayed. The drying can be performed using techniques well-known to those skilled in the art; preferably, drying is carried out in an oven at a temperature of 100–120°C, preferably 110°C, for a time of 0.5–2 hours, preferably 1 hour.

[0063] Then, the prepared alginate solution is added to a mold with an alginate film coated on its inner wall, and a metal salt solution is sprayed onto the surface of the alginate solution, allowing the metal salt to react with the alginate solution to form a film. The presence of this film facilitates the orderly downward permeation of metal ions from the subsequently added metal salt solution, i.e., into the alginate solution, thereby forming an alginate-based gel with parallel-arranged macropores after a period of static reaction. In this invention, the solvent of the metal salt solution is water, and the solute is a metal salt, preferably a divalent metal salt. The divalent metal cation present can be any one or more of copper ions, calcium ions, barium ions, zinc ions, strontium ions, or iron ions. Specifically, the metal salt can be any one or more of calcium chloride, copper chloride, copper sulfate, zinc chloride, barium chloride, strontium chloride, or ferric chloride. The concentration of the metal salt solution is preferably 0.2–2 mol / L, and can be 0.2 mol / L, 0.5 mol / L, 0.8 mol / L, 1.0 mol / L, 1.2 mol / L, 1.5 mol / L, 1.8 mol / L, or 2.0 mol / L, etc. In this invention, the standing reaction time is 6–72 hours, and can be 6 hours, 8 hours, 10 hours, 20 hours, 30 hours, 40 hours, 50 hours, 60 hours, 70 hours, or 72 hours, etc.

[0064] In some embodiments of the present invention, according to the above-mentioned concentration range of alginate solution and metal salt solution, the volume ratio of alginate solution to metal salt solution is 20:(5-15), which can be 20:5, 20:6, 20:7, 20:8, 20:9, 20:10, 20:11, 20:12, 20:13, 20:14 or 20:15, etc.

[0065] In some preferred embodiments of the present invention, the alginate solution further includes additives, which are one or more organic and inorganic nano-components, including but not limited to zero-dimensional nanoparticles (bioceramic oxide nanoparticles, such as β-TCP, hydroxyapatite, calcium carbonate, amorphous calcium phosphate, etc.), one-dimensional nanofibers (chitin fibers, carbon nanotubes, calcium silicate nanowires, hydroxyapatite nanowires, etc.), two-dimensional nanosheets (graphene oxide (GO), montmorillonite (MMT), calcium phosphate nanosheets, calcium carbonate nanosheets, etc.), and organic components (polyvinyl alcohol (PVA), gelatin, silk protein, collagen fibers, etc.). The preferred mass ratio of alginate to additives in the alginate solution is (70-99.9):(0.1-30), and can be 70:30, 75:25, 80:20, 85:15, 90:10, 95:5, 98:2, 99:1, 99.5:0.5, or 99.1:0.1, etc.

[0066] In this invention, the specific values ​​listed above are merely for illustrative purposes and are not limited thereto. Other point values ​​within the range of values ​​are also applicable, but to avoid complexity, they will not be described in detail.

[0067] The aforementioned organic and inorganic nano-components are all osteogenic. Studies have shown that adding them to alginate solutions does not affect the pore structure of the final alginate-based aerogel. Therefore, this invention can select the aforementioned osteogenic organic and inorganic nano-components to add to the alginate solution according to different needs. Furthermore, this invention has discovered that within a certain range, the pore size in the aerogel can be controlled by changing the concentration of the additives; therefore, this invention has strong scalability.

[0068] After obtaining an alginate-based gel with parallel-arranged macropores, the present invention preferably cuts the alginate-based gel to a suitable size or shape. The size and shape are not specifically limited; cutting can be performed using tools such as scalpels according to actual usage requirements. Then, the alginate-based gel is flipped at a certain angle (0–180°, preferably 90°) and oriented frozen until the upper surface of the gel is solid. The purpose of flipping at a certain angle is to obtain an oriented pore structure at an angle to the macropores. The oriented freezing is a conventional technique well-known to those skilled in the art. Specifically, a metal platform is immersed in a liquid nitrogen environment, with a thermocouple connected to the surface of the metal platform. The temperature of the metal platform surface is controlled by adjusting the amount of liquid nitrogen added. This method can control the temperature error of the metal platform surface within 3°C. The present invention preferably places the alginate-based gel, flipped at a certain angle (preferably 90°), on the surface of a metal platform for oriented freezing. The metal platform is preferably a copper block. During this process, water gradually freezes along the temperature gradient, forming ice crystals. These ice crystals grow at a certain angle (0–180°), preferably perpendicular to the direction parallel to the macropores, resulting in a layered microstructure. The polymer and optional organic and inorganic nanoparticles are concentrated in the spaces between the ice crystals, creating a layered, uniform scaffold, a structure that is a replica of ice. The frozen sample is then dried to obtain an alginate-based aerogel. The drying is preferably freeze-drying, which causes the ice crystals in the sample to sublimate into gas and escape, thus obtaining an alginate-based aerogel with oriented channels perpendicular to the macropores. In this invention, the freeze-drying temperature is -110°C, and the time is 60–75 hours, preferably 72 hours.

[0069] The preparation method provided by this invention can prepare alginate-based aerogels with multi-level, anisotropic porous structures. This method is simple, safe and reliable, uses readily available and inexpensive raw materials, takes less time, and is scalable, making it suitable for large-scale industrial application.

[0070] This invention presents performance tests on alginate-based aerogels with anisotropic, multi-scale porous structures prepared using the above-described method. The results show that the density of the alginate-based aerogel prepared in this invention is only about 50 mg / cm³. 3 It is lightweight. At the same time, it also has excellent compressive strength, with a maximum compressive modulus of over 100 kPa within its elastic limit, and can withstand compressive forces 10,000 times its own weight without deformation, exhibiting high strength.

[0071] Based on this, the present invention also provides a bone scaffold material, comprising the alginate-based aerogel involved in the above-mentioned technical solutions. Because the microstructure and mechanical properties of the resulting alginate-based aerogel can be controlled by simple changes in the material ratio during the preparation process, and it also exhibits good compressibility, the bone scaffold material provided by the present invention has broader application prospects compared to traditional polymer scaffold materials.

[0072] To further illustrate the present invention, the following embodiments provide a detailed description. The experimental materials used in the following embodiments of the present invention are all commercially available products.

[0073] Example 1

[0074] This embodiment provides an alginate-based aerogel, the preparation method of which is as follows:

[0075] a. Disperse 8g of sodium alginate (Aladdin) in 400mL of deionized water and stir overnight to obtain a homogeneous sodium alginate solution.

[0076] b. Clean a 25 mL beaker in a plasma cleaner for 5 min, coat the surface with a thin layer of the above sodium alginate solution, dry in an oven at 110 °C for 1 h to form a film, then add 20 mL of the above sodium alginate solution to the beaker, spray a thin layer of 1 M calcium chloride solution on the surface, and after the film forms, slowly add 12.5 mL of calcium chloride solution, let it stand for 24 h to obtain an alginate-based hydrogel.

[0077] c. Remove the alginate-based hydrogel and cut it to obtain a 1cm thick layer at the bottom. Invert the hydrogel 90° and place it on a copper block. Add liquid nitrogen around the copper block and freeze it perpendicular to the macropore direction using an orientation freezing technique until the upper surface of the hydrogel is solid. Then, dry it in a freeze dryer at -110°C for 72 hours to obtain an alginate-based aerogel.

[0078] A photograph of the alginate-based aerogel prepared in Example 1 of this invention is shown below. Figure 1 As shown in the diagram. A schematic diagram of the macroporous structure in the prepared alginate-based aerogel is shown in the diagram. Figure 2As shown, the large holes are arranged in parallel; a schematic diagram of the oriented channel structure (i.e., the cross-section of the large holes) is shown below. Figure 3 As shown, it is distributed in layers. (From...) Figures 1-3 It can be seen that the prepared alginate-based aerogel has anisotropic and multi-scale pore structure.

[0079] Example 2

[0080] This embodiment provides an alginate-graphene oxide aerogel, the preparation method of which is as follows:

[0081] a. The preparation of sodium alginate solution is the same as in Example 1;

[0082] b. Add 20 mL of 1 mg / mL graphene oxide dispersion (Suzhou Carbon Fiber Technology, industrial graphene aqueous solution) to the sodium alginate solution described in step a, then add 180 mL of deionized water, ultrasonically disperse for 30 min, stir overnight to obtain a uniform sodium alginate-graphene oxide solution.

[0083] c. Clean a 25 mL beaker in a plasma cleaner for 5 min, coat the surface with a thin layer of the above sodium alginate-graphene oxide solution, dry in an oven at 110 °C for 1 h to form a film, then add 20 mL of the above sodium alginate-graphene oxide solution to the beaker, spray a thin layer of 1 M calcium chloride solution on the surface, wait for the film to form, slowly add 12.5 mL of calcium chloride solution, let stand for 24 h to obtain alginate-graphene oxide hydrogel;

[0084] d. Remove the alginate-graphene oxide hydrogel described above, cut off a 1 cm thick layer at the bottom, rotate the hydrogel 90° and place it on a copper block. Add liquid nitrogen around the copper block and freeze it perpendicular to the macropore direction using an orientation freezing technique until the upper surface of the hydrogel is solid. Then, dry it in a freeze dryer at -110°C for 72 hours to obtain an alginate-graphene oxide aerogel.

[0085] A photograph of the alginate-graphene oxide aerogel prepared in Example 2 of this invention is shown below. Figure 4 As shown in the figure. A schematic diagram of the macroporous structure in the prepared alginate-graphene oxide aerogel is shown in the figure. Figure 5 As shown, the large holes are arranged in parallel; a schematic diagram of the oriented channel structure (i.e., the cross-section of the large holes) is shown below. Figure 6 As shown, it is distributed in layers. (From...) Figures 4-6 It can be seen that the prepared alginate-graphene oxide aerogel has anisotropic and multi-scale pore structure.

[0086] Example 3

[0087] This embodiment provides an alginate-polyvinyl alcohol aerogel, the preparation method of which is as follows:

[0088] a. The preparation of sodium alginate solution is the same as in Example 1;

[0089] b. Disperse 100 mg of polyvinyl alcohol in 20 mL of deionized water to obtain a homogeneous solution with a concentration of 5 mg / mL.

[0090] c. Add 16 mL of a 5 mg / mL polyvinyl alcohol solution to the sodium alginate solution described in step a, then add 184 mL of deionized water and stir overnight to obtain a homogeneous sodium alginate-polyvinyl alcohol solution.

[0091] d. The preparation of alginate-polyvinyl alcohol hydrogel is the same as in Example 2;

[0092] e. The preparation of alginate-polyvinyl alcohol aerogel is the same as in Example 2, and alginate-polyvinyl alcohol aerogel is finally obtained.

[0093] A photograph of the alginate-polyvinyl alcohol aerogel prepared in Example 3 of this invention is shown below. Figure 7 As shown in the figure. A schematic diagram of the macroporous structure in the prepared alginate-polyvinyl alcohol aerogel is shown in the figure. Figure 8 As shown, the large holes are arranged in parallel; a schematic diagram of the oriented channel structure (i.e., the cross-section of the large holes) is shown below. Figure 9 As shown, it is distributed in layers. (From...) Figures 7-9 It can be seen that the prepared alginate-polyvinyl alcohol aerogel has anisotropic and multi-scale pore structure.

[0094] Example 4

[0095] This embodiment provides an alginate-montmorillonite aerogel, the preparation method of which is as follows:

[0096] a. The preparation of sodium alginate solution is the same as in Example 1;

[0097] b. Disperse 20 mg of montmorillonite in 20 mL of deionized water and sonicate to obtain a homogeneous montmorillonite solution.

[0098] c. Add 20 mL of montmorillonite solution to the sodium alginate solution described in step a, then add 180 mL of deionized water, sonicate for 30 min, stir overnight to obtain a homogeneous sodium alginate-montmorillonite solution.

[0099] d. The preparation of alginate-montmorillonite hydrogel is the same as in Example 2;

[0100] e. The preparation of alginate-montmorillonite aerogel is the same as in Example 2, and alginate-montmorillonite aerogel is finally obtained.

[0101] A photograph of the alginate-montmorillonite aerogel prepared in Example 4 of this invention is shown below. Figure 10 As shown in the diagram. A schematic diagram of the macroporous structure in the prepared alginate-montmorillonite aerogel is shown below. Figure 11 As shown, the large holes are arranged in parallel; a schematic diagram of the oriented channel structure (i.e., the cross-section of the large holes) is shown below. Figure 12 As shown, it is distributed in layers. (From...) Figures 10-12 It can be seen that the prepared alginate-montmorillonite aerogel has anisotropic and multi-scale pore structure.

[0102] Example 5

[0103] This embodiment provides a series of alginate-graphene oxide aerogels containing different concentrations of graphene oxide, and their preparation methods are as follows:

[0104] a. Disperse 8g of sodium alginate (Aladdin) in 200mL of deionized water and stir overnight to obtain a homogeneous sodium alginate solution.

[0105] b. Add the 4 mg / mL graphene oxide dispersion to the sodium alginate solution described in step a in volumes of 5 mL, 10 mL, 20 mL, 100 mL, and 200 mL, respectively. Then add 195 mL, 190 mL, 180 mL, 100 mL, and 0 mL of deionized water, respectively. Sonicate the solution for 30 min and stir overnight to obtain a homogeneous sodium alginate-graphene oxide solution with concentrations of 0.25%, 0.5%, 1%, 5%, and 10% (relative to the mass of sodium alginate).

[0106] c. Clean a 25mL beaker in a plasma cleaner for 5 minutes, coat the surface with a thin layer of sodium alginate-graphene oxide solution described in step b, dry in an oven at 110℃ for 1 hour, add 20mL of sodium alginate-graphene oxide solution described in step b, spray a thin layer of 1M calcium chloride solution on the surface, wait for the film to form, slowly add 12.5mL of calcium chloride solution, let it stand for 24 hours to obtain alginate-graphene oxide hydrogel.

[0107] d. Remove the above-mentioned alginate-graphene oxide hydrogel, cut it to obtain a 1cm thick hydrogel at the bottom, rotate the hydrogel 90° and place it on a copper block, add liquid nitrogen around the copper block, and freeze it perpendicular to the macropore direction using an orientation freezing technique until the upper surface of the hydrogel is solid. Then, dry it in a freeze dryer at -110℃ for 72 hours to obtain alginate-graphene oxide aerogels with different pore sizes.

[0108] The following are photographs of a series of alginate-graphene oxide aerogels containing different concentrations of graphene oxide prepared in the embodiments of the present invention, along with their corresponding macropore and oriented pore structures: Figure 13As shown, this invention can control the pore size of the macropores in the final aerogel by adjusting the incorporation content of graphene oxide in alginate.

[0109] Example 6

[0110] This embodiment provides an alginate-chitin fiber aerogel, the preparation method of which is as follows:

[0111] a. The preparation of sodium alginate solution is the same as in Example 1;

[0112] b. Disperse 20 mg of chitin fiber in 20 mL of deionized water and sonicate to obtain a uniform chitin fiber solution.

[0113] c. Add 20 mL of the chitin fiber solution described in step b to the sodium alginate solution described in step a, then add 180 mL of deionized water, sonicate for 30 min, stir overnight to obtain a uniform sodium alginate-chitin fiber solution.

[0114] d. The preparation of the alginate-based hydrogel is the same as in Example 2;

[0115] e. The preparation of alginate-chitin fiber aerogel is the same as in Example 2, and finally alginate-chitin fiber aerogel is obtained.

[0116] The actual image of the alginate-chitin fiber aerogel and the structure of the macropores and oriented channels are similar to those in Example 1.

[0117] Example 7

[0118] This embodiment provides an alginate-hydroxyapatite aerogel, the preparation method of which is as follows:

[0119] a. The preparation of sodium alginate solution is the same as in Example 1;

[0120] b. Disperse 20 mg of hydroxyapatite nanoparticles in 20 mL of deionized water and ultrasonically disperse to obtain a uniform hydroxyapatite nano solution.

[0121] c. Add 20 mL of the hydroxyapatite nano solution described in step b to the sodium alginate solution described in step a, then add 180 mL of deionized water, ultrasonically disperse for 30 min, stir overnight to obtain a uniform sodium alginate-hydroxyapatite nano solution.

[0122] d. The preparation of sodium alginate-hydroxyapatite hydrogel is the same as in Example 2;

[0123] e. The preparation of sodium alginate-hydroxyapatite aerogel is the same as in Example 2, and sodium alginate-hydroxyapatite aerogel is finally obtained.

[0124] The physical image of the sodium alginate-hydroxyapatite aerogel and the structure of the macropores and oriented channels are similar to those in Example 1.

[0125] Example 8

[0126] This embodiment provides an alginate-silk protein aerogel, the preparation method of which is as follows:

[0127] a. The preparation of sodium alginate solution is the same as in Example 1;

[0128] b. Extraction of silk protein: Step 1: Degumming. Dry silkworm cocoons are cut into small pieces and placed in 2L of a 0.02 mol / L hot sodium carbonate solution. The mixture is magnetically stirred for 30 minutes until the cocoons gradually dissolve and disappear into white filaments. The cocoons are rinsed 3-5 times with deionized water and dried in a 35℃ oven for 2 days to obtain degummed silk. Step 2: Redissolution. The degummed silk is quickly placed in a fresh 9.3 mol / L lithium bromide solution. The final silk protein concentration is controlled at 10 w / v%. The mixture is centrifuged at 8000 rpm for 10 minutes to remove air bubbles. The supernatant is transferred to an MWCO3500 dialysis bag and dialyzed with ultrapure water for 2 days, changing the water 6 times. The final silk protein is then diluted with ultrapure water to 1 w / v% to obtain a silk protein solution.

[0129] c. Add 20 mL of the silk protein solution described in step b to the sodium alginate solution described in step a, then add 180 mL of deionized water, sonicate for 30 min, stir overnight to obtain a uniform sodium alginate-silk protein solution.

[0130] d. The preparation of alginate-silk protein hydrogel is the same as in Example 2;

[0131] e. The preparation of alginate-silk protein aerogel is the same as in Example 2, and alginate-silk protein aerogel is finally obtained.

[0132] The actual image of the alginate-silk protein aerogel and the structure of the macropores and oriented channels are similar to those in Example 1.

[0133] Comparative Example 1

[0134] This comparative example provides an alginate-based aerogel, the preparation method of which is as follows:

[0135] a. Disperse 8g of sodium alginate (Aladdin) in 400mL of deionized water and stir overnight to obtain a homogeneous sodium alginate solution.

[0136] b. Clean a 25mL beaker in a plasma cleaner for 5 minutes, coat the surface with a thin layer of the above sodium alginate solution, dry in an oven at 110℃ for 1 hour, add 20mL of the above sodium alginate solution, spray a thin layer of 1M calcium chloride solution on the surface, and after the film is formed, slowly add 12.5mL of calcium chloride solution and let it stand for 24 hours to obtain an alginate-based hydrogel.

[0137] c. Remove the alginate hydrogel, cut it to obtain a 1 cm thick layer at the bottom, and oriented it by freezing in a direction parallel to the pore direction. Then, dry it in a freeze dryer at -110°C for 72 hours to obtain an alginate-based aerogel.

[0138] A photograph of the alginate-based aerogel prepared in Comparative Example 1 of this invention is shown below. Figure 14 As shown in the diagram. A schematic diagram of the macroporous structure in the prepared alginate-based aerogel is shown in the diagram. Figure 15 As shown, the large holes are arranged in parallel; a schematic diagram of the cross-section of the large holes is shown below. Figure 16 As shown, the channel structure is parallel to the large hole, rather than perpendicular to it.

[0139] Performance testing

[0140] The mechanical properties of the alginate-based aerogel obtained in Example 1 were tested using the following methods:

[0141] Cut the sample into a cube approximately 15mm × 15mm × 7mm in size, place a 500g weight on the top surface of the sample, and take a photo after 10 minutes.

[0142] Test results are as follows Figure 17 As shown, the alginate-based aerogel provided by this invention can withstand a compressive force 10,000 times its own weight without deformation, exhibiting high strength.

[0143] The compressive mechanical properties of the aerogels obtained in Examples 1-4 were tested using the following methods:

[0144] Compression tests were conducted on an Instron 5565-A mechanical testing instrument, which has two planar compression platforms, a 10N loading sensor, and a loading rate of 0.05 mm / min. Samples were cut into cubes approximately 7 mm × 7 mm × 7 mm in size, and the values ​​were measured using vernier calipers and input into the software for compression testing. The test was stopped when the compressive strain reached 80%, and each sample group was tested at least five times.

[0145] Test results are as follows Figure 18 As shown, the prepared aerogel has excellent compressive strength, with a maximum compressive modulus exceeding 100 kPa within the elastic limit.

[0146] The above description of the disclosed embodiments enables those skilled in the art to make or use the invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the invention. Therefore, the invention is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. An alginate-based aerogel, characterized in that, It has parallel large holes and oriented channels at an angle to the large holes; The angle is 90°; The macropores are distributed in the same direction inside the alginate-based aerogel; The average pore diameter of the macropore is 380~420 μm; The average diameter of the orientation channel is 80~100 μm.

2. The method for preparing alginate-based aerogel according to claim 1, characterized in that, Includes the following steps: S1: Provides an alginate-based gel with parallel-arranged macropores; S2: After flipping the alginate-based gel in S1 at a certain angle, it is oriented and frozen until the upper surface of the gel is solid. The frozen sample is then dried to obtain alginate-based aerogel. The angle is 90°.

3. The preparation method according to claim 2, characterized in that, Step S1 specifically involves adding an alginate solution to a mold with an alginate film coated on the inner wall, and spraying a metal salt solution onto the surface of the alginate solution. After the film is formed, the metal salt solution is added, and the mixture is allowed to stand and react to obtain an alginate-based gel with parallel macropores. The metal salt solution is selected from any one or more of calcium chloride, copper chloride, copper sulfate, strontium chloride, zinc chloride, barium chloride, or ferric chloride.

4. The preparation method according to claim 3, characterized in that, The solute in the alginate solution is sodium alginate; The concentration of the alginate solution is 2~100 g / L; The concentration of the metal salt solution is 0.2~2 mol / L.

5. The preparation method according to claim 4, characterized in that, The volume ratio of the alginate solution to the metal salt solution is 20:(5~15).

6. The preparation method according to claim 3, characterized in that, The alginate solution also includes additives; The additive is selected from any one or more of hydroxyapatite, calcium carbonate, calcium phosphate, chitin fiber, carbon nanotubes, graphene oxide, montmorillonite, polyvinyl alcohol, gelatin, silk protein, or collagen fiber.

7. The preparation method according to claim 6, characterized in that, The mass ratio of alginate to additives in the alginate solution is (70~99.9):(0.1~30).

8. The preparation method according to claim 3, characterized in that, The static reaction time is 6-72 h.

9. A bone scaffold material, characterized in that, Includes the alginate-based aerogel according to claim 1 or the alginate-based aerogel prepared by the preparation method according to any one of claims 2 to 8.

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