Preparation method of extrusion type high-precision 3D printing hydrogel assisted by salt crystallization

Abstract

The invention provides a preparation method of salt-crystallization-assisted extrusion type high-precision 3D printing hydrogel, which comprises the following steps: mixing a salt solution and a hydrogel solution to prepare printing ink, laying a layer of crystal nucleus on a forming platform of an extrusion type 3D printer, and printing a hydrogel model by using the 3D printer to obtain the salt-crystallization-assisted extrusion type high-precision 3D printing hydrogel. Finally, the hydrogel with high precision, high porosity and good biocompatibility is prepared through illumination cross-linking curing and deionized water cleaning. According to the preparation method, the stability of a printing structure can be kept by using salt crystallization at room temperature, the problems of low printing precision and easy collapse of the structure in the existing hydrogel printing technology are solved, the preparation method has no sample size limitation, and especially, a large-size sample can be prepared in the Z-axis direction; meanwhile, porous hydrogel can be prepared through crystals in the porous hydrogel; in addition, the used salt can be completely removed through deionized water cleaning, no residue exists, and the obtained hydrogel has high biocompatibility.

Description

Technical Field

[0001] The present invention belongs to the technical field of 3D printing, and in particular relates to a method for preparing a salt crystallization-assisted extrusion-type high-precision 3D printing hydrogel. Background Art

[0002] Extrusion 3D printed hydrogels have strong material compatibility, can handle high-viscosity materials, have good structural complexity and multifunctional printing capabilities. These characteristics make them have great potential in the fields of tissue engineering, drug release and regenerative medicine.

[0003] Extrusion 3D printing hydrogel uses the shear thinning effect of hydrogel to make the material have a lower viscosity during the extrusion process. However, once the material leaves the nozzle, the shear force disappears and the viscosity quickly recovers, making it difficult for the material to flow and spread when it is piled up, maintaining the shape and details of the print. However, hydrogels usually have a soft texture and a low modulus. When the gravity of the printed structure exceeds its yield stress, the hydrogel is prone to deformation or even collapse, which directly affects the stability and printing accuracy of its printed structure.

[0004] In order to make the printed part (hydrogel) have sufficient mechanical strength to improve the fidelity of the structure, it can be achieved through a rapid curing mechanism (such as light curing and heat curing, etc.), but this method is prone to cause nozzle clogging, resulting in the termination of the printing process. Or the printing ink is frozen at low temperature to ensure the structure of the hydrogel, however, this method requires extremely low temperature to generate sufficient temperature, and the size of the printed sample is limited in the Z axis.

[0005] Therefore, it is necessary to provide a hydrogel suitable for 3D printing to solve the current problem of low hydrogel printing accuracy and promote the development of tissue engineering and regenerative medicine. Summary of the invention

[0006] In order to solve the problems existing in the prior art, the present invention provides a method for preparing a high-precision 3D-printed hydrogel assisted by salt crystallization, which overcomes the problems of low printing precision and structural collapse existing in the existing hydrogel printing technology, and significantly improves the structural retention ability and precision of hydrogel printing. The hydrogel prepared by the preparation method has the characteristics of high precision, high porosity and good biocompatibility.

[0007] A method for preparing a salt crystallization-assisted extrusion-type high-precision 3D printing hydrogel comprises the following steps:

[0008] (1) uniformly mixing a hydrogel monomer, a photoinitiator, a thickener and water to prepare a hydrogel solution; dissolving salt in water to prepare a salt solution;

[0009] (2) mixing the hydrogel solution and the salt solution to prepare a printing ink;

[0010] (3) placing a layer of crystal cores on the molding platform of the 3D printer, using printing ink as raw material, and printing a preset hydrogel scaffold using an extrusion 3D printer;

[0011] (4) The printed hydrogel scaffold is subjected to photo-crosslinking, and then the cured hydrogel scaffold is cleaned with deionized water to remove the salt crystals, thereby obtaining the extruded high-precision 3D printed hydrogel.

[0012] In the above step (1):

[0013] The water used to prepare the hydrogel solution is preferably deionized water; the water used to prepare the salt solution is preferably purified water.

[0014] Preferably, the hydrogel monomer is one or more of acrylamide, acrylic acid, methacrylylated gelatin, methacrylylated hyaluronic acid, methacrylylated chitosan, and methacrylylated silk fibroin, and more preferably acrylamide.

[0015] Preferably, in the hydrogel solution, the mass ratio of hydrogel monomer to water is (0.1-1.4):1.

[0016] As further preferred, when the hydrogel monomer is selected from acrylamide and / or acrylic acid, the mass ratio of the hydrogel monomer to water in the hydrogel solution is (0.7-1.1):1, and more preferably 0.9:1.

[0017] As further preferred, when the hydrogel monomer is selected from one or more of methacrylated gelatin, methacrylated hyaluronic acid, methacrylated chitosan, and methacrylated silk fibroin, the mass ratio of the hydrogel monomer to water in the hydrogel solution is (0.1-0.5):1. More preferably, it is 0.3:1.

[0018] Preferably, the photoinitiator is phenyl (2,4,6-trimethylbenzoyl) lithium phosphate. The photoinitiator is a substance that generates free radicals under the action of light and further initiates the polymerization of hydrogel monomers.

[0019] Preferably, the mass ratio of the hydrogel monomer to the photoinitiator is (1-200):1.

[0020] As further preferred, when the hydrogel monomer is selected from acrylamide and / or acrylic acid, the mass ratio of the hydrogel monomer to the photoinitiator is (80-120):1, and more preferably 108:1.

[0021] As further preferred, when the hydrogel monomer is selected from one or more of methacrylated gelatin, methacrylated hyaluronic acid, methacrylated chitosan, and methacrylated silk fibroin, the mass ratio of the hydrogel monomer to the photoinitiator is (5-15):1, and more preferably 12:1.

[0022] As further preferred, when the hydrogel monomer is one or both of acrylamide and acrylic acid, a crosslinking agent is simultaneously added to the hydrogel solution.

[0023] More preferably, the cross-linking agent is N,N'-methylenebisacrylamide.

[0024] Preferably, the mass ratio of the hydrogel monomer to the crosslinking agent is (15 to 150): 1. More preferably, it is (40 to 60): 1. The mass ratio of the hydrogel monomer to the crosslinking agent is preferably 54:1.

[0025] Preferably, the salt is sodium acetate or a mixture of sodium acetate and carbonamide. Further, the sodium acetate is anhydrous sodium acetate.

[0026] As a further preferred embodiment, when the salt is sodium acetate, the mass ratio of sodium acetate to water in the salt solution is (0.2-1.7): 1. More preferably, it is (1-1.5): 1. As a further preferred embodiment, when the salt is sodium acetate, the mass ratio of sodium acetate to water in the salt solution is 1.2: 1.

[0027] As a further preferred embodiment, when the salt is a mixture of sodium acetate and carbonic acid amide, the mass ratio of sodium acetate to water in the salt solution is (0.2-1.7):1; the mass ratio of carbonic acid amide to water is (0.2-0.8):1. As a further preferred embodiment, when the salt is a mixture of sodium acetate and carbonic acid amide, the mass ratio of sodium acetate to water in the salt solution is (1-1.5):1; the mass ratio of carbonic acid amide to water is (0.3-0.6):1. As a further preferred embodiment, when the salt is a mixture of sodium acetate and carbonic acid amide, the mass ratio of sodium acetate to water in the salt solution is 1.25:1; the mass ratio of carbonic acid amide to water is 0.5:1.

[0028] Preferably, the thickener is one or more of polyacrylamide, polyacrylic acid, polyethylene glycol, gelatin, cellulose or its derivatives, starch or its derivatives, fumed silica, and carbomer. More preferably, polyacrylamide is used.

[0029] More preferably, the molecular weight of the polyacrylamide is 1 to 14 million, more preferably 5 to 10 million, and even more preferably 7 million.

[0030] Preferably, in the hydrogel solution, the mass ratio of the thickener to water is 0.005:1 to 1:5, and more preferably (0.01 to 0.05):1.

[0031] In the above step (2):

[0032] Preferably, in the printing ink, the volume ratio of the hydrogel solution to the salt solution is 1:17 to 10:1, and more preferably 1:(1 to 4).

[0033] In the above step (3),

[0034] Preferably, the 3D printing parameters are: barrel temperature of 50-80°C, nozzle temperature of 40-80°C, printing speed of 75-4000 mm / min, extrusion flow rate of 0.01-0.5 mL / min; nozzle diameter of 80-1000 μm.

[0035] As a further preference, the 3D printing parameters are: barrel temperature of 55-65°C, nozzle temperature of 55-65°C, printing speed of 1000-3000 mm / min, extrusion flow rate of 0.01-0.05 mL / min; nozzle diameter of 100-400 μm.

[0036] Preferably, the entire printer is at room temperature (25° C.), which is lower than the crystallization temperature of the salt in the printing ink, and is conducive to rapid cooling of the printing ink after leaving the print head and being in a supersaturated state.

[0037] Preferably, the distance between the print head and the molding platform is 15-100 μm, so as to ensure that the extruded ink can directly contact the molding platform.

[0038] Preferably, the wavelength of the light source used for photo-crosslinking is 380-500 nm. More preferably, the wavelength of the light source used for photo-crosslinking is 405 nm.

[0039] Preferably, the printed hydrogel scaffold is subjected to a first light crosslinking, and then the printed hydrogel scaffold is flipped 180° and subjected to a second light crosslinking; wherein the illumination time of the first light crosslinking and the second light crosslinking is independently 3 to 10 minutes. As a further preference, the illumination time of the first light crosslinking and the second light crosslinking is 5 minutes.

[0040] Preferably, the crystal nucleus is sodium acetate trihydrate powder.

[0041] As a preferred method, a glass plate is used as a forming platform of a 3D printer. The forming platform is used to receive the ink after printing.

[0042] As a preferred method, the specific operation of laying a layer of crystal cores on the 3D printer molding platform is as follows:

[0043] Soak the molding platform in an aqueous solution of sodium acetate trihydrate, take it out, and allow it to dry naturally until there is no liquid on the surface of the molding platform.

[0044] More preferably, in the aqueous solution of sodium acetate trihydrate, the mass ratio of sodium acetate trihydrate to water is (1 to 1.5):1. More preferably, it is 1.3:1.

[0045] Preferably, the 3D printer is an extrusion 3D printer, including a pneumatic extrusion 3D printer and a mechanical extrusion 3D printer, and more preferably a mechanical extrusion 3D printer.

[0046] In the above step (4),

[0047] Preferably, the specific steps of washing the cured hydrogel scaffold with deionized water to remove salt crystals are:

[0048] Soak the solidified hydrogel scaffold in deionized water for 60 minutes and take it out; repeat this process 3 times.

[0049] The method for preparing a salt crystallization-assisted extrusion-type high-precision 3D printing hydrogel of the present invention is to prepare a 3D printing ink by mixing a salt solution with a hydrogel solution. A layer of crystal nuclei is laid on the molding platform of the extrusion-type 3D printer, and printing is performed using the 3D printer; during the extrusion printing process, the temperature of the printing ink gradually decreases after leaving the nozzle, and crystallization is induced after contacting the crystal nucleus seeds on the molding platform; the printing ink is rapidly solidified through a crystal phase change, thereby effectively maintaining the stability of the printed structure; subsequent layers are stacked, and crystals grow upward from the previous layer, so that crystallization can be continuous. Finally, the salt is removed through photocrosslinking and deionized water washing steps to prepare a hydrogel with high precision, high porosity and good biocompatibility.

[0050] The preparation method of the present invention overcomes the problems of low printing accuracy and easy structural collapse in the existing hydrogel printing technology, significantly improves the structural retention ability and accuracy of hydrogel printing, and contributes to the development of tissue engineering and regenerative medicine.

[0051] Compared with the prior art, the present invention has the following beneficial effects:

[0052] (1) The salt crystallization-assisted extrusion high-precision 3D printed hydrogel preparation method of the present invention is a supplement to the existing 3D printed hydrogel preparation method, which expands the existing 3D printed hydrogel manufacturing method, and the prepared hydrogel has the characteristics of high precision, high porosity and good biocompatibility.

[0053] (2) The salt crystallization-assisted extrusion high-precision 3D printing hydrogel preparation method of the present invention can utilize salt crystallization to maintain the stability of the printed structure at room temperature, overcoming the problems of low printing accuracy and easy structural collapse in the existing hydrogel printing technology. There is no sample size limitation, especially in the Z-axis direction, and large-sized samples can be prepared.

[0054] (3) The salt crystallization-assisted extrusion high-precision 3D printing hydrogel preparation method of the present invention can prepare porous hydrogel through crystallization therein.

[0055] (4) In the method for preparing the salt crystallization-assisted extrusion-type high-precision 3D printing hydrogel of the present invention, the salt used can be completely removed by washing with deionized water without any residue, and the obtained hydrogel has high biocompatibility. BRIEF DESCRIPTION OF THE DRAWINGS

[0056] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the drawings required for use in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

[0057] Figure 1 Schematic diagram of the extrusion structure, printing and crystallization process of the 3D printer used in Example 1;

[0058] Figure 2 This is an optical photograph of the hydrogel scaffold after cross-linking and curing in Example 1;

[0059] Figure 3 This is an optical photograph of the hydrogel prepared in Example 1 after being immersed in deionized water;

[0060] Figure 4 This is a micrograph of the high-precision hydrogel prepared in Example 1 after curing and washing. DETAILED DESCRIPTION

[0061] In order to make the purpose, technical scheme and advantages of the present invention clearer, the technical scheme of the present invention will be clearly and completely described below in combination with the embodiments and the drawings of the specification. Obviously, the described embodiments are part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in the field without making creative work are within the scope of protection of this application.

[0062] Embodiment 1:

[0063] like Figure 1As shown, a method for preparing a salt crystallization-assisted extrusion high-precision 3D printing hydrogel comprises the following steps:

[0064] (1) First, prepare a hydrogel solution: use an electronic balance to weigh 5.4 g of acrylamide, 0.1 g of N,N'-methylenebispropionamide, 0.05 g of phenyl (2,4,6-trimethylbenzoyl) lithium phosphate and 0.1 g of polyacrylamide (molecular weight 7 million), respectively, put them into 6 mL of deionized water, and mix them by magnetic stirring to form a clear and transparent hydrogel solution; the hydrogel solution is subjected to a light-shielding treatment, and the purpose of the light-shielding treatment is to prevent external light from interfering with the solution.

[0065] (2) Prepare a salt solution: Use an electronic balance to weigh 24 g of anhydrous sodium acetate, add it to 20 mL of pure water, and mix it. Heat it in a water bath for one hour to completely dissolve it into a clear and transparent solution to obtain a salt solution.

[0066] (3) The hydrogel solution and the salt solution are uniformly mixed to obtain 3D printing ink, and a light-shielding treatment is performed to prevent external light from interfering with the solution.

[0067] (4) Load the printing ink into the barrel of a mechanical extrusion 3D printer, set the barrel temperature and nozzle temperature to 60°C, set the printing speed to 3000 mm / min, the distance between the nozzle and the molding platform to 15 μm, the extrusion flow rate to 0.01 mL / min, and the nozzle diameter to 100 μm;

[0068] A layer of crystal nuclei is laid on the 3D printer forming platform (glass plate). The specific method is: soak the glass plate in a sodium acetate trihydrate aqueous solution (wherein the mass ratio of sodium acetate trihydrate to water is 1.3:1), take out the glass plate and dry it naturally. When it is dried until there is no liquid on the surface of the glass, a forming platform with sodium acetate trihydrate crystal nuclei on the surface is obtained.

[0069] The printing model was set up. The printed model was generated by the printing software of Suzhou Yongqinquan Intelligent Equipment Co., Ltd. The generated parameters were: XY plane size 2cm*2cm, line spacing 2mm, layer height 30μm, and 500 layers of tic-tac-toe grid, and then 3D printing was performed at room temperature.

[0070] (5) After 3D printing, the printed model was photocrosslinked for 5 min using a 405 nm wavelength light source. Then, the printed model was flipped 180° and photocrosslinked for another 5 min to obtain a cured hydrogel scaffold. The optical photograph is shown in FIG. Figure 2 As shown by Figure 2 It can be seen that the hydrogel scaffold has high precision and structural integrity.

[0071] (6) Finally, the cured hydrogel scaffold was immersed in deionized water for 60 min and then taken out; this process was repeated three times to remove the residual salt in the scaffold, and finally a high-precision hydrogel with high biocompatibility was obtained.

[0072] Optical photograph of the hydrogel scaffold (high-precision hydrogel) after washing with deionized water Figure 3 As shown by Figure 3 It can be seen that after washing and removing the salt, the scaffold changes from white to translucent and the structure remains intact.

[0073] The cleaned hydrogel scaffold (high-precision hydrogel) was observed under a microscope. Figure 4 shown by Figure 4 It can be seen that the porous structure and layer patterns in this high-precision hydrogel are clearly visible.

[0074] Embodiment 2:

[0075] (1) Preparation of hydrogel solution: 0.6 g of methacryloyl gelatin freeze-dried sample, 0.05 g of phenyl (2,4,6-trimethylbenzoyl) lithium phosphate powder and 0.1 g of polyacrylamide were weighed by an electronic balance and placed in 2 mL of deionized water, and mixed, and mixed by magnetic stirring to form a clear and transparent hydrogel solution. The hydrogel solution was shielded from light to prevent external light from interfering with the solution.

[0076] (2) Preparation of salt solution: 5 g of anhydrous sodium acetate and 2 g of carbonamide were weighed using an electronic balance, and the mixture was placed in 4 mL of pure water and heated in a water bath for one hour to completely dissolve the mixture into a clear and transparent solution, thereby obtaining a salt solution.

[0077] (3) Using steps (3)-(6) in Example 1, a methacrylylated gelatin hydrogel scaffold with high biocompatibility is obtained.

[0078] Embodiment 3:

[0079] (1) Using steps (1)-(3) in Example 1, 3D printing ink is obtained.

[0080] (2) Load the printing ink into the barrel of a mechanical extrusion 3D printer, set the barrel temperature and nozzle temperature to 60°C, set the printing speed to 1000 mm / min, the distance between the nozzle and the molding platform to 100 μm, the extrusion flow rate to 0.05 mL / min, and the nozzle diameter to 350 μm;

[0081] A layer of crystal nuclei is laid on the forming platform (glass plate) of the 3D printer. The specific method is: soak the glass plate in a sodium acetate trihydrate aqueous solution (wherein the mass ratio of sodium acetate trihydrate to water is 1.3:1), take out the glass plate and dry it naturally. When it is dried until there is no liquid on the surface of the glass, a forming platform with sodium acetate trihydrate crystal nuclei on the surface is obtained.

[0082] The printing model was set up. The printed model was generated by the printing software of Suzhou Yongqinquan Intelligent Equipment Co., Ltd. The generated parameters were: XY plane size 2cm*2cm, line spacing 2mm, layer height 50μm, and 500 layers of tic-tac-toe grid. Then 3D printing was performed at room temperature.

[0083] (3) Using steps (5)-(6) in Example 1, a high-precision hydrogel with high biocompatibility is finally obtained.

[0084] It should be noted that, in this application, relational terms such as "first" and "second" are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Moreover, the terms "include", "comprise" or any other variants thereof are intended to cover non-exclusive inclusion, so that a process, method, article or device including a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, article or device. In the absence of further restrictions, the elements defined by the sentence "comprise a ..." do not exclude the presence of other identical elements in the process, method, article or device including the elements.

[0085] The above description is only a specific implementation of the present application, so that those skilled in the art can understand or implement the present application. Various modifications to these embodiments will be apparent to those skilled in the art, and the general principles defined herein can be implemented in other embodiments without departing from the spirit or scope of the present application. Therefore, the present application will not be limited to the embodiments shown herein, but will conform to the widest range consistent with the principles and novel features applied for herein.

Claims

1. A method for preparing a salt crystallization-assisted extrusion-type high-precision 3D printing hydrogel, characterized in that: The following steps are involved: (1) uniformly mixing a hydrogel monomer, a photoinitiator, a thickener and water to prepare a hydrogel solution; dissolving salt in water to prepare a salt solution; (2) mixing the hydrogel solution and the salt solution to prepare a printing ink; (3) placing a layer of crystal cores on the molding platform of the 3D printer, using printing ink as raw material, and printing a preset hydrogel scaffold using an extrusion 3D printer; (4) The printed hydrogel scaffold is cross-linked by light, and then the cured hydrogel scaffold is cleaned with deionized water to remove salt crystals, thereby obtaining the extruded high-precision 3D printed hydrogel.

2. The method for preparing a salt crystallization-assisted extrusion-type high-precision 3D printing hydrogel according to claim 1, characterized in that: The hydrogel monomer is one or more of acrylamide, acrylic acid, methacrylylated gelatin, methacrylylated hyaluronic acid, methacrylylated chitosan, and methacrylylated silk fibroin; In the hydrogel solution, the mass ratio of hydrogel monomer to water is (0.1-1.4):

1.

3. The method for preparing a salt crystallization-assisted extrusion-type high-precision 3D printing hydrogel according to claim 2, characterized in that: When the hydrogel monomer is one or both of acrylamide and acrylic acid, a crosslinking agent is simultaneously added to the hydrogel solution; Wherein, the cross-linking agent is N,N'-methylenebispropionamide.

4. The method for preparing a salt crystallization-assisted extrusion-type high-precision 3D printing hydrogel according to claim 1, characterized in that: The salt is sodium acetate or a mixture of sodium acetate and carbamide; When the salt is sodium acetate, the mass ratio of sodium acetate to water in the salt solution is (0.2-1.7):1; When the salt is a mixture of sodium acetate and carbon amide, in the salt solution, the mass ratio of sodium acetate to water is (0.2-1.7):1; the mass ratio of carbon amide to water is (0.2-0.8):

1.

5. The method for preparing a salt crystallization-assisted extrusion-type high-precision 3D printing hydrogel according to claim 1, characterized in that: The thickener is one or more of polyacrylamide, polyacrylic acid, polyethylene glycol, gelatin, cellulose or its derivatives, starch or its derivatives, fumed silica, and carbomer; In the hydrogel solution, the mass ratio of the thickener to water is 0.005:1 to 1:

5.

6. The method for preparing a salt crystallization-assisted extrusion-type high-precision 3D printing hydrogel according to claim 1, characterized in that: In the printing ink, the volume ratio of the hydrogel solution to the salt solution is 1:17 to 10:

1.

7. The method for preparing a salt crystallization-assisted extrusion-type high-precision 3D printing hydrogel according to claim 1, characterized in that: In step (3), the 3D printing parameters are: barrel temperature is 50-80°C, nozzle temperature is 40-80°C, printing speed is 75-4000 mm / min, extrusion flow rate is 0.01-0.5 mL / min; nozzle diameter is 80-1000 μm.

8. The method for preparing a salt crystallization-assisted extrusion-type high-precision 3D printing hydrogel according to claim 1, characterized in that: The wavelength of the light source used for photo-crosslinking is 380-500nm.

9. The method for preparing a salt crystallization-assisted extrusion-type high-precision 3D printing hydrogel according to claim 1, characterized in that: The crystal nucleus is sodium acetate trihydrate powder.

10. The method for preparing a salt crystallization-assisted extrusion-type high-precision 3D printing hydrogel according to claim 1, characterized in that: The specific steps of washing the cured hydrogel scaffold with deionized water to remove salt crystals are as follows: Soak the solidified hydrogel scaffold in deionized water for 60 minutes and take it out; repeat this process 3 times.

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