CN116925396A

CN116925396A - Silk protein-based ink and application thereof in 3D printing preparation of tissue engineering scaffold

Info

Publication number: CN116925396A
Application number: CN202310884684.5A
Authority: CN
Inventors: 郭成辰; 郑自立
Original assignee: Westlake University
Current assignee: Westlake University
Priority date: 2023-07-19
Filing date: 2023-07-19
Publication date: 2023-10-24

Abstract

The invention belongs to the technical field of 3D printing materials, and relates to silk fibroin-based ink and application thereof in preparing a tissue engineering scaffold by 3D printing. Adding a small molecular plasticizer and a mechanical property regulator into the silk protein aqueous solution; and regulating the concentration of the silk fibroin solution to obtain the silk fibroin-based ink. Taking the silk fibroin-based ink as a raw material, and performing 3D printing on a freezing platform by using an extrusion type 3D printer to obtain a three-dimensional bracket; and freezing the obtained three-dimensional scaffold at low temperature to self-assemble the silk protein so as to obtain the tissue engineering scaffold. Compared with the prior art, the method for preparing the tissue engineering scaffold ensures solidification and qualitative property of the tissue engineering scaffold by utilizing the way of self-assembling and generating beta-sheet by silk fibroin, does not need to add chemical cross-linking agents or other thickening agents, and ensures the biocompatibility of the scaffold. The mechanical properties of the silk protein three-dimensional scaffold can be accurately regulated and controlled by regulating and controlling the contents of the plasticizer and the mechanical property regulator in the ink, and the mechanical requirements of different tissue engineering scaffolds can be met.

Description

Silk protein-based ink and application thereof in 3D printing preparation of tissue engineering scaffold

Technical Field

The invention belongs to the technical field of 3D printing materials, and particularly relates to silk fibroin-based ink and application thereof in preparing a tissue engineering scaffold by 3D printing.

Background

In recent years, three-dimensional additive manufacturing (also called 3D printing) technology has been rapidly developed, and has become one of important means for manufacturing materials with complex three-dimensional structures. Bionic biological materials with complex structures can be constructed by utilizing a 3D printing technology so as to be applied to the biomedical field, such as artificial blood vessels, stents, organ chips and the like. And by regulating and controlling printing ink and printing parameters, the precise control of the material structure and performance can be realized. In the field of tissue engineering scaffolds, tissue engineering scaffolds for different clinical applications can be prepared by 3D printing. The 3D printing materials commonly used at present comprise gelatin, alginic acid, hyaluronic acid, collagen, polylactic acid and the like, however, the materials have certain defects, such as poor bioactivity of the gelatin, easy degradation, severe collagen printing conditions, low mechanical strength and acidic degradation of the polylactic acid. The ideal 3D printing material not only meets the requirements of biocompatibility, bioactivity, mechanical strength matched with target tissues and the like required by the tissue engineering scaffold, but also has excellent printability.

The silk protein is a structural protein extracted from natural silk, has excellent biocompatibility and biodegradability, and degradation products of the silk protein are harmless to human bodies and can be easily metabolized. The aqueous phase regenerated silk fibroin solution has the property of shear thinning, namely the behavior that the viscosity of the aqueous phase regenerated silk fibroin solution is reduced along with the increase of shear stress, and the driving force required for printing can be reduced, so that the printing precision is improved. And meanwhile, the bracket obtained by 3D printing is subjected to aftertreatment, and the silk fibroin secondary structure can be regulated and controlled, so that the mechanical property and degradation time of the bracket are accurately regulated and controlled, and the time and space requirements of different tissue repair processes can be matched.

Current silk fibroin-based inks often require blending with other thickeners to improve their printability, or modification of the silk fibroin molecular chains to shape them by chemical cross-linking.

For example, chinese patent CN116118177a discloses a 3D printed hydrogel scaffold for high molecular weight regenerated silk proteins and a method for preparing the same. Blending and heating three components of high molecular weight regenerated silk protein (HMWRSF) solution, hydroxypropyl methylcellulose (HPMC) solution and Urea (Urea) to obtain thixotropic hydrogel, wherein the thixotropic hydrogel can be directly used for 3D printing; and (3) curing the 3D-printed HMWRSF/HPMC/Urea hydrogel by ethanol and replacing the solvent by deionized water to obtain the 3D-printed HMWRSF/HPMC hydrogel bracket. This patent is a HMWRSF/HPMC blend system.

Chinese patent CN109666302a discloses a preparation method of 3D printing silk protein hydrogel, comprising the following steps: preparing pre-crosslinked silk protein hydrogel and 3D printing silk protein hydrogel, adding double bond modified cyclodextrin and photoinitiator into silk protein solution, stirring to obtain single network crosslinked silk protein hydrogel, forming pre-crosslinked silk protein hydrogel by ultraviolet irradiation, and crosslinking cyclodextrin in fiber silk and tyramine on molecular chains of silk protein again by a 3D printing mode, and stacking layer by layer to form the 3D printing silk protein hydrogel, and simultaneously providing the 3D printing silk protein hydrogel. The patent utilizes the interaction of main object between cyclodextrin and tyramine radical on silk protein molecular chain to construct the three-dimensional network structure of hydrogel.

However, these approaches on the one hand reduce the mechanical strength of the silk proteins and on the other hand chemical crosslinking is detrimental to the encapsulation of bioactive substances or cells. There is therefore a need to develop a new silk fibroin-based ink for use in preparing tissue engineering scaffolds that does not require the addition of thickeners and that is not chemically cross-linked.

Disclosure of Invention

Based on the current situation that a thickener and non-chemically crosslinked silk protein-based 3D printing ink are not needed in the prior art, the invention provides silk protein-based ink and application of the silk protein-based ink in preparing a tissue engineering scaffold by 3D printing.

The invention firstly provides novel silk protein-based ink, wherein a small molecular plasticizer and a mechanical property regulating agent are added to endow the silk protein-based ink with excellent printability and excellent mechanical property of a 3D printing tissue engineering scaffold.

The silk protein-based ink can be subjected to sol-gel transformation by utilizing the freezing platform so as to keep the shape of the silk protein-based ink, and the small molecular plasticizer can be combined with hydroxyl groups in silk protein molecular chains through hydrogen bond interaction, so that the interaction force among the silk protein molecular chains is weakened, the movement capacity of the silk protein molecular chains is improved, and the silk protein-based scaffold can be subjected to conformational transformation at low temperature so as to generate beta-folding, so that the shape of the scaffold is stable. The mechanical property and biodegradability of the scaffold are related to the beta-sheet content and crystallinity of the silk protein, and the higher the crystallinity of the beta-sheet is, the better the mechanical property of the scaffold is, and the longer the degradation time is, so the mechanical property and biodegradability of the silk protein-based scaffold can be regulated and controlled by adding the mechanical property regulator, thereby expanding the application of the silk protein-based scaffold in the field of tissue engineering.

Based on the silk fibroin-based ink provided by the invention, the silk fibroin-based tissue engineering scaffold can be prepared through 3D printing, a thickening agent (generally a substance for improving the viscosity of the printing ink, for example, hydroxypropyl cellulose in China patent CN116118177A or cyclodextrin in China patent CN109666302A is a polymer with larger molecular weight) or chemical crosslinking is not needed for preparing the silk fibroin-based tissue engineering scaffold, excellent mechanical property and biocompatibility of the silk fibroin can be maintained, and meanwhile, possibility is provided for loading bioactive substances, medicines and cells.

It is an object of the present invention to provide a silk fibroin-based ink for 3D printing.

Another object of the invention is to provide a tissue engineering scaffold based on 3D printing of silk-fibroin-based inks.

It is a further object of the present invention to provide the use of a tissue engineering scaffold based on 3D printing of silk-fibroin-based inks.

The aim of the invention can be achieved by the following technical scheme:

the invention firstly provides a preparation method of silk fibroin-based ink, which comprises the following steps:

(1) Adding a small molecular plasticizer and a mechanical property regulator into the silk protein aqueous solution; and

(2) Regulating the concentration of the silk fibroin solution to obtain silk fibroin-based ink;

wherein the small molecule plasticizer is polyalcohol, and the mechanical property regulator is selected from inorganic compounds which are metal ions.

In one embodiment of the present invention, the small molecule plasticizer is selected from one or a combination of several of ethylene glycol, propylene glycol, glycerin, sorbitol, erythritol.

In one embodiment of the present invention, the mechanical property controlling agent is selected from one or a combination of several of calcium chloride, hydroxyapatite, lithium chloride or lithium bromide.

The selected micromolecular plasticizer is the polyalcohol, hydroxyl in the structure of the micromolecular plasticizer can be combined with hydroxyl on a silk protein molecular chain through hydrogen bond interaction, so that intermolecular interaction force of the silk protein molecular chain is weakened, and the movement capacity of the silk protein molecular chain is improved, and the action of plasticization is achieved. The small molecular plasticizer is different from the thickener used for improving the viscosity of the viscosity printing ink in the prior art.

The selected mechanical property regulating agent respectively contains metal ions such as calcium ions, lithium ions and the like, and the ions can be chelated with a silk protein molecular chain so as to break a hydrogen bond network among silk protein molecules, thereby regulating the mechanical property of the silk protein scaffold.

In some embodiments of the invention, the silk protein of step (1) is prepared by:

(a) The method comprises the following steps Adding silkworm cocoons into aqueous solution of sodium carbonate, heating and boiling for 30-120 minutes, removing sericin, rinsing with water for multiple times to remove sodium carbonate, and drying at room temperature to obtain degummed silk;

(b) The method comprises the following steps Adding degummed silk into aqueous solution of lithium bromide, heating, dissolving silk, and dialyzing to obtain silk protein.

In some embodiments of the invention, in step (1), the mass ratio of silk protein in the aqueous silk protein solution to the small molecule plasticizer is from 100:0.1 to 100:50, preferably from 100:1 to 100:30.

In some embodiments of the invention, in step (1), the mass ratio of silk protein in the silk protein aqueous solution to the mechanical property modulator is from 100:1 to 100:10, preferably from 100:2 to 100:5.

In some embodiments of the invention, in step (2), a bioactive substance, drug or cell may be added to the silk fibroin solution.

In some embodiments of the invention, in step (2), a bioactive substance, such as HRP, BSA, BMP-2, bfgf, acellular matrix, or the like, is added to the silk protein solution.

In some embodiments of the invention, in step (2), suspension cells are added to the silk protein solution prior to adjusting the concentration of the silk protein solution.

In some embodiments of the invention, the suspension cells are selected from stem cells, fibroblasts, osteoblasts, and the like.

In some embodiments of the invention, in step (2), the method of adjusting the concentration of the silk fibroin solution is: the dilution is obtained by adding water.

In some embodiments of the invention, in step (2), the method of adjusting the concentration of the silk fibroin solution is: and (5) naturally air-drying to obtain concentrated solution.

In some embodiments of the invention, in step (2), the method of adjusting the concentration of the silk fibroin solution is: the concentrate was obtained by reverse dialysis.

In some embodiments of the invention, in step (2), the method of adjusting the concentration of the silk fibroin solution is: concentrating by vacuum centrifugation to obtain concentrated solution.

The invention further provides the silk fibroin-based ink obtained based on the preparation method.

The invention further provides application of the silk fibroin-based ink, wherein the silk fibroin-based ink is used for 3D printing to obtain a tissue engineering scaffold.

The invention further provides a preparation method of the tissue engineering scaffold, which takes the silk fibroin-based ink as a raw material and obtains the tissue engineering scaffold by a freezing 3D printing method, wherein the method comprises the following steps:

(S1) taking the silk fibroin-based ink as a raw material, and performing 3D printing on a freezing platform by using an extrusion type 3D printer to obtain a three-dimensional bracket;

(S2) carrying out low-temperature freezing or vacuum freeze drying on the three-dimensional scaffold obtained in the step (S1) to enable silk proteins to self-assemble so as to obtain the tissue engineering scaffold.

In some embodiments of the invention, in step (S1), the concentration of silk protein in the silk protein-based ink is from 1wt% to 40wt%.

In some embodiments of the invention, in step (S1), the temperature of the freezing stage used is from 0 ℃ to-25 ℃.

In some embodiments of the present invention, in step (S1), the printing head used in the extrusion type 3D printer is a dispensing head of 18G to 34G.

In some embodiments of the present invention, in step (S2), the conditions under which the low temperature freezing is performed are: at least low temperature freezing is performed for 6 hours at a freezing temperature of 0 ℃ to-25 ℃.

In some embodiments of the present invention, in step (S2), the conditions under which vacuum freeze drying is performed are: the resulting three-dimensional scaffold was transferred to liquid nitrogen, frozen for one hour and then transferred to a vacuum freeze dryer for freeze drying.

The invention further provides the tissue engineering scaffold prepared based on the method.

The invention further provides application of the tissue engineering scaffold prepared based on the method, and the tissue engineering scaffold is used for cell culture and tissue regeneration.

Compared with the prior art, the invention has the beneficial effects that:

(1) The silk protein required by the scheme of the invention is directly extracted from the silkworm cocoons, has wide sources and low price, and has higher economic benefit; the added plasticizer and mechanical property regulator are common chemical raw materials, are low in price, do not have biotoxicity, do not influence the biocompatibility of silk protein, and meet the basic requirements of tissue engineering scaffolds.

(2) The silk fibroin-based ink provided by the invention has the advantages of simple preparation mode, good biocompatibility, low viscosity and good fluidity, can be suitable for different 3D printing modes, such as extrusion type or ink jet type, has strong printability and quick solidification, and can be used for preparing tissue engineering scaffolds with complex structures.

(3) According to the invention, the silk fibroin-based ink is used as a raw material, and 3D printing is performed on a freezing platform by using an extrusion type 3D printer to obtain a three-dimensional bracket; and then freezing the obtained three-dimensional scaffold at low temperature to self-assemble the silk protein so as to obtain the tissue engineering scaffold. The invention adds a small molecular plasticizer into the silk protein-based ink, so that silk protein can self-assemble to generate beta-sheet in the freezing environment, and the scaffold is not dissolved in the freezing environment, thereby maintaining the solidification and the qualitative property of the tissue engineering scaffold.

(4) The invention does not need to add chemical cross-linking agent or other thickening agent (the thickening agent refers to a substance for improving the viscosity of printing ink, such as hydroxypropyl cellulose in Chinese patent CN116118177A or cyclodextrin in Chinese patent CN109666302A is a polymer with larger molecular weight), and the small molecular plasticizer is a small molecular compound, so that the purpose of the invention is to promote the movement of silk fibroin molecular chains instead of improving the viscosity, and ensure the biocompatibility of the bracket. The mechanical properties of the silk protein three-dimensional scaffold can be accurately regulated and controlled by regulating and controlling the contents of the plasticizer and the mechanical property regulator in the ink, and the mechanical requirements of different tissue engineering scaffolds can be met.

(5) The scheme of the invention can add bioactive substances into silk protein solution, and the biological activity of the bioactive substances can be effectively maintained in a low-temperature 3D printing environment and in freeze preservation.

Drawings

FIG. 1 is a photograph of a silk fibroin-based ink prepared in example 1 of the present invention.

FIG. 2 is a photograph of a tissue engineering scaffold obtained by freeze printing of silk fibroin-based ink in example 1 of the present invention.

FIG. 3 is a graph showing rheological properties of silk fibroin-based inks prepared in accordance with examples of the present invention at different temperatures.

FIG. 4 is a photograph of the silk fibroin-based tissue engineering scaffold prepared in example 1 and comparative example of the present invention and a photograph of both soaked in water for 24 hours.

FIG. 5 is a graph showing the mechanical properties of silk fibroin-based tissue engineering scaffolds prepared in examples 1 and 5 of the present invention, A is a tensile strength and elongation at break, and B is a Young's modulus (dry state).

FIG. 6 is a representation of the cytocompatibility of silk fibroin-based tissue engineering scaffolds prepared in examples 1 and 5 of the present invention.

FIG. 7 is a fluorescent chart of cytoskeletal staining of adherent cells on the surface of a silk fibroin-based tissue engineering scaffold prepared in example 5 of the present invention.

FIG. 8 shows the reaction process of the silk fibroin-based tissue engineering scaffold prepared in example 8 of the present invention with TMP.

FIG. 9 is a photograph of silk fibroin-based tissue engineering scaffolds prepared in examples 12 and 13 of the present invention.

Detailed Description

The invention will now be described in detail with reference to the drawings and specific examples.

Example 1

The embodiment provides a preparation method of a silk fibroin-based tissue engineering scaffold, which comprises the following steps:

(1) An aqueous sodium carbonate solution at a concentration of 0.02mol/L was prepared, heated to boiling, and the minced cocoons were added to the boiling aqueous sodium carbonate solution and boiled for 30 minutes to remove sericin. Rinsing the degummed silk in clear water to remove sodium carbonate, and air-drying at room temperature to obtain degummed silk. Preparing a lithium bromide solution with the concentration of 9.3mol/L, adding degummed silk, preserving the temperature at 60 ℃ for 4 hours to fully dissolve the silk, and then dialyzing to obtain a silk protein aqueous solution.

(2) Adding glycerol into silk protein aqueous solution to obtain silk protein: and concentrating the solution with the mass ratio of glycerin of 100:20 by a vacuum concentrator until the mass fraction of silk protein is 30wt%, thereby obtaining silk protein-based ink (silk protein 3D printing ink).

(3) Loading silk fibroin 3D printing ink into a charging basket of a 3D printer, programming a mesh-shaped bracket program in a printing device, and performing 3D printing under the conditions of air pressure of 0.25MPa, printing speed of 10mm/s, layer height of 0.15mm, filling spacing of 0.5mm and freezing platform temperature of-18 ℃ by using a 27G TT dispensing head to prepare the mesh-shaped bracket. The 3D printing bracket is frozen and stored for 24 hours at the temperature of minus 18 ℃, and the bracket is solidified and qualitative in a way that the silk protein self-assembles to form beta-sheet.

The photo of the silk fibroin-based ink prepared in the embodiment 1 is shown in fig. 1, which shows that the silk fibroin-based ink obtained by the invention is clear and transparent and has better uniformity.

A photograph of the tissue engineering scaffold obtained by freeze-printing the silk fibroin-based ink in the embodiment 1 is shown in FIG. 2, which shows that the silk fibroin-based tissue engineering scaffold obtained by the invention can maintain a complete morphology without post-treatment.

Example 2

The difference from example 1 is that:

in step (2), the solution was concentrated to 35wt% by a vacuum concentrator.

The other points are the same as in example 1.

Example 3

The difference from example 1 is that:

in the step (2), glycerol is added into the silk protein aqueous solution to obtain silk protein: a solution with a mass ratio of glycerin of 100:10.

The other points are the same as in example 1.

Example 4

The difference from example 1 is that:

in the step (2), glycerol is added into the silk protein aqueous solution to obtain silk protein: a solution with a mass ratio of glycerin of 100:30.

The other points are the same as in example 1.

Example 5

The difference from example 1 is that:

in the step (2), calcium chloride is added to the aqueous silk protein solution in addition to glycerin to obtain silk protein: glycerol: and the mass ratio of the calcium chloride is 100:20:2.

The other points are the same as in example 1.

Example 6

The difference from example 1 is that:

in the step (2), calcium chloride is added to the aqueous silk protein solution in addition to glycerin to obtain silk protein: glycerol: and the mass ratio of the calcium chloride is 100:20:5.

The other points are the same as in example 1.

Example 7

The difference from example 1 is that:

in the step (2), calcium chloride is added to the aqueous silk protein solution in addition to glycerin to obtain silk protein: glycerol: and the mass ratio of the calcium chloride is 100:20:10.

The other points are the same as in example 1.

Example 8

The difference from example 1 is that:

in step (2), horseradish peroxidase (HRP) was added to the aqueous silk protein solution in addition to glycerol to obtain a solution having an HRP concentration of 10 u/mL.

The other points are the same as in example 1.

Example 9

The difference from example 1 is that:

in step (3), a 25G TT dispensing head is used.

The remainder was identical to example 1.

Example 10

The difference from example 1 is that:

in step (3), 30G TT dispensing heads are used.

The remainder are identical to those of example 1

Example 11

The difference from example 1 is that:

in step (3), a cylindrical support program is written in the printing apparatus.

The remainder was the same as in example 1, to obtain a cylindrical stent.

Example 12

The difference from example 1 is that:

in step (3), a nose shape bracket program is written in the printing apparatus.

The remainder was identical to example 1, resulting in a nasal morphology stent.

Example 13

The difference from example 1 is that:

in step (3), an ear-shaped holder program is written in the printing apparatus.

The remainder was identical to example 1, and an ear morphology scaffold was obtained.

Comparative example 1

For comparison with the silk fibroin-based bio-ink prepared by the present invention, a silk fibroin scaffold without small molecule plasticizers and mechanical property modifiers was prepared as follows:

(2) The quantitative silk protein aqueous solution is taken, and the solution is concentrated to a silk protein mass fraction of 30wt% by a vacuum concentrator.

(3) Loading the solution in the step (2) into a charging basket of a 3D printer, programming a mesh-shaped bracket program in a printing device, and performing 3D printing under the conditions of 0.25MPa of air pressure, 10mm/s of printing speed, 0.15mm of layer height, 0.5mm of filling space and-18 ℃ of a freezing platform by using a 27G TT dispensing head to prepare the mesh-shaped bracket. And (3) freezing and preserving the 3D printing bracket at the temperature of minus 18 ℃ for 24 hours, wherein the silk protein bracket is not added with a small molecular plasticizer and a mechanical property regulator.

Test example 1

The silk fibroin ink prepared in example 1 was characterized for its rheological properties using a rotary rheometer. The silk fibroin ink was placed between the rotary rheometer grips and tested for changes in storage modulus and loss modulus of the silk fibroin ink with temperature. The rheological properties are shown in figure 3.

Test example 2

The water stability of the silk fibroin scaffolds prepared in example 1 and comparative example 1 was tested by soaking in water. The silk fibroin scaffolds prepared in example 1 and comparative example 1 were immersed in 5mL of deionized water for 24 hours, and then observed by photographing. The photograph is shown in fig. 4.

Test example 3

The dry mechanical properties of the silk fibroin scaffolds prepared in examples 1 and 5 were tested by a mechanical testing machine equipped with a 50N load cell. The samples were cut into dumbbell-shaped specimens according to ASTM standards, and then loaded onto the furniture of the machine. For each test, the stretch rate was 100% strain/min for all samples until the stretching ceased after the samples had broken, at least 5 replicates per group of samples. The cross-sectional area of each sample was calculated by multiplying the thickness by the gauge width. Stress and strain are calculated based on the original cross-sectional area and length, respectively. Young's modulus, elongation at break and strength at break are determined from stress-strain curves. The results of the mechanical property characterization are shown in fig. 5.

Test example 4

The cytocompatibility of the silk fibroin scaffolds prepared in example 1 and example 5 was achieved by the use of L929 cellsCo-culture, cell activity at specific time points was tested for characterization. Inoculation of 2X 10 in 24 well plates ⁴ L292 cell of cell/well, after cell wall adhesion, adding sample, each group is equipped with at least 6 multiple holes, hole without sample is used as blank control, at 37deg.C, 5% CO ₂ Incubate under a concentrated atmosphere, and change the solution every 2 days. All samples were autoclaved using an autoclave prior to addition to the well plate. Cell viability was measured using CCK8 kit at 3 days and 5 days of incubation. The results of the cell compatibility are shown in FIG. 6.

Test example 5

Cell adhesion properties of the silk fibroin scaffolds prepared in example 5 cell adhesion was observed by fluorescent staining at specific time points by co-culturing with L929 cells. Samples were added to 24 well plates, each set was equipped with at least 6 multiplex wells, and then inoculated with 2X 10 ⁴ L292 cells of cell/well were incubated at 37℃in an atmosphere of 5% CO2 concentration, and the cells were changed every 2 days. All samples were autoclaved using an autoclave prior to addition to the well plate. And (3) when the incubation is carried out until the 7 th day, the culture solution is discarded, 4% paraformaldehyde solution is added for fixation, the fixation solution is discarded after fixation for 2 hours, 0.1% Triton X-100 is added for permeation, the permeation solution is discarded after permeation for 15 minutes, phalloidin working solution is added, and the cytoskeleton is stained after incubation for two hours. Cells adhering to the stent surface were observed using a laser confocal microscope. The fluorescence staining image of the cytoskeleton is shown in fig. 7.

Test example 6

The functionality of the silk protein scaffolds prepared in example 8 was tested by reaction with 3,3'5,5' -Tetramethylbenzidine (TMB). The silk fibroin scaffold prepared in example 8 was added to 1mL of TMB solution, and the color change of the solution was recorded by photographing. The color change chart of the solution is shown in fig. 8.

Analysis of results:

it can be seen from fig. 3 that the loss modulus of the silk fibroin-based ink is higher than its storage modulus in the temperature range of 25 ℃ to-10 ℃, indicating that the silk fibroin-based ink exhibits liquid fluidity at this time, and that the storage modulus and loss modulus suddenly rise when the temperature reaches-10 ℃ while the storage modulus is higher than the loss modulus, indicating that the silk fibroin-based ink exhibits a solid nature upon sol-gel transition, indicating that the silk fibroin-based ink is capable of rapidly solidifying upon contact with a freezing platform, thereby maintaining a morphology.

As can be seen from fig. 4, the addition of glycerol makes the structure of the silk fibroin scaffold more stable, and can maintain the shape in water, while the pure silk scaffold without plasticizer added is frozen and then quickly thawed by rewarming, and is largely dissolved in water, and cannot maintain the complete shape.

As can be seen from fig. 5, the silk protein scaffold prepared in example 1 has better mechanical properties, and the tensile strength, elongation at break and young modulus of the scaffold are obviously improved after calcium chloride is added, which indicates that the calcium chloride has the effect of adjusting the mechanical properties of the silk protein scaffold.

As can be seen from fig. 6, the silk protein scaffolds prepared in example 1 and example 5 have no significant difference between cell viability and the blank group at the third and fifth days, indicating that the silk protein scaffolds have excellent biocompatibility.

As can be seen from fig. 7, the silk fibroin scaffold prepared in example 5 can support adhesion and growth of cells.

As can be seen from fig. 8, the silk fibroin scaffold prepared in example 8 has the ability to catalyze TMB, which indicates that the silk fibroin-based ink and printing mode developed by the present invention do not affect the function of the active substance.

The previous description of the embodiments is provided to facilitate a person of ordinary skill in the art in order to make and use the present invention. It will be apparent to those skilled in the art that various modifications can be readily made to these embodiments and the generic principles described herein may be applied to other embodiments without the use of the inventive faculty. Therefore, the present invention is not limited to the above-described embodiments, and those skilled in the art, based on the present disclosure, should make improvements and modifications without departing from the scope of the present invention.

Claims

1. A method of preparing a silk fibroin-based ink, the method comprising the steps of:

wherein the micromolecular plasticizer is polyalcohol, and the mechanical property regulator is an inorganic compound containing metal ions.

2. The method for preparing a silk fibroin-based ink according to claim 1, wherein the small molecule plasticizer is selected from one or more of ethylene glycol, propylene glycol, glycerin, sorbitol, erythritol, sorbitol, and erythritol.

3. The method for preparing silk fibroin-based ink according to claim 1, wherein the mechanical property controlling agent is selected from one or a combination of several of calcium chloride, hydroxyapatite, lithium chloride or lithium bromide.

4. The method for preparing a silk fibroin-based ink according to claim 1, wherein the silk fibroin in step (1) is prepared by the steps of:

5. The method of preparing a silk fibroin-based ink according to claim 1, wherein in step (1), the mass ratio of silk proteins in the silk protein aqueous solution to the small molecule plasticizer is 100:0.1 to 100:50, preferably 100:1 to 100:30.

6. The method of preparing a silk fibroin-based ink according to claim 1, wherein in step (1), the mass ratio of silk proteins in the silk protein aqueous solution to the mechanical property controlling agent is 100:1 to 100:10, preferably 100:2 to 100:5.

7. The method of preparing a silk fibroin-based ink according to claim 1, wherein in step (2), a bioactive substance, drug or cell is added to the silk fibroin solution before the concentration of the silk fibroin solution is adjusted.

8. The method for preparing a silk fibroin-based ink according to claim 7, wherein the bioactive substance is selected from one or more of HRP, BSA, BMP-2, bFGF or acellular matrix; the cells are selected from stem cells, fibroblasts or osteoblasts.

9. The method for preparing a silk fibroin-based ink according to claim 1, wherein the method for adjusting the concentration of the silk fibroin solution comprises: the diluted solution is obtained by adding water, or the concentrated solution is obtained by natural air drying, or the concentrated solution is obtained by reverse dialysis, or the concentrated solution is obtained by vacuum centrifugation and concentration.

10. Silk fibroin-based ink obtainable based on the method of any one of claims 1-9.

11. The use of the silk fibroin-based ink of claim 10, wherein the silk fibroin-based ink is used for 3D printing to obtain a tissue engineering scaffold.

12. A method for preparing a tissue engineering scaffold, which is characterized in that the silk fibroin-based ink as claimed in claim 10 is used as a raw material, and the tissue engineering scaffold is obtained by a freezing 3D printing method, and the method comprises the following steps:

13. The method of claim 12, wherein in the step (S1), the concentration of silk protein in the silk protein-based ink is 1wt% to 40wt%.

14. The method according to claim 12, wherein in the step (S1), the freezing stage is used at a temperature of 0 ℃ to-25 ℃.

15. The method according to claim 12, wherein in the step (S1), the printing needle used in the extrusion type 3D printer is a dispensing needle of 18G to 34G.

16. The method of claim 12, wherein in the step (S2), the conditions for performing low-temperature freezing are as follows: at least low temperature freezing is performed for 6 hours at a freezing temperature of 0 ℃ to-25 ℃.

17. The method of claim 12, wherein in the step (S2), the vacuum freeze-drying is performed under the following conditions: the resulting three-dimensional scaffold was transferred to liquid nitrogen, frozen for one hour and then transferred to a vacuum freeze dryer for freeze drying.

18. A tissue engineering scaffold prepared based on the method of any one of claims 12-17.

19. Use of the tissue engineering scaffold of claim 18 for cell culture and tissue regeneration.