Sodium alginate / calcium citrate / amorphous calcium phosphate composite porous bone tissue scaffold material and preparation method thereof

Abstract

The invention discloses a sodium alginate / calcium citrate / amorphous calcium phosphate composite porous bone tissue scaffold material and a preparation method thereof, the scaffold takes sodium alginate as a matrix, and calcium citrate / amorphous calcium phosphate double salt is introduced to enhance the functionality of the scaffold. By adding the double salt, the composite scaffold material keeps an alginate matrix and improves the mechanical strength at the same time; the porous structure provides an ideal environment for proliferation and differentiation of tissue cells, and the repair process of an injured part is accelerated; besides, the stent material has degradability and can be gradually degraded into small molecular substances after being implanted into a human body, and then the small molecular substances are absorbed by human cells or discharged out of the human body through blood circulation, so that complications possibly caused by long-term implantation are reduced; due to the characteristics, the stent material disclosed by the invention has remarkable application potential in the field of bone tissue engineering.

Description

Technical Field

[0001] The present invention relates to the technical field of bone tissue engineering scaffolds, and particularly relates to a composite porous bone tissue scaffold material of sodium alginate / calcium citrate / amorphous calcium phosphate and a preparation method thereof. Background Art

[0002] Damage, diseases, infections and dislocations of bone tissues can significantly affect the quality of life of individuals. Bone defects caused by factors such as trauma, tumors, infections, etc. are the long-term focus in the medical field. Traditional bone repair methods, such as autologous bone transplantation and allogeneic bone transplantation, have many limitations and risks, including limited donor sources, high infection risks, and immune rejection. Therefore, bone tissue engineering is considered one of the most promising bone repair methods in the orthopedic field. In bone tissue engineering, scaffold materials are the basic elements for constructing bone repair structures. An ideal porous scaffold should provide necessary structural support and mechanical properties to promote the repair and regeneration of bone tissues.

[0003] Sodium alginate has advantageous properties such as good biocompatibility, relatively low extraction and processing costs, non-toxicity, and biodegradability, and is widely used in various biomedical fields. However, pure calcium alginate porous scaffold materials cannot meet the actual application requirements of tissue engineering due to their poor mechanical properties and low biological activity. To solve these problems, Liu S et al. developed a bioactive sodium alginate (SA) / nano-hydroxyapatite (HAP) porous gel scaffold in Macromolecular Materials and Engineering (Liu S, Hu Y, Zhang J, et al. Bioactive and biocompatible macroporous scaffolds with tunable performances prepared based on 3D printing of the pre-crosslinked sodium alginate / hydroxyapatite hydrogel ink [J]. Macromolecular Materials and Engineering, 2019, 304(4): 1800698.), which releases Ca under the action of glucono delta-lactone (GDL) 2+Crosslinking was carried out. The research shows that with the increase in the amount of nano-HAP, the mechanical strength of the alginate porous scaffold material has been improved, that is, HAP can improve the mechanical strength of the hydrogel porous scaffold, and its porous scaffold has good bioactivity and biocompatibility. Hydroxyapatite nanoparticles were selected to fabricate the porous scaffold because their chemical composition is similar to that of natural bone, so they have excellent ability to induce bone regeneration and improve the mechanical properties of the porous SA scaffold.

[0004] Calcium citrate is an important organic calcium salt, which has no toxic or side effects on the human body. When it degrades in the body, it releases Ca 2+ The process is very stable, which is conducive to inducing and promoting bone regeneration. Shao C et al. demonstrated in the study of Citrate improves collagen mineralization via interface wetting: a physicochemical understanding of biomineralization control (Shao C, Zhao R, Jiang S, et al. Citrate improves collagen mineralization via interface wetting: a physicochemical understanding of biomineralization control[J]. Advanced materials, 2018, 30(8): 1704876.) that citrate molecules are adsorbed on collagen fibers, which can significantly reduce the interfacial energy between the biological matrix and the amorphous calcium phosphate precursor, enhance its wetting effect in the early stage of biomineralization, thus promoting the in-fiber formation of hydroxyapatite, resulting in an inorganic-organic composite material, which plays an important role in bone formation. Ruiz-Agudo E also mentioned in Citrate stabilizes hydroxylapatite precursors: implications for bone mineralization (Ruiz-Agudo E, Ruiz-Agudo C, Di Lorenzo F, et al. Citrate stabilizes hydroxylapatite precursors: implications for bone mineralization[J]. ACS biomaterials science & engineering, 2021, 7(6): 2346-2357.) that citrate can affect the bone mineralization mode before the formation of any solid phase (amorphous or crystalline). Summary of the Invention

[0005] The object of the present invention is to provide a sodium alginate / calcium citrate / amorphous calcium phosphate composite porous bone tissue scaffold material and its preparation method to solve the above problems. The sodium alginate / calcium citrate / amorphous calcium phosphate composite porous bone tissue scaffold provided by the present invention uses sodium alginate as the matrix material, and sodium citrate combines with amorphous calcium phosphate and uses amorphous calcium phosphate as the functional enhancer, and is prepared by the freeze-drying method. The prepared composite porous scaffold has a good porosity, good biocompatibility, and is conducive to cell proliferation and differentiation. Secondly, the composite material has high compressive strength and elastic modulus, can be degraded in vivo, can promote osteogenesis, and is helpful for fracture repair and bone tissue regeneration.

[0006] The present invention realizes the above object through the following technical solutions:

[0007] A sodium alginate / calcium citrate / amorphous calcium phosphate composite porous bone tissue scaffold material, including sodium alginate, and adding a calcium citrate / amorphous calcium phosphate double salt as a functional enhancer.

[0008] A further scheme is that the mass ratio of sodium alginate to calcium citrate / amorphous calcium phosphate double salt is 1:0.1-1.

[0009] A further scheme is that the preparation method of the calcium citrate / amorphous calcium phosphate double salt includes the following steps:

[0010] Step 1, mix the sodium citrate dihydrate solution and the diammonium hydrogen phosphate solution and add them to a separatory funnel for titration;

[0011] Step 2, place the calcium chloride solution on a magnetic stirrer, open the piston of the separatory funnel, slowly drip the mixed solution in Step 1 into the stirred calcium chloride solution, and then continuously add ammonia water to keep the pH value of the solution around 10, and add anhydrous ethanol;

[0012] Step 3, continue to stir and react for 30-60 min after dripping, wait for 5-7 days to complete precipitation, and continuously remove the supernatant and add deionized water during this period;

[0013] Step 4, centrifuge the suspension, wash the obtained precipitate with anhydrous ethanol and then centrifuge again, and put the obtained precipitate into a vacuum drying oven to dry to obtain the calcium citrate / amorphous calcium phosphate double salt.

[0014] A further scheme is that in Step 1, the concentrations of the sodium citrate dihydrate solution and the diammonium hydrogen phosphate solution are 0.3 mol·L -1 , 500 ml of the sodium citrate dihydrate solution and 500 ml of the diammonium hydrogen phosphate solution.

[0015] In a further embodiment, in step 2, the concentration of the calcium chloride solution is 0.3 mol·L -1 ; 500 ml of the calcium chloride solution and 500 ml of absolute ethanol.

[0016] On the other hand, the present invention also provides a method for preparing a sodium alginate / calcium citrate / amorphous calcium phosphate composite porous bone tissue scaffold material, comprising the following steps:

[0017] Step 1, adding the calcium citrate / amorphous calcium phosphate double salt into deionized water, and continuously stirring with a magnetic stirrer until a milky suspension state is presented;

[0018] Step 2, slowly adding sodium alginate and continuously stirring until the sodium alginate is completely dissolved;

[0019] Step 3, after standing, taking it out and putting it into a beaker, adding a calcium chloride solution with a concentration of 0.3 mol·L-1 to crosslink for 48 - 60 h, and then putting it into a refrigerator for pre-freezing for 12 - 24 h;

[0020] Step 4, putting it into a vacuum freeze dryer for drying and then taking it out to obtain the sodium alginate / calcium citrate / amorphous calcium phosphate composite porous scaffold.

[0021] In a further embodiment, in step 1, the rotation speed of the magnetic stirrer is 1500 - 2000 r·min-1 and the temperature is at room temperature; in step 2, the rotation speed of the magnetic stirrer is 3000 - 4000 r·min-1 and the temperature is at room temperature.

[0022] In a further embodiment, in steps 1 and 2, the mass ratio of the sodium alginate to the calcium citrate / amorphous calcium phosphate double salt is 1:0.1 - 1; 500 ml of the calcium chloride solution.

[0023] In a further embodiment, the vacuum freeze dryer dries for 72 h, the temperature is -50 °C, and the pressure is 200 Pa.

[0024] On the other hand, the present invention also provides the use of the above-mentioned scaffold material or the scaffold material obtained by the above-mentioned preparation method in the field of bone scaffold repair.

[0025] The beneficial effects of the present invention are as follows:

[0026] A composite porous bone tissue scaffold material of sodium alginate / calcium citrate / amorphous calcium phosphate and its preparation method. The scaffold uses sodium alginate as the matrix and introduces a calcium citrate / amorphous calcium phosphate double salt to enhance its functionality. Sodium alginate, as a green and non-toxic matrix material, exhibits good biocompatibility in the human body. The addition of the double salt not only provides the calcium ions required for promoting bone cell regeneration but also endows the scaffold with key properties such as stability, strength, and anti-fracture ability, and enhances cell adhesion, further improving the biocompatibility of the material.

[0027] By adding the calcium citrate / amorphous calcium phosphate double salt, the composite scaffold material of the present invention improves the mechanical strength while maintaining the alginate matrix; its porous structure provides an ideal environment for the proliferation and differentiation of tissue cells, accelerating the repair process of the damaged site; in addition, the scaffold material has degradability and can gradually degrade into small molecule substances after being implanted into the body, and then be absorbed by human cells or excreted from the body through blood circulation, thus reducing the complications that may be caused by long-term implantation; these characteristics make the scaffold material of the present invention have significant application potential in the field of bone tissue engineering. Brief Description of the Drawings

[0028] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the following will briefly introduce the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings in the following description are only some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained based on these drawings.

[0029] Figure 1 SEM photograph of the calcium citrate / amorphous calcium phosphate double salt prepared according to the present invention;

[0030] Figure 2 Compressive strength diagram of the composite porous bone tissue scaffolds of Examples 1-6 of the present invention;

[0031] Figure 3 Elastic modulus diagram of the composite porous bone tissue scaffolds of Examples 1-6 of the present invention;

[0032] Figure 4 SEM photograph of the composite porous bone tissue scaffolds of Examples 1-6 of the present invention;

[0033] Figure 5 Degradation rate of the composite porous bone tissue scaffolds of Examples 1-6 of the present invention. Detailed Description of the Embodiments

[0034] To make the objectives, technical solutions and advantages of the present invention clearer, the technical solutions of the present invention will be described in detail below. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all of them. All other implementation manners obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts belong to the scope protected by the present invention.

[0035] Example 1, blank control group (without adding double salt):

[0036] The alginate / calcium citrate / amorphous calcium phosphate composite porous bone tissue scaffold provided in this example is composed of alginate as the matrix and calcium citrate / amorphous calcium phosphate double salt as the functional enhancer, and the ratio of the two of the alginate / calcium citrate / amorphous calcium phosphate double salt is = 10:0. The specific implementation steps are as follows:

[0037] (1) Slowly add 10 g of alginate to 100 ml of deionized water, and use a magnetic stirrer to stir for about 2 h until the alginate powder is completely dissolved;

[0038] (2) Take out the alginate solution after standing for a period of time and put it into a beaker, and then add 0.3 mol·L -1 Calcium chloride solution for crosslinking for 48 h; the volume of the calcium chloride solution is 500 mL;

[0039] (3) Take out the crosslinked composite and put it into the refrigerator for pre-freezing at -20 °C for 12 h;

[0040] (4) Put the composite into a vacuum freeze dryer and dry it for 72 h (temperature is -50 °C, pressure is 200 Pa), and take it out after completion to obtain the composite porous bone tissue scaffold.

[0041] Use a ceramic density tester to measure the porosity of this example. The porosity of the prepared composite porous bone tissue scaffold in this example is 75.81%; the pore distribution is relatively uniform, the pore shape is relatively regular, and the pore diameter is mainly distributed between 200 - 600 μm; it is a preparation method without adding calcium citrate / amorphous calcium phosphate double salt, and the compressive strength and elastic modulus values are the smallest, indicating that its mechanical strength is very poor.

[0042] Example 2:

[0043] The alginate / calcium citrate / amorphous calcium phosphate composite porous bone tissue scaffold provided in this example is composed of alginate as the matrix and calcium citrate / amorphous calcium phosphate double salt as the functional enhancer, and the ratio of the two of the alginate / calcium citrate / amorphous calcium phosphate double salt is = 9:1. The specific implementation steps are as follows:

[0044] (1) Add 1 g of calcium citrate / amorphous calcium phosphate complex salt to 100 ml of deionized water according to the composite ratio, and continuously stir with a magnetic stirrer (rotation speed is 1500 r·min -1 , at room temperature) until a milky white suspension state is presented;

[0045] (2) Slowly add 9 g of sodium alginate and continuously stir (rotation speed is 3000 r·min-1) until the calcium citrate / amorphous calcium phosphate complex salt and sodium alginate are completely mixed.

[0046] (3) Take out the composite after standing for a period of time and put it into a beaker, then add 0.3 mol·L -1 calcium chloride solution for crosslinking for 48 h;

[0047] The volume of the calcium chloride solution is 500 mL;

[0048] (4) Take out the crosslinked composite and pre-freeze it in a refrigerator at -20 °C for 12 h;

[0049] (5) Put the composite into a vacuum freeze dryer and dry it for 72 h (temperature is -50 °C, pressure is 200 Pa), and take it out after completion to obtain the composite porous bone tissue scaffold.

[0050] Use a ceramic density tester to measure the porosity of this example. The porosity of the prepared composite porous bone tissue scaffold in this example is 70.15%; the pore distribution is relatively uniform, the pore regularity slightly decreases, the pore diameter is mainly distributed between 400 - 600 μm, and the pore diameter slightly increases.

[0051] Example 3:

[0052] The sodium alginate / calcium citrate / amorphous calcium phosphate composite porous bone tissue scaffold provided by this example is composed of sodium alginate as the matrix and calcium citrate / amorphous calcium phosphate complex salt as the functional enhancer, and the ratio of the two of the sodium alginate / calcium citrate / amorphous calcium phosphate complex salt is = 8:2. The specific implementation steps are as follows:

[0053] (1) Add 2 g of calcium citrate / amorphous calcium phosphate complex salt to 100 ml of deionized water according to the composite ratio, and continuously stir with a magnetic stirrer (rotation speed is 1500 r·min -1 , at room temperature) until a milky white suspension state is presented;

[0054] (2) Slowly add 8 g of sodium alginate and continuously stir (rotation speed is 3000 r·min-1) until the calcium citrate / amorphous calcium phosphate complex salt and sodium alginate are completely mixed.

[0055] (3) Take out the composite after standing for a period of time and put it into a beaker, then add 0.3 mol·L -1Calcium chloride solution cross-linking for 48h;

[0056] The volume of calcium chloride solution is 500mL;

[0057] (4) taking out the cross-linked composite and pre-freezing it in a refrigerator at -20°C for 12 h;

[0058] (5) The composite was placed in a vacuum freeze dryer and dried for 72 h (temperature: -50°C, pressure: 200 Pa). After drying, the composite porous bone tissue scaffold was obtained by taking it out.

[0059] The porosity of this example was measured using a ceramic density tester. The porosity of the composite porous bone tissue scaffold prepared in this example was 55.53%, and the porosity decreased significantly; the pore distribution began to become uneven, the pore regularity decreased significantly, and the pore size was mainly distributed between 200-800 μm.

[0060] Embodiment 4:

[0061] The sodium alginate / calcium citrate / amorphous calcium phosphate composite porous bone tissue scaffold provided in this embodiment is composed of sodium alginate as a matrix and calcium citrate / amorphous calcium phosphate complex salt as a functional enhancement body, and the ratio of sodium alginate / calcium citrate / amorphous calcium phosphate complex salt is 7:3. The specific implementation steps are as follows:

[0062] (1) Add 3 g of calcium citrate / amorphous calcium phosphate complex salt to 100 ml of deionized water according to the composite ratio and stir with a magnetic stirrer (speed 1500 r / min) -1 , the temperature is room temperature) and stirred continuously until a milky white suspension appears;

[0063] (2) Slowly add 7 g of sodium alginate and continue stirring (at a speed of 3000 r·min-1) until the calcium citrate / amorphous calcium phosphate double salt and the sodium alginate are completely mixed.

[0064] (3) After standing for a period of time, the complex was taken out and placed in a beaker, and then 0.3 mol·L -1 Calcium chloride solution cross-linking for 48h;

[0065] The volume of calcium chloride solution is 500mL;

[0066] (4) taking out the cross-linked composite and pre-freezing it in a refrigerator at -20°C for 12 h;

[0067] (5) The composite was placed in a vacuum freeze dryer and dried for 72 h (temperature: -50°C, pressure: 200 Pa). After drying, the composite porous bone tissue scaffold was obtained by taking it out.

[0068] The porosity of this example was measured using a ceramic density tester. The porosity of the composite porous bone tissue scaffold prepared in this example was 48.09%. The pore distribution was uneven, and the pore sizes varied. The pore sizes were mainly distributed between 200-600 μm, and macropores larger than 1000 μm appeared.

[0069] Embodiment 5:

[0070] The sodium alginate / calcium citrate / amorphous calcium phosphate composite porous bone tissue scaffold provided in this embodiment is composed of sodium alginate as a matrix and calcium citrate / amorphous calcium phosphate complex salt as a functional enhancement body, and the ratio of sodium alginate / calcium citrate / amorphous calcium phosphate complex salt is 6:4. The specific implementation steps are as follows:

[0071] (1) Add 4 g of calcium citrate / amorphous calcium phosphate complex salt to 100 ml of deionized water according to the composite ratio and stir with a magnetic stirrer (speed 1500 r / min) -1 , the temperature is room temperature) and stirred continuously until a milky white suspension appears;

[0072] (2) Slowly add 6 g of sodium alginate and continue stirring (rotation speed of 3000 r·min-1) until the calcium citrate / amorphous calcium phosphate double salt and sodium alginate are completely mixed.

[0073] (3) After standing for a period of time, the complex was taken out and placed in a beaker, and then 0.3 mol·L -1 Calcium chloride solution cross-linking for 48h;

[0074] The volume of calcium chloride solution is 500mL;

[0075] (4) taking out the cross-linked composite and pre-freezing it in a refrigerator at -20°C for 12 h;

[0076] (5) The composite was placed in a vacuum freeze dryer and dried for 72 h (temperature: -50°C, pressure: 200 Pa). After drying, the composite porous bone tissue scaffold was obtained by taking it out.

[0077] The porosity of this example was measured using a ceramic density tester. The porosity of the composite porous bone tissue scaffold prepared in this example was 44.06%. The pore distribution was uneven, the pore structure was irregular, the number of through holes was significantly reduced, and the pore diameter was mainly distributed between 200-600 μm.

[0078] Embodiment 6:

[0079] The sodium alginate / calcium citrate / amorphous calcium phosphate composite porous bone tissue scaffold provided in this embodiment is composed of sodium alginate as a matrix and calcium citrate / amorphous calcium phosphate complex salt as a functional enhancement body, and the ratio of sodium alginate / calcium citrate / amorphous calcium phosphate complex salt is 5:5. The specific implementation steps are as follows:

[0080] (1) Add 5 g of calcium citrate / amorphous calcium phosphate complex salt to 100 ml of deionized water according to the composite ratio and stir with a magnetic stirrer (speed 1500 r / min) -1 , the temperature is room temperature) and stirred continuously until a milky white suspension appears;

[0081] (2) Slowly add 5 g of sodium alginate and continue stirring (rotation speed of 3000 r·min-1) until the calcium citrate / amorphous calcium phosphate double salt and the sodium alginate are completely mixed.

[0082] (3) After standing for a period of time, the complex was taken out and placed in a beaker, and then 0.3 mol·L -1 Calcium chloride solution cross-linking for 48h;

[0083] The volume of calcium chloride solution is 500mL;

[0084] (4) taking out the cross-linked composite and pre-freezing it in a refrigerator at -20°C for 12 h;

[0085] (5) The composite was placed in a vacuum freeze dryer and dried for 72 h (temperature: -50°C, pressure: 200 Pa). After drying, the composite porous bone tissue scaffold was obtained by taking it out.

[0086] Embodiment 7:

[0087] The preparation method of calcium citrate / amorphous calcium phosphate complex salt provided in this embodiment is specifically implemented as follows (the concentration of the salt solution used is 0.3 mol·L -1 ):

[0088] (1) Step 1, 250 ml of sodium citrate dihydrate solution and 250 ml of diammonium hydrogen phosphate solution were mixed and added to a separatory funnel for titration;

[0089] (2) Step 2, place 250 ml of calcium chloride solution on a magnetic stirrer, open the piston of the separatory funnel, slowly drip the mixed solution in step 1 into the stirred calcium chloride solution, then continuously drip ammonia water to keep the pH value of the solution at about 10, and add 250 ml of anhydrous ethanol;

[0090] (3) Step 3, after the addition is complete, continue to stir the reaction for 30-60 minutes, wait for 5-7 days for complete precipitation, during which time the supernatant is continuously removed and deionized water is added;

[0091] (4) Step 4, centrifuging the suspension, washing the obtained precipitate with anhydrous ethanol and centrifuging again, and drying the obtained precipitate in a vacuum drying oven to obtain calcium citrate / amorphous calcium phosphate double salt.

[0092] Figure 1 From the scanning electron micrograph of the calcium citrate / amorphous calcium phosphate complex salt shown, it can be seen that its appearance is like fish roe, the particles are in close contact, and are prone to agglomeration, causing them to overlap with each other. This indicates that the prepared calcium citrate / amorphous calcium phosphate complex salt is suitable for the preparation of porous scaffolds, which is beneficial to promoting the proliferation and differentiation of bone cells and accelerating the regeneration of bone tissue. The porosity of this example was measured using a ceramic density tester. The porosity of the prepared composite porous bone tissue scaffold in this example was 40.65%, and the porosity decreased with the increase of the content of calcium citrate / amorphous calcium phosphate complex salt. The porosity in Example 6 was the lowest, and the pore distribution was uneven, the pore sizes were different, the number of through holes was significantly reduced, and the number of closed holes increased. This may be because the amount of calcium citrate / amorphous calcium phosphate complex salt added increased, Ca 2+ The increase in the content of calcium citrate / amorphous calcium phosphate double salt leads to a rapid local cross-linking, which will hinder the cross-linking of the rest of the alginate, resulting in discontinuous pores and an increase in the number of closed pores, so that the porosity of the scaffold gradually decreases. Secondly, the compressive strength and elastic modulus of the scaffold show a trend of continuous enhancement with the increase of the content of calcium citrate / amorphous calcium phosphate double salt. The mechanical strength in Example 6 is significantly improved, indicating that the addition of calcium citrate / amorphous calcium phosphate double salt can make up for the lack of mechanical properties of alginate as a scaffold material.

[0093] The above is only a specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Any technician familiar with the technical field can easily think of changes or replacements within the technical scope disclosed by the present invention, which should be included in the protection scope of the present invention. Therefore, the protection scope of the present invention should be based on the protection scope of the claims. It should also be noted that the various specific technical features described in the above specific embodiments can be combined in any suitable manner without contradiction. In order to avoid unnecessary repetition, the present invention will not further explain various possible combinations. In addition, the various different embodiments of the present invention can also be combined arbitrarily, as long as they do not violate the concept of the present invention, they should also be regarded as the contents disclosed by the present invention.

Claims

1. A sodium alginate / calcium citrate / amorphous calcium phosphate composite porous bone tissue scaffold material, characterized in that, It includes sodium alginate, and calcium citrate / amorphous calcium phosphate double salt is added as a function enhancer.

2. The alginate / calcium citrate / amorphous calcium phosphate composite porous bone tissue scaffold material according to claim 1, wherein, The mass ratio of the sodium alginate to the calcium citrate / amorphous calcium phosphate double salt is 1:0.1-1.

3. A sodium alginate / calcium citrate / amorphous calcium phosphate composite porous bone tissue scaffold material according to claim 1, characterized in that, The method for preparing the calcium citrate / amorphous calcium phosphate double salt comprises the following steps: Step 1, mixing sodium citrate dihydrate solution and diammonium hydrogen phosphate solution and adding them into a separatory funnel for titration; Step 2, placing the calcium chloride solution on a magnetic stirrer, opening the piston of the separating funnel, slowly dripping the mixed solution in step 1 into the stirred calcium chloride solution, then continuously dripping ammonia water to keep the pH value of the solution at about 10, and adding anhydrous ethanol; Step 3, after the addition is complete, continue stirring the reaction for 30-60 minutes, wait for 5-7 days for complete precipitation, during which time the supernatant is continuously removed and deionized water is added; Step 4, centrifuging the suspension with a centrifuge, washing the obtained precipitate with anhydrous ethanol and centrifuging again, and drying the obtained precipitate in a vacuum drying oven to obtain calcium citrate / amorphous calcium phosphate double salt.

4. A sodium alginate / calcium citrate / amorphous calcium phosphate composite porous bone tissue scaffold material according to claim 3, characterized in that, In Step 1, the concentrations of the sodium citrate dihydrate solution and the diammonium hydrogen phosphate solution are 0.3 mol·L -1 , 500 ml of the sodium citrate dihydrate solution and 500 ml of the diammonium hydrogen phosphate solution.

5. The alginate / calcium citrate / amorphous calcium phosphate composite porous bone tissue scaffold material according to claim 3, characterized in that, In Step 2, the concentration of the calcium chloride solution is 0.3 mol·L -1 ; 500 ml of calcium chloride solution and 500 ml of absolute ethanol.

6. The preparation method of a sodium alginate / calcium citrate / amorphous calcium phosphate composite porous bone tissue scaffold material according to any one of claims 1-5, characterized in that, The following steps are involved: Step 1, adding calcium citrate / amorphous calcium phosphate double salt to a sufficient amount of deionized water, and stirring continuously with a magnetic stirrer until a milky white suspension is present; Step 2, slowly add sodium alginate and stir continuously until the sodium alginate is completely dissolved; Step 3, after standing still, take it out and put it into a beaker, add a calcium chloride solution with a concentration of 0.3 mol·L -1 Crosslink for 48 - 60 h, then put it into the refrigerator for pre-freezing for 12 - 24 h; Step 4, putting it into a vacuum freeze dryer and taking it out after drying, so as to obtain a sodium alginate / calcium citrate / amorphous calcium phosphate composite porous scaffold.

7. The preparation method of a sodium alginate / calcium citrate / amorphous calcium phosphate composite porous bone tissue scaffold material according to claim 6, characterized in that, In the said step 1, the rotational speed of the magnetic stirrer is 1500 - 2000 r·min -1 , and the temperature is room temperature; in the said step 2, the rotational speed of the magnetic stirrer is 3000 - 4000 r·min -1 , and the temperature is room temperature.

8. The preparation method of a sodium alginate / calcium citrate / amorphous calcium phosphate composite porous bone tissue scaffold material according to claim 6, characterized in that, In steps 1 and 2, the mass ratio of sodium alginate to calcium citrate / amorphous calcium phosphate double salt is 1:0.1-1; 500 ml of calcium chloride solution.

9. The preparation method of a sodium alginate / calcium citrate / amorphous calcium phosphate composite porous bone tissue scaffold material as described in claim 6, characterized in that, Dry in a vacuum freeze dryer for 72 h at a temperature of -50 °C and a pressure of 200 Pa.

10. Use of the scaffold material according to any one of claims 1 to 5 or the scaffold material obtained by the preparation method according to any one of claims 6 to 9 in the field of bone scaffold repair.

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