WO2023087830A1 - Surface coating capable of degrading magnesium and magnesium alloy, and preparation method therefor - Google Patents

Abstract

Disclosed in the present invention are a surface coating capable of degrading magnesium and a magnesium alloy, and a preparation method therefor. The surface coating comprises an inner layer and an outer layer; the inner layer is a magnesium phosphate salt conversion layer; and the outer layer is a hydroxyapatite coating. The coating prepared by the present invention is of a double-layer structure, and the magnesium phosphate salt conversion layer of the inner layer provides growth sites for the hydroxyapatite coating of the outer layer, so that the binding force of the coating and a base material is effectively enhanced, and the bonding strength can reach 50 MPa or above. In addition, the thickness of the hydroxyapatite coating is controllable, the degradation time can be adjusted according to needs, and the degradation time of a magnesium alloy implant can be controlled to be 12-18 months.

Description

A kind of surface coating of degradable magnesium and magnesium alloy and preparation method thereof technical field

The invention relates to the technical field of surface coatings of magnesium and magnesium alloys, in particular to a surface coating of degradable magnesium and magnesium alloys and a preparation method thereof.

Background technique

At present, the common bone implant materials used in clinical practice are mostly non-degradable stainless steel, titanium alloy, and cobalt-based alloy materials, which remain in the body for a long time after implantation and will stimulate the surrounding body tissues to varying degrees. After recovery, the patient usually needs to undergo a second operation to remove the metal implant, which in turn brings more pain and financial burden to the patient. In addition, the elastic modulus of these materials is much higher than that of bone tissue, which will lead to the effect of "stress shielding" and affect the repair of bone tissue. Compared with the above traditional implant materials for bone repair, magnesium alloy has the following advantages: 1) It can Degradability, magnesium alloy has a low corrosion potential, it is easy to corrode in the body environment containing chloride ions, and completely degrades in the body in a slow corrosion manner; 2) High biological safety, Mg is an essential nutrient element for the human body, Participate in almost all energy metabolism in the body, and play an important role in neuromotor function, physiological function, and prevention of circulatory system diseases and ischemic heart disease; excessive magnesium will be excreted through urinary system metabolism and decomposition, which has good biological safety; 3) Good biomechanical compatibility. Magnesium is currently the metal material with the closest biomechanical properties to human bone among all metal materials, which can effectively alleviate the clinical "stress shielding" effect of traditional medical metal materials.

However, there are still some problems in the clinical application of magnesium and magnesium alloys as orthopedic implant materials. The chemical properties of magnesium and magnesium alloys are relatively active, and the degradation rate is too fast after implantation in the body. It is difficult to maintain sufficient structural integrity and mechanical strength before tissue repair, regeneration and recovery. Degradation will generate hydrogen gas at the same time. If the degradation is too fast, hydrogen gas will accumulate, which will affect the adhesion and proliferation of surrounding osteoblasts and the healing of bone tissue.

Surface coating is currently an effective technical means to control the degradation of magnesium alloys. At present, there are many technical reports such as polymer coating, hydroxyapatite coating, magnesium oxide coating, and calcium-phosphorus coating. Calcium-phosphorus coating has a composition similar to that of bone tissue, which can improve the corrosion resistance and biocompatibility of bone implants, and is a commonly used coating. Among them, hydroxyapatite has good crystallinity and is closest to bone components, which can improve osseointegration ability and accelerate bone tissue healing, and its solubility is the lowest among all kinds of calcium-phosphorus coatings, and the degradation products are slightly alkaline, which is beneficial to prevent corrosion. The chemical reaction equilibrium angle further inhibits the magnesium matrix degradation. At present, chemical deposition, electrodeposition, sol-gel method, etc. are commonly used to prepare hydroxyapatite coating on the surface of magnesium alloy. However, most of them have technical problems such as complex preparation process, low thickness or non-dense coating structure, and insufficient bonding strength.

Patent CN106544714B discloses a method for preparing the surface coating of Mg-Zn-Ca magnesium alloy bone screws. The material is subjected to micro-arc electrophoresis treatment and then hydrothermal synthesis treatment to prepare the hydroxyapatite coating. The problem is that there are a large number of micropores and cracks on the surface of the micro-arc electrophoretic coating, which provide ion channels for the infiltration of corrosive media, and directly affect the protection performance of the coating layer against corrosion degradation of the magnesium substrate. Patent CN103484845B discloses a ZK60 magnesium alloy calcium-phosphorus coating composite material, which uses a hydrothermal method to synthesize the calcium-phosphorus coating in one step. But there are problems and deficiencies: 1) the calcium source used in this method is calcium nitrate, and there is no complexing agent in the system, so it is difficult to adjust the pH value of the solution; The mechanical properties of the matrix; 3) Since hydroxyapatite is not easy to deposit directly on the surface of magnesium and magnesium alloys, the thickness, coverage and interfacial bonding strength of the coating will be obviously lacking; 4) The surface of the coating cannot form a higher biological activity. Composite morphology of micro- and nanoscale hierarchical structures. CN 111973812A discloses a method for preparing a magnesium alloy double-layer coating, the inner layer is a magnesium fluoride layer, and the outer layer is a hydroxyapatite conversion coating. The existing problems and shortcomings are: 1) The fluoride ions produced by the degradation of the magnesium fluoride layer may have a negative impact on the local bone tissue, causing problems such as fluorosis; 2) The preparation process is cumbersome and takes a long time, and brushite needs to be prepared first It is then converted into hydroxyapatite; 3) The production process requires the use of toxic reagents such as high-concentration hydrogen fluoride, which is very dangerous.

technical problem

The object of the present invention is to provide a surface coating of degradable magnesium and magnesium alloys and a preparation method thereof in view of the deficiencies in the prior art.

technical solution

For realizing above-mentioned object, the technical scheme that the present invention takes is:

The first aspect of the present invention is to provide a surface coating of degradable magnesium and magnesium alloys, the surface coating includes an inner layer and an outer layer, the inner layer is a magnesium phosphate conversion layer, and the outer layer is a hydroxyl phosphorus Gray stone coating.

Further, the magnesium phosphate conversion layer has a thickness of 50 nm-10 μm, and the hydroxyapatite coating has a thickness of 0.1 μm-500 μm.

Further, the binding force between the surface coating and the magnesium or magnesium alloy substrate is above 50 MPa, and the atomic ratio of Ca/P in the hydroxyapatite coating is 1.5-1.67.

The second aspect of the present invention provides the preparation method of above-mentioned surface coating, comprises the following steps:

S1: heating and soaking magnesium or magnesium alloy material in an acidic solution containing magnesium salt and phosphate, forming a magnesium phosphate conversion layer on the surface of magnesium or magnesium alloy material;

S2: The magnesium or magnesium alloy material treated in step S1 is transferred to an alkaline solution containing calcium salt and phosphate, heated and soaked, and a hydroxyapatite coating is formed on the surface of the magnesium phosphate conversion layer.

Further, the magnesium salt described in step S1 is one or more of magnesium nitrate, magnesium chloride, magnesium sulfate, magnesium phosphate, magnesium perchlorate, magnesium acetate, magnesium hydroxide, and its concentration is 0.001~10 mol /L; the phosphate is sodium dihydrogen phosphate, disodium hydrogen phosphate, potassium dihydrogen phosphate, dipotassium hydrogen phosphate, magnesium dihydrogen phosphate, dimagnesium hydrogen phosphate, diammonium hydrogen phosphate, ammonium dihydrogen phosphate, phosphoric acid One or more of calcium dihydrogen and dicalcium phosphate, the concentration of which is 0.001~10 mol/L.

Further, the molar concentration ratio of magnesium ions to phosphate ions in the solution in step S1 is (0.2-5):1, more preferably (0.8-1.2):1.

Further, the pH of the acidic solution described in step S1 is 2 to 7, and one or more of nitric acid, sulfuric acid, hydrochloric acid, phosphoric acid, and acetic acid are used to adjust the pH; the reaction temperature in step S1 is 5 to 99°C, soaking The time is 5min-12h.

Further, the phosphate described in step S2 is sodium dihydrogen phosphate, disodium hydrogen phosphate, potassium dihydrogen phosphate, dipotassium hydrogen phosphate, magnesium dihydrogen phosphate, dimagnesium hydrogen phosphate, diammonium hydrogen phosphate, dihydrogen phosphate One or more of ammonium, calcium dihydrogen phosphate, and dicalcium phosphate, the concentration of which is 0.001~10 mol/L; the calcium salt is calcium dihydrogen phosphate, dicalcium phosphate, EDTA-Ca, lemon Calcium Acetate, Calcium Acetate, Calcium Chloride, Calcium Nitrate, Calcium Maleate, Calcium Polyacrylate, Calcium Polymethacrylate, and its concentration is 0.001~10mol/L.

Further, the molar concentration ratio of the phosphate salt and the calcium salt is (0.2-5):1, more preferably (0.8-1.2):1.

Further, the pH of the alkaline solution described in step S2 is 7-13, and one or more of sodium hydroxide, potassium hydroxide, and ammonia water is used to adjust the pH; the reaction temperature in step S2 is 5-99°C, Soaking time is 5min-48h.

Further, the magnesium alloy is Mg-Zn series, Mg-Ca series, Mg-Li series, Mg-Mn series or Mg-Re series bare metal magnesium alloy series without any treatment.

Beneficial effect

The present invention adopts the above technical scheme, and compared with the prior art, it has the following technical effects:

1) The magnesium alloy coating in the prior art has insufficient ability to control degradation, and it degrades completely within 6 months after being implanted in the body. The coating prepared by the invention can control the degradation time of the magnesium alloy implant within 12 to 18 months.

2) Most of the magnesium alloy coatings in the prior art are single-layer coatings, and the thickness and uniformity are not easy to control, and the degradation time is not controlled. The coating prepared by the present invention consists of a double-layer structure, the inner layer is a magnesium phosphate conversion layer, and the outer layer is a hydroxyapatite coating with a controllable thickness; the thickness of the hydroxyapatite coating is controllable, and the degradation time can be adjusted according to needs Make adjustments.

3) The magnesium alloy coating in the prior art has insufficient bonding strength, and scratches and falls off due to friction during use, especially in the process of screwing in bone nails. The coating prepared by the present invention consists of a double-layer structure, wherein the magnesium phosphate conversion layer of the inner layer provides growth sites for the hydroxyapatite coating of the outer layer, effectively improving the bonding force between the coating and the substrate, and the bonding strength can be Up to 50MPa or more.

4) The preparation method of the present invention does not require high temperature and high pressure reaction conditions, the production process is simple, the cost is low, and it can be applied to magnesium and magnesium alloy implants with arbitrary complex shapes.

Description of drawings

Fig. 1 is the degradation weight reduction curve figure of coating AZ31 magnesium alloy of the present invention and uncoated AZ31 magnesium alloy;

FIG. 2 is a CT scan in Verification Example 2.

BEST MODE FOR CARRYING OUT THE INVENTION

The present invention will be further described below in conjunction with the accompanying drawings and specific embodiments, but not as a limitation of the present invention. It should be noted that, in the case of no conflict, the embodiments of the present invention and the features in the embodiments can be combined with each other.

Example 1

Prepare a controllable degradable coating on the surface of AZ31 magnesium alloy rods, the specific steps are as follows:

1) First, AZ31 magnesium alloy is made into a Φ3×10mm sample, polished with 800#, 1200#, 2000# sandpaper in turn, ultrasonically cleaned in anhydrous acetone for 5 minutes to remove the surface oil, and dried after cleaning;

2) Prepare a solution containing 0.25mol/L magnesium nitrate and 0.25mol/L sodium dihydrogen phosphate, adjust the pH of the solution to 3.5 with dilute nitric acid, and heat it in a water bath to 75°C;

3) Put the AZ31 magnesium alloy sample into the heated solution, soak and react for 60 minutes, then take it out and rinse it with deionized water, and dry it to obtain the AZ31 magnesium alloy sample with a magnesium phosphate conversion layer;

4) Prepare a solution containing 0.25mol/L calcium citrate and 0.25mol/L sodium dihydrogen phosphate, and use sodium hydroxide to adjust the pH to 9.5;

5) Put the AZ31 magnesium alloy sample with magnesium phosphate conversion layer obtained in step 3) into the solution prepared in step 4), put it in a water bath and heat it to 95°C, and heat it for 6 hours. After the reaction, take it out and cool down , rinsed with deionized water and dried to obtain a sample with a uniform and complete surface;

6) The bonding force between the coating and the substrate was measured to be 63MPa using a universal mechanical testing machine.

Example 2

Prepare a controllable degradable coating on the surface of AZ31 magnesium alloy rods, the specific steps are as follows:

1) First, AZ31 magnesium alloy is made into a Φ3×10mm sample, polished with 800#, 1200#, 2000# sandpaper in turn, ultrasonically cleaned in anhydrous acetone for 5 minutes to remove the surface oil, and dried after cleaning;

2) Prepare a solution containing 0.5 mol/L magnesium sulfate and 0.5 mol/L potassium dihydrogen phosphate, adjust the pH of the solution to 2.5 with dilute sulfuric acid, and heat it in a water bath to 60°C;

3) Put the AZ31 magnesium alloy sample into the heated solution, soak and react for 120 minutes, then take it out and rinse it with deionized water, and dry it to obtain the AZ31 magnesium alloy sample with a magnesium phosphate conversion layer;

4) Preparation containing 0.15mol/L EDTA-Ca calcium and 0.15mol/L potassium dihydrogen phosphate solution, use potassium hydroxide to adjust the pH to 9.0;

5) Put the AZ31 magnesium alloy sample with magnesium phosphate conversion layer obtained in step 3) into the solution prepared in step 4), put it in a water bath and heat it to 80°C, and heat it for 12 hours. After the reaction, take it out and cool down , rinsed with deionized water and dried to obtain an AZ31 magnesium alloy sample whose surface is evenly covered with white particle coating;

6) Using a universal mechanical testing machine, the bonding force between the coating and the substrate is measured to be 58MPa.

Example 3

Prepare a controllable degradable coating on the surface of ZK60 magnesium alloy rods, the specific steps are as follows:

1) First, make a Φ3×10mm sample of ZK60 magnesium alloy, polish it with 800#, 1200#, 2000# sandpaper in turn, and ultrasonically clean it in anhydrous acetone for 5 minutes to remove the surface oil, and then dry it after cleaning;

2) Prepare a solution containing 0.25 mol/L magnesium dihydrogen phosphate, adjust the pH of the solution to 3.0 with phosphoric acid, and heat to 70°C in a water bath;

3) Put the ZK60 magnesium alloy sample into the heated solution, soak and react for 45 minutes, then take it out and rinse it with deionized water, and dry it to obtain a K60 magnesium alloy sample with a magnesium phosphate conversion layer;

4) Preparation containing 0.10mol/L A solution of calcium citrate and 0.10 mol/L sodium dihydrogen phosphate, using sodium hydroxide to adjust the pH to 9.0;

5) Put the K60 magnesium alloy sample with magnesium phosphate conversion layer obtained in step 3) into the solution prepared in step 4), put it in a water bath and heat it to 80°C, and heat it for 6 hours. After the reaction is over, take it out and cool down , rinsed with deionized water and dried to obtain a ZK60 magnesium alloy sample with a uniform and complete surface;

6) The bonding force between the coating and the substrate is measured at 70MPa using a universal mechanical testing machine.

Example 4

Prepare a controllable degradable coating on the surface of LZ91 magnesium alloy rods, the specific steps are as follows:

1) First, make LZ91 magnesium alloy into a Φ3×10mm sample, polish it with 800#, 1200#, 2000# sandpaper in turn, and ultrasonically clean it in anhydrous acetone for 5 minutes to remove the surface oil, and then dry it after cleaning;

2) Prepare a solution containing 0.35 mol/L magnesium dihydrogen phosphate, adjust the pH of the solution to 3.0 with phosphoric acid, and heat it in a water bath to 75°C;

3) Put the LZ91 magnesium alloy sample into the heated solution, soak and react for 60 minutes, then take it out and rinse it with deionized water, and dry it to obtain a LZ91 magnesium alloy sample with a magnesium phosphate conversion layer;

4) Preparation containing 0.15mol/L EDTA-Ca and 0.15mol/L sodium dihydrogen phosphate solution, use sodium hydroxide to adjust the pH to 7.5;

5) Put the LZ91 magnesium alloy sample with a magnesium phosphate conversion layer obtained in step 3) into the solution prepared in step 4), put it in a water bath and heat it to 80°C, and heat it for 12 hours. After the reaction is over, take it out and cool down , rinsed with deionized water and dried to obtain a LZ91 magnesium alloy sample with a uniform and complete surface;

6) Using a universal mechanical testing machine, the bonding force between the coating and the substrate was measured to be 73MPa.

Verification example 1

The samples prepared in the above examples 1 and 2 and the uncoated AZ31 magnesium alloy sample of the same size were placed in a 3% sodium chloride solution, soaked at 37°C for accelerated degradation test. Change the solution every 3-4 days, weigh every week, and observe the surface corrosion and overall degradation of each sample at the same time. The obtained weight loss curve is shown in Fig. 1 . It can be seen that the weight of the uncoated magnesium alloy is significantly reduced by more than 50% after immersion for 30 days, while the weight of the magnesium alloys prepared in Example 1 and Example 2 is only reduced by about 10% after immersion for 30 days, indicating that the coating greatly reduces the weight of the magnesium alloy. degradation.

Verification example 2

AZ31 magnesium alloy was processed into a bone nail shape, and coated magnesium alloy screws were prepared according to the method in Example 1. Taking uncoated magnesium alloy screws as a control example, they were respectively implanted in the tibial plateaus of the left and right legs of goats. , CT scans were performed at 3, 6, 12, and 18 months to observe the degradation of magnesium alloy screws. It can be seen from Figure 2 that the uncoated magnesium alloy screw began to degrade immediately after implantation and produced a large amount of gas, forming a cavity in the bone tissue (white arrow in Figure 2). The coated magnesium alloy screws were basically degraded, and no magnesium alloy screws could be seen 12 and 18 months after implantation. However, for the coated magnesium alloy screw of the present invention, the existence of the screw can be clearly seen within 12 months after the operation, and the thread structure of the screw remains almost unchanged. After 18 months, the magnesium alloy screw nearly disappears, and it can be seen that The coated magnesium alloy screw of the present invention rarely degrades within 12 months, and degrades completely within 12 to 18 months. It shows that the coating effectively controls the degradation of magnesium alloy in vivo, and the degradation time is controlled within 12-18 months.

The above are only preferred embodiments of the present invention, and are not intended to limit the implementation and protection scope of the present invention. For those skilled in the art, they should be able to realize that all equivalents made by using the contents of the description and illustrations of the present invention The solutions obtained by replacement and obvious changes shall all be included in the protection scope of the present invention.

Claims (10)

1. A surface coating for degradable magnesium and magnesium alloys, characterized in that the surface coating includes an inner layer and an outer layer, the inner layer is a magnesium phosphate conversion layer, and the outer layer is a hydroxyapatite coating layer.
2. The surface coating according to claim 1, characterized in that, the magnesium phosphate conversion layer has a thickness of 50 nm-10 μm, and the hydroxyapatite coating has a thickness of 0.1 μm-500 μm.
3. The surface coating according to claim 1, wherein the binding force between the surface coating and the magnesium or magnesium alloy substrate is above 50MPa, and the Ca/P atomic ratio in the hydroxyapatite coating is 1.5 -1.67.
4. A method for preparing a surface coating as claimed in any one of claims 1-3, comprising the steps of:

   S1: heating and soaking magnesium or magnesium alloy material in an acidic solution containing magnesium salt and phosphate, forming a magnesium phosphate conversion layer on the surface of magnesium or magnesium alloy material;

   S2: The magnesium or magnesium alloy material treated in step S1 is transferred to an alkaline solution containing calcium salt and phosphate, heated and soaked, and a hydroxyapatite coating is formed on the surface of the magnesium phosphate conversion layer.
5. The preparation method according to claim 4, wherein the magnesium salt described in step S1 is one of magnesium nitrate, magnesium chloride, magnesium sulfate, magnesium phosphate, magnesium perchlorate, magnesium acetate, and magnesium hydroxide Or several, its concentration is 0.001～10 mol/L; Described phosphate is sodium dihydrogen phosphate, disodium hydrogen phosphate, potassium dihydrogen phosphate, dipotassium hydrogen phosphate, magnesium dihydrogen phosphate, dimagnesium hydrogen phosphate, One or more of diammonium hydrogen phosphate, ammonium dihydrogen phosphate, calcium dihydrogen phosphate, and dicalcium hydrogen phosphate, the concentration of which is 0.001~10 mol/L.
6. The preparation method according to claim 5, characterized in that the molar concentration ratio of magnesium ions to phosphate ions in the solution in step S1 is (0.2-5):1.
7. The preparation method according to claim 4, wherein the pH of the acidic solution described in step S1 is 2 to 7, and one or more of nitric acid, sulfuric acid, hydrochloric acid, phosphoric acid, and acetic acid are used to adjust the pH; step The reaction temperature in S1 is 5~99℃, and the soaking time is 5min-12h.
8. The preparation method according to claim 4, wherein the phosphate described in step S2 is sodium dihydrogen phosphate, disodium hydrogen phosphate, potassium dihydrogen phosphate, dipotassium hydrogen phosphate, magnesium dihydrogen phosphate, hydrogen phosphate One or more of dimagnesium, diammonium hydrogen phosphate, ammonium dihydrogen phosphate, calcium dihydrogen phosphate, and dicalcium hydrogen phosphate, the concentration of which is 0.001~10 mol/L; the calcium salt is calcium dihydrogen phosphate , dicalcium hydrogen phosphate, EDTA-Ca, calcium citrate, calcium acetate, calcium chloride, calcium nitrate, calcium maleate, calcium polyacrylate, calcium polymethacrylate, the concentration is 0.001 ~10mol/L; the molar concentration ratio of the phosphate and calcium salt is (0.2~5):1.
9. The preparation method according to claim 4, wherein the pH of the alkaline solution described in step S2 is 7 to 13, and one or more of sodium hydroxide, potassium hydroxide, and ammonia are used to adjust the pH; In step S2, the reaction temperature is 5-99°C, and the soaking time is 5min-48h.
10. The preparation method according to claim 4, characterized in that the magnesium alloy is a bare metal of Mg-Zn system, Mg-Ca system, Mg-Li system, Mg-Mn system or Mg-Re system without any treatment Magnesium alloy series.