A highly corrosion-resistant medical magnesium alloy vascular stent and its preparation method

Abstract

The present invention provides a highly corrosion-resistant medical magnesium alloy vascular stent and a preparation method thereof. The stent is made of a magnesium alloy, and the magnesium alloy comprises the following components in weight percentage: Zn 0.5-1.7%, Al 0.01-0.04%, Eu 1.14-2.33%, Si 0.07-0.19%, Sr 0.01-0.09%, Dy 0.5-1.4%, and the balance is Mg. The stent of the present invention has excellent mechanical properties, and at the same time, it can ensure high corrosion resistance, can be embedded in the blood vessel wall to provide necessary support, and the prepared stent is safe and has no toxic or side effects.

Description

Technical Field

[0001] The present invention belongs to the technical field of medical stents, and particularly relates to a highly corrosion-resistant medical magnesium alloy vascular stent and a preparation method thereof. Background Art

[0002] A cardiovascular stent is a medical device used to support the blood vessel wall and maintain smooth blood flow. Traditional stents are usually made of metal materials such as stainless steel, nickel-titanium alloy or cobalt-chromium alloy, and have been widely used clinically. However, these metal stents may cause local inflammatory reactions, thereby increasing the risk of late thrombosis.

[0003] To address the above problems, drug-coated stents have been developed in the prior art. Such stents can gradually release drugs after being implanted into the human body to inhibit the formation of scar tissue around the stent. However, over time, the drug coating will gradually be depleted, and at this time, the exposed metal stent may still cause inflammatory reactions. To solve the inflammatory problems that may be caused by metal stents, magnesium alloys have become one of the ideal choices for such new stents due to their good biocompatibility and controllable degradation rate.

[0004] However, as one of the few biodegradable metal materials, magnesium alloys cannot fully meet the requirements of ideal vascular stent materials due to their low plastic deformation ability. And magnesium alloys are prone to corrosion due to their high activity, which is a characteristic required for absorbable vascular implants. Although the design concept of a fully absorbable stent is to be ultimately absorbed by the body, if the degradation process of the stent in the body is too fast, the absorbable stent may not be able to embed into the blood vessel wall in time to provide the necessary support, and instead may cause partial detachment of the stent and migration with the blood flow, posing a threat to the patient's life.

[0005] Therefore, there is an urgent need for a highly corrosion-resistant medical magnesium alloy vascular stent and a preparation method thereof. Summary of the Invention

[0006] The purpose of the present invention is to provide a highly corrosion-resistant medical magnesium alloy vascular stent and a preparation method thereof.

[0007] To achieve the above purpose, the present invention provides the following technical solutions:

[0008] A highly corrosion-resistant medical magnesium alloy vascular stent, the stent is made of a magnesium alloy, and the magnesium alloy comprises the following components in weight percentage: Zn 0.5 - 1.7%, Al 0.01 - 0.04%, Eu 1.14 - 2.33%, Si 0.07 - 0.19%, Sr 0.01 - 0.09%, Dy 0.5 - 1.4%, and the balance is Mg.

[0009] Furthermore, the sum of the weight percentages of Zn and Si is greater than the weight percentage of Eu.

[0010] In the present invention, by adding Zn, Si, and Eu to the magnesium matrix simultaneously, the tensile strength of the magnesium alloy can be improved. The analysis is that when zinc dissolves in the magnesium matrix to form a solid solution, it will hinder the movement of dislocations. Si and Eu can enhance the tensile strength of the magnesium alloy by forming fine and dispersed strengthening phases. However, it was found in the experiments that there is a restrictive relationship in the addition amounts of these three elements. Improper addition will instead reduce the tensile strength of the magnesium alloy. When the sum of the weight percentages of Zn and Si is greater than the weight percentage of Eu, the tensile strength of the magnesium alloy is more excellent. The analysis is that there is a problem of competition for binding positions among the three elements, resulting in not all the added elements being able to effectively play their expected roles. Adding too much calcium may affect the stability of the beneficial phases formed between the magnesium matrix and zinc or silicon, and at the same time improve the elastic modulus of the magnesium alloy.

[0011] Furthermore, the sum of the weight percentages of Al, Sr, and Dy is less than 1%.

[0012] In the system of the present invention, when the sum of the weight percentages of Al, Sr, and Dy is less than 0.3%, the corrosion resistance of the magnesium alloy can be improved. The analysis is that the addition of aluminum can change the electrochemical properties of the alloy. Strontium can refine the grains in the magnesium alloy, and grain refinement can reduce the micro-inhomogeneity inside the alloy. The addition of dysprosium can improve the microstructure of the magnesium alloy, making the alloy more uniform, thus reducing the corrosion tendency. At the same time, when the sum of the weight percentages of Al, Sr, and Dy is less than 1%, the element segregation in the aluminum-magnesium alloy can be reduced, and it has better corrosion resistance.

[0013] Furthermore, the weight percentage ratio of Zn:Dy is greater than 1.

[0014] During the experiment process, by adjusting the addition amounts of the two groups of elements Zn, Si, and Eu, as well as Al, Sr, and Dy, the tensile strength and corrosion resistance of the magnesium alloy can be improved. However, under this condition, the yield strength of the magnesium alloy is not ideal. Through a large number of experiments, it was found that when the weight percentage ratio of Zn:Dy is greater than 1, the yield strength of the magnesium alloy can be improved. This is mainly because the interaction between zinc and dysprosium can better control the morphology and distribution of the precipitated phases, contributing to the formation of more uniform and finer precipitated phases, while dysprosium helps to maintain the stability and uniform distribution of these precipitated phases. The two have a synergistic effect, thus having a positive impact on improving the yield strength.

[0015] The present invention provides a method for preparing the high-corrosion-resistance medical magnesium alloy vascular stent, including the following steps:

[0016] (1) Ingredients: Weigh the components of the magnesium alloy according to the ratio, and heat and melt them under an argon atmosphere to obtain a magnesium alloy melt;

[0017] (2) Refining: Heat the magnesium alloy melt to 740 - 760 °C and add a refining agent for refining;

[0018] (3) Casting: Then carry out casting and demoulding to obtain an ingot;

[0019] (4) Solution heat treatment: Carry out solution heat treatment on the ingot under an argon atmosphere, and then quench it with water at 25 - 30 °C to obtain an ingot after solution heat treatment;

[0020] (5) Aging treatment: Under an argon atmosphere, put the ingot after solution heat treatment into a heating furnace for aging treatment, and then quench it into water at 25 - 30 °C to obtain an ingot after aging treatment;

[0021] (6) Making magnesium alloy bars: Extrude the ingot after aging treatment into magnesium alloy bars with a diameter of 8 - 12 mm by hot extrusion;

[0022] (7) Making a stent: Engrave and polish the magnesium alloy bars to prepare a highly corrosion-resistant medical magnesium alloy vascular stent.

[0023] Further, the heating temperature in step (1) is 710 - 730 °C.

[0024] Further, the addition amount of the refining agent in step (2) is 2 - 3% of the total weight of the magnesium alloy melt. The refining agent is purchased from Jinzhou Shida Flux New Materials Co., Ltd.

[0025] Further, the conditions for solution heat treatment in step (4) are: the temperature is 420 - 440 °C, and the holding time is 20 - 25 h.

[0026] The magnesium alloy of the present invention can improve the elongation at break of the magnesium alloy through solution heat treatment under specific conditions. After the magnesium alloy of the present invention is solution-treated, the alloying elements are evenly distributed, which helps to form a more uniform microstructure, reduce the weak links in the material, and improve the uniform plastic deformation ability of the material; appropriate temperature and time can inhibit the formation of adverse precipitation phases and avoid the embrittlement that these phases may cause to the material.

[0027] Further, the conditions for aging treatment in step (5) are: holding at a temperature of 220 - 260 °C for 30 - 40 h.

[0028] Further, the temperature for hot extrusion in step (6) is 320 - 340 °C, and the extrusion speed is 0.4 - 0.6 mm / s.

[0029] Compared with the prior art, the advantages and beneficial effects of the present invention are as follows:

[0030] 1. By adding Zn, Si, and Eu to the magnesium matrix, the tensile strength of the magnesium alloy can be enhanced in the present invention. When the sum of the weight percentages of Zn and Si is greater than the weight percentage of Eu, the tensile strength of the magnesium alloy is more excellent. At the same time, the elastic modulus of the magnesium alloy is improved.

[0031] 2. In the system of the present invention, when the sum of the weight percentages of Al, Sr, and Dy is less than 0.3%, the corrosion resistance of the magnesium alloy can be improved.

[0032] 3. When the weight percentage ratio of Zn:Dy is greater than 1, the yield strength of the magnesium alloy can be improved.

[0033] 4. The magnesium alloy of the present invention can improve the elongation at break after solution heat treatment under specific conditions. Detailed Embodiments

[0034] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Apparently, the described embodiments are only a part of the embodiments of the present invention, rather than all of the embodiments. All other embodiments obtained by those of ordinary skill in the art without creative efforts based on the embodiments of the present invention belong to the scope of protection of the present invention.

[0035] Example 1

[0036] This example provides a highly corrosion-resistant medical magnesium alloy vascular stent, which is prepared from a magnesium alloy. The magnesium alloy includes the following components by weight percentage: Zn 1.2%, Al 0.02%, Eu 1.20%, Si 0.1%, Sr 0.05%, Dy 0.8%, and the balance is Mg.

[0037] The preparation method of the highly corrosion-resistant medical magnesium alloy vascular stent includes the following steps:

[0038] (1) Batching: Weigh the components of the magnesium alloy according to the ratio, and heat and melt them at 720 °C under an argon atmosphere to obtain a magnesium alloy melt;

[0039] (2) Refining: Heat the magnesium alloy melt to 750 °C and add a refining agent for refining; the addition amount of the refining agent is 3% of the total weight of the magnesium alloy melt. The refining agent is purchased from Jinzhou Shida Flux New Materials Co., Ltd., model M15;

[0040] (3) Casting: Then carry out casting and demolding to obtain an ingot;

[0041] (4) Solution heat treatment: Under an argon atmosphere, the ingot is subjected to solution heat treatment at a temperature of 430 °C for 23 h, and then quenched in water at 27 °C to obtain the ingot after solution heat treatment;

[0042] (5) Aging treatment: Under an argon atmosphere, the ingot after solution heat treatment is placed in a heating furnace for aging treatment: kept at a temperature of 240 °C for 36 h, and then quenched in water at 27 °C to obtain the ingot after aging treatment;

[0043] (6) Fabricating magnesium alloy bars: The ingot after aging treatment is extruded into magnesium alloy bars with a diameter of 10 mm by hot extrusion; the temperature of hot extrusion is 330 °C, and the extrusion speed is 0.5 mm / s;

[0044] (7) Fabricating the stent: The magnesium alloy bars are engraved and polished to prepare a highly corrosion-resistant medical magnesium alloy vascular stent.

[0045] Example 2

[0046] This example provides a highly corrosion-resistant medical magnesium alloy vascular stent, which is made of magnesium alloy. The magnesium alloy includes the following components by weight percentage: Zn 1.7%, Al 0.01%, Eu 1.5%, Si 0.07%, Sr 0.01%, Dy 0.9%, and the balance is Mg.

[0047] The preparation method of the highly corrosion-resistant medical magnesium alloy vascular stent includes the following steps:

[0048] (1) Batching: Weigh the components of the magnesium alloy according to the ratio, and heat and melt them at 710 °C under an argon atmosphere to obtain a magnesium alloy melt;

[0049] (2) Refining: Heat the magnesium alloy melt to 740 °C and add a refining agent for refining; the addition amount of the refining agent is 2% of the total weight of the magnesium alloy melt. The refining agent is purchased from Jinzhou Shida Flux New Material Co., Ltd., model M15;

[0050] (3) Casting: Then carry out casting and demolding to obtain an ingot;

[0051] (4) Solution heat treatment: Under an argon atmosphere, the ingot is subjected to solution heat treatment at a temperature of 420 °C for 20 h, and then quenched in water at 25 °C to obtain the ingot after solution heat treatment;

[0052] (5) Aging treatment: Under an argon atmosphere, the ingot after solution heat treatment is placed in a heating furnace for aging treatment: kept at a temperature of 220 °C for 30 h, and then quenched in water at 25 °C to obtain the ingot after aging treatment;

[0053] (6) Manufacturing magnesium alloy bars: Extruding the aged ingot into magnesium alloy bars with a diameter of 10 mm by hot extrusion; the temperature of hot extrusion is 320 °C, and the extrusion speed is 0.4 mm / s;

[0054] (7) Manufacturing the stent: Engraving and polishing the magnesium alloy bars to prepare a highly corrosion-resistant medical magnesium alloy vascular stent.

[0055] Example 3

[0056] This example provides a highly corrosion-resistant medical magnesium alloy vascular stent, which is made of magnesium alloy. The magnesium alloy includes the following components by weight percentage: Zn 1.6%, Al 0.04%, Eu 1.14%, Si 0.19%, Sr 0.09%, Dy 0.5%, and the balance is Mg.

[0057] The preparation method of the highly corrosion-resistant medical magnesium alloy vascular stent includes the following steps:

[0058] (1) Batching: Weigh the components of the magnesium alloy according to the ratio, and heat and melt them at 730 °C under an argon atmosphere to obtain a magnesium alloy melt;

[0059] (2) Refining: Raise the temperature of the magnesium alloy melt to 760 °C and add a refining agent for refining; the addition amount of the refining agent is 3% of the total weight of the magnesium alloy melt. The refining agent is purchased from Jinzhou Shida Flux New Materials Co., Ltd., model M15;

[0060] (3) Casting: Then carry out casting and demoulding to obtain an ingot;

[0061] (4) Solution heat treatment: Carry out solution heat treatment on the ingot under an argon atmosphere, the temperature is 440 °C, the holding time is 25 h, and then quench with water at 30 °C to obtain an ingot after solution heat treatment;

[0062] (5) Aging treatment: Put the ingot after solution heat treatment into a heating furnace for aging treatment under an argon atmosphere: Keep it at a temperature of 260 °C for 40 h, and then quench it into water at 30 °C to obtain an ingot after aging treatment;

[0063] (6) Manufacturing magnesium alloy bars: Extruding the aged ingot into magnesium alloy bars with a diameter of 10 mm by hot extrusion; the temperature of hot extrusion is 340 °C, and the extrusion speed is 0.6 mm / s;

[0064] (7) Manufacturing the stent: Engraving and polishing the magnesium alloy bars to prepare a highly corrosion-resistant medical magnesium alloy vascular stent.

[0065] Comparative Example 1

[0066] The difference between this comparative example and Example 1 is that the components are not within the range.

[0067] The magnesium alloy includes the following components by weight percentage: Zn 2.2%, Al 0.02%, Eu 0.6%, Si 0.23%, Sr 0.05%, Dy 0.05%, and the balance is Mg.

[0068] Comparative Example 2

[0069] The difference between this comparative example and Example 1 is that the sum of the weight percentages of Al, Sr, and Dy is greater than 1%.

[0070] The magnesium alloy includes the following components by weight percentage: Zn 1.2%, Al 0.04%, Eu 1.20%, Si 0.1%, Sr 0.19%, Dy 1.0%, and the balance is Mg.

[0071] Comparative Example 3

[0072] The difference between this comparative example and Example 1 is that the sum of the weight percentages of Zn and Si is less than the weight percentage of Eu.

[0073] The magnesium alloy includes the following components by weight percentage: Zn 0.8%, Al 0.02%, Eu 1.20%, Si 0.07%, Sr 0.05%, Dy 0.8%, and the balance is Mg.

[0074] Comparative Example 4

[0075] The difference between this comparative example and Example 1 is that the weight percentage ratio of Zn:Dy is less than 1.

[0076] The magnesium alloy includes the following components by weight percentage: Zn 0.5%, Al 0.02%, Eu 0.20%, Si 0.1%, Sr 0.05%, Dy 0.8%, and the balance is Mg.

[0077] Comparative Example 5

[0078] The difference between this comparative example and Example 1 is that the conditions for solution heat treatment are: temperature 400 °C, holding time 30 h.

[0079] Comparative Example 6

[0080] The difference between this comparative example and Example 1 is that the conditions for solution heat treatment are: temperature 460 °C, holding time 15 h.

[0081] Performance Test

[0082] Perform performance tests on the magnesium alloy bars prepared in Examples 1-3 and Comparative Examples 1-6:

[0083] The corrosion resistance was determined with reference to ASTM-G31-72 (Hank's simulated body fluid, 37 °C); the tensile strength and elongation at break were determined with reference to DIN EN 10002-1; the elastic modulus was determined with reference to GB / T 232-2010; and the yield strength was determined with reference to DIN 50106.

[0084] The results are shown in Table 1:

[0085] Table 1 Performance test results

[0086]

[0087] From the above performance test results, it can be seen that the comprehensive performance of the magnesium alloy bars in Examples 1-3 is the most prominent, which is mainly due to the synergistic effect of the components of the magnesium alloy. The degradation rate (corrosion rate) of this material is ideal and can be used as a biodegradable in-vivo implant material.

[0088] Tested according to the ISO10993 method, the cytotoxicity of the scaffolds prepared in Examples 1-3 is all grade 2, with no obvious cytotoxicity, no intracutaneous irritation, no sensitization and no genetic toxicity.

[0089] In the comparative examples, because the necessary technical solutions were not adopted, their performance in the corresponding performance tests was significantly worse than that of the examples. As can be seen from Table 1, the components of the magnesium alloy in Comparative Example 1 were not within the range, and its comprehensive performance decreased to varying degrees. In particular, the corrosion rate was too fast, affecting the supporting performance of the scaffold, proving that the synergistic effect between the components improved the performance of the scaffold; in Comparative Example 2, the sum of the weight percentages of Al, Sr and Dy was greater than 1%, affecting the corrosion resistance of the magnesium alloy, and the degradation rate of the scaffold in the body was too slow; in Comparative Example 3, the sum of the weight percentages of Zn and Si was less than the weight percentage of Eu, affecting the tensile strength and elastic modulus of the magnesium alloy; in Comparative Example 4, the weight percentage ratio of Zn:Dy was less than 1, and the yield strength of the magnesium alloy decreased; in Comparative Examples 5 and 6, the conditions of solution heat treatment were different, affecting the elongation at break of the magnesium alloy. The above experimental results further prove the importance of the technical solutions defined in the present invention for its technical effects.

[0090] The above is the preferred embodiment of the present invention. It should be noted that for those of ordinary skill in the art, without departing from the principle described in the present invention, several improvements and refinements can be made, and these improvements and refinements should also be regarded as the protection scope of the present invention.

Claims

1. A highly corrosion-resistant medical magnesium-aluminum alloy vascular stent, characterized in that: The bracket is made of magnesium-aluminum alloy, and the magnesium-aluminum alloy includes the following components in weight percentage: Zn 0.5-1.7%, Al 0.01-0.04%, Eu 1.14-2.33%, Si 0.07-0.19%, Sr 0.01-0.09%, Dy 0.5-1.4%, and the balance is Mg; The sum of the weight percentages of Zn and Si is greater than the weight percentage of Eu; The sum of the weight percentages of Al, Sr and Dy is less than 1%; The weight percentage ratio of Zn:Dy is greater than 1; The preparation method of the highly corrosion-resistant medical magnesium-aluminum alloy vascular stent comprises: (1) Ingredients: Weigh the components of the magnesium-aluminum alloy according to the proportion, heat and melt them in an argon atmosphere to obtain a magnesium-aluminum alloy melt; (2) Refining: The magnesium-aluminum alloy melt is heated to 740-760°C and a refining agent is added for refining; (3) Casting: Casting is then performed, demoulding is performed, and an ingot is obtained; (4) Solution heat treatment: The ingot is subjected to solution heat treatment in an argon atmosphere, and then quenched in water at 25-30°C to obtain an ingot after solution heat treatment; the conditions for solution heat treatment are: temperature of 420-440°C and holding time of 20-25h; (5) Aging treatment: In an argon atmosphere, the ingot after solution heat treatment is placed in a heating furnace for aging treatment, and then quenched in water at 25-30°C to obtain an ingot after aging treatment; (6) Making magnesium-aluminum alloy rods: Extruding the aged ingot into magnesium-aluminum alloy rods with a diameter of 8-12 mm by hot extrusion; (7) Stent production: The magnesium-aluminum alloy rod is carved and polished to prepare a highly corrosion-resistant medical magnesium-aluminum alloy vascular stent.

2. The highly corrosion-resistant medical magnesium-aluminum alloy vascular stent according to claim 1, characterized in that: The heating temperature in step (1) is 710-730°C.

3. The highly corrosion-resistant medical magnesium-aluminum alloy vascular stent according to claim 1, characterized in that: The amount of the refining agent added in step (2) is 2-3% of the total weight of the magnesium-aluminum alloy melt.

4. The highly corrosion-resistant medical magnesium-aluminum alloy vascular stent according to claim 1, characterized in that: The aging treatment conditions in step (5) are: keeping the temperature at 220-260° C. for 30-40 hours.

5. The highly corrosion-resistant medical magnesium-aluminum alloy vascular stent according to claim 1, characterized in that: The temperature of the hot extrusion in step (6) is 320-340° C., and the extrusion speed is 0.4-0.6 mm / s.

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