A self-catalytically degradable porous iron-based bone implant and its preparation method

Abstract

The present invention relates to a kind of autocatalytic degradation porous iron-based bone implant and its preparation method, and belongs to the field of degradable biomedical metals. The autocatalytic degradation porous iron-based bone implant is composed of an iron matrix and sodium chloride, wherein the mass percentage of sodium chloride is 1.1-4.5 wt.%. The sodium chloride powder and the iron powder mixed powder are mechanically mixed and ball-milled and then formed by electric spark sintering. The beneficial effect of the present invention is that it can be formed into a large-scale porous iron-based bone implant quickly below the melting point of iron, and has an autocatalytic degradation effect, and many small and evenly distributed microscopic corrosions form macroscopic rapid degradation.

Description

Technical Field

[0001] The invention relates to a biomedical iron-based bone implant and belongs to the field of degradable biomedical metals. Background Art

[0002] With the increasing aging of the population and the frequent occurrence of accidents such as traffic accidents and sports injuries, the number of patients with bone defects, such as bone necrosis and osteoarticular trauma, has increased significantly. This has greatly stimulated the demand for bone implants. Given the load-bearing function of bone, bone implants need to have sufficient strength to withstand loads. Metal bone implants have excellent mechanical properties and meet the basic requirements for load bearing. Orthopedic implants are mainly made of metal materials, with stainless steel, cobalt-nickel alloys, and titanium alloys being the three most commonly used. In addition, there are memory alloys and precious metals. After implantation, these metals have good affinity with the human body, are non-toxic, and do not have severe rejection reactions. They are highly chemically stable and not prone to corrosion. They are effective in treating bone defects in the early stages of implantation. However, after bone tissue heals, these inert implants act as foreign bodies and are prone to inflammation, requiring surgical removal.

[0003] In recent years, biodegradable biomedical metals, known for their excellent biocompatibility and ability to dissolve completely within the body, have garnered significant attention. These metals, capable of corroding in the human physiological environment, gradually degrade while bone tissue is repaired, ultimately dissolving completely within the host. This avoids the psychological and financial burdens placed on patients and their families by secondary surgeries after bone tissue has fully recovered. These orthopedic implants hold great clinical promise and have been hailed as "revolutionary metal biomaterials."

[0004] Studies have shown that degradable biomedical metals mainly include magnesium and its alloys, zinc and its alloys, and iron and its alloys. From the perspective of bone-bearing function, the strength of magnesium and its alloys, and zinc and its alloys as compact bones needs to be further improved. Iron and its alloys have sufficient strength and good toughness, and have great application potential as bone implants. At the same time, iron is an essential trace element for the human body and plays an important physiological role in the human body, such as participating in oxygen transport. The human body needs to supplement a certain amount of iron every day to maintain normal physiological functions. However, the corrosion potential of biomedical iron and its alloys is relatively high (about -0.4V), the corrosion kinetics is slow, and the degradation rate is lower than the bone tissue repair rate. Therefore, it is urgent to regulate its biodegradation rate to accelerate its biomedical use. Summary of the Invention

[0005] To address the problem of slow degradation of biomedical iron in existing technologies, making it difficult to meet bone tissue repair requirements, the present invention proposes the preparation of an iron / sodium chloride bone implant. During the degradation process of this bone implant, sodium chloride releases chloride and sodium ions, creating a porous structure within the iron matrix. The released chloride ions have a small radius and are highly adsorbable and capable of penetrating the iron matrix, enhancing corrosion extension and penetration, resulting in an autocatalytic effect. Chloride ions are the primary negative ions in human body fluids, primarily responsible for controlling the membrane potential and cell volume of resting cells and also regulating glycine and gamma-aminobutyric acid. The released sodium ions are the primary positively charged ions in extracellular fluids, participating in water metabolism, ensuring water balance in the body, and participating in the regulation of cardiac muscle and nerve function. Therefore, based on the physiological effects of sodium chloride, its introduction into bone implants has a certain degree of biosafety.

[0006] In order to accelerate the degradation of iron, the present invention provides the following technical solutions:

[0007] The invention discloses a self-catalytically degradable porous iron-based bone implant, which consists of an iron matrix and sodium chloride, wherein the mass percentage of the sodium chloride is 1.1-4.5 wt.%.

[0008] Furthermore, in the self-catalytically degradable porous iron-based bone implant, the mass percentage of sodium chloride is 1.2-3.2 wt.%.

[0009] Furthermore, in the self-catalytically degradable porous iron-based bone implant, the mass percentage of sodium chloride is 2.8 wt.%.

[0010] Furthermore, the particle size of the sodium chloride powder is 20-45 microns, and the size of the iron powder is 40-80 microns.

[0011] In the self-catalytically degradable porous iron-based bone implant, sodium chloride can quickly dissolve around it, leaving behind numerous evenly distributed microscopic pores. The metal potential around the microscopic pores is relatively negative and is in an activated state; the metal potential outside the microscopic pores is relatively positive and is in a passivated state. As a result, an active state, namely a passive microgalvanic corrosion unit, is formed inside and outside the microscopic pores. In this unit, the anode (activated metal around the microscopic pores) has a small area, while the cathode (passivated metal outside the microscopic pores) has a large area, resulting in a small anode and a large cathode phenomenon. This causes a high anode current density, intensified anode dissolution, and the ability of corrosion to dig deep and expand. In other words, self-catalysis accelerates corrosion to a deep level, and numerous small, evenly distributed microscopic corrosions form macroscopic rapid degradation.

[0012] Furthermore, the autocatalytically degradable porous iron-based bone implant has a density of 85-95%.

[0013] Furthermore, the autocatalytically degradable porous iron-based bone implant has a density of 87-93%.

[0014] The autocatalytically degradable porous iron-based bone implant of the present invention is prepared by the following technical steps:

[0015] Step 1 Mechanical mixing:

[0016] After drying the sodium chloride powder at a constant temperature, a certain mass is weighed and introduced into the iron powder in equal amounts in 2-5 portions, stirring for 3-5 minutes. During the stirring process, the powder is turned upside down to evenly disperse the sodium chloride powder.

[0017] Step 2: Ball milling dispersion:

[0018] After mechanical mixing, the mixed powder of iron powder and sodium chloride powder is loaded into a ball mill for ball milling dispersion, with a ball-to-material ratio of 7:1. The speed of the ball mill is 150-220 r / min. During the ball milling dispersion process, the ball mill runs for 30-45 minutes and stops for 3-5 minutes to avoid excessive heat generation in the ball mill due to friction. The ball milling time is 70-90 minutes.

[0019] Step 3: Electric spark sintering:

[0020] The iron powder and sodium chloride mixed powder after ball milling dispersion is solidified and formed by electric spark sintering process, the sintering temperature is 550-850 degrees, the sintering pressure is 0.5-1.1kN, and the holding time is 3-5 minutes;

[0021] Furthermore, in the self-catalytically degradable porous iron-based bone implant, the rotation speed of the ball mill is 200 r / min.

[0022] Furthermore, in the self-catalytically degradable porous iron-based bone implant, the electric spark sintering temperature is 600-750 degrees.

[0023] Furthermore, in the self-catalytically degradable porous iron-based bone implant, the electric spark sintering pressure is 0.7-1.1 kN.

[0024] In the present invention, the melting temperature of iron is higher than 1500 degrees, and the boiling point of sodium chloride is lower than 1500 degrees. Therefore, before the iron is fully melted, the sodium chloride will volatilize. In order to retain the sodium chloride to the greatest extent and avoid the loss of sodium chloride, the present invention uses an electric spark sintering process. This process can sinter and form at a temperature lower than the melting point of iron, thereby ensuring the chemical structure and physical properties of the sodium chloride, and fully exerting its self-catalytic effect to accelerate the degradation of the iron matrix.

[0025] The electric spark sintering process used can quickly form iron / sodium chloride bone implants. The rapid temperature rise limits grain growth and has a fine grain strengthening effect. At the same time, during the melting and solidification of the iron / sodium chloride bone implant, it is subjected to a certain amount of extrusion, avoiding structural defects such as micropores and cracks in conventional powder molding processes, improving structural integrity, and ensuring the mechanical stability of the iron / sodium chloride bone implant during degradation.

[0026] The electric spark sintering rapid prototyping of iron / sodium chloride bone implants is used, which can form large-sized block-shaped dense samples in one go. The size and shape of the sample can be formed according to the mold, which is convenient for subsequent processing and meets the requirements of large-sized complex structure bone implants.

[0027] In the present invention, after sodium chloride is added, it first hydrolyzes into chloride ions and sodium ions. This creates numerous micropores in the iron matrix, altering the surface morphology and increasing the surface area, causing localized corrosion. Large areas of localized corrosion manifest as macroscopic corrosion overall, thereby accelerating the degradation of the iron matrix. More importantly, the released active chloride ions have a small radius and a strong ability to adsorb and penetrate the iron matrix, further penetrating the crystal lattice, creating lattice defects and increasing the ability of corrosion to extend and expand. Simultaneously, the released chloride ions enhance local electrical conductivity, accelerate the separation of iron and electrons, and increase the dissolution rate of the iron matrix.

[0028] The sodium chloride content in the present invention needs to be strictly controlled. Although chloride ions are common components in the human body, chlorine is a highly corrosive ion. Excessive addition may cause uneven mixing in the iron matrix, accelerate pitting or crevice corrosion at local locations, and produce overall fracture failure forms such as localized corrosion deep holes. Therefore, the mechanical mixing and ball milling dispersion process steps of the iron / sodium chloride mixed powder are particularly important, including stirring time, ball milling time, ball-to-material ratio, etc.; if the amount of sodium chloride added is limited, the effect of improving the corrosion performance of the iron matrix is ​​limited, and it is difficult to achieve microscopic and macroscopic accelerated degradation effects. Therefore, it is necessary to reasonably select the powder ratio. In addition, the sodium chloride particle size also affects the corrosion effect.

[0029] The electric spark sintering process has a great influence on the forming performance of iron / sodium chloride bone implants. If the electric spark sintering temperature is low, the mixed powder is difficult to melt completely, the molded part contains powder particles and is soft, and the mechanical integrity of the molded sample is poor; if the electric spark sintering pressure is small, the density is greatly affected and the densification performance is low.

[0030] Compared with the prior art, the present invention has the following advantages:

[0031] (1) In the present invention, the iron / sodium chloride bone implant can gradually degrade as bone tissue repairs. The degradation process can be regulated by changing the sodium chloride content and the microstructure of the iron / sodium chloride bone implant, thereby overcoming the disadvantage of requiring secondary surgery to remove inert biomedical metals in clinical applications.

[0032] (2) In the present invention, the iron matrix degrades to produce substances such as iron oxides and hydroxides, which can be phagocytosed by phagocytes or excreted from the body through metabolism, without causing severe inflammation or toxicity, and thus have a certain degree of biosafety.

[0033] (3) In the present invention, the sodium chloride releases chloride ions and sodium ions. Chloride ions have a small radius and a strong ability to adsorb and penetrate the iron matrix, thereby enhancing the corrosion dynamics. At the same time, chloride ions are the main negative ions in human body fluids and are biosafe.

[0034] (4) In the present invention, the preparation method of the iron / sodium chloride bone implant is simple and reliable. The electric spark sintering can quickly solidify the iron and sodium chloride mixed powder, shorten the preparation time, and improve the performance of the sintered body.

[0035] (5) In the present invention, the sodium chloride as a physiological solution has important application value in many aspects such as medicine and biology. It can induce the polymerization of actin monomers, treat intestinal colic, supplement sodium salt, etc. At the same time, it is low in price and meets the needs of implants.

[0036] (6) In the present invention, the electric spark sintering rapid prototyping iron / sodium chloride bone implant can easily form large-sized block-shaped dense samples, and the sample forming performance is good, the operation is simple, and it saves time and labor.

[0037] (7) In the present invention, the spark-sintered iron / sodium chloride bone implant is easily formed into a porous structure after being washed with distilled water to dissolve the sodium chloride. DETAILED DESCRIPTION

[0038] Example 1

[0039] 2.8 wt.% sodium chloride was weighed and dried at a constant temperature. The sodium chloride had an average particle size of 30 microns. The mixture was introduced into iron powder with an average particle size of 64 microns in four equal portions and stirred for 5 minutes. The mixture was turned upside down during the stirring process to uniformly disperse the sodium chloride powder. After mechanical mixing, the iron powder and sodium chloride powder mixture was loaded into a ball mill for ball milling dispersion. The ball-to-material ratio was 7:1. The speed of the ball mill was 200 r / min. During the ball milling dispersion process, the ball mill was operated for 40 minutes and then stopped for 5 minutes, resulting in a ball milling time of 84 minutes. The iron powder and sodium chloride mixed powder after ball milling dispersion was solidified and formed using an electric spark sintering process. The sintering temperature was 710 degrees, the sintering pressure was 0.8 kN, and the holding time was 4 minutes.

[0040] Implementation effect:

[0041] The iron / sodium chloride bone implant prepared by the method has a density of 90% after being washed in distilled water. In an immersion test, the implant corrodes quickly and evenly, with an average corrosion depth of 24 microns after 5 days.

[0042] Example 2

[0043] 3.5 wt.% sodium chloride was weighed and dried at a constant temperature. The sodium chloride had an average particle size of 30 microns. The mixture was introduced into an iron powder with an average particle size of 64 microns in five equal portions and stirred for 5 minutes. The mixture was turned upside down during the stirring process to uniformly disperse the sodium chloride powder. After mechanical mixing, the iron powder and sodium chloride powder mixture was loaded into a ball mill for ball milling dispersion. The ball mill had a ball-to-material ratio of 7:1 and a rotation speed of 220 r / min. During the ball milling dispersion process, the ball mill was operated for 40 minutes and then stopped for 5 minutes, resulting in a ball milling time of 90 minutes. The iron powder and sodium chloride mixed powder after ball milling dispersion was solidified and formed using an electric spark sintering process. The sintering temperature was 750 degrees, the sintering pressure was 1.0 kN, and the holding time was 4 minutes.

[0044] Implementation effect: The density of the iron / sodium chloride bone implant prepared by this method was 88% after washing in distilled water. In the immersion test, it corroded quickly and evenly. After 5 days, the average corrosion depth was 27 microns.

[0045] Example 3

[0046] 1.2 wt.% sodium chloride was weighed and dried at a constant temperature to obtain an average particle size of 30 microns. The mixture was then introduced into an iron powder having an average particle size of 64 microns in three equal portions and stirred for 5 minutes. The mixture was turned upside down during the stirring process to uniformly disperse the sodium chloride powder. After mechanical mixing, the iron powder and sodium chloride powder mixture was loaded into a ball mill for ball milling dispersion at a ball-to-material ratio of 7:1. The ball mill rotated at a speed of 160 r / min. During the ball milling dispersion process, the ball mill was operated for 40 minutes and then stopped for 5 minutes, resulting in a ball milling time of 72 minutes. The iron powder and sodium chloride mixed powder after ball milling dispersion was solidified and formed using an electric spark sintering process. The sintering temperature was 730 degrees, the sintering pressure was 0.9 kN, and the holding time was 4 minutes.

[0047] Implementation effect: The density of the iron / sodium chloride bone implant prepared by this method was 94% after washing in distilled water. In the immersion test, it corroded quickly and evenly. After 5 days, the average corrosion depth was 15 microns.

[0048] Example 4

[0049] 1.8 wt.% sodium chloride was weighed and dried at a constant temperature to an average particle size of 30 microns. The mixture was then introduced into an iron powder having an average particle size of 64 microns in three equal portions and stirred for 5 minutes. The mixture was turned upside down during the stirring process to uniformly disperse the sodium chloride powder. After mechanical mixing, the iron powder and sodium chloride powder mixture was loaded into a ball mill for ball milling dispersion at a ball-to-material ratio of 7:1. The speed of the ball mill was 170 r / min. During the ball milling dispersion process, the ball mill was operated for 40 minutes and then stopped for 5 minutes, resulting in a ball milling time of 78 minutes. The iron powder and sodium chloride mixed powder after ball milling dispersion was solidified and formed using an electric spark sintering process. The sintering temperature was 750 degrees, the sintering pressure was 1.0 kN, and the holding time was 4 minutes.

[0050] Implementation effect: The density of the iron / sodium chloride bone implant prepared by this method was 92% after washing in distilled water. In the immersion test, it corroded quickly and evenly. After 5 days, the average corrosion depth was 17 microns.

[0051] Comparative Example 1

[0052] All other conditions were consistent with those in Example 1, except that sodium chloride powder and iron powder were stirred and mixed in a mass ratio of 15:85 to obtain a degradable iron-based implant. After washing with distilled water, the density was found to be low and the microscopic pore distribution was uneven. After compression of the block, lateral movement of the sample was found during the compression process, which may be due to uneven force in local areas. After immersion for 5 days, large corrosion pits were found, indicating the presence of localized corrosion.

[0053] Comparative Example 2

[0054] All other conditions were consistent with those in Example 1, except that sodium chloride powder and iron powder were stirred and mixed at a mass ratio of 0.3:99.5 to obtain a degradable iron-based implant. Testing revealed a high density of 98%, excellent overall molding performance, and slow corrosion after immersion for 5 days, approaching the corrosion level of pure iron.

[0055] Comparative Example 3

[0056] Other conditions were consistent with those in Example 2, except that the spark sintering temperature was 280 degrees, and a degradable iron-based implant was obtained. Testing found that the overall forming performance of the sample was poor and it did not have good mechanical integrity.

[0057] Comparative Example 4

[0058] Other conditions were consistent with those in Example 1, except that the ball-to-material ratio was 3:1, the ball mill speed was 80 r / min, and the ball milling time was 20 minutes. A degradable iron-based implant was obtained, and severe local corrosion holes and uneven corrosion were found.

[0059] As can be seen from Examples 1, 2, 3, and 4 and Comparative Examples 1, 2, 3, and 4, the components and preparation process of the present invention are an organic whole. When any one or more key parameters are outside the scope of protection of the present invention, the effect is significantly reduced. By comparing Example 1 of the present invention with Example 2, Example 3, and Example 4, it is found that the preferred embodiment of the present invention has an unexpected effect.

Claims

1. An autocatalytically degradable porous iron-based bone implant, characterized in that: The method for preparing the autocatalytically degradable porous iron-based bone implant comprises the following steps: (1) Mechanical mixing: After drying the sodium chloride powder at a constant temperature of 40-60 degrees, a certain mass is weighed and introduced into the iron powder in equal amounts in 2-5 batches and stirred for 3-5 minutes. During the stirring process, the sodium chloride powder is evenly dispersed by turning it upside down; (2) Ball milling dispersion: The iron powder and sodium chloride powder are mixed and loaded into a ball mill for ball milling dispersion, with a ball-to-material ratio of 7:

1. The rotation speed of the ball mill is 150-220 r / min. During the ball milling dispersion process, the ball mill runs for 30-45 minutes and stops for 3-5 minutes to avoid excessive heat generation in the ball mill due to friction. The ball milling time is 70-90 minutes. (3) Electric spark sintering: The iron powder and sodium chloride mixed powder after ball milling dispersion is solidified and formed by electric spark sintering process. The sintering temperature is 550-850 degrees, the sintering pressure is 0.5-1.1kN, and the holding time is 3-5 minutes.

2. The autocatalytically degradable porous iron-based bone implant according to claim 1, characterized in that: In the self-catalytically degradable porous iron-based bone implant, the mass percentage of sodium chloride is 1.2-3.2 wt.%.

3. The autocatalytically degradable porous iron-based bone implant according to claim 1, characterized in that: In the self-catalytically degradable porous iron-based bone implant, the mass percentage of sodium chloride is 2.8 wt.%.

4. The autocatalytically degradable porous iron-based bone implant according to claim 1, characterized in that: In the self-catalytically degradable porous iron-based bone implant, the size of the sodium chloride powder is 20-45 microns, and the size of the iron powder is 40-80 microns.

5. The autocatalytically degradable porous iron-based bone implant according to claim 1, characterized in that: The iron-based bone implant has a density of 85-95%.

6. The autocatalytically degradable porous iron-based bone implant according to claim 5, characterized in that: The iron-based bone implant has a density of 87-93%.

7. The method for preparing a self-catalytically degradable porous iron-based bone implant according to claim 1, characterized in that: The rotation speed of the ball mill is 200 r / min.

8. The method for preparing a self-catalytically degradable porous iron-based bone implant according to claim 1, characterized in that: The electric spark sintering temperature is 600-750 degrees.

9. The method for preparing a self-catalytically degradable porous iron-based bone implant according to claim 1, characterized in that: The spark burning pressure is 0.7-1.1kN.