Absorbable Iron Alloy Stent

Abstract

The invention discloses an absorbable iron alloy stent, comprising an iron alloy substrate and a degradable polymer in contact with the surface of the substrate, in which the degradable polymer has a weight average molecular weight of more than or equal to 20,000 and less than or equal to 1,000,000 and a polydispersity index of more than 1.0 and less than or equal to 50. After the iron alloy stent is implanted into the body, the degradable polymer degrades to produce a carboxyl group. After the degradable stent is implanted into the human body, the effects of oxygen-consuming corrosion enable the stent both to mainly function as a mechanical support and then to degrade gradually, and the amount of hydrogen produced in the degradation process does not reach the level that can lead to a risk of air embolism.

Description

TECHNICAL FIELD[0001]The present invention relates to a degradable implantable medical device, and particularly relates to an absorbable iron-based alloy device capable of degrading rapidly and controllably within a predetermined period.BACKGROUND ART[0002]At present, the implantable medical devices are usually made from metals and their alloys, ceramics, polymers and the related composite materials, wherein the metal-based implantable medical devices are particularly popular because of their superior mechanical properties, such as high strength, and high toughness.[0003]Iron as an important element in the human body, is involved in many biochemical processes, such as in the delivery of oxygen. Easily corrosive pure iron stents each of the shape similar to that of a clinically used metal stent, made by Peuster M et al. through a laser engraving method, were respectively implanted to the descending aortas of 16 New Zealand rabbits. The animal experimental results showed that there wa...

AI Technical Summary

Benefits of technology

[0012]The term “rapid” means that the degradable polyester can accelerate the corrosion of the iron-based alloy substrate, so that the iron-based alloy substrate can completely corrode within 5 years after being implanted into the body.

[0013]The term “controllable” means that the corrosion of the iron-based alloy substrate caused by the degradable polyester ensures that the iron-based alloy stent has good mechanical properties at early stage after being implanted into the human body, and also enables the stent to produce a small amount of hydrogen or no hydrogen. A small amount of hydrogen refers to an amount that is not sufficient to form a risk of air embolism clinically.

[0044]Compared with the prior art, the specific degradable polymer used by the absorbable iron-based alloy stent provided by the present invention can allow the iron-based alloy substrate to undergo oxygen-consuming corrosion under the action of the degradable polymer, with minimal or no hydrogen produced, thus avoiding the clinical air embolism risk caused by a large amount of hydrogen being produced by hydrogen evolution corrosion in the prior art, and also meeting the clinical early mechanical property requirements for the stent.

Problems solved by technology

But the study also found that the corrosion rate of pure iron was relatively slow in vivo, which cannot meet the clinical degradation time requirement for the degradable stent, thus the corrosion rate of iron needed to be accelerated.

The literature also indicated that the degradation process of iron-based alloy was accompanied by the oxygen-consuming corrosion process and the hydrogen evolution corrosion process, and because the highest oxygen-consuming corrosion rate of a solution in the local subacid environment is a constant value, it is difficult to improve the corrosion rate of the iron-based alloy by speeding up the oxygen-consuming corrosion rate.

In addition, the literature only provided experimental data to indicate that the corrosion rate of iron-based alloy was increased under the action of polyester, and did not disclose the molecular weight and molecular weight distribution of the polymer, namely, did not disclose the match between the degradable polymer degradation and the iron-based alloy substrate corrosion.

The literature also did not provide any experimental data to prove that the iron-based alloy stent can meet the clinical early mechanical property requirement after being implanted into the human body, and also did not disclose the corrosion period of the stent, so that whether the stent meets the clinical property requirement for the stent cannot be known by those skilled in the art.

In fact, a large amount of hydrogen produced by hydrogen evolution corrosion will cause the tissue tolerance risk such as formation of air embolism, so that the stent cannot be used clinically.

If the corrosion rate of iron is too rapid, it is possible that the iron-based alloy stent at early stage (such as 3 months) after the implanting would not have sufficient structural integrity, and it is difficult to reach the radial support force required by the blood vessel clinically, so that the stent loses its clinical application value.

Otherwise, if an increase in the corrosion rate of iron caused by the polymer is limited, the corrosion period of the iron-based alloy is longer, and it is difficult to meet the clinical degradation time requirement for the degradable stent.

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