Intracranial artery stenosis is an important cause of ischemic stroke.
At present, stent placement is one of the effective means to treat intracranial artery stenosis, but most cerebral vascular stents are made of traditional alloy materials and cannot be degraded.
Therefore, the stent will be permanently indwelled in the body after implantation, which is very likely to cause symptoms such as chronic vascular inflammation, delayed vascular healing, and stent thrombosis. Patients need to take antiplatelet drugs for life to reduce the chance of complications, which will naturally cause a huge psychological burden on patients and put pressure on medical resources.
Based on 22 years of clinical research experience on cerebrovascular diseases, Professor Liu and his team from BJTT Medical Devices Corporation observed this medical pain point and began to study degradable cerebrovascular stents. After 6 years, finally developed the "degradable zinc alloy head and neck support"
Professor Liu told us: "This degradable cerebrovascular stent can be said to be the first. It not only has good support, but also has a fast degradation speed. It has great application space in the field of cerebrovascular."
Magnesium alloy materials can not only meet the support force, but also achieve cell phagocytosis and degradation, which is almost a perfect material. However, the degradation rate of magnesium alloys is too fast, and it is completely degraded in 6-12 months. Such a short degradation time does not guarantee complete recovery of blood vessels, therefore, this material is not suitable.
Because the mechanical properties of zinc alloy materials are much greater than the requirements of biodegradable vascular stent materials and orthopedic implant materials. And in vivo and in vitro studies can prove that the zinc alloy is non-toxic and has good biocompatibility. All in all, both in terms of support and degradation speed, zinc alloys are the most ideal material for the fit.
Professor Liu introduced: "From our experimental results, we can see that the zinc alloy material begins to degrade gradually after half a year, and can achieve 90%-95% degradation in about two to three years, ensuring the support of our blood vessels. It is a very good material for cerebrovascular stents.
Finalizing the material is only the first step in the development of degradable vascular stents. Professor Liu has his own ingenuity in stent shaping, material thickness and drug coating.
The first is stent shaping. Because the diameter of cerebral blood vessels is very small, much thinner than that of cardiac blood vessels, the requirements for the fineness of stents are even higher.
Professor Liu explored the scientific laws of the solidification and cold and hot forming process of zinc-copper alloys through multi-scale simulation methods.
Professor Liu's successful exploration of the laws of zinc alloys is not only a major breakthrough in the "degradable cerebral vascular stent" project, but also lays a solid foundation for the application and development of zinc alloy materials in the future.
The second is to control the thickness of the stent. In order to ensure that after the stent is implanted, the inner diameter of the blood vessel will not be compressed and affect the blood flow, the thickness of the stent must be very thin.
Of course, the thickness control can be achieved through industrial technology, but industrial technology cannot achieve the control of 0.8-0.7 mm, so we have to work hard on the structure.
Professor Liu adopted the "double S" structure design, which reduces the area of materials used and the space occupied by blood vessels.
"The stent formed by the 'double S' structure is thinner than the existing intracranial stent, and the blood flow is definitely better, reducing the risk of vascular blockage in patients. At present, our technology can reduce the thickness of the stent. It remains at 0.8mm, but at this stage the world's thinnest can be 0.7mm. In the next step, we also hope to improve the thickness of the stent to 0.7mm. This is the limit and our goal."
Finally, pharmaceutical coatings are just as critical. After the stent is implanted in the body, it is very likely to have a rejection reaction, so it is necessary to cover the surface of the stent with a drug coating to reduce the risk of rejection.
Professor Liu used asymmetric coating technology. The stent is coated with a drug coating, and can be rapidly endothelialized when it is implanted into the body in contact with the vascular endothelium. The stent will be wrapped into the vascular endothelium, and the stability and vascular support will be greatly improved.
The invention of this technology can not only be used for intracranial stents, but also can be used and expanded in fields such as cardiac stents.
Professor Liu introduced: "Our research on asymmetric coating drug technology is a technology pioneered in China, and it has obtained the international PCT patent authorization.