【Popular Science Tips on Polymers and Materials】--025 Popular Science Tips on Polymer Materials Used in Medical \"Artificial Blood Vessels\" + ljtjbx

Polyester artificial blood vessels were the first vascular materials to be used, and due to their high patency rate, they have been successfully employed for the replacement of large blood vessels for a long time; however, they cannot fully meet the requirements for manufacturing small-diameter artificial blood vessels. The silk artificial blood vessels developed later were limited in their clinical application due to the unstable spiral wrinkling, which caused the vessels to collapse, as well as their poor shape retention and low strength. The most widely used artificial vascular material both domestically and internationally is expanded polytetrafluoroethylene, which possesses good biocompatibility and anticoagulant properties; however, it has poor compliance, and the patency rate of grafts using this material is only 30%. These shortcomings are even more pronounced in ePTFE artificial blood vessels with a diameter of less than 6 mm, resulting in an extremely poor long-term patency rate. The fundamental flaw of all three of them is their very poor compliance; they lack entirely the flexibility and elasticity of human arteries. This defect becomes particularly evident when connecting to small-diameter arteries, and it is also the main reason why blood clots tend to form at the site of the connection. The research and development of small-diameter artificial blood vessels have been a hot topic internationally over the past decade, but to date no commercial products have been developed. The reason for this is that the biocompatibility and anticoagulant properties required for small-diameter artificial blood vessels are much higher than those needed for conventional large-diameter ones. Currently, around 1 million heart disease patients worldwide need to undergo coronary artery bypass surgery each year. The blood vessels used for these surgeries are still taken from the patients’ own bodies, but the supply of such blood vessels is limited, and the procedure involves significant trauma. What is urgently needed now is the development of small-diameter artificial blood vessels that meet the requirements for bypass surgery, and the market prospects for such products are very promising. In recent years, polyurethane (PU) materials have attracted considerable attention. Compared with ePTFE, these materials exhibit better biocompatibility. Some believe that artificial blood vessels made from PU materials can solve the aforementioned problems; therefore, it is a research focus for many scholars abroad at present. There are also numerous research reports on PU-type small-diameter artificial blood vessels in China. The microphase-separated structure of polyurethane materials endows them with better biocompatibility than other polymer materials, including blood compatibility and tissue compatibility. This structure is very similar to the inner wall of blood vessels in living organisms: on a macroscopic level it presents as a highly smooth surface, but at the microscopic level it consists of a double-layer lipid liquid matrix with various glycoproteins and glycolipids embedded within it. This structure, which is macroscopically smooth but microscopically multiphase-separated, endows the blood vessel wall with excellent anticoagulant properties. At the same time, PU possesses excellent fatigue resistance, wear resistance, high elasticity, and high strength; therefore, it is widely used in the field of biomedical materials for manufacturing artificial hearts, artificial livers, interventional catheters, and polymers for controlled drug release, among other applications. PU has been used in living organisms for many years, while research on its use in artificial blood vessels is only 10 years old. Gupta combined PU with polyester to create an artificial blood vessel with an inner diameter of 4–6 mm, whose compliance was very similar to that of the human common carotid artery. Tests in dogs showed that after 6 months of implantation, this vessel maintained good patency, and a thin layer of stable intimal tissue formed on its surface. Jeschke developed PU blood vessels with an inner diameter of 1.5 mm and a length of 10 mm; animal experiments comparing these carbonized PU blood vessels with ePTFE blood vessels showed that the PU blood vessels had superior performance. Although PU has been implanted in the human body for 30 years, the existing PU materials still fail to meet the high standards required for the clinical use of artificial blood vessels. If it is found during long-term use that PU undergoes aging, degradation, and calcification in the body, cracks may appear in the material, or it may even be completely destroyed. Many researchers have studied the degradation mechanism of PU, suggesting that it is primarily caused by oxidative degradation mediated by immune cells such as macrophages and giant cells. From the animal experiments we conducted earlier, we found that in small-diameter PU composite artificial blood vessels implanted into dog carotid arteries, histopathological examination performed after 2 months revealed significant infiltration of inflammatory cells within the vessel walls, further confirming the aforementioned conclusion. Therefore, the inflammatory response is the fundamental factor that triggers degradation; thus, improving the tissue compatibility of a material means preventing or minimizing the inflammatory response induced by that material in the body. However, when the material is modified to improve its tissue compatibility, it often has a negative impact on the material’s mechanical properties and even its blood compatibility.

Scientists use 3D printing technology: German scientists have recently succeeded in developing an artificial blood vessel using 3D printing technology. This research finding is expected to be used in human trials and drug testing. After years of relentless research, this challenge has now been solved by scientists at Germany’s Fraunhofer Institute. They used composite polymer materials combined with biomolecules capable of effectively resisting rejection reactions to create a special \"printing ink.\" The material printed using this ink can form an elastic solid through chemical reactions, allowing scientists to shape it into 3D artificial blood vessels based on the structure of human blood vessels. In fact, the precision of 3D printing technology is truly astonishing. To create artificial blood vessels with the highest degree of similarity to natural ones, scientists also used two-photon polymerization technology, employing laser light to stimulate the cross-linking of molecules in the material of the artificial blood vessels, after which the resulting blood vessels were implanted onto the inner wall of cells. With the rapid advancement of biomedical technology, scientists have successfully created small human organs such as artificial intestines and artificial tracheas. However, the production of large artificial organs often encounters bottlenecks, mainly due to the lack of the necessary technology for creating capillaries; as a result, these organs cannot be supplied with the essential nutrients required for them to function properly and survive. It is reported that this research achievement will significantly advance the production of large human organs. Although the dream of transplanting artificial organs is still far off, the rapid advancement in technology for manufacturing human organs can provide more effective and humane experimental methods for medical research, such as using artificial organs instead of animals in the development of new drugs.

The requirements for artificial blood vessels are stable physical and chemical properties； The mesh density is appropriate ； It possesses a certain degree of strength and flexibility ； It has good sutureability during bypass surgery, and this gives excellent results. . . . . . . . . . . . .

Is it expensive? Is it helpful for blood clots?

This technology already exists. But it will probably take a very long time before this is applied to ordinary people – maybe even several years! The progress of science is unstoppable

It looks really premium, but its practicality will have to be tested by time

No wonder there are some old perverts. . . :shut up:

The standard of medical care is really crucial! Just like that certain basketball star’s narrow escape, I truly admire the level of medical care. If it were handled by us, we would have issued a notice long ago

I’ve learned something new; one should keep learning throughout life