The latest Development of Medical Stainless Steel Research
Medical stainless steel has become a widely used medical implant material and medical tool material due to its good biocompatibility, mechanical properties, body fluid corrosion resistance, excellent processing and forming properties, and low cost. Medical stainless steel is different from industrial stainless steel. It is required to maintain excellent corrosion resistance (including resistance to intergranular corrosion, stress corrosion, and other local corrosion), so as to prevent premature failure of implanted devices, reduce the dissolution of harmful metal ions, and ensure stainless steel implanted devices Safety in clinical application.
Therefore, medical stainless steel mainly uses austenitic stainless steel with the best corrosion resistance as the implant material. At present, 316L and 317L of the Fe-Cr-Ni-Mo composition system are mainly used in clinical practice with stable austenitic structures. Stainless steel material.
However, due to the relatively low strength and high elastic modulus of austenitic stainless steel, steel generally contains more than 10% nickel. Compared with other structural materials currently in clinical applications, it faces increasing challenges. Therefore, it has important practical significance to develop new medical stainless steel and further improves the performance of medical stainless steel. At present, domestic research institutions have developed a series of new medical stainless steels such as high-nitrogen nickel-free austenitic stainless steel, antibacterial stainless steel, and anti-ISR (in-stent restenosis) stainless steel for cardiovascular stents.
High nitrogen nickel-free austenitic stainless steel has excellent performance
In view of the possible harm caused by nickel in stainless steel, research and development of low-nickel and nickel-free medical austenitic stainless steel has become a major development and application trend of medical stainless steel in the world. Nitrogen (N) has a strong effect on stabilizing the austenite structure in steel. Therefore, using (nitrogen + manganese) to replace nickel in stainless steel can stabilize the austenite structure and significantly improve the mechanical properties and corrosion resistance of stainless steel.
Performance has become the main way to develop nickel-free austenitic stainless steel. The high-nitrogen nickel-free stainless steel (Fe-21Cr-22Mn-1Mo-1N) listed in the American material standard (ASTM-F2229) has begun to be used in the European and American medical markets and used to replace the Cr-Ni series of stainless steel to process bone fixation equipment and Surgical tools.
My country’s research in this area has also made important progress. A new type of medical high-nitrogen nickel-free austenitic stainless steel (Fe-l7Cr-14Mn-2Mo-(0.45~0.7)N) has been developed, which has obtained a national invention patent. At the same time, the enterprise standard (QKJ.05.10-2008) of high-nitrogen nickel-free austenitic stainless steel for surgical implantation was also promulgated.
A large number of studies have shown that compared with 316L stainless steel, this new type of high-nitrogen nickel-free stainless steel has better mechanical properties. The tensile strength, fatigue strength, and wear resistance are increased by more than two times. The anticoagulant performance is also significantly improved.
The application prospect of antibacterial stainless steel is broad
Data shows that in the United States, there are as many as 2 million nosocomial infections every year, of which 1 million nosocomial infections are caused by implanted medical devices. In the UK, it costs 7 to 11 million pounds to treat bacterial infections caused by implanted medical devices each year. Moreover, as more and more resistant bacteria appear, the treatment of bacterial infections becomes more and more difficult.
To this end, the Ministry of Health and the General Logistics Department of my country formulated and issued the “2011 Special Remediation Activities Plan for the Clinical Application of Antimicrobial Drugs” in 2011, and decided to carry out special remediation activities for the clinical application of antimicrobial drugs nationwide and throughout the military. It is foreseeable that in the future, the application of antibacterial stainless steel in my country’s medical field will become wider and wider.
Antibacterial stainless steel is based on the chemical composition of medical stainless steel with antibacterial elements, and after appropriate antibacterial heat treatment, the stainless steel has a sterilization function. Further studies have shown that antibacterial stainless steel can strongly inhibit the formation of bacterial biofilm on its surface, thereby inhibiting the occurrence of infections caused by bacterial biofilm.
Therefore, the copper-containing antibacterial stainless steel is expected to exert its unique antibacterial properties and necessary mechanical load-bearing capacity in the repair and replacement of hard tissues such as orthopedics and stomatology, as well as in medical clinical fields such as cardiovascular stent intervention.
Anti-ISR stainless steel is expected to be used in the manufacture of cardiovascular stents
The cardiovascular intervention has treated a large number of patients with coronary heart disease caused by coronary artery stenosis. However, after stent implantation, it is easy to cause the clinical problem of ISR, especially within 3~6 months after stent implantation, the incidence of ISR is as high as 20%~30%. Studies have found that trace copper has many benefits to the cardiovascular system of the human body. If the trace copper is continuously released in situ in the stent, the occurrence of restenosis in the stent can be suppressed from the material aspect.
To this end, domestic research institutions have developed copper-containing stainless steel for cardiovascular stents based on the widely used clinically widely used 316L stainless steel for cardiovascular stents, which can continuously release trace copper elements in situ after implantation. So that the stent can inhibit ISR while playing mechanical support.
Research results show that copper-containing stainless steel can significantly reduce the adhesion of platelets on its surface, thereby reducing the tendency of thrombus formation. It can be seen that the copper-containing stainless steel should have the medical function of significantly inhibiting the occurrence of ISR, so it is expected to be used in the manufacture of cardiovascular stents.