High-Nitrogen Nickel-Free Stainless Steel: An Attractive Material with Potential for Biomedical Application

Metal materials such as stainless steel, cobalt-based alloy, and NiTi alloy used in clinic contain a certain amount of nickel (Ni) for the structure stability. Nickel ions can gradually dissolve into the human body even with much slow corrosion rate, causing allergic, inflammation, local tissue proliferation, and other adverse reactions to some people. To avoid these adverse effects of nickel, a new high-nitrogen nickel-free stainless steel (HNNFSS) using nitrogen and manganese instead of nickel to stabilize the austenite structure is developed, which exhibits much better mechanical properties, good corrosion resistance, and biocompatibility. Compared with the conventional orthopedic metal implants, the adhesion strength of HNNFSS implant with the surrounding tissue in animal is found to be stronger with new bone formation, promoted by both alkaline phosphatase (ALP) and osteocalcin (OCN) expressions. The vascular stent made of HNNFSS shows lower restenosis rate compared with the traditional 316L stainless steel stent, which is attributed to the promotion of endothelial cell and inhibition of smooth muscle cells, and superior blood compatibility. In conclusion, results from large number of studies show that high-nitrogen nickel-free stainless steel as a new kind of high-performance biomedical metallic material possesses great application potential.