A new chemical bonding process can add new functions to stainless steel and make it a more useful material for implanted biomedical devices. Developed by an interdisciplinary team at the University of Alberta and Canada’s National Institute for Nanotechnology, this new process was developed to address some of the problems associated with the introduction of stainless steel into the human body.
Implanted biomedical devices, such as cardiac stents, are implanted in more than two million people every year. Most of the implants are made from stainless steel. While stainless steel has many benefits, including strength, stability and the ability to maintain the required shape long after implantation, it can also cause severe problems: blood clotting, if it is implanted in an artery, or an allergenic response caused by release of metal ions such as nickel ions.
In the process of developing new synthetic nanomaterials that modify the body’s immune response before an organ transplant, researchers needed to attach sophisticated carbohydrate (sugar) molecules to the stainless steel surface to bring about the necessary interaction with the body’s immune system. Its inherent stainless characteristic makes stainless steel a difficult material to augment with new functions, particularly with the controlled and close-to-perfect coverage needed for biomedical implants. The Edmonton-based researchers found that by coating the stainless steel surface first with a very thin layer (60 atoms deep) of glass silica by means of atomic layer deposition (ALD)—a technique that is available at the National Institute for Nanotechnology—they could overcome the material’s inherent nonreactivity. The silica provides a well-defined “chemical handle” by which the carbohydrate molecules, prepared in the Alberta Ingenuity Centre for Carbohydrate Science, can be attached. Once the stainless steel had been controlled, the researchers were able to demonstrate that the carbohydrate molecules covered the stainless steel in a highly controlled way and in the correct orientation to interact with the immune system.Yvonne Klöpping