Carbohydrate adhesion gives stainless steel implants beneficial new functions

Implanted biomedical devices, such as cardiac stents, are implanted in over 2 million people every year, with the majority made from stainless steel. Stainless steel has many benefits -- strength, generally stability, and the ability to maintain the required shape long after it has been implanted. But, it can also cause severe problems, including blood clotting if implanted in an artery, or an allergenic response due to release of metal ions such as nickel ions.

The University of Alberta campus is home to a highly multidisciplinary group of researchers, the CIHR Team in for Glyconanotechnology in Transplantation, that is looking to develop new synthetic nanomaterials that modify the body's immune response before an organ transplant. The ultimate goal is to allow cross-blood type organ transplants, meaning that blood types would not necessarily need to be matched between donor and recipient when an organ becomes available for transplantation. Developing new nanomaterials that engage and interact with the body's immune system are an important step in the process. In order to overcome the complex range of requirements and issues, the project team drew on expertise from three major areas: surface science chemistry and engineering, carbohydrate chemistry, and immunology and medicine.

For the transplantation goals of the project, sophisticated carbohydrate (sugar) molecules needed to be attached 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 team found that by first coating the surface of the stainless steel with a very thin layer (60 atoms deep) of glass silica using a technique available at the National Institute for Nanotechnology, called Atomic Layer Deposition (ALD), they could overcome the inherent non-reactivity of the stainless steel. The silica provide a well-defined "chemical handle" through which the carbohydrate molecules, prepared in the Alberta Ingenuity Centre for Carbohydrate Science, could be attached. Once the stainless steel had been controlled, the researchers demonstrated that the carbohydrate molecules covered the stainless steel in a highly controlled way, and in the correct orientation to interact with the immune system.