Utilization of Metals to Frontier Medical Devices

The demand for metallic materials in medical and dental devices is large. These materials are conventionally used because of their high durability, strength, and formability. Metallic materials in medical devices cannot be replaced with ceramics or polymers at present, mainly because the metallic materials have greater strength and toughness. However, metallic materials are generally not expected to be the biomaterials of the future at the research level because they do not have bioactive and biofunctional properties. This viewpoint is shortsighted and reflects misunderstandings. Biomaterials are always used in contacting tissues. Therefore, interactions among material surfaces and tissues must be well understood: This knowledge is essential to develop new novel materials. In particular, metal surface-biomolecule reactions and/or metal surface-cell reactions are important. A good knowledge of these reactions can help to add biofunctions to metallic materials that already have excellent mechanical properties. Finally through surface modification techniques such as multi-layer coating and patterning of multi-functional layers, it is possible to arrive at an optimal range of biofunctions in a biomaterial. Biofunctions are required for metals recently. For example, stents are placed at stenotic blood vessels for dilatation, and blood compatibility or prevention of adhesion of platelet is necessary. In guide wires and guiding cathetels, sliding lubrication in blood vessel is important when those are inserted into there. In addition, if metals were used for a sensing device, the control of cell adhesion is necessary. Also, application of metals will be expanded to new medical devices, scaffold for tissue engineering, artificial organs, etc. with the addition of biofunction. Therefore, immobilization or combination of functional polymers to metals is significant subject for the application of metals to biofunctional materials and sensors.