Amperometric biosensors typically use a working electrode made of a noble metal such as gold, titanium, or nickel, or coated carbon with bioreceptor elements. Indium tin oxide (ITO) is also a commonly used material for this purpose. When a potential is applied, the enzymatic conversion or absorption of proteins on the surface of the electrode generates current. This current is directly proportional to the concentration of the analyte and can be used to quantify its presence. The sensitivity and selectivity of the biosensor depend on the bioreceptor used and the properties of the electrode material.