Immobilization of cytochrome c oxidase into electrode-supported lipid bilayer membranes for in vitro cytochrome c sensing

Blood and tissue biochemical oxidation-reduction (redox) reactions are ubiquitous and are reflective of many important biological processes in the body, ranging from the state of cellular oxygenation to the overall antioxidant status. It is likely that, similar to acid-base balance, the body optimally operates within a narrow redox potential range made possible by various homeostatic mechanisms, and that deviation from this range will occur in tissue damage. A means to monitor the redox potential of blood or tissue would be valuable in both the diagnosis and treatment of diseases or conditions that adversely affect the body's redox potential. The biosensor described herein involves the immobilization of bovine cytochrome c oxidase (CCO) into electrode-supported lipid bilayer membranes. As a first proof of concept, the biosensor was used to potentiometrically monitor the concentration ratio of a redox pair (oxidized and reduced cytochrome c) in an in vitro system. The response of this modified electrode is reproducible and exhibits Nernstian behavior consistent with the four-electron reduction of the CCO. The oxidase-modified electrode can also operate as an amperometric biosensor for the detection of solution-resident ferrocytochrome c at concentrations as low as 0.1 mu M. Because this biosensor uses an electron sensor native to the body, it may be of future value to explore the biosensor as a point of care test to measure blood redox potential or perhaps as an implantable sensor to measure tissue redox potential in many settings.