Electrochemistry and biosensing activity of cytochrome c immobilized in macroporous materials

An amperometric biosensor for hydrogen peroxide (H(2)O(2)) has been constructed by immobilizing cytochrome c on an indium/tin oxide (ITO) electrode modified with a macroporous material. Cyclic voltammetry showed that the direct and quasi-reversible electron transfer of cytochrome c proceeds without the need for an electron mediator. A surface-controlled electron transfer process can be observed with an apparent heterogeneous electron-transfer rate constant (k(s)) of 29.2 s(-1). The biosensor displays excellent electrocatalytic responses to the reduction of H(2)O(2) to give amperometric responses that increase steadily with the concentration of H(2)O(2) in the range from 5 mu M to 2 mM. The detection limit is 0.61 mu M at pH 7.4. The apparent Michaelis-Menten constant (K(m)) of the biosensor is 1.06 mM. This investigation not only provided a method for the direct electron transfer of cytochrome c on macroporous materials, but also established a feasible approach for durable and reliable detection of H(2)O(2).