Superoxide dismutase-based third-generation biosensor for superoxide anion.
A third-generation biosensor for superoxide anion (O2-) was developed by immobilizing superoxide dismutase (SOD) on a self-assembled monolayer of cysteine on gold electrode; i.e., a SOD/cysteine-modified gold electrode (SOD/Cys/Au) was fabricated. A rapid and direct electron transfer of SOD was realized at the gold electrode by using the cysteine molecule as an electron-transfer promoter. The promoted direct electron transfer of SOD and biomolecular recognition by the exploitation of specific and significant enzyme-substrate reactivity of SOD toward O2- combined with the low operating potential enabled a sensitive measurement of O2-. At SOD/Cys/Au, O2- could be specifically oxidized and reduced to O2 and hydrogen peroxide, respectively, through the inherent catalytic reaction of SOD. This allowed us to measure O2- by polarizing the electrode both anodically and cathodically. We could successfully measure O2- by suitably polarizing the electrode, typically at 300 and -200 mV versus Ag/AgCl without the virtual interference from physiological levels of H2O2, ascorbic acid, uric acid, and metabolites of neurotransmitters. The response mechanism of SOD/Cys/Au to O2- and its sensor characteristics are also presented and discussed.
Tian
Yang
Y
Department of Electronic Chemistry, Interdisciplinary Graduate School of Science and Engineering, Tokyo Institute of Technology, Yokohama, Japan.
Mao
Lanqun
L
Okajima
Takeyoshi
T
Ohsaka
Takeo
T
D000818:Animals; D015374:Biosensing Techniques / Q000379:methods*; D002417:Cattle; D004566:Electrodes; D004800:Enzymes, Immobilized; D012680:Sensitivity and Specificity; D013379:Substrate Specificity; D013482:Superoxide Dismutase / Q000378:metabolism*; D013481:Superoxides / Q000032:analysis*
D004800:Enzymes, Immobilized; D013481:Superoxides; D013482:Superoxide Dismutase