Direct electron transfer and bioelectrocatalysis of hemoglobin on nano-structural attapulgite clay-modified glassy...

Direct electrochemistry of hemoglobin (Hb) on natural nano-structural attapulgite clay film-modified glassy carbon (GC) electrode was investigated. The interaction between Hb and attapulgite was examined using UV-vis, FTIR spectroscopy, and electrochemical methods. The immobilized Hb displayed a couple of well-defined and quasi-reversible redox peaks with the formal potential (E(0')) of about -0.366 V (versus SCE) in 0.1 M phosphate buffer solution of pH 7.0. The current was linearly dependent on the scan rate, indicating that the direct electrochemistry of Hb in that case was a surface-controlled electrode process. The formal potential changed linearly from pH 5.0 to 9.0 with a slope value of -48.2 mV/pH, which suggested that a proton transfer was accompanied with each electron transfer in the electrochemical reaction. The immobilized Hb exhibited excellent electrocatalytic activity for the reduction of hydrogen peroxide without the aid of an electron mediator. The electrocatalytic response showed a linear dependence on the H(2)O(2) concentration ranging from 5.4 x 10(-6) to 4.0 x 10(-4) M with the detection of 2.4 x 10(-6) M at a signal-to-noise ratio of 3. The apparent Michaelis-Menten constant K(M)(app) for the H(2)O(2) sensor was estimated to be 490 microM, showing a high affinity.