TY  - JOUR
A1  - Zeng, Ting
A1  - Leimkühler, Silke
A1  - Koetz, Joachim
A1  - Wollenberger, Ursula
T1  - Effective Electrochemistry of Human Sulfite Oxidase Immobilized on Quantum-Dots-Modified Indium Tin Oxide Electrode
JF  - ACS applied materials & interfaces
N2  - The bioelectrocatalytic sulfite oxidation by human sulfite oxidase (hSO) on indium tin oxide (ITO) is reported, which is facilitated by functionalizing of the electrode surface with polyethylenimine (PEI)-entrapped CdS nanoparticles and enzyme. hSO was assembled onto the electrode with a high surface loading of electroactive enzyme. In the presence of sulfite but without additional mediators, a high bioelectrocatalytic current was generated. Reference experiments with only PEI showed direct electron transfer and catalytic activity of hSO, but these were less pronounced. The application of the polyelectrolyte-entrapped quantum dots (QDs) on ITO electrodes provides a compatible surface for enzyme binding with promotion of electron transfer. Variations of the buffer solution conditions, e.g., ionic strength, pH, viscosity, and the effect of oxygen, were studied in order to understand intramolecular and heterogeneous electron transfer from hSO to the electrode. The results are consistent with a model derived for the enzyme by using flash photolysis in solution and spectroelectrochemistry and molecular dynamic simulations of hSO on monolayer-modified gold electrodes. Moreover, for the first time a photoelectrochemical electrode involving immobilized hSO is demonstrated where photoexcitation of the CdS/hSO-modified electrode lead to an enhanced generation of bioelectrocatalytic currents upon sulfite addition. Oxidation starts already at the redox potential of the electron transfer domain of hSO and is greatly increased by application of a small overpotential to the CdS/hSO-modified ITO.
KW  - human sulfite oxidase
KW  - direct electrochemistry
KW  - bioelectrocatalysis
KW  - photocurrent
KW  - CdS quantum dots
Y1  - 2015
U6  - https://doi.org/10.1021/acsami.5b06665
SN  - 1944-8244
VL  - 7
IS  - 38
SP  - 21487
EP  - 21494
PB  - American Chemical Society
CY  - Washington
ER  -