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Electrochemical sensing of membrane potential and enzyme function using gallium arsenide electrodes functionalized with supported membranes

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Grunze,  Michael
Cellular Biophysics, Max Planck Institute for Medical Research, Max Planck Society;

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Citation

Gassull, D., Ulman, A., Grunze, M., & Tanaka, M. (2008). Electrochemical sensing of membrane potential and enzyme function using gallium arsenide electrodes functionalized with supported membranes. The Journal of Physical Chemistry B, 112(18), 5736-5741. doi:10.1021/jp711068b.


Cite as: https://hdl.handle.net/21.11116/0000-0001-9A49-0
Abstract
We deposit phospholipid monolayers on highly doped p-GaAs electrodes that are precoated with methyl-mercaptobiphenyl monolayers and operate such a biofunctional electrolyte-insulator-semiconductor (EIS) setup as an analogue of a metal-oxide-semiconductor setup. Electrochemical impedance spectra measured over a wide frequency range demonstrate that the presence of a lipid monolayer remarkably slows down the diffusion of ions so that the membrane-functionalized GaAs can be subjected to electrochemical investigations for more than 3 days with no sign of degradation. The biofunctional EIS setup enables us to translate changes in the surface charge density Q and bias potentials Ubias into the change in the interface capacitance Cp. Since Cp is governed by the capacitance of semiconductor space charge region CSC, the linear relationships obtained for 1/Cp2 vs Q and 1/Cp2 vs Ubias suggests that Cp can be used to detect the surface charges with a high sensitivity (1 charge per 18 nm2). Furthermore, the kinetics of phospholipids degradation by phospholipase A2 can also be monitored by a significant decrease in diffusion coefficients through the membrane by a factor of 104. Thus, the operation of GaAs membrane composites established here allows for electrochemical sensing of surface potential and barrier capability of biological membranes in a quantitative manner.