Journal
BIOSENSORS & BIOELECTRONICS
Volume 77, Issue -, Pages 208-214Publisher
ELSEVIER ADVANCED TECHNOLOGY
DOI: 10.1016/j.bios.2015.09.023
Keywords
Ion-selective electrode; Potentiometry; Protein adsorption; X-ray photoelectron spectroscopy; Cyclic voltammetry
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Funding
- MEXT of Japan [2306, 26107705]
- Nakatani Foundation of Electronic Measuring Technology Advancement
- Japan Science and Technology Agency (JST)
- Grants-in-Aid for Scientific Research [26107705] Funding Source: KAKEN
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There is a growing demand for an in situ measurement of local pH and ion concentrations in biological milieu to monitor ongoing process of bioreaction and bioresponse in real time. An ion-selective microelectrode can meet the requirements. However, the contact of the electrode with biological fluids induces biofouling by protein adsorption to result in a noise signal. Therefore, we investigated the relationship between the amount of nonspecific protein adsorption and the electrical signals in potentiometry by using ion-selective microelectrodes, namely silver/silver chloride (Ag/AgCl), iridium/iridium oxides (Ir/IrOx), and platinum/iridium oxides (Pt/IrOx). The microelectrodes reduced a potential change following the adsorption of bovine serum albumin (BSA) by comparison with the original metal microelectrodes without oxide layers. Suppression in the noise signal was attributed to the increased capacitance at the electrode/solution interface due to the formation of granulated metal oxide layer rather than a decrease in the amount of protein adsorbed. Ion sensitivity was maintained for Ir/IrOx against proton, but it was not for Ag/AgCI against chloride ion (Cl-), because of the interference of the equilibrium reaction by adsorbed BSA molecules on the electrode surface at <10(-2) M [Cl-] in the solution. The results open up the application of the Ir/IrOx microelectrode for measuring local pH in realistic dirty samples with a limited influence of electrode pollution by protein adsorption. (C) 2015 Elsevier B.V. All rights reserved.
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