title: Potentiometric responses of ion-selective microelectrode with bovine serum albumin adsorption.
abstract: 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/AgCl 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.
authors.affiliation: Institute of Biomaterials and Bioengineering, Tokyo Medical and Dental University, 2-3-10 Kanda-Surugadai, Chiyoda, Tokyo 101-0062, Japan. Electronic address: goda.bsr@tmd.ac.jp.
authors.forename: Tatsuro
authors.initials: T
authors.lastname: Goda
authors.affiliation: Institute of Biomaterials and Bioengineering, Tokyo Medical and Dental University, 2-3-10 Kanda-Surugadai, Chiyoda, Tokyo 101-0062, Japan.
authors.forename: Eriko
authors.initials: E
authors.lastname: Yamada
authors.affiliation: Institute of Biomaterials and Bioengineering, Tokyo Medical and Dental University, 2-3-10 Kanda-Surugadai, Chiyoda, Tokyo 101-0062, Japan.
authors.forename: Yurika
authors.initials: Y
authors.lastname: Katayama
authors.affiliation: Institute of Biomaterials and Bioengineering, Tokyo Medical and Dental University, 2-3-10 Kanda-Surugadai, Chiyoda, Tokyo 101-0062, Japan.
authors.forename: Miyuki
authors.initials: M
authors.lastname: Tabata
authors.affiliation: Institute of Biomaterials and Bioengineering, Tokyo Medical and Dental University, 2-3-10 Kanda-Surugadai, Chiyoda, Tokyo 101-0062, Japan.
authors.forename: Akira
authors.initials: A
authors.lastname: Matsumoto
authors.affiliation: Institute of Biomaterials and Bioengineering, Tokyo Medical and Dental University, 2-3-10 Kanda-Surugadai, Chiyoda, Tokyo 101-0062, Japan. Electronic address: miyahara.bsr@tmd.ac.jp.
authors.forename: Yuji
authors.initials: Y
authors.lastname: Miyahara
mesh_terms: D000327:Adsorption; D016477:Artifacts; D004867:Equipment Design; D019544:Equipment Failure Analysis; D006863:Hydrogen-Ion Concentration; D017736:Ion-Selective Electrodes; D008839:Microelectrodes; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D012710:Serum Albumin, Bovine / Q000032:analysis / Q000737:chemistry*
chemical_list: D012710:Serum Albumin, Bovine
keywords: Cyclic voltammetry; Ion-selective electrode; Potentiometry; Protein adsorption; X-ray photoelectron spectroscopy