Electrodeposited Iridium Oxide pH Electrode for Measurement of Extracellular Myocardial Acidosis during Acute Ischemia

Abstract

In the present paper, fabrication, characterization, and physiological applications of a solid-state pH electrode are described. The pH sensing layer was based on an anodic electrodeposited iridium oxide film (AEIROF). Sputtered platinum electrodes (1 mm diameter) fabricated on flexible Kapton films or platinum wires were used as planar or cylindrical supports. Each electrode site was coated with Nafion to attenuate the interference of anionic redox species and to protect the electrode surface during in vivo measurements. Performance of the AEIROF was evaluated, for the first time, as a pH electrode and proved to have a slightly super-Nernstian response with slope of -63.5 +/- 2.2 mV/pH unit for both wire and planar sputtered platinum electrodes. Linear pH responses were obtained in the pH range 2-10. The electrodes have a working lifetime of at least 1 month with accuracy of about 0.02 pH unit and fast response time. The electrodes showed very low sensitivities for different species, such as Na+, K+, Li+, NH4+, Ca2+, Mg2+, dissolved oxygen, lactate, ascorbate, and urate, which are important for physiological applications. The electrodes were applied in extracellular pH measurements during brief regional ischemia in a swine heart and no-flow ischemia in an isolated rabbit papillary muscle. A first report on extracellular pH, K+, and lactate simultaneous measurements during no-flow ischemia using the AEIROF pH electrode and the previously described K+ and lactate electrodes is presented as well.

On-chip acidification rate measurements from single cardiac cells confined in sub-nanoliter volumes

“…The deposition solution was prepared based on the method proposed by Yamanaka (1989Yamanaka ( , 1991 and Marzouk et al (1998;Marzouk, 2003). A Multi-channel CHI 1030 potentiostat was used for the electrochemical deposition of iridium oxide films onto Pt thin film microelectrode arrays in the galvanostatic mode.…”

A microfluidic optical platform for real-time monitoring of pH and oxygen in microfluidic bioreactors and organ-on-chip devices

“…25 Microfluidic detection methods are highly suited for integration with organ-on-chip devices due to their potential for the analysis of low-volume liquids and high degree of automation. 29 A variety of microfluidic optical and electrochemical techniques have been developed to measure oxygen 22,[30][31][32][33][34][35][36][37][38] and pH 31,34,37,[39][40][41][42][43][44] for cell-based studies. Moreover, in some instances, the optical methods are preferred over electrical methods since they do not require electrical connections and electrodes which may be prone to biofouling and corrosion.…”

Fabrication and Characterization of Dual Function Nanoscale pH-Scanning Ion Conductance Microscopy (SICM) Probes for High Resolution pH Mapping

“…17,18 SECM pH probes employing a variety of metal/metal oxides have been reported previously. 15,[19][20][21] Iridium oxide-based pH ultramicroelectrodes have proven particularly popular for spatially resolved pH measurements in SECM, owing to their fast response time, long termstability over a wide range of pHs, temperatures and pressures, all-solid format and capability for miniaturization. 15,22,23 Iridium oxide pH electrodes have been prepared by either electrochemical oxidation, 22 thermal decomposition 24 and sputter deposition 25 of iridium metal, or by the electrodeposition of iridium oxide from alkaline solutions of iridium salts.…”