Light-Addressable Ion Sensing for Real-Time Monitoring of Extracellular Potassium

Abstract

We report here on a light addressable potassium (K⁺ ) sensor where light illumination of a semiconducting silicon electrode substrate results in a localized activation of the faradaic electrochemistry at the illuminated spot. This allows one, by electrochemical control, to oxidize surface bound ferrocene moieties that in turn trigger K⁺ transfer from the overlaid K⁺ -selective film to the solution phase. The resulting voltammetric response is shown to be K⁺ -selective, where peak position is a direct function of K⁺ activity at the surface of electrode. This concept was used to measure extracellular K⁺ concentration changes by stimulating living breast cancer cells. The associated decrease of intracellular K⁺ level was confirmed with a fluorescent K⁺ indicator. In contrast to light addressable potentiometry, the approach introduced here relies on dynamic electrochemistry and may be performed in tandem with other electrochemical analysis when studying biological events on the electrode.

Keywords: ion-selective electrode; light-activated electrochemistry; physiological condition; potassium; potentiometry.