Phenylboronic Acid Monolayer-Modified Electrodes Sensitive to Ribonucleosides

Abstract

The surface of a gold (Au) disk electrode was modified with a self-assembled monolayer consisting of phenylboronic acid residue to prepare a ribonucleoside-sensitive electrode. The cyclic voltammetric response of the modified electrode to [Fe(CN)₆]³⁻ ion dissolved in the sample solution was found to be dependent of the type of ribonucleoside and its concentration. In other words, the peak current in the cyclic voltammogram of [Fe(CN)₆]³⁻ ion was significantly decreased when uridine or cytidine was added in the working buffer, while the response to thymidine, 2′-deoxyuridine, and 2′-deoxycytidine was rather small. The voltammetric response was rationalized on the basis of the electrostatic repulsion between [Fe(CN)₆]³⁻ ion and the negatively-charged electrode surface, which originates from the addition of OH⁻ ion on the electrode as a result of the formation of phenylboronic acid-ribonucleoside conjugate on the surface of the monolayer.