An electrochemical biosensor for ultratrace terbium based on Tb3+ promoted conformational change of human telomeric G-quadruplex

A new electrochemical biosensor for the monitoring of ultratrace terbium based on the conformational change of DNA containing a single guanine (G)-rich stretch was described here. The biosensor was fabricated by immobilizing a thiolated DNA containing a single G-rich stretch on the gold surface as probe surface. The G-rich DNA probe was found to be capable of changing its configuration from flexible single-stranded structures to rigid tetramolecular G-quadruplex in the presence of terbium III, which provided a switchable charge transport path for the oxidation of [Fe(CN)6]4−. The switchable surface provided a sensing platform for the single-step and reagentless detection of Tb3+. Using this reusable electrochemical sensing platform, a simple, rapid, and selective biosensor for the determination of ultratrace terbium ions with a detection limit of 6.0 × 10−11 M has been developed. The success in the present biosensor served as a significant step toward the development of monitoring ultratrace Tb3+ in river water or seawater.