Coupling electrochemistry with a fluorescence reporting reaction enabled by bipolar electrochemistry

A bipolar electrochemistry setup for the sensitive indirect detection of redox active analytes by means of a fluorescence signal generated by the oxidation of dihydroresorufin is proposed. The redox conversion leads to the in situ and real time formation of the oxidized form resorufin, a highly fluorescent molecule. A photomultiplier tube is used for the detection of the emitted fluorescence light. The system was first characterized using the electrochemical reduction of [Fe(CN)(6)](3-) as model analyte at the cathodic bipolar pole, promoting an increase in the fluorescence signal which is proportional to the concentration of [Fe(CN)(6)](3-) in solution. Indirect quantification is enabled with a linear range between 10 mu M and 50 mu M and a limit of detection down to 0.2 mu M. The system was successfully applied for the detection of glucose and hydrogen peroxide using enzyme modified electrodes at the detection pole. The use of a closed bipolar system allows translating the electrochemical redox process for analyte detection into a fluorescence reporting reaction, providing (bio)sensing capabilities with adequate sensitivity and the possibility for optically monitoring non-fluorogenic redox reactions. (C) 2020 Elsevier B.V. All rights reserved.