Zero-current chronopotentiometry for wired biosensors.

Enzyme biosensors used in continuous monitoring applications rely on amperometry as redout, which continuously draws energy, introduces ohmic drops and requires a reasonably reliable reference electrode. To help address these challenges a new experimental “zero-current” chronopotentiometry readout for wired glucose biosensors is introduced. The method records the transition time needed to chemically reduce the wired redox probe at the electrode by the enzymatically catalyzed turnover of glucose. After an electrochemical oxidation step, the open circuit potential changes over time because the enzymatic turnover continuously reduces the redox probe, thereby altering the ratio of reduced to oxidized form at the electrode. The exhaustion of the oxidized probe is indicated by an inflection of the potential at a specific transition time. The inverse value of the transition time is found to be proportional to glucose concentration, consistent with mass transport-limited kinetics across the diffusion limiting membrane and serves as sensor signal. For this reason, the specific potential value is not important for the measurement, allowing one to employ less accurate reference electrodes. Lower glucose concentrations result in longer transition times, resulting in a method that successfully covers the entire physiological concentration range.