Calibration-free disposable electrochemical sensor with co-facing electrodes: Theory and characterisation with fixed and changing mediator concentration

Abstract

The use of electrochemical sensors containing oxidoreductase enzymes or redox-active substrates has become an area of particular interest due to its wide potential applications. This work presents the construction, theory and characterisation of a calibration-free disposable electrochemical sensor with co-facing electrodes. Each co-facing electrode is used as an anode or cathode to achieve high sensitivity based on a reversible redox mediator-recycling signal amplification system. Furthermore, this system can simultaneously report on the concentration and diffusion coefficient of the limiting electrochemical mediator. Supporting experimental evidence is provided in systems where the viscosity of the solution is systematically varied. The theory for a constant limiting electrochemical mediator concentration is presented and extended to treat the case where the mentioned concentration increases linearly with time. The theory is applied to three specific cases to validate the developed theory. The sensor presented in this paper may be applied to developing novel low-volume and high-sensitivity disposable, point-of-care electrochemical biosensors.