Importance of Diffusional Constraints for the Quantitative Evaluation of Calibration Curves of Enzymatic Micro- and Nanoelectrochemical Sensors

Electrochemical calibration curves recorded at enzyme-modified micro- or nanoelectrodes are often quantitatively analysed using graphical approaches directly derived from the practice widely used in enzymatic analysis when enzymes as well as their substrate and cofactors are homogeneously distributed in the solution. Here, using a simple but highly representative model we demonstrate that this practice yields incorrect interpretation of the experimental results even for a simple Michaelis-Menten mechanism. The present modelling makes it possible to establish the correct relationships linking calibration currents and bulk substrate concentrations by a simple method allowing to take into account the biases due to diffusional constraints. These correct relationships provide kinetic data characterizing a given sensor that ought to be considered whenever a calibrated enzymatic electrochemical sensor is aimed to be used under non-steady state condition, e.g., as for monitoring transient concentration releases of target analytes under in vivo or pseudo in vivo conditions.