Model analysis of enzyme monolayer- and bilayer-modified electrodes: the steady-state response.

The steady-state sensor responses of enzyme monolayer- and heterobilayer-modified electrodes were theoretically analyzed with a simple model. Parameters used here are the surface coverage and rate constants of the enzyme, the concentrations and diffusion coefficients of the substrate and mediator, the rate constant of the electrode process, the thickness of the diffusion layer, and the distance between the enzyme and electrode. The sensor response was divided into three factors; the efficiencies of substrate and mediator supply to the enzyme, the enzyme/electrode charge-transfer efficiency, and the potential rate of enzymatic reaction where the supply efficiencies are unity. Contributions of the parameters to these factors or the total sensor response are described by simple formulas. The experimental observations are successfully interpreted in terms of these theoretical results.