Fig. 2.

Schematic of a microelectrode biosensor. The electrode 7–50 μm in diameter protrudes from a glass body. The sensing tip is covered with multiple layers designed to enhance the selectivity and biocompatibility of the biosensor. The enzymatic layer contains the cascades of Fig. 1 and thereby impart sensitivity to the desired analyte by producing changes in H₂O₂ in proportion to the concentration of the analyte. The H₂O₂ can permeate the permselectivity layer to be detected at the microelectrode surface (usually polarized at 500–600 mV with respect to an Ag/AgCl reference electrode). Interferences are unable to permeate the inner and outer permselectivity layers