Figure 7.

Illustration of two configurations used in screen-printed aptasensors for lysozyme analysis in wine. Steps 1 and 2 depict the construction of an impedimetric aptasensor where a biotinylated aptamer is covalently immobilized on a carboxyl-functionalized surface (1). Lysozyme binding (2) is detected directly by EIS. In a second assay, a biotinylated antibody is added after lysozyme binding (3), this detection antibody is labeled with streptavidin-alkaline phosphatase conjugate (ALP), the enzyme substrate, 1-naphtyl phosphate (1-NPP) is added (4) and the enzymatic product 1-naphtol is detected by DPV. Introduction of steps 3 and 4 and detection by DPV allowed improving the detection limit from 0.1 µM to 4.3 fM. Adapted from [39] and [34] with permission.