Justified Choice of a Substrate for Alkaline Phosphatase Based on the Enzymatic Kinetics and Electrochemical Characteristics of Screen-Printed Carbon Electrodes in Immunosensors

In this study, a substantiated selection of a substrate for further use in electrochemical enzyme immunoassay is carried out based on the parameters describing the enzymatic kinetics and the electrochemical characteristics of the products of electroenzymatic reactions. Data from an analysis of the electrochemical characteristics of screen-printed graphite electrodes (SPE) using various surface pretreatments are presented. Using SPE pretreatment in sulfuric acid, it was possible to achieve a significant decrease in the background current and lower the detection limit of 1-naphthol, which is a product of the enzymatic reaction catalyzed by alkaline phosphatase, to 0.73 ?M in the differential pulse voltammetry (DPV) mode and to 0.09 ?M in the chronoamperometry (CA) mode without the use of additional catalysts. The selected substrate and pretreatment were used in a quantitative electrochemical enzyme-linked assay for the determination of procalcitonin (PCT). The sensitivity coefficient and detection limit were 109 nA×mL/mg and 0.8 ng/mL, respectively.