Sensitive electrochemical detection of horseradish peroxidase at disposable screen-printed carbon electrode

A rapid, simple and sensitive electrochemical assay of horseradish peroxidase (HRP) performed on disposable screen-printed carbon electrode was developed. HRP activities were monitored by square-wave voltammetric (SWV) measuring the electroactive enzymatic product in the presence of o-aminophenol and hydrogen peroxide substrate solution. SWV analysis demonstrated a greater sensitivity and shorter analysis time than the widely used amperometric and differential-pulsed voltammetric methods. The voltammetric characteristics of substrate and enzymatic product as well as the parameters of SWV analysis were optimized. Under optimized conditions. a linear response for HRP from 0.003 to 0.1 U/mL and a detection limit of 0.002 U/mL (1.25 x 10(-15) mol in 25 mu L) were obtained with a good precision (RSD = 8%; n = 6). This rapid and sensitive HRP assay with microliter-assay volume could be readily integrated to portable devices and point-of-care (POC) diagnosis applications.