Detection of C Reactive Protein (CRP) in Serum by an Electrochemical Aptamer-Based Sandwich Assay

A disposable electrochemical assay involving magnetic particles and carbon-based screen-printed electrodes (SPCEs) was developed for the detection of C Reactive Protein (CRP). CRP is a plasma protein and is among the most expressed proteins in acute phase inflammation cases, being a known biomarker for inflammatory states. The assay was based on a sandwich format in which a RNA aptamer was coupled to a monoclonal antibody and alkaline phosphatase (AP) was used as enzymatic label. After the sandwich assay, the modified magnetic beads were captured by a magnet on the surface of a graphite working electrode and the electrochemical detection was thus achieved through the addition of the AP substrate (a-naphthyl-phosphate) and a-naphthol produced during the enzymatic reaction was detected using differential pulse voltammetry (DPV). The parameters influencing the different steps of the assay were optimized in order to reach the best sensitivity and specificity.With the optimized conditions, the assay was applied to the analysis of CRP free serum and serum samples.