Disposable Amperometric Immunosensor for theDetermination of the E-Cadherin Tumor SuppressorProtein in Cancer Cells and Human Tissues

Abstract

This paper describes the results obtained in the development of the first electrochemical immunosensor described to date for the detection of E-cadherin (E-cad) protein, a relevant biomarker of prognosis and metastasis in cancer, based on the use of magnetic microcarriers (MBs) and amperometric transduction at screen-printed carbon electrodes (SPCEs). Thus, the determination of E- cad protein involved the use of two specific antibodies against this protein (one of them labelled with HRP) in a sandwich configuration onto HOOC-MBs. The magnetic bioconjugates were captured onto SPCEs and the ampero- metric transduction was performed using the H2 O2/hydro- quinone (HQ) system. Under optimal conditions, this bioplatform demonstrated a wide linear concentration range (0.50–25 ng mL 1 ) and a detection limit as low as 0.16 ng mL 1 , well below the optimal cut-off level for the E-cad protein (defined as 10,000 ng mL 1 for soluble E- cad levels in serum). The developed sensor also showed a good reproducibility among measurements with seven different sensors constructed in the same manner (RSD, 5.4 %), stability for more than 15 days and good specificity towards other proteins commonly found on biological samples. The applicability of this simple handling bioplat- form for the direct determination of this protein in cell lysates with different metastatic potential and extracts from paraffined-embedded human colorectal cancer tis- sues of different grade were also demonstrated.