Artificial enzyme-based catalytic sensor for the electrochemical detection of 5-hydroxyindole-3-acetic acid tumor marker in urine

Abstract

A novel approach towards the development of biomimetic electrochemical sensors is presented. It is basedon magnetic-core/porous-shell molecularly imprinted composites as recognition phase. The selected sub-strate is 5-hydroxyindole-3-acetic acid (5-HIAA), an urinary metabolite used as carcinoid tumor maker.Using 5-HIAA as template molecule, hemin, 4-vinylpyridine and ethylenglycoldimethacrylate crosslinkerare polymerized onto the magnetic core to obtain an artificial enzyme with peroxidase activity. An aliquotof a suspension of the resulting material is deposited onto a carbon screen printed electrode, and the solidmaterial is fixed with a permanent magnet to prepare the sensor. The product of the catalytic oxidation of5-HIAA at the sensing phase is monitored by differential pulse voltammetry. This sensor allows the detec-tion of 5-HIAA with good sensitivity (0.72 ± 0.01 nA M−1) and linear response over a concentration rangecovering the whole window of normal and pathologic urinary levels of 5-HIAA 1–50 M (0.2–9.6 ppm)with a detection limit of 1.4 M (0.27 ppm). Urine samples of healthy individuals, spiked with knownconcentrations of 5-HIAA, yield good recovery values and reproducibility for normal and pathologicalconcentrations (90–100% recovery values, with RSD below 10%).