An Innovative Design of an Efficient Layered Electrochemical Sensor for Determination of Tyrosine and Tryptophan in the Presence of Interfering Compounds in Biological Fluids

Abstract

The aromatic amino acids tyrosine (TY) and tryptophan (TP) are important as precursors of catecholamines and 5-hydroxytryptamine. An innovative strategy was proposed in preparation of a novel layered sensor based on layer-by-layer modification of a glassy carbon electrode surface (GC) with graphene (RGO), ionic liquid crystal (ILC), multi-walled carbon nanotubes (CNT) and Fe–Zn nano-alloy (GC/RGO/ILC/CNT/Fe–Zn). The conductive layered electrode offered good sensitivities and low detection limit values for determination of tyrosine (TY) and tryptophan (TP) due to the synergistic impact of its components. A major problem expected during electrochemical assays of TY or TP in human biological fluids is overlap of their current responses with ascorbic acid (AA) and uric acid (UA) compounds when using the unmodified electrodes. Thus, the proposed sensor resolved this problem and exhibited excellent electrocatalytic activity towards determination of TY or TP in presence of AA and UA in human serum with low detection limit values 5.1 nM, 86 nM, 2.6 nM for TY, AA and UA and 3.8 nM, 91 nM, 2.9 nM for TP, AA and UA, respectively. Moreover, the proposed sensor displayed good sensitivity towards simultaneous determination of dopamine (DA) and serotonin (ST) with TY or TP. Recovery tests of TY and TP compounds were successful.