Electrochemical quantification of levothyroxine at disposable screen-printed electrodes

Abstract

The concentration of thyroxine hormone is linked to a large variety of medical conditions, where the best therapy is hormone substitution, through administration of levothyroxine (LT4) medication. Herewith, the detection of these biomolecules still lacks a simple, reliable tool, such as label-free sensors. In this work, the performances of commercial screen-printed carbon electrodes, containing different nanostructured materials (carbon nanotubes, graphene, and gold nanoparticles), used as sensors for LT4 detection, were described and compared. Electrochemical methods were used for the characterization of the nanostructure-based sensors. Several optimization steps were undertaken to achieve optimum performances for selective LT4 quantification. The redox behaviour of LT4 at sensors surface together with the interfacial changes, which occur due to the interaction between nanostructures and LT4, were studied by electrochemical impedance spectroscopy (EIS) and cyclic voltammetry (CV). Differential pulse voltammetry (DPV) was used for LT4 detection, where best performances were obtained in the presence of carbon nanotubes, with a detection limit of 30 nM.