Layer-by-Layer assembled films of chitosan and multi-walled carbon nanotubes for the electrochemical detection of 17α-ethinylestradiol

Abstract

Endocrine disruptor compounds (EDCs) are environmental pollutant chemicals that can affect the endocrine system of some organisms. Such compounds are excreted by humans and released into aquatic environments via sewage treatment plant. One example of EDC is 17α-ethinylestradiol (EE2), a synthetic estrogen widely used as oral contraceptive and considered a powerful estrogenic. Although there has been a deep concern about the EDC presence in surface and drinking waters, there are only a few works in the scientific literature regarding EE2 electrochemical detection. Here we present the development of a new nanostructured sensing platform aimed at the electrochemical detection of EE2. The platform was based on a fluorine doped tin oxide (FTO) electrode coated with nanostructured Layer-by-Layer (LbL) films of chitosan/multi-walled carbon nanotubes (Chi/CNTs). The physicochemical properties of the films were evaluated by atomic force microscopy (AFM) and Fourier transform infrared spectroscopy (FTIR). Electrochemical characterization revealed a decrease in the film resistance as the number of bilayers increased from 1 to 3, as a direct consequence of the augment in the amount of conductive material (CNTs). Cyclic voltammetric measurements showed that the three bilayer electrode, namely FTO-(Chi/CNTs)3, are suitable to EE2 detection, through an irreversible and adsorption-controlled electrochemical oxidation process. Square Wave Voltammetry (SWV) yielded a linear response for EE2 detection in range from 0.05 to 20μmolL−1, with a detection limit of 0.09μmolL−1 (S/N=3). The sensor showed a good reproducibility with the relative standard deviation (RSD) equal to 3.2% and 6.6% to intra- and inter-electrode, respectively. Furthermore, the sensor platform showed to be suitable to EE2 selective electrochemical detection, with no significant interference from common interfering compounds. The concepts behind the EE2 electrochemical behavior can be potentially harnessed for designing new electrochemical sensors and biosensors with the architecture described here.