Development of a multianalyte electrochemical sensor for depression biomarkers based on a waste of the steel industry for a sustainable and one-step electrode modification

Abstract

This study aimed to reuse waste from the steel industry as a sustainable electrode modifier material in a simple and one-step modification approach for the electrochemical monitoring of the neurotransmitters dopamine (DA), serotonin (5-HT), and tryptophan (TRP), biomarkers related to depression diagnostics. Iron oxides constitute the mill scale (MS), composed of wüstite (FeO), magnetite (Fe3O4), and hematite (Fe2O3). This material was generated from the hot rolling process, and later it was ball milled using a high-energy shaker mill. X-ray powder diffraction (XRPD) was used to investigate the structural and microstructural evolution of the MS with milling time. Effects of mechanical force on solids include a reduction in the crystalline size by controlling the milling time, with consequently peculiar properties and chemical reactivity. The magnetic measurements show superparamagnetic characteristics in the samples, governed mainly by small crystallites of iron oxides. Two samples (milled for 2 and 30 min) were applied in the construction of new sensors. The MS carbon paste electrode (MS/CPE) with 30 min-sample allowed more defined oxidation peaks through a simple and one-step electrode modification step. Selectivity for the detection of the multianalytes was achieved after the modification of the carbonaceous substrate with the mixture of metal oxides with magnetic properties; overlapping peaks were observed for DA and 5-HT using the unmodified electrode. Under optimum conditions of square wave voltammetry, a linear relationship was observed between the peak current intensities and the concentrations of the analytes. Linear responses were obtained for DA, 5-HT, and TRP in the 0.49–21, 0.49–13.6, and 2.9–25 µmol L−1 concentration ranges, with detection limits of 0.21, 0.13, and 2.18 µmol L−1, respectively. The reuse of waste as a sustainable electrode modifier material for clinical and biomedical applications, with improved selectivity and sensibility, is hereby present.