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A novel electrochemical sensor was developed for the detection of salivary cortisol levels. The sensor employs a combination of a molecularly imprinted polymer (MIP) and gold nanoparticles (AuNPs) that are electrodeposited onto a screen-printed electrode (SPE). The study utilised density functional theory and molecular docking techniques to determine the geometry of molecular orbitals, electrostatic potential energies, and binding energy of cortisol and the polymers. The thin film of cortisol-imprinted polymer on the SPE was created by electro-polymerizing pyrrole and thiophene-3-carboxylic acid on the electrode surface along with cortisol as the template molecule. The MIP film was characterised using scanning electron microscopy (SEM), Fourier-transform infrared spectroscopy (FTIR), and electrochemical techniques. The sensor exhibited a linear response in the concentration range of 0.05 nmol L−1 to 2.5 μmol L−1, with a limit of detection of 0.01 nmol L−1, as determined by differential pulse voltammetry. This method offers a simple yet efficient and sensitive approach to detecting cortisol levels in human saliva samples. [Display omitted] • A new electrochemical sensor is presented that can selectively detect salivary cortisol levels using a molecularly imprinted polymer (MIP). • Gold nanoparticles (AuNPs) were electrochemically deposited on a screen-printed electrode (SPE) as a substrate for the cortisol-imprinted polymer thin film. • The cortisol-imprinted polymer thin film was synthesized on the SPE through the electro-polymerization of pyrrole and thiophene-3-carboxylic acid. • The study used density functional theory and molecular docking techniques to compute the geometry of molecular orbitals, electrostatic potential energies, and binding energy for the interacting molecules. • The differential pulse voltammetry method showed a linear response in the concentration range of 0.05 nmol L−1 to 2.5 μmol L−1 with a limit of detection of 0.016 nmol L−1. • This simple approach is an efficient and sensitive method for detecting cortisol levels in human saliva samples. [ABSTRACT FROM AUTHOR]

The remarkable features of a carbon fiber paper sensor (CP) were employed for detection of the estrogenic hormone 17α-ethinylestradiol (EE2), considered a contaminant of emerging concern due to its potential ecotoxicity and widespread in the aquatic ecosystems. In this work, an unpreceded CP pre-treatment study was conducted with the (Il)-hexacyanoferrate(III) ion pair, however a bare sensor without pre-treatment revealed higher efficiency on the oxidation of EE2 compared to a chemical and electrochemical pre-treated CP and a gold nanoparticles modified CP, being thus selected for EE2 determinations. The analytical conditions were thoroughly optimized in terms of electrolyte pH (pH 7), differential pulse voltammetry parameters (modulation time 0.003 s, amplitude 0.09 V, interval time 0.1 s and step potential 0.01 V), and analyte preconcentration potential (0.4 V) and time (180 s). The hormone can be determined by the CP in a wide linear range from 0.1 to 1000 nM, achieving a detection limit of 0.14 ± 0.005 nM and an outstanding sensitivity of 1636 ± 232 μA μM−1 cm−2 in the lowest linear zone (0.1–1 nM). The sensor was validated in river water and fish reaching good recoveries (91.2 ± 4.6 to 109.0 ± 7.1%), reproducibility and repeatability. Moreover, the sensor showed high selectivity to EE2 in the presence of several potential interfering compounds and frequently prescribed drugs, though it could not discriminate the similar hormone, 17β-estradiol, being the total concentration obtained in this case. CP-based sensors emerge as efficient electroanalytical tools, suggesting that modification of the surface may not always be beneficial in terms of sensitivity. [Display omitted] • A simple and effective carbon paper sensor was used for 17α-ethinylestradiol sensing. • The best analytical signal was obtained with an untreated and unmodified carbon paper. • The optimized sensor achieved high sensitivity (1636 μA μM−1 cm−2) and LOD of 0.14 nM. • Application in complex samples of fish resulted in recoveries from 102 to 109%. • Carbon paper sensors can be become valuable tools in the electroanalytical field. [ABSTRACT FROM AUTHOR]