Simple and sensitive voltammetric sensor for in-situ clinical and environmental 17-β-estradiol monitoring

The direct electrochemical oxidation of 17-β-estradiol (E2) at conventional electrodes gives weak current signals making detection at trace levels diffi- cult, as required for clinical and environmental applications. In order to strengthen the electrochemical behavior of E2, a simple and sensitive sensor has been realized based on a graphite screen printed electrode (GSPE) func- tionalized according to a two-step procedure: i) drop-casting deposition of gold nanoparticles (AuNPs); ii) electropolymerization of methylene blue (MB). The final PMB-AuNPs-GSPE platform was characterized by scanning electron microscopy (SEM), cyclic voltammetry (CV) and electrochemical im- pedance spectroscopy (EIS). The pH value was optimized in order to obtain the best detection efficiency and the highest peak current response was ob- tained at pH 7.0. The synergistic contributions of both AuNPs and PMB al- lowed the proposed sensor to show a wide linear range from 0.5 to 125.0 μmol L􏰀 1 with a LOD of 41 nmol L􏰀 1, long-term stability and good re- producibility (RSD=2.9% for n=10). Moreover, the sensor was able to dis- tinguish E2 from several interfering compounds commonly present in urine and river water as well as from other endocrine- disrupting chemicals (EDCs), denoting its high specificity to E2 molecule. Finally, the developed electrode platform was successfully applied to the determination of E2 in both human urine and river water samples without any purification step under the stan- dard addition method.