Achieving direct electrochemical detection of 17β-estradiol (E2) at low concentrations remains a challenge due to the weak electrochemical activity of E2. In this study, we report a simple, cheap, and sensitive electrochemical sensor based on nanocomposite for the direct detection of E2 in wastewater. The nanocomposite sensing electrode was developed by electrochemical in-situ polymerization. Due to the π-π stacking and hydrogen bonding between poly-L-tyrosine (P(L-tyr)) with E2, we prepared P(L-tyr) electrode based on dopamine-modified multi-walled carbon nanotubes (PDA-CNTs) and gold nanoclusters (AuNCs). Then P(L-tyr)/AuNCs/PDA-CNTs/GCE sensing system was obtained. Meanwhile, the synergistic effect of fast electron transfer of AuNCs and the signal amplification effect of PDA-CNTs enables sensitive and direct detection of E2. The results showed that P(L-tyr)/AuNCs/PDA-CNTs/GCE sensor had a linear response to E2 concentration from 0.05 to 10 μmol·L−1 with a detection limit of 7.1 nmol·L−1. Then, the trace amount of E2 in pharmaceutical wastewater samples can be directly detected against several interferences from complex matrix, with recoveries from 91.0 to 107.5%. P(L-tyr)/AuNCs/PDA-CNTs/GCE showed good stability when placed at room temperature. Therefore, it can meet the requirements of the sensitive detection of E2 in complex matrix.

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Due to poor electro-active and less structural differences of glucocorticoids, it is still a challenge to realize simultaneous electrochemical detection of different glucocorticoids in wastewater. Here an electrochemical biosensing platform was constructed through electrochemical in situ polymerization. A poly(sulphosalicylic acid) (PSSA) composite electrode was prepared based on polymerized L-arginine (Arg) doped with carbon quantum dots (QDs) and GCE-Arg-PSSA-QD sensor was obtained. Transmission electron microscopy, scanning electron microscopy, and an energy dispersive spectrometer were used to characterize the morphology and physical property of obtained electrodes. The PSSA layer mimics the sulfonated metabolism of glucocorticoids in vivo, allowing for direct reduction of glucocorticoids on the surface of electrode, thus enabling the capture of different glucocorticoids. Meanwhile, the fast electron transfer of QDs and the signal magnification effect of Arg allow a sensitive and direct detection of dexamethasone (DXM) and hydrocortisone (HC) simultaneously. Differential pulse voltammetry was used to investigate the analytical properties of prepared biosensing platform. The results show that GCE-Arg-PSSA-QD sensor delivered an analytical performance for both DXM and HC with a limit of detection of 9 nM and 37 nM. Then, the method was utilized for simultaneous detection of DXM and HC in real wastewater samples with favorable results.

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