Electrochemical characterization of 17β‐estradiol with fast‐scan cyclic voltammetry

Abstract

We have developed a sensitive and stable electrochemical method for 17β‐estradiol (E2) detection using fast‐scan cyclic voltammetry (FSCV). Recently, E2 was proposed to function as a rapid synaptocrine signaling molecule in the brain; however, methods to directly monitor subsecond fluctuations in E2 are currently unavailable, limiting our understanding of the dynamics and mechanism of rapid E2 release. FSCV at carbon‐fiber microelectrodes enables subsecond detection of electroactive neurochemicals directly in tissues like the brain. Here, we have electrochemically characterized E2 using FSCV for use in a tissue matrix. The limit of detection of E2 is 31.2±2.5 nM with FSCV, which will enable low nanomolar fluctuations in extracellular E2 to be monitored with hundred millisecond temporal resolution. We also identify specific parameters for waveform modification to improve future detection. This method will significantly improve E2 sensing capabilities and will have far‐reaching impacts on improving our understanding of dynamic E2 signaling in the brain.

Subsecond Codetection of Dopamine and Estradiol at a Modified Sharkfin Waveform

“…E2 is theorized to interact at carbon surfaces through π−π stacking and has previously been established to experience no improvement in peak current at higher switching potentials. 46 Our findings are consistent with this behavior; E2 experiences at best a marginal increase in maximum current at 1.45 V, with no statistical difference in current between 1.1 and 1.3 V (Figure 6C, one-way ANOVA with Bonferroni post-test, p 1.2 V vs 1.45 V = 0.0202, p 1.3 V vs 1.45 V = 0.0454, n = 4). However, DA's current increases substantially at higher switching potentials, increasing 1.7-fold between 1.1 and 1.3 V (Figure 6D).…”

“…At potentials of 1.3 V and higher, the carbon surface of the electrode oxidizes and adds oxide groups that can facilitate adsorption interactions, particularly for catecholamines, such as DA. E2 is theorized to interact at carbon surfaces through π–π stacking and has previously been established to experience no improvement in peak current at higher switching potentials . Our findings are consistent with this behavior; E2 experiences at best a marginal increase in maximum current at 1.45 V, with no statistical difference in current between 1.1 and 1.3 V (Figure C, one-way ANOVA with Bonferroni post-test, p 1.2 V vs 1.45 V = 0.0202, p 1.3 V vs 1.45 V = 0.0454, n = 4).…”

“…Having optimized the parameters for DA detection, E2 optimization presents greater challenges. As demonstrated in previous work, E2’s oxidation is complex, its sensitivity at an unmodified triangle waveform is mediocre, and it undergoes moderate fouling . Additionally, E2’s primary oxidation occurs at 0.92 at 400 V/s and is easily obscured by more sensitive analytes.…”

“…This is the upper bound of the waveform, and therefore, in addition to playing an essential role in optimization for E2 and DA, it also determines which other neurochemicals can oxidize and interfere with detection at this waveform. As previously established, fast scan rates shift E2’s oxidation peak past its oxidation potential by a substantial amount, necessitating switching potentials of 1.1 V or higher. We tested switching potentials between 1.1 and 1.45 V (Figure A).…”

“…Modified waveforms often forsake the traditional triangular sweep cyclic voltammetry (CV) employs. A sawhorse waveform for Met-enkephalin detection has previously been developed that employs multiple scan rates and an amperometric period for enhanced detection. , DA is easily detectable at a traditional triangular waveform with FSCV, and feasible detection of E2 has recently been demonstrated . Here, we present a modified sharkfin waveform that teases apart DA and E2’s oxidation peaks and enables low nanomolar level codetection of both analytes with 100 ms temporal resolution.…”