Review-Recent Advances in FSCV Detection of Neurochemicals via Waveform and Carbon Microelectrode Modification

Abstract

Fast scan cyclic voltammetry (FSCV) is an analytical technique that was first developed over 30 years ago. Since then, it has been extensively used to detect dopamine using carbon fiber microelectrodes (CFMEs). More recently, electrode modifications and waveform refinement have enabled the detection of a wider variety of neurochemicals including nucleosides such as adenosine and guanosine, neurotransmitter metabolites of dopamine, and neuropeptides such as enkephalin. These alterations have facilitated the selectivity of certain biomolecules over others to enhance the measurement of the analyte of interest while excluding interferants. In this review, we detail these modifications and how specializing CFME sensors allows neuro-analytical researchers to develop tools to understand the neurochemistry of the brain in disease states and provide groundwork for translational work in clinical settings.

Figure 1.

The detection of dopamine with FSCV and CFMEs. (A) Applied potential waveform using −0.4 V holding potential, +1.3 V switching potential, 400 V s⁻¹ scan rate, and 10 Hz repetition rate. (B) Example CVs with background: blank (PBS pH 7.4) (black) and buffer with 1 μM dopamine (red). Dashed boxes emphasize the difference between them. (C) Background-subtracted CV of 1 μM dopamine. (D) Three-dimensional current–potential–time plot and (E) conventional false color plot with anodic peak current–time trace of 5 s bolus injection of 1 μM dopamine. Reproduced from Ref. with permission from The Royal Society of Chemistry. (Puthongkham and B. J. Venton, Analyst, 2020, 145, 1087 DOI: 10.1039/C9AN01925A).

Figure 2.

SEM images carbon fiber 7 μm × 100 μm for Bare carbon (a), PEDOT:Nafion (b), PEDOT:Nafion-SDS (c), PEDOT:Nafion-SDBS (d). The PEDOT:Nafion coatings were deposited from a solution containing 200 μM EDOT. Reproduced with permission from Ref. . Copyright The Electrochemical Society.

Figure 3.

Waveforms tested. (A). Traditional serotonin “Jackson” waveform with a 1.0 V switching potential and 1000 V s−1 scan rate. (B). Traditional dopamine waveform with a −0.4 V holding potential, extended 1.3 V switching potential, and 400 V s−1 scan rate. C. Extended serotonin waveform (ESW) with 1.3 V switching potential and 1000 V s−1 scan rate. (D). Extended hold serotonin waveform (EHSW) with a 1 ms hold at 1.3 V and 400 V s−1 scan rate. All waveforms were repeated at 10 Hz. Reproduced from Ref. with permission from The Royal Society of Chemistry. K. E. Dunham and B. J. Venton, Analyst, 145, 7437–7446 (2020).

Figure 4.

A schematic showing background subtracted, unfolded CVs of adenosine, ATP, and hydrogen peroxide using the modified sawhorse waveform. Copyright 2014 American Chemical Society.

Figure 5.

Triple detection of guanosine, adenosine, and dopamine using the scalene waveform. (A) Example false-color plot showing 5 μM (each) dopamine (DA), guanosine (GN), and adenosine (AD). Dopamine oxidation occurs at 0.46 V when the modified waveform is used. (B) Opened cyclic voltammogram for the purine–dopamine mix. The Δt between dopamine and guanosine, its nearest neighbor, is 6.96 ms. Reprinted with permission from M. T. Cryan and A. E. Ross, Anal. Chem., 91, 5987–5993 (2019). Copyright 2019 American Chemical Society.