Modified Sawhorse Waveform for the Voltammetric Detection of Oxytocin

Abstract

Carbon fiber microelectrodes (CFMEs) have been used to detect neurotransmitters and other biomolecules using fast-scan cyclic voltammetry (FSCV) for the past few decades. This technique measures neurotransmitters such as dopamine and, more recently, physiologically relevant neuropeptides. Oxytocin, a pleiotropic peptide hormone, is physiologically important for adaptation, development, reproduction, and social behavior. This neuropeptide functions as a stress-coping molecule, an anti-inflammatory agent, and serves as an antioxidant with protective effects especially during adversity or trauma. Here, we measure tyrosine using the Modified Sawhorse Waveform (MSW), enabling enhanced electrode sensitivity for the amino acid and oxytocin peptide. Applying the MSW, decreased surface fouling and enabled codetection with other monoamines. As oxytocin contains tyrosine, the MSW was also used to detect oxytocin. The sensitivity of oxytocin detection was found to be 3.99 ± 0.49 nA/µM, (n=5). Additionally, we demonstrate that applying the MSW on CFMEs allows for real time measurements of exogenously applied oxytocin on rat brain slices. These studies may serve as novel assays for oxytocin detection in a fast, sub-second timescale with possible implications for in vivo measurements and further understanding of the physiological role of oxytocin.

Perspective—Advances in Voltammetric Methods for the Measurement of Biomolecules

“…This velocity, computerized control, and signal averaging enable repetitive trials and increase the signal-to-noise-ratio (SNR). 15 Recent work has introduced continuous SWV (cSWV) which collects current continuously during the SWV waveform to extract multiple voltammograms from a single scan. 16 This shows promise for conformation switching biosensors by rapidly assessing frequency dependence.…”

“… 49 Other studies have used this waveform to differentiate dopamine and other monoamines from other tyrosine-containing neuropeptides such as oxytocin based on the varied oxidation potentials of the molecules. 15 When applied with MSW (multiple scan rates) on CFMEs, FSCV also provides information on real-time oxytocin effects on rat brain slices, exposing its impact on physiology and social behavior. 15 , 50 The Jackson (serotonin) N-shaped waveform was also shown to be optimal for the detection of serotonin with FSCV.…”

“… 15 When applied with MSW (multiple scan rates) on CFMEs, FSCV also provides information on real-time oxytocin effects on rat brain slices, exposing its impact on physiology and social behavior. 15 , 50 The Jackson (serotonin) N-shaped waveform was also shown to be optimal for the detection of serotonin with FSCV. 51 This waveform holds at a potential of +0.2 V to avoid serotonin fouling byproduct adsorption, and rapidly increases to 1.0 V at 1000 V s −1 to prevent fouling, and then scans down to −0.1 V during the reverse sweep to produce the cathodic peaks.…”

Electrochemical Detection of Hormones Using Nanostructured Electrodes

“…These investigations demonstrated the potential of innovative methods for detecting oxytocin in a rapid, sub-second timeframe. This could have important ramifications for measuring oxytocin levels in living organisms and advancing our knowledge of the physiological functions of oxytocin [181].…”

Carbon Electrode Sensor for the Measurement of Cortisol with Fast-Scan Cyclic Voltammetry

“…Using CFMEs and FSCV has several advantages over other techniques as they have fast electron transfer kinetics [ 21 ], high spatiotemporal resolution [ 22 ], biocompatibility [ 23 ] and are minimally invasive. CFMEs have also been used for the detection of other molecules in addition to neurotransmitters such as metals [ 24 , 25 , 26 ] and more complex molecules such as amino acids [ 27 , 28 ] and neuropeptides [ 29 ]. Through waveform modification, it has been shown that the detection of several molecules can be optimized with FSCV.…”