Investigations of the Purine-Electrode Interface with Fast-Scan Cyclic Voltammetry
Authors: Li Yuxin , Ostertag Blaise J , Ross Ashley E 
Published: July 2021

Understanding how the brain functions in both spatial and temporal domains is still unknown but vital for advancing knowledge of fundamental brain processes. One important class of brain biomolecules, purines, are involved in signal transduction, development, neuroinflammation, and neuromodulation. Despite their importance, purines remain difficult to detect with high specificity, sensitivity, and with adequate temporal resolution to capture signaling dynamics. Fast-scan cyclic voltammetry (FSCV) at carbon-fiber microelectrodes is a popular electrochemical technique most often used to study dopamine signaling in the brain due to its subsecond temporal resolution and excellent spatial resolution. Recent advances from our lab and others have demonstrated utility of using FSCV at carbon-based electrodes for adenosine and guanosine detection: two important purine signaling molecules in the brain. Despite these advances, a fundamental understanding of purine electrochemical detection at carbon-based electrodes is poorly understood, especially for anionic purinergic compounds like adenosine triphosphate (ATP) and guanosine triphosphate (GTP). Here, we will discuss our recent work which helps describe the extent to which the electrode surface chemistry, topographical structure, and geometry impact purine detection with FSCV. This work will ultimately lead to more sensitive and selective detection of purinergic signaling in the brain.

Carbon-fibers have been a prominent electrode material for neurochemical detection with fast-scan cyclic voltammetry (FSCV) for the last several decades. Recently, the field has expanded to novel carbon nanomaterials due to their improved detection sensitivities and electron transfer kinetics. Despite, exploration to novel carbon materials, the majority of FSCV labs still use carbon-fiber microelectrodes on a routine basis for neurochemical analysis. Because of this, our lab has focused on tuning analyte-electrode interactions at carbon-fiber microelectrodes using a combination of surface modification strategies and novel carbon-fiber materials.

We will discuss our latest efforts to improve purine detection with novel carbon surfaces. Plasma-treated carbon surfaces can dramatically change the functionality and topology of the surface. We have used O2, N2, and Ar gas to change the surface topology and functionality of carbon-fiber microelectrodes for improved purine detection. Overall, we show that the effects induced by plasma-treatment improve purine detection significantly more than catecholamine detection due to significantly roughened electrode surfaces with increased oxide and amine functionalization. In addition to plasma-treated surfaces, the chemical composition of the carbon-fiber surface can be modified by chemically reacting specific functionalities onto the surface. Traditionally, anionic detection with FSCV is limited due to minimal interactions of anions on the anionic carbon-fiber surface. We have used a chemical modification strategy involving both ethylenediamine (EDA) and N-ethyl-N’-(3-dimethylaminopropyl) carbodiimide (EDC) to functionalize the carbon-fiber surface with positively charged amines. In addition to chemical functionalization strategies for improved anionic purine detection, we have also investigated Au and Pt nanoparticle modified carbon-fibers for improved electrocatalysis of purines at the surface. Lastly, we have synthesized and developed new carbon-fiber geometries with improved edge-plane character on the surface which facilitate enhanced purine-electrode interactions.

Overall, we provide new insights into the electrode-analyte interface for purine detection which has significantly improved our understanding of purine electrochemistry.