Plasma-treated carbon-fiber microelectrodes for improved purine detection with fast-scan cyclic voltammetry

Here, we developed N-2 and O-2 plasma-treated carbon-fiber microelectrodes (CFME) for improved purine detection with fast-scan cyclic voltammetry (FSCV). Plasma treatment affects the topology and functionality of carbon which impacts the electrode-analyte interaction. CFME's are less sensitive to purines compared to catecholamines. Knowledge of how the electrode surface drives purine-electrode interaction would provide insight into methods to improve purine detection. Here, plasma-treated CFME's with N-2 and O-2 plasma was used to investigate the extent to which the surface functionality and topology affects purine detection and to improve purine sensing with FSCV. On average, O-2 plasma increased the oxidative current for adenosine and ATP by 6.0 +/- 1.2-fold and 6.4 +/- 1.6-fold, and guanosine and GTP by 2.8 +/- 0.47-fold and 5.8 +/- 1.4-fold, respectively (n = 9). The O-2 plasma increased the surface roughness and oxygen functionality. N-2 plasma increased the oxidative current for adenosine and ATP by 1.5 +/- 0.15-fold and 1.9 +/- 0.23-fold, and guanosine and GTP by 1.4 +/- 0.20-fold and 1.5 +/- 0.20-fold, respectively (n = 11). N-2 plasma increased the nitrogen functionality with minimal increases in roughness. Both plasma treatments impacted purines more than dopamine. Langmuir isotherms revealed that both plasma gases impact the theoretical surface coverage and adsorption strength of purines at the electrode. Overall, we show that purine detection is improved at surfaces with increased surface roughness, and oxygen and amine functionality. Plasma-treated CFMEs could be used in the future to study the analyte-electrode interaction of other neurochemicals.