Flame Etching Enhances the Sensitivity of Carbon-Fiber Microelectrodes

• Published in: Analytical chemistry (Washington) Vol. 80; no. 10; pp. 3708 - 3715
• Main Authors: Strand, Andrew M, Venton, B. Jill
• Format: Journal Article
• Language: English
• Published: Washington, DC American Chemical Society 15.05.2008
• Subjects: Analytical chemistry; Biosensors; Carbon; Chemistry; Comparative studies; Electrochemical methods; Electrodes; Exact sciences and technology; Flow Injection Analysis; General, instrumentation; Kinetics; Methods; Microelectrodes; Microscopy, Electron, Scanning; Neurotransmitter Agents - analysis; Neurotransmitters; Oxidation-Reduction; Sensitivity and Specificity; Cyclic voltammetry; Nanometer scale; In vivo; Engraving; Sensitivity; Ascorbic acid; Dopamine; Electrochemical method; Microelectrode; Chemical sensor; Quantitative analysis; Carbon fiber
• ISSN: 0003-2700; 1520-6882
• DOI: 10.1021/ac8001275

Small sensors are useful for in vivo measurements and probing small spaces. In this paper, we compare two methods of fabrication of small, cylindrical carbon-fiber microelectrodes: flame-etching and electrochemical etching. With both methods, microelectrodes can be fabricated with tip diameters of 1 to 3 µm. Electrodes were tested with fast-scan cyclic voltammetry. Flame etching resulted in electrodes that have larger S/N ratios and higher currents per unit area for 1 µM dopamine than normal carbon-fiber microelectrodes or electrochemically etched electrodes. Therefore, the increased sensitivity is not just a property of size. The flame-etched surfaces had nanometer-scale surface features that were not observed on the other electrodes and exhibited increased sensitivity for other electroactive compounds found in the brain, including ascorbic acid, DOPAC, and serotonin. Faster kinetics and a faster response to a step change in dopamine were also observed, when the applied waveform was −0.4 to 1.0 V and back at 400 V/s. The sensitivity of the flame-etched electrodes was enhanced by overoxidizing the surface. The flame-etched electrodes were used to detect dopamine release in anesthetized rats after a single stimulation pulse. The small flame-etched electrodes will facilitate measurements of low concentrations in discrete brain regions or small organisms.