Electrodeposited Gold on Carbon-Fiber Microelectrodes for Enhancing Amperometric Detection of Dopamine Release from Pheochromocytoma Cells

Exocytosis is an ultrafast cellular process which facilitates neuron-neuron communication in the brain. Microelectrode electrochemistry has been an essential tool for measuring fast exocytosis events with high temporal resolution and high sensitivity. Due to carbon fiber's irreproducible and inhomogeneous surface conditions, however, it is often desirable to develop simple and reproducible modification schemes to enhance a microelectrode's analytical performance for single-cell analysis. Here we present carbon-fiber microelectrodes (CFEs) modified with a thin film of electrodeposited gold for the detection of exocytosis from rat pheochromocytoma cells (PC12), a model cell line for neurosecretion. These new probes are made by a novel voltage-pulsing deposition procedure and demonstrate improved electron-transfer characteristics for catecholamine oxidation, and their fabrication is tractable for many different probe designs. When we applied the probes to the detection of catecholamine release, we found that they outperformed unmodified CFEs. Further, the improved performance was conserved at cells incubated with L-DOPA (l-3,4-dihydroxyphenylalanine), a precursor to dopamine that increases the quantal size of the release events. Future use of this method may allow nanoelectrodes to be modified for highly sensitive detection of exocytosis from chemical synapses.