Cathophoresis paint insulated carbon fibre ultramicro disc electrode and its application to in vivo amperometric monitoring of quantal secretion from single rat melanotrophs Original Research Article

This paper reports the preparation and characterization of carbon fibre ultramicro disc electrodes (CUMDEs) by employing cathodic electrophoresis paint to electrically and chemically insulate a carbon fibre protruding from a pulled glass capillary housing. A thin and uniform paint coating was deposited electrochemically onto a carbon fibre of 7 μm in diameter, and then heat cured. The film thickness and its resistivity can be controlled by varying parameters such as the cathodic deposition voltage, the curing temperature, etc. Then, the coated carbon fibre was cut to expose a disc-shaped electrode surface with an overall tip diameter of about 12 μm. The electrodes were examined by optical and scanning electron microscopy and their electrochemical behaviour and properties were characterized using cyclic voltammetry, amperometry and electrochemical impedance spectroscopy. Cyclic voltammograms of hexacyanoferrate(III) in aqueous and of ferrocene in acetonitrile media displayed low-noise, low-background sigmoidal responses with virtually no current hysteresis. The high performance of the proposed cathophoresis paint insulated CUMDEs was verified successfully by carrying out in vivo amperometric monitoring of the secretory activity of stimulated single rat melanotrophs. The extremely low current noise (1–2 pA rms) and high temporal resolution ensure the suitability of the proposed electrode for studying peptide hormone release at a single cell level.