Dopamine detection in vivo at fouling-resistant hydrogenated electrodes

In this study, we report the fabrication of physically small fouling-resistant hydrogenated carbon electrodes (typically 1 - 2 μm tip diameter, 8 mm axial length) and their application to detect the neurotransmitter dopamine in vivo. Dopamine is an important neurotransmitter in the brain. A loss of dopamine containing neurons or its transmission has been associated with a number of illnesses and conditions including Parkinson's disease, schizophrenia, motivational habit, reward mechanisms and the regulation of motor functions and in the function of the central nervous, hormonal and cardiovascular systems. It is therefore of interest to measure dopamine in the extracellular fluid in animals in order to monitor neurotransmission processes and correlate neurochemistry with behaviour. However, a common problem encountered in the voltametric determination of dopamine in vivo is interference from ascorbic acid, which is not only present in much higher concentrations (125 - 420 μM compared to 0.2 - 2.0 μM for dopamine) but also exhibits similar oxidation potentials. In addition, voltammetric electrodes are often affected by fouling from hydrophilic proteins, peptides and lipids adsorbing to its surface. To overcome this, physically small carbon electrodes were modified by a hydrophobic hydrogenated film. This film retards the adsorption process and hence protects the electrodes from fouling. The hydrogenated film was formed using RF plasma chemical vapour deposition. The modified surface was characterised in several redox systems including hexamineruthenium(III) chloride dopamine, potassium ferricyanide and ferrocene. Results of the surface studies performed on the electrodes using scanning electron microscopy, atomic force microscopy, Raman spectroscopy and X-ray photoelectron spectroscopy will also be included. In addition, selectivity of these electrodes for dopamine in the presence of ascorbic acid will be demonstrated. Finally, the effectiveness of hydrogenated carbon electrodes determined via in vitro and in vivo dopamine detection will be discussed.1 page(s