Fast-scan cyclic voltammetry for dopamine detection

Bloq question: How can we study changes in dopamine concentration inside cells in vivo?

The principle behind this technology is the readily oxidation of dopamine in air and the unique transfer of electrons to a microelectrode as dopamine changes into its oxidized form (o-quinone).

Fast-scan cyclic voltammetry (FSCV) is a modified method of the classic cyclic voltammetry technique that is used to detect electroactive molecules based in changes in their redox potentials. FSCV provides a much higher temporal resolution at a subsecond time scale for analyte detection. The carbon-fiber microelectrodes monitor the extracellular concentration of electroactive molecules and are suitable for the in situ and in vivo monitoring of dopamine concentration inside dopaminergic cells in awake animals or in single cells.

The potential at the microelectrode is held at a voltage below the oxidizing potential (-0.4 V in reference to a silver/silver chloride electrode) of dopamine and it is linearly ramped to an oxidizing potential (+1.3 V) and back. During this cycle, characteristic of a redox reaction, electrons are transferred between the microelectrode and dopamine-o-quinone at the positive sweep and back to dopamine in the negative sweep. The scan rate of the microelectrode is held at a high rate and it is set to measure the flux of electrons (as current) multiple times each second. Current is proportional to the number of dopamine o-quinone molecules generated by the electro-oxidation reaction normalized to a standard. Current is plotted against potential to yield a cyclic voltammogram (CV) graph that is used to identify the analyte, since each electroactive molecule behaves differently during a redox reaction. The peak in the cyclic voltammeter plot is representative of dopamine o-quinone (~+1.3 V) and the change in the peak height is proportional to change in concentration when normalized to a standard.

FSCV permits the study of changes in the dopamine concentration over time by plotting the peak oxidation potential at different time points or over a range of biological preparations.

Reviews
Probing brain chemistry Stamford JA and Justice JB Jr Analytical Chemistry 68, 359A-363A (1996)

Critical guidelines for validation of the selectivity of in-vivo chemical microsensors Phillips PEM and Wightman RM Trends in Analytical Chemistry 22, 509-514 (2003)

Detection technologies. Probing cellular chemistry in biological systems with microelectrodes Wightman RM Science 311, 1570-1574 (2006)