Enabling long term monitoring of dopamine using dimensionally stable ultrananocrystalline diamond microelectrodes (original) (raw)
Chronic dopamine (DA) monitoring is a critical enabling technology to identify the neural basis of human behavior. Carbon fiber microelectrodes (CFM), the current gold standard electrode for in vivo fastscan cyclic voltammetry (FSCV), rapidly loses sensitivity due to surface fouling during chronic neural testing. Periodic voltage excursions at high anodic potentials regenerate fouled CFM surfaces, but they also chemically degrade the CFMsurfaces. Here, we compare the dimensional stability of 150 μm boron-doped ultrananocrystalline diamond (BDUNCD) microelectrodes in 1X PBS during ‘electrochemical cleaning’ with a similar-sized CFM. Scanning electron microscopy and Raman spectroscopy confirm the exceptional dimensional stability of BDUNCD after 40 h of FSCV cycling (∼8 million cycles). The fitting of electrochemical impedance spectroscopy data to an appropriate circuit model shows a 2x increase in charge transfer resistance and an additional RC element, which suggests oxidation of the BDUNCD electrode surface. This could have likely increased the DA oxidation potential by ∼34% to +308 mV. A 2x increase in BDUNCD grain capacitance and a minor change in grain boundary impedance suggests regeneration of grains and the exposure of new grain boundaries, respectively. DA voltammogram signals were reduced by only ∼20% of BDUNCD during chronic DA sensing. In contrast, the CFM is wholly etched with a ∼90% reduction in the DA signal using the same cleaning conditions. Thus, BDUNCD provides a robust electrode surface amenable to repeated and aggressive cleaning, which could be used for chronic DA sensing.