Cavity Carbon-Nanopipette Electrodes for Dopamine Detection

Abstract

Microelectrodes are typically used for neurotransmitter detection, but nanoelectrodes are not because there is a trade-off between spatial resolution and sensitivity, which is dependent on surface area. Cavity carbon nanopipette electrodes (CNPEs), with tip diameters of a few hundred nanometers, have been developed for nano-scale electrochemistry. Here, we characterize the electrochemical performance of CNPEs with fast-scan cyclic voltammetry (FSCV) for the first time. Dopamine detection is compared at cavity CNPEs, with a depth equivalent to a few radii, and open-tube CNPEs, an essentially infinite geometry. Open-tube CNPEs have very slow temporal response that changes over time as the liquid rises in the pipette. However, the cavity CNPEs have a fast temporal response to a bolus of dopamine that is not different than traditional carbon-fiber microelectrodes. Cavity CNPEs, with a tip diameter of 200-400 nm, have high currents because the small cavity traps and increases the local dopamine concentration. The trapping also leads to a FSCV frequency independent response and the appearance of cyclization peaks that are normally observed only with large concentrations of dopamine. CNPEs have high dopamine selectivity over ascorbic acid (AA) due to the repulsion of AA by the negative electric field at the holding potential and the irreversible redox reaction. In mouse brain slices, cavity CNPEs detected exogenously-applied dopamine, showing they do not clog in tissue. Thus, cavity CNPEs are promising neurochemical sensors that provide spatial resolution on the scale of hundreds of nanometers, useful for small model organisms or locating near specific cells.

Hydrogel Patterning with Catechol Enables Networked Electron Flow

“…In this case, an electrode is used as a “reading” instrument by immersing the film in a mediator solution (0.1 m m Fc, 0.1 m m Ru 3+ ), placing the electrode directly above the hydrogel, biasing the electrode to induce a mediator reaction (in our case, Fc oxidation was induced by imposing an oxidizing voltage +0.4 V versus Ag/AgCl), and linearly scanning the electrode across the surface (0.35 mm s −1 ) to detect the regions that can undergo redox‐cycling. [ 50–55 ] The first plot in Figure 2d shows that little Fc‐oxidation currents were measured in the unpatterned regions while considerably larger currents were observed in regions pattered with catechol. This larger current is consistent with the Fc mediator undergoing oxidative redox‐cycling in the patterned catechol region.…”

Biosensors and sensors for dopamine detection

“…Yang et al reported a cavity carbon‐nanopipette electrodes (CNPE) with FSCV for dopamine detection with increased sensitivity compared to typical nanoelectrodes, and the detailed dopamine‐oxidation−reduction is shown in Figure 9A, and a modeled dopamine concentration change in the cavity is shown in Figure 9B 104 . The CNPEs have high selectivity for dopamine even in the presence of interfering AA.…”

Correlating Molecule Count and Release Kinetics with Vesicular Size Using Open Carbon Nanopipettes

“…CNPs prepared by chemical vapor deposition (CVD) of carbon into prepulled quartz nanopipettes have proven to be applicable to electroactive transmitter detection. 18 , 19 After modification with Pt black, they were also employed in measurements of reactive oxygen and nitrogen species inside single organelles and vesicles. 20 , 21 In this work, we controlled the orifice size of open CNPs in VIEC measurements, and the distribution of N molecules was correlated with the vesicle size.…”