Electrochemical Detection of Dopamine via Assisted Ion Transfer at Nanopipet Electrode Using Cyclic Voltammetry

Abstract

We present here the detection of dopamine (DA) at nanopipet electrodes with radii of hundreds of nanometers ranging from 160 nm to 480 nm. Dibenzo-18-crown-6 (DB18C6) was employed as an ionophore to facilitate DA transfer, resulting in a half-wave transfer potential, E1/2, DA, of −0.322 (±0.020) V vs. E1/2, TBA. Well-defined steady-state sigmoidal cyclic voltammograms were observed for the transfer of DA. High resolution scanning electron microscopy was used to measure the size and taper angle of the nanopipet electrodes. The detection is linear with concentration of DA ranging from 0.25 mM to 2 mM; calculated diffusion coefficient at nanopipet electrodes with above mentioned sizes is 4.87 (±0.28) × 10−10 m2/s. The effect of the common interferent ascorbic acid on DA detection with nanopipet electrodes was evaluated, where DA detection still shows linear behavior with well-defined sigmoidal CVs with E1/2, DA being −0.328 (±0.029) V vs. E1/2, TBA. The diffusion coefficient for DA transfer in MgCl2 with the presence of 2 mM AA was measured to be 1.93 (±0.59) × 10−10 m2/s on nanoelectrodes with radii from 161 nm to 263 nm, but the physiological concentration of 0.1 mM AA had no effect on DA’s diffusion coefficient.

GABA Detection with Nano-ITIES Pipet Electrode: A New Mechanism, Water/DCE–Octanoic Acid Interface

“…21,29,30 Briefly, the diffusion limited steady state current at nanoITIES pipet electrodes can be expressed as 35 $$i=4\text{italicxnFDca}$$where i is the steady-state current, x is a function of the quantity RG = r g / a ( r g and a are outer and inner tip radii, respectively), 35 n is the number of transferred charges, F is Faraday’s constant, a is the radius of the electrode, D is the diffusion coefficient of the neurotransmitter, and c is the concentration of the neurotransmitter. A proposed disk geometry for the nanopipet tip was used for the calculation.…”

“…The current values from three replicate background CVs at the diffusion limited potential of GABA transfer were used to calculate the standard deviation of the background, as done in our previous study. 29,30 …”

A Nanopipette Platform for Delivering Nanoliter Volumes of Acetylcholine

“…A nanopipette with approximate radii of 160-480 nm was generated using the pulling parameters as described in previous work. 38 The pulled pipette was back-filled with 1 M ACh chloride solution (0.8 μL) which was then brought to the tip by gentle vibrations created with an alligator clip. After that, an oil phase consisting of TDDATFAB + DCE was added to the pipette and gentle tapping was used to bring the oil phase to be in contact with the aqueous phase.…”

“…Details on nanoITIES electrodes fabrication and characterization can be found in recent publications from our group. [37][38][39] Delivery experiments.-A Nanopipette delivery probe as described above was immersed into the aqueous cellular medium, the artificial seawater (ASW), after which a voltage was applied to induce the delivery of ACh. To prevent an unwanted ingress during the immersion process, a retaining voltage of 0.8 V vs Ag/AgCl was applied while the pipette was lowered into the ASW.…”

Electroanalytical Opportunities Derived from Ion Transfer at Interfaces between Immiscible Electrolyte Solutions

“…A recent report for this group also extends the detection of dopamine to nanopipettes ITIES, although detection levels were within the 100 µM region. [99] These relatively high detection levels might be suitable for detection of local concentrations at points of release, e.g. from neural cells.…”