Transparent Electrode Materials for Simultaneous Amperometric Detection of Exocytosis and Fluorescence Microscopy

Abstract

We have developed and tested transparent microelectrode arrays capable of simultaneous amperometric measurement of oxidizable molecules and fluorescence imaging through the electrodes. Surface patterned microelectrodes were fabricated from three different conducting materials: Indium-tin-oxide (ITO), nitrogen-doped diamond-like carbon (DLC) deposited on top of ITO, or very thin (12–17 nm) gold films on glass substrates. Chromaffin cells loaded with lysotracker green or acridine orange dye were placed atop the electrodes and vesicle fluorescence imaged with total internal reflection fluorescence (TIRF) microscopy while catecholamine release from single vesicles was measured as amperometric spikes with the surface patterned electrodes. Electrodes fabricated from all three materials were capable of detecting amperometric signals with high resolution. Unexpectedly, amperometric spikes recorded with ITO electrodes had only about half the amplitude and about half as much charge as those detected with DLC or gold electrodes, indicating that the ITO electrodes are not as sensitive as gold or DLC electrodes for measurement of quantal catecholamine release. The lower sensitivity of ITO electrodes was confirmed by chronoamperometry measurements comparing the currents in the presence of different analytes with the different electrode materials.

3D printed microfluidic devices with integrated versatile and reusable electrodes

“…46-48 Here, we demonstrate the amenability of a rigid, 3D printed device for electrochemical detection of oxygen in a stream of flowing hypoxic RBCs, while simultaneously collecting the ATP released from these cells in a transwell insert incorporated into the device. This device (Figures 5 and 6) facilitated measurement of these two analytes by including a threaded port (5/16-24 threading) for the removable Nafion-coated gold and Ag/AgCl electrode and two wells to house membrane inserts (0.4 μm pores).…”

Parallel recording of neurotransmitters release from chromaffin cells using a 10×10 CMOS IC potentiostat array with on-chip working electrodes

“…These include platinum (Dias et al 2002; Berberian et al 2008), pyrolyzed photoresist (Zachek et al 2009), carbon (Zhang et al 2008; Lin et al 2012), ITO (Kisler et al 2012), nitrogen-doped diamond-like carbon (DLC:N) (Barizuddin et al 2010), boron-doped nanocrystalline diamond (Carabelli et al 2010) and organic polymers (Yang et al 2011). The limitation of such microelectrode arrays is that for parallel recordings each electrode needs to be connected to an external amplifier, and such devices are therefore not scalable.…”

Vesicular exocytosis and microdevices – microelectrode arrays

“…Briefly, an evanescent wave is created by the total internal reflection of a laser beam at the interface cell/coverslip. 43 The question of the ideal transparent and conducting electrode material remains an important issue and comparisons considering various conducting/transparent materials have been made. It also has the advantage to offer a high signal-to-noise ratio in the x-y plane.…”