Surface-modified CMOS IC electrochemical sensor array targeting single chromaffin cells for highly parallel amperometry measurements

Abstract

Amperometry is a powerful method to record quantal release events from chromaffin cells and is widely used to assess how specific drugs modify quantal size, kinetics of release, and early fusion pore properties. Surface-modified CMOS-based electrochemical sensor arrays allow simultaneous recordings from multiple cells. A reliable, low-cost technique is presented here for efficient targeting of single cells specifically to the electrode sites. An SU-8 microwell structure is patterned on the chip surface to provide insulation for the circuitry as well as cell trapping at the electrode sites. A shifted electrode design is also incorporated to increase the flexibility of the dimension and shape of the microwells. The sensitivity of the electrodes is validated by a dopamine injection experiment. Microwells with dimensions slightly larger than the cells to be trapped ensure excellent single-cell targeting efficiency, increasing the reliability and efficiency for on-chip single-cell amperometry measurements. The surface-modified device was validated with parallel recordings of live chromaffin cells trapped in the microwells. Rapid amperometric spikes with no diffusional broadening were observed, indicating that the trapped and recorded cells were in very close contact with the electrodes. The live cell recording confirms in a single experiment that spike parameters vary significantly from cell to cell but the large number of cells recorded simultaneously provides the statistical significance.

A Bidirectional-Current CMOS Potentiostat for Fast-Scan Cyclic Voltammetry Detector Arrays

“…The tip of the carbon fiber was entirely coated with wax and then cut such that only the circular area at the end of the cut fiber was exposed as the working electrode. The area of such a CFM is similar to that of onchip electrodes after post-fabrication [11], [13], which also will be fabricated in the future on the FSCV chip described here. The CFM was immersed into a petri dish filled with a buffer solution containing 140 mM NaCl, 5 mM KCl, 5 mM CaCl 2 , 1 mM MgCl 2 , and 10 mM HEPES/NaOH pH 7.3.…”

“…The detector array provides a five-fold increase in temporal resolution over the unidirectional-current detector array we reported previously in [11], [13]. …”

“…Surface-patterned planar MEAs using noble metals such as gold and platinum and other materials have recently been applied to measure quantal release events from single cells [10]. Scalable arrays incorporate CMOS potentiostats with on-chip electrodes for parallel recordings from large numbers of cells [11]–[14]. …”

Parallel 1024-ch Cyclic Voltammetry on Monolithic CMOS Electrochemical Detector Array

“…Using an array of 100 amperometric amplifiers in a CMOS device, the neurotransmitter release from chromaffin cells were recorded [6], [7].…”

Transistors for Chemical Monitoring of Living Cells

“…Even if it is possible to use conventional carbon fiber ultramicroelectrodes to record exocytosis events, microfabrication techniques have significantly improved electrochemical sensing, particularly arrays of sensors [ 11 ]. For example, recent reviews have demonstrated that it is possible to record not only electrical cellular activity [ 12 ], but also to sense exocytosis events on conventional microelectrode arrays (MEA) [ 13 , 14 ]. Therefore, MEA may be used in basic research or clinical diagnostics for cell analysis–based drug discovery or environmental monitoring, where they help to monitor in-situ (in Petri dishes) not only cell functions via neurotransmitters release, but also enzymatic activity or cells respiratory activity (glucose consumption, lactate production), using electrochemical reactions on sensing electrodes [ 15 ].…”