Redox Cycling at an Array of Interdigitated Bipolar Electrodes for Enhanced Sensitivity in Biosensing**

Abstract

An array of many bipolar electrodes (BPEs) can be controlled by a single pair of driving electrodes yet allows for multiplexed analysis of many individual biomarkers or single cells at once. A wide range of bipolar electrochemical sensors have been devised, many of which operate under battery power and produce visible signals (e.g., luminescent, electrochromic) appropriate for smartphone or naked eye readout. These features of BPEs are advantageous in the context of clinical and environmental sensing applications at the point of need. However, the sensitivity of BPEs is poor in comparison to direct measurement of current at an individual electrode, and therefore, the enhancement of signals obtained at BPEs is an active area of research. Here, we describe signal amplification by redox cycling accomplished by interdigitation of each BPE in an array with a shared driving electrode. We evaluate amplification obtained for interelectrode spacing in the range of 35 m to 15 m. Each interdigitated BPE (IDBPE) in the array has an independent, reproducible, and linear response to a reversible electroactive analyte. Therefore, this universal amplification strategy allows for multiplexed or spatially resolved sensing in point-of-need applications.

Array of Interdigitated Bipolar Electrodes for Selective Capture and Analysis of Melanoma Cells

“…As described in our previous work, interdigitation of the cathodic end of BPEs supports redox cycling, which amplifies the current when sensing redox active species -as demonstrated with both ferricyanide and PAP. [38] Circular microwells (85 mm diameter, 13 mm depth) were patterned in a photoresist film on top of the IDBPE cathodic end to aid in cell retention (Figure 2a,b). Simulation work by Fujii and coworkers [12] informed the dimensions of the microwells employed to attract and retain the cells.…”

“…[38] The amplification of the signal by redox cycling allowed for detection of analytes in the micromolar range, making this device sufficiently sensitive for biologically relevant detection limits. [38] We hypothesized that this IDBPE array could be utilized to capture cells by DEP for their subsequent electrochemical analysis. However, the IDBPE array lacked structures to retain cells following cessation of the AC voltage utilized for DEP.…”

“…For example, the ECL intensity in a 5 mm-gap device showed a 6.3-fold increase over a device with a 15 mm gap. [38] The amplification of the signal by redox cycling allowed for detection of analytes in the micromolar range, making this device sufficiently sensitive for biologically relevant detection limits. [38] We hypothesized that this IDBPE array could be utilized to capture cells by DEP for their subsequent electrochemical analysis.…”

Wireless light-emitting device for the determination of chirality in real samples

“…Recently electrochemistry-based light-emitting systems have gained considerable attention due to the possible direct visualization of chemical information. Different light-emitting systems, based 3 on electroluminescence [10][11][12][13][14] or fluorescence [15] have been exploited for the quantification of different analytes of interest [16][17][18][19][20]. However, these methods require the use of additional chemicals, such as luminophores, co-reactants, fluorescent dyes, and often the light emission is triggered by complex reactions pathways.…”

Automated Measurement of Electrogenerated Redox Species Degradation Using Multiplexed Interdigitated Electrode Arrays

“…Another generation-collection method consists of using microfabricated devices based on interdigitated electrode arrays (IDAs). The IDA electrode geometry has been used in a range of applications involving electrochemical biosensing, with many applications taking advantage of its high collection efficiencies and possibility for miniaturization. − It consists of two interdigitated arrays of microband electrodes with a consistent interelectrode gap width (Figure a). Generation-collection experiments are performed with the two electrodes, and the diffusional time-of-flight is set by the gap width.…”