Previously, we demonstrated label-free selective capture of tumor cells by dielectrophoresis (DEP) at an array of wireless bipolar electrodes (BPEs). This platform potentiates parallel electrochemical analysis of the isolated cells at the BPEs. However, traditional BPEs with an electrogenerated chemiluminescence (ECL) readout are not sufficiently sensitive for biologically relevant detection limits, and therefore, they require a means of signal amplification. To address this limitation, we recently developed interdigitated bipolar electrodes (IDBPEs), with 5-micron gaps between microbands, to facilitate redox cycling of electroactive analytes at the sensing pole of each BPE for amplification of the resulting ECL signal at the reporting pole. Additionally, we used this IDBPE device to capture multiple cells in microwells overlying each IDBPE and to analyze them electrochemically (unpublished result).<br/><br/>In this presentation, we report the selective dielectrophoretic capture and electrochemical analysis of single melanoma cells at an array of electrochemical biosensors consisting of two interlocking spirals made of gold thin film patterned on a glass substrate. One spiral serves as the driving electrode, while the other as the sensing pole of a BPE. The reporting pole of each BPE is located in a fluidically isolated compartment containing reagents for ECL. Picoliter-scale chambers overlay the spirals, with the entrance of the chamber restricting the number of cells that can be captured by DEP. Under an externally applied AC voltage, melanoma cells are attracted to this pocket by a positive dielectrophoretic force. When the AC voltage is turned off, captured cells are drawn into the chambers hydrodynamically. Once cells are retained in the chambers, electrochemical analysis may begin.<br/><br/>In the present study, the interlocked spiral end of the BPE is utilized for electrochemical enzyme-linked immunosorbent assay (eELISA) to quantify the expression of a cell surface antigen, melanoma cell adhesion marker (MCAM). This work is significant because it allows for the sensitive analysis of a single melanoma cell in a device amenable to point-of-care application by combining selective enrichment of malignant cells by dielectrophoresis with the amplification and facile arraying afforded by IDBPEs.

Array of interlocked spiral bipolar electrodes for dielectrophoretic capture and electrochemical enzyme-linked immunosorbent assay of single melanoma cells

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ACS Fall 2022

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