Negative Dielectrophoretic Capture and Repulsion of Single Cells at a Bipolar Electrode: The Impact of Faradaic Ion Enrichment and Depletion

Abstract

This paper describes the dielectrophoretic (DEP) forces generated by a bipolar electrode (BPE) in a microfluidic device and elucidates the impact of faradaic ion enrichment and depletion (FIE and FID) on electric field gradients. DEP technologies for manipulating biological cells provide several distinct advantages over other cell-handling techniques including label-free selectivity, inexpensive device components, and amenability to single-cell and array-based applications. However, extension to the array format is nontrivial, and DEP forces are notoriously short-range, limiting device dimensions and throughput. BPEs present an attractive option for DEP because of the ease with which they can be arrayed. Here, we present experimental results demonstrating both negative DEP (nDEP) attraction and repulsion of B-cells from each a BPE cathode and anode. The direction of nDEP force in each case was determined by whether the conditions for FIE or FID were chosen in the experimental design. We conclude that FIE and FID zones generated by BPEs can be exploited to shape and extend the electric field gradients that are responsible for DEP force.

Nanoslit design for ion conductivity gradient enhanced dielectrophoresis for ultrafast biomarker enrichment in physiological media

“…[20][21][22][23] Furthermore, the highly localized nature of DEP behavior, due to its dependence on rE 2 , limits its spatial extent. 13,24 Herein, by initiating ICP at lateral perm-selective constrictions of large surface charge non-uniformity, we create conductivity differences across the nanoslit length to enhance the spatial extent for biomarker depletion. As a result, the localized field (E) is enhanced due to ion depletion at the constriction tips, whereas ion accumulation along the constriction sidewalls increases the field gradient (rE), thereby dramatically enhancing the magnitude and spatial extent of nDEP, due to its rE 2 dependence.…”

A Self‐Digitization Dielectrophoretic (SD‐DEP) Chip for High‐Efficiency Single‐Cell Capture, On‐Demand Compartmentalization, and Downstream Nucleic Acid Analysis

“…Compared to the single-cell isolation and analysis devices with multi-layer architecture, the SD-DEP chip described here does not require complex device fabrication and operations such as valves and mixing. The steps of cell analysis using SD-DEP chip are depicted in Scheme 1: A) prime the device with Pluronic F-127 solution to effectively inhibit cell adhesion on PDMS surface, B) fill the trapping channels and chambers with specific buffers and reagents (here, low electrical conductivity (LEC) DEP buffer [18] (8.0% sucrose, 0.3% dextrose, and 0.1% BSA in 1.0 mM Tris (pH 8.0, conductivity σ = 6.2 mS/m)) was applied for cell trapping), C) apply optimized trapping voltage and flow in the cell sample and trap cells at chamber openings, D) flush the excess cells with LEC buffer, turn off the trapping voltage and inject fresh loop mediated isothermal amplification (LAMP) reaction buffer to dispense the trapped cells into the chambers, E) fill the channel with the immiscible phase to isolate cells in the compartments, F) lyse cells and initiate single-cell LAMP reaction. The strength of this experimental design is three-fold.…”

“…Second, the active cell sorting method developed here relies on external DEP force without the use of cell labeling, which provides greater specificity and control of the force employed for cell capture than passive sorting mechanisms or spontaneous digitization alone. [18, 20] This label free cell sorting method has important advantages for conducting high fidelity single cell molecular analyses, such as minimized antibody related costs, applicability to cells lacking biomarkers, and maintaining integrity of endogenous biomarker expression. Finally, features such as the dimensions of the chamber opening and control over DEP force provide means to limit capture in each chamber to one cell.…”

“…[17] Herein, we present the development of aself-digitization dielectrophoretic (SD-DEP) chip that enables rapid, convenient, and highly efficient capture and on-demand release of single suspended cells into separated chambers for downstream nucleic acid analysis using inexpensive and simple components.C ompared to the single-cell isolation and analysis devices with multi-layer architecture,t he SD-DEP chip described herein does not require complex device fabrication and operations such as valves and mixing. The steps of cell analysis using SD-DEP chip are depicted in Scheme 1: A) Thed evice is primed with Pluronic F-127 solution to effectively inhibit cell adhesion on PDMS surface, B) the trapping channels and chambers are filled with specific buffers and reagents (here,low electrical conductivity (LEC) DEP buffer [18] (8.0 %sucrose,0.3 %dextrose,and 0.1 %BSA in 1.0 mm Tris (pH 8.0, conductivity s = 6.2 mS m À1 )) was applied for cell trapping), C) optimized trapping voltage and flow are applied in the cell sample and cells trapped at chamber openings,D )the excess cells are flushed with LEC buffer, the trapping voltage turned off,a nd fresh loop mediated isothermal amplification (LAMP) reaction buffer injected to dispense the trapped cells into the chambers, E) the channel is filled with the immiscible phase to isolate cells in the compartments,a nd F) cells are lysed and single-cell LAMP reaction initiates.The strength of this experimental design is three-fold. First, the introduction of an immiscible phase takes advantage of an existing robust technology self-digitization (SD) chip that we have developed.…”

“…[19] This technology employs inherent fluidic phenomena to spontaneously divide an aqueous solution into nanoliter-scale waterin-oil plugs in an array of microfluidic chambers.Each waterin-oil emulsion plug formed on the SD-DEP chip can function as an independent chemical reactor, handling an extremely small volume of liquid containing cells and reagents for following molecular analysis of single cell lysates.Second, the active cell sorting method developed herein relies on external DEP force without the use of cell labeling,w hich provides greater specificity and control of the force employed for cell capture than passive sorting mechanisms or spontaneous digitization alone. [18,20] This label-free cell-sorting method has important advantages for conducting high-fidelity single-cell molecular analyses,such as minimized antibody related costs, applicability to cells lacking biomarkers,a nd maintaining integrity of endogenous biomarker expression. Finally,f eatures such as the dimensions of the chamber opening and control over DEP force provide means to limit capture in each chamber to one cell.…”