Rapid and selective concentration of bacteria, viruses, and proteins using alternating current signal superimposition on two coplanar electrodes

Chang-Ho Han,Jaesung Jang,Jyoti Bhardwaj,Seong Yong Woo,Abhinav Sharma

doi:10.1038/s41598-018-33329-7

Chang-Ho Han, Jaesung Jang + Show 3 more

Open Access

https://doi.org/10.1038/s41598-018-33329-7

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Abstract

Dielectrophoresis (DEP) is usually effective close to the electrode surface. Several techniques have been developed to overcome its drawbacks and to enhance dielectrophoretic particle capture. Here we present a simple technique of superimposing alternating current DEP (high-frequency signals) and electroosmosis (EO; low-frequency signals) between two coplanar electrodes (gap: 25 μm) using a lab-made voltage adder for rapid and selective concentration of bacteria, viruses, and proteins, where we controlled the voltages and frequencies of DEP and EO separately. This signal superimposition technique enhanced bacterial capture (Escherichia coli K-12 against 1-μm-diameter polystyrene beads) more selectively (>99%) and rapidly (~30 s) at lower DEP (5 Vpp) and EO (1.2 Vpp) potentials than those used in the conventional DEP capture studies. Nanometer-sized MS2 viruses and troponin I antibody proteins were also concentrated using the superimposed signals, and significantly more MS2 and cTnI-Ab were captured using the superimposed signals than the DEP (10 Vpp) or EO (2 Vpp) signals alone (p < 0.035) between the two coplanar electrodes and at a short exposure time (1 min). This technique has several advantages, such as simplicity and low cost of electrode fabrication, rapid and large collection without electrolysis.

Highlights

Dielectrophoresis (DEP) refers to the movement of polarizable particles in a non-uniform electric field[1,2]
As alternating current (AC) EO is exerted on fluids rather than particles, the use of AC EO alone may be limited in several applications such as sorting, separation, selective concentration, and focusing based on their electrical properties
The AC electrical potentials and frequencies for DEP and EO of the particles were determined. To determine these values for the optimal DEP-capture of the bacteria against the beads, the real parts of the Clausius–Mossotti (CM) factors for the bacteria and beads were plotted with respect to the AC frequency[37] (Fig. S1a)

Summary

Introduction

Dielectrophoresis (DEP) refers to the movement of polarizable particles in a non-uniform electric field[1,2] This technique is an effective means of manipulating a specific type of biological particle, for example, particular species[3], size[4], or life state[5] in a heterogeneous particle mixture[6]. As AC EO is exerted on fluids rather than particles, the use of AC EO alone may be limited in several applications such as sorting, separation, selective concentration, and focusing based on their electrical properties In this regard, DEP and EO need to be combined to enable the selective and rapid concentration of particles far from the electrodes as well as near the electrodes onto a particular spot, such as a sensing element, thereby increasing the sensitivity of a sensor to biological particles such as bacteria, proteins, and viruses[17,18]. Few studies have been conducted using both EO and DEP on planar electrodes; in those studies, two electrodes generating www.nature.com/scientificreports/

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