Integrating a DNA Strand Displacement Reaction with a Whispering Gallery Mode Sensor for Label-Free Mercury (II) Ion Detection.

Fengchi Wu,Yuqiang Wu,Frank Vollmer,Zhongwei Niu

doi:10.3390/s16081197

Abstract

Mercury is an extremely toxic chemical pollutant of our environment. It has attracted the world’s attention due to its high mobility and the ease with which it accumulates in organisms. Sensitive devices and methods specific for detecting mercury ions are, hence, in great need. Here, we have integrated a DNA strand displacement reaction with a whispering gallery mode (WGM) sensor for demonstrating the detection of Hg2+ ions. Our approach relies on the displacement of a DNA hairpin structure, which forms after the binding of mercury ions to an aptamer DNA sequence. The strand displacement reaction of the DNA aptamer provides highly specific and quantitative means for determining the mercury ion concentration on a label-free WGM sensor platform. Our approach also shows the possibility for manipulating the kinetics of a strand displacement reaction with specific ionic species.

Highlights

A number of important techniques have been reported for Hg2+ detection, such as those based on colorimetry and fluorescence [1,2], nanoparticles [3] or functional polymers [4], these established methods often have drawbacks due to time-consuming assay procedures, complex sample preparations and requirements for specific laboratory equipment
We have demonstrated in proof-of-principle experiments a label-free method for determining the concentration of Hg2+ ions using a DNA strand displacement reaction integrated on a whispering gallery mode (WGM)
We have demonstrated in proof-of-principle experiments a label-free method for determining the concentration of Hg2+ ions using a DNA strand displacement reaction integrated on a WGM sensor

Summary

Introduction

A number of important techniques have been reported for Hg2+ detection, such as those based on colorimetry and fluorescence [1,2], nanoparticles [3] or functional polymers [4], these established methods often have drawbacks due to time-consuming assay procedures, complex sample preparations and requirements for specific laboratory equipment. Label-free detection strategies have the additional advantage that they can be more integrated on sensor devices, where different transducers are available for readout in the electrical [7,8], mechanical [9,10], and optical domain [11,12] Among these systems, optical whispering gallery mode (WGM) sensors are an emerging technology platform [13,14] for the label-free detection of a large variety of analytes including virus [15,16], oligonucleotide [17,18], protein [19,20], nanoparticle [21,22], and small molecule [23,24]. WGM sensors transduce the binding of target analytes into a resonance frequency/wavelength shift, thereby sensing the small variations of the effective refractive index in the immediate surroundings of the optical

Methods

Results

Conclusion