Sensitive label-free oligonucleotide-based microfluidic detection of mercury (II) ion by using exonuclease I

• Published in: Biosensors & bioelectronics 2012-01, Vol.31 (1), p.330-336
• Main Authors: Yuan, Min, Zhu, Yonggang, Lou, Xinhui, Chen, Chen, Wei, Gang, Lan, Minbo, Zhao, Jianlong
• Format: Article
• Language: English
• Subjects: Biological and medical sciences; Biosensing Techniques - instrumentation; Biosensors; Biotechnology; Deoxyribonucleic acid; DNA - chemistry; Electrophoresis; Electrophoresis, Capillary - instrumentation; Equipment Design; Equipment Failure Analysis; Escherichia coli; Exodeoxyribonucleases - chemistry; Exonuclease I; Fluorescence; Fundamental and applied biological sciences. Psychology; Ions; Label-free DNA; Mercury; Mercury - analysis; Mercury - chemistry; Mercury ions; Microfluidic Analytical Techniques - instrumentation; Microfluidic detection; Microfluidics; Oligonucleotide Array Sequence Analysis - instrumentation; Reproducibility of Results; Sensitivity and Specificity; Separation; Staining and Labeling
• ISSN: 0956-5663; 1873-4235
• DOI: 10.1016/j.bios.2011.10.043

► A novel method based on Exo I, DNA and electrophoresis for Hg2+ detection. ► Selective digestion of Exo I on ssDNA. ► Quenching effect of Hg2+ on excited fluorescence states. ► Limit of detection around 15nM. ► Excellent selectivity over five other metal ions without any secondary reagent. Mercury is a highly toxic metal that can cause significant harm to humans and aquatic ecosystems. This paper describes a novel approach for mercury (Hg2+) ion detection by using label-free oligonucleotide probes and Escherichia coli exonuclease I (Exo I) in a microfluidic electrophoretic separated platform. Two single-stranded DNAs (ssDNA) TT-21 and TT-44 with 7 Thymine–Thymine mispairs are employed to capture mercury ions. Due to the coordination structure of T–Hg2+–T, these ssDNAs are folded into hairpin-like double-stranded DNAs (dsDNA) which are more difficult to be digested by Exo I, as confirmed by polyacrylamide gel electrophoresis (PAGE) analysis. A series of microfluidic capillary electrophoretic separation studies are carried out to investigate the effect of Exo I and mercury ion concentrations on the detected fluorescence intensity. This method has demonstrated a high sensitivity of mercury ion detection with the limit of detection around 15nM or 3ppb. An excellent selectivity of the probe for mercury ions over five interference ions Fe3+, Cd2+, Pb2+, Cu2+ and Ca2+ is also revealed. This method could potentially be used for mercury ion detection with high sensitivity and reliability.