A Sensitive Nanoporous Gold-Based Electrochemical DNA Biosensor for Escherichia coli Detection

Abstract

A sensitive electrochemical DNA biosensor based on a mixed monolayer structure self-assembled at nanoporous gold (NPG) electrode surface was prepared for Escherichia coli (E. coli) detection. The NPG was fabricated on gold electrode, onto which thiolated oligonucleotides (SH-DNA) and mercaptohexanol (MCH) were covalently linked forming a mixed self-assembled monolayer (SAM). The hybridization between the SH-DNA/MCH modified biosensor and E. coli DNA was monitored with differential pulse voltammetry measurement using methylene blue (MB) as the hybridization indicator. The biosensor can detect 1 × 10⁻¹² M DNA target and 50 cfu/μL E. coli without any nucleic acid amplification steps. The detection limit was lowered to 50 cfu/mL after 5.0 h of incubation.

Keywords:

• Escherichia coli (E. coli)
• Electrochemical DNA biosensor
• Mercaptohexanol (MCH)
• Methylene blue (MB)
• Mixed self-assembled monolayer (SAM)

Acknowledgments

We greatly appreciate the financial support of the National Nature Science Foundation of China (20775026), Science and Technology Commission of Shanghai Municipality (No. 1052nm06500), and Shanghai Key Laboratory of Green Chemistry and Chemical Process.