Detection of Escherichia coli with a label-free impedimetric biosensor based on lectin functionalized mixed self-assembled monolayer

A highly sensitive impedimetric lectin-based biosensor for the determination of Escherichia coli (E. coil) was developed based on the affinity of lectin with glycosyl complex on cellular surface. The biosensor was fabricated by co-assembling 11-mercaptoundecanoic acid (MUA) and dithiothreitol (DTT) on the surface of gold electrode, and then the lectin was covalently immobilized using carbodiimide chemistry. A well-known lectin, Concanavalin A (Con A) was used to demonstrate proof-of-concept of the recognition interface. In the measurement of E. coli DH5 (as a model target), the change in interfacial electron transfer resistance of lectin-based biosensor was monitored using a redox couple of Fe(CN)(6)(3-/4-). The increase in the electron transfer resistance was in logarithmically direct proportion to the concentration of E. coli over a range from 1.0 x 10(2) to 1.0 x 10(5) cells/mL. The detection limit of this sensor was 75 cells/mL. Additionally, the EIS biosensor also showed satisfactory selectivity in discriminating gram negative E. coli from gram-positive bacteria. The strategy developed in this study may be a promising approach and could be extended to the design of EIS biosensors for highly sensitive and rapid detection of other desired bacteria. (C) 2016 Published by Elsevier B.V.