Real-time label-free affinity biosensors for enumeration of total bacteria based on immobilized concanavalin A

Abstract

This work presents the results of the use of flow injection surface plasmon resonance and impedimetric affinity biosensors for detecting and enumerating total bacteria based on the binding between E. coli and Con A, immobilized on a modified gold electrode. The single analysis time for both techniques was less than 20 min. Dissociation between the immobilized Con A and the E. coli using 200 mM of glucose in HCl at pH of 2.00 enabling the sensor to be reused for between 29–35 times. Impedimetric detection provided a much lower limit of detection (12 CFU mL⁻¹) than the surface plasmon resonance method (6.1 × 10⁷ CFU mL⁻¹). Using the impedimetric system, real sample analysis was performed and the results were compared to the plate count agar method. Cell concentrations obtained by the biosensor were only slightly different from the result obtained from the plate count agar. The proposed system offers a rapid and useful tool for screening detection and enumeration of total bacteria.

Keywords:

• Bacteria
• surface plasmon resonance
• impedance
• biosensor
• high sensitivity
• real-time

Acknowledgments

The authors are grateful for the grant for Jongjit Jantra under The Royal Golden Jubilee Ph.D. Program (RGJ:PHD/0191/2548) supported by The Thailand Research Fund. Financial support from the National Research University Project of Thailand, Office of the Higher Education Commission; the Center for Innovation in Chemistry (PERCH-CIC); Trace Analysis and Biosensor Research Center (TAB-RC); Graduate School and Faculty of Science, Prince of Songkla University, Hat Yai, Thailand were gratefully acknowledged. The authors also thank Dr. Brian Hodgson, Prince of Songkla University, Hat Yai, Songkhla, Thailand for assistance with the manuscript.