P2-46 A Nanowell-based Immunosensor for Rapid and Sensitive Detection of E. coli O157:H7

Tuesday, August 2, 2016
America's Center - St. Louis
Ronghui Wang, University of Arkansas, Fayetteville, AR
Xiaofan Yu, University of Arkansas, Fayetteville, AR
Tony Huang, Penn State University, University Park, PA
Yanbin Li, University of Arkansas, Fayetteville, AR
Introduction: Escherichia coli O157:H7 is one of the most dangerous foodborne pathogens. The development of a rapid, sensitive, and specific detection method for E. coli O157:H7 is continuously needed to improve food safety and security.

Purpose: The objective of the present study was to develop a nanowell-based immunosensor using a screen printed interdigitated electrode (SPIE) for rapid and sensitive detection of E. coli O157:H7 in foods.

Methods: A nanoporous-gold-film (NGF) with a thickness of 120 nm and a pore size of ~20 nm was prepared by a metallic corrosion method. Then, the NGF was coated onto the gold surface of a SPIE through a self-assembled monolayer to form a nanowell-based electrode. Polyclonal antibodies against E. coli O157:H7 were immobilized on the electrode surface through covalent bonding. After a blocking solution was applied, a test sample was added. Target E. coli O157:H7 presented in the sample was captured by the immobilized antibody, resulting in a change in the impedance of the nanowell-based electrode surface.

Results: The results showed that the developed nanowell-based immunosensor was able to detect E. coli O157:H7 with an enhanced impedance signal when compared to an immunosensor without nanowell. The impedance value of the nanowell-based electrode was observed to increase a 10-fold for detection of E. coli O157:H7 in pure culture at a concentration of 105 CFU/ml in an applied volume of 45 µl. It was a label-free detection with a total detection time from adding the sample to obtain the final result within one hour. Further work will be concentrated on the optimization of conditions of the nanowell-based immunosensor, and detection of target bacteria in different foods.

Significance: The outcome of this study will improve the sensitivity of the immunosensor due to the greatly increased gold surface area with the help of nanowell-based electrodes, which will provide a sensitive, rapid and label-free method for detection of foodborne pathogens.