Electrochemical detection of foodborne Escherichia coli using carbon nanotube-incorporated pencil-drawn paper-based disposable biosensors

Abstract

Background: In this study, electrochemical flexible paper-based biosensors were developed for rapid and sensitive detection of Escherichia coli, a pathogen and a significant concern in both public health and the food industry. The electrodes were fabricated by a simple pencil drawing method utilizing a commercial, cost-effective cutting tool. Using automated cutting tool to form the conductive graphite patterns enabled the fabrication of pencil-drawn paper-based electrodes with a high reproducibility. The polyclonal E. coli antibody-hybridized multi-walled carbon nanotubes (MWCNTs) were immobilized onto the working electrode surface to construct the biosensors. Results: The performance of the biosensors against E. coli was evaluated using cyclic voltammetry (CV) and differential pulse voltammetry (DPV) techniques. To the immobilization and performance conditions optimization results, the developed sensor demonstrated the best results at 7.2 pH, 10 mu g mL- 1 Ab-MWCNT conjugate loadings and 30-min incubation time. The pencil-drawn flexible paper-based biosensors showed a linear range of 10 degrees-107 CFU mL- 1 with a low limit of detection (LOD) of 2.6 x 101 CFU mL-1. The sensor exhibited high repeatability with a low Relative Standard Deviation (RSD) % of 2.8. The sensors demonstrated remarkable selectivity against various culture environments and good performance in detecting E. coli in apple juices as real samples. In addition, the developed biosensor successfully detected a wild-type E. coli strain which was isolated from a street food and genetically confirmed as E. coli in this study. Significance: Our results suggested that disposable paper-based pencil-drawn flexible electrodes can be used to develop low-cost biosensors with high sensitivity and selectivity against E. coli. To the best of our knowledge, it is the first report using the pencil-drawing method for electrode fabrication for detection of E. coli and its appli-cation in real samples.