Label-free, rapid Listeria monocytogenes biosensor based on a stimulus response nanobrush and nanometal hybrid electrode

S. Althawab, D.A. Oliveira, C. Smith, E.S. McLamore, C. Gomes
Texas A&M University,
United States

Keywords: biosensor, food safety, Listeria monocytogenes


Recent foodborne outbreaks have heightened public concern about food safety and created a greater impetus to improve methods for foodborne pathogen detection. The most prevalent foodborne pathogens that persistently cause infections include Salmonella Typhimurium, Listeria monocytogenes and the “big six” diarrheagenic Escherichia coli pathotypes (Koluman and Dikici 2013). To meet the need of supplying fresh, high quality, and safe food to a growing world population, rapid and sensitive monitoring techniques are needed which can determine foodborne pathogen presence. Recent recalls related to L. monocytogenes contamination highlight the importance of rapid tools that could be used to monitor pathogens such as Listeria. To reduce the economic and quality of life burden from listeriosis, there is a pressing need to develop rapid biosensors that can discriminate L. monocytogenes in a wide range of food environments. The goal of this study was to develop rapid, label-free L. monocytogenes biosensors based on composites of pH-responsive polymer nanobrushes and aptamers. To achieve this goal two approaches were used, the first was to design the sensing platform by combining pH-responsive polymer nanobrushes and platinum nanoparticles structures, and the second was embedding the pH-responsive polymer nanobrush with platinum nanoparticles. These studies allowed us to determine the optimum arrangement for nanobrush actuation and pathogen capture, while maintaining electrical properties of the sensor film. Biosensors were characterized electrochemically by electroactive surface area (ESA) and electrochemical impedance spectroscopy analyses, and also by SEM and surface roughness analysis to evaluate chitosan-platinum nanobrush formation and response to stimulus. For the first approach, chitosan nanobrushes electrodeposition was optimized to 0.5% (w/v) low molecular weight chitosan at 2 V for 5 min, increasing the ESA to 0.101 ± 0.004 cm2. Actuation tests of chitosan nanobrushes revealed pH 4 and pH 8 were the ideal pHs for capturing and sensing bacteria, respectively. While for the second approach, the ESA values for electrode submitted to the one-step grafting for 240 s was equivalent (p