Electrochemical Immunosensor for Detection of Francisella Tularensis

Abstract

An immunosensor for rapid and sensitive detection of Francisella tularensis (Ft) was developed using screen-printed sensors with multiple (4) Au working electrodes. The sensing zones were modified with a biolayer of anti-Ft polyclonal antibody attached through the covalently immobilized Protein A. The sandwich assay format was employed with anti-Ft IgG-peroxidase conjugate as tracer. For electrochemical measurements, an automated portable detector was developed; it consisted of a digitally controlled potentiostat and four embedded miniperistaltic pumps. The flow-through measurement involved sequential incubations with sample (10 min), tracer (10 min) and substrate mixture (iodide and hydrogen peroxide). The enzymatically-produced iodine was detected electrochemically at - 50 mV. The limit of detection was 100 Ft cells/ml; the response was significantly higher (3x) when using the living cells compared to the heat inactivated ones.