Development of an Antibody Functionalized Carbon Nanotube Biosensor for Foodborne Bacterial Pathogens

Abstract

With increasing reports on bioterrorism and other bio-threats, rapid and real time detection methods for various pathogens are warranted. Attempts have been made to improve electrochemical biosensor performance by incorporating Carbon Nanotubes (CNTs). The high surface area of CNTs allows both immobilization of antibodies and electrochemical measurements. Salmonella monoclonal antibodies were covalently attached onto CNTs by using diimide activated imidation coupling. CNTs functionalized with antibodies were immobilized onto a glassy carbon electrode and the presence of pathogen was detected by studying the changes in charge transfer resistance and impedance, before and after the formation of antigen-antibody complex. CNTs behave as molecular wires allowing electrical communication between the underlying electrode and the conjugated antigen-antibody complex. Nyquist plots and cyclic voltammograms were studied and comparisons have been made between glassy carbon electrodes as working-electrode by itself, electrodes immobilized with antibodies and after the formation of antigen-antibody complex. Cyclic voltammeter experiments had a potential scan rate of 100 mVs-1, step height of 1.0 mV and applied potential from -1.0 V to 1.0 V. The electrochemical impedance experiments applied a frequency range of 100 kHz -100 mHz with an AC sine wave amplitude of 10 mV. Amplification in the current density was observed for CNTs immobilized on the electrode surface and decrease in current density and increased impedance was observed after the antigens bound specific antibodies. Enzyme-Linked Immune Sorbent Assay (ELISA) was done to determine the titer of the antibodies and their sensitivity at different dilutions for antigen detection. This technique could be an effective way to sense the formation of antigen-antibody complexes, with the potential to make the detection process rapid as compared to conventional pathogen detection methods.