Novel electrochemical biosensor for Escherichia coli using gold-coated tungsten wires and antibody functionalized short multiwalled carbon nanotubes

Rapid and easy detection of pathogens, especially bacteria, plays an important role in daily life in the face of increasing environmental pollution. Nanosensors focus on carbon nanotubes, which can bind various molecules to large surfaces and have high electron conductivity. They are widely used in the development of electrochemical biosensors. In this study, a new design of electrochemical biosensors is presented by integrating gold-coated tungsten wires (GC-TW) and acid-functionalized multi-walled carbon nanotubes (MWCNTs) in a two-step coating process. GC-TWs are coated with acid-functionalized short MWCNTs. Fourier transforms infrared spectroscopy (FTIR), transmission electron microscopy (TEM), and scanning electron microscopy (SEM) results show efficient immobilization of the electrodes. The performance for Escherichia coli (E. coli) K-12 is evaluated based upon the change in current following antibody-antigen interactions. Bioimpedance measurements are performed from 50 Hz to 10 MHz to achieve optimal coverage of impedance changes. The measurements show that the electrode has a detection limit of 0.8 CFU/mL. The response of the electrode saturates when the bacterial concentration is increased to 1.70 x 10² CFU/mL. The biosensor is capable of detecting E. coli between 0.8 and 1.70 × 10² CFU/mL. The data show that this MWCNT-based biosensor can be developed into a highly sensitive device for E. coli.