DNA electrochemical biosensor for early detection of Salmonella using direct electrodeposited gold nanoparticles

Early diagnosis of typhoid is a worldwide concern since the conventional Widal test or Tube agglutination test is questionable for its limitations in terms of delayed implementation and false negative response for detection of Salmonella typhi (the most common food / water borne causative of typhoid) [1-2]. An improved and specific DNA hybridization electrochemical biosensor using direct electrodeposited gold-nano-particles (AuNPs) onto indium tin oxide (ITO) coated glass plate has been fabricated for early detection of Salmonella typhi. The fabrication of this biosensor electrode involves a new and easy approach to achieve a stable and excellent biocompatible AuNPs coated ITO surface to covalently link single stranded (ss) DNA probes specific to Salmonella typhi through self assembled monolayer of 11-Mercaptoundecanoic acid (MUA). The fabricated DNA-AuNPs-ITO electrode has been characterized using Scanning Electron Microscopy, Energy Dispersive X-ray Spectroscopy, UV-Visible Spectroscopy, Atomic Force Microscopy, Fourier Transform Infrared Spectroscopy, XRD-powder, Impedance Spectroscopy, Cyclic Voltammetry and Differential Pulse Voltammetry (DPV). The DNA-AuNPsITO electrode can detect complementary targets upto 300 attomoles with in 60 s hybridization time by monitoring guanine oxidation using DPV at 25oC. This highly specific DNA-AuNPs-ITO electrode was able to distinguish complementary, non-complementary and one base mismatch target spiked serum samples. This type of biosensor electrode has implications towards detection of other pathogens like M. tuberculosis, Compylobacter, H. Pylori, E. coli etc for clinical diagnostics, food quality control and environmental monitoring.