Detection of Salmonella typhimurium (LT2) invA Gene Using PNA Probe Biosensor by Electrochemical Impedance

A peptide nucleic acid sequence with thiol groups at 5-end was covalently linked onto the Au electrode surface via S-Au binding for identifying the invasion A gene (invA) of Salmonella typhimurium (LT2). The hybridization event was monitored by using electrochemical impedance spectroscopy. The combination of electrochemical impedance spectroscopy technique and peptide nucleic acid probe achieved the ideal sensitivity and selectivity for detection of target DNA and the process of the probe immobilization was simplified. Tie electrochemical impedance response was linear with the logarithm of invA gene concentrations in the range from 1.0 x 10(-13) mol L-1 to 10 x 10-(10) mol L-1 with the detection limit of 3.3 x 10(-14) mol L-1. Compared with DNA probe, peptide nucleic acid probe provided the sensor with wider linear range and more effective distinguish in mismatch DNAs. The sensor was successfully applied to the detection of invA gene extracted from S. typhimurium (LT2) sample.