Label free electrical detection of salmonella typhimurium pathogens by microcellular trapping channels

Salmonalla is one of the major causes of worldwide foodborne diseases. Conventional microbiological detection methods are time consuming and the recent signal transduction schemes based on fluorescence spectroscopy, surface plasmon resonance and others require specialized bulky and expensive instruments, which will increase the overall production cost in the food industry. This paper reports for the first time the use of microcellular trapping channels of oxidized macroporous silicon substrate with stable contacts directly from macroporous silicon using antibody-antigen binding method for label free, rapid, field deployable and inexpensive electrical detection of Salmonella Typhimurium by impedance measurements. Macroporous silicon is a regular array of pores of 1-2mum diameter which act as microcellular trapping medium for capture of bacteria. The preliminary reports show that a 2mm by 1mm electrode structure with a spacing of 1mm on oxidized macroporous silicon, without any optimization has been able to detect 10³CFU-10⁷CFU/ml of Salmonella Typhimurium using this microcellular trapping medium at a significantly lower processing cost and is comparable to much more sophisticated impedimetric measurements using interdigitated microelectrode array with dielectrophoresis (DEP). The relatively high sensitivity achieved with large electrode spacing can be attributed to the localization of fringing electric field lines through the trap holes occupied by bacterial analyte solution near the electrode. Using this technique an array of such sensitive sensors can be easily realized to yield a biochip for detection of various foodborne pathogens down to 10³CFU/ml.