Impedance biosensing using phages for bacteria detection: Generation of dual signals as the clue for in-chip assay confirmation

In the present work, we compare the use of antibodies (Ab) and phages as bioreceptors for bacteria biosensing by Electrochemical Impedance Spectroscopy (EIS). With this aim, both biocomponents have been immobilised in parallel onto interdigitated gold microelectrodes. The produced surfaces have been characterised by EIS and Fourier Transform Infra-Red (FTIR) Spectroscopy and have been applied to bacteria detection. Compared to immunocapture, detection using phages generates successive dual signals of opposite trend over time, which consist of an initial increase in impedance caused by bacteria capture followed by impedance decrease attributed to phage-induced lysis. Such dual signals can be easily distinguished from those caused by non-specific adsorption and/or crossbinding, which helps to circumvent one of the main drawbacks of reagentless biosensors based in a single target-binding event. The described strategy has generated specific detection of Escherichia coli in the range of 104–107 CFU mL−1 and minimal interference by non-target Lactobacillus. We propose that the utilisation of phages as capture biocomponent for bacteria capture and EIS detection allows in-chip signal confirmation.