PCR-Free Ultrasensitive Capacitive Biosensor for Selective Detection and Quantification of Enterobacteriacea DNA

Abstract

This paper presents a flow-based ultrasensitive capacitive biosensor for the detection of bacterial DNA. The used sensor chip consists of a gold electrode, insulated with a polytyramine layer and covalently tagged with a DNA capture probe. The hybridization of target DNA to the capture probe resulted in sensor response. The sensor response was linear vs. log concentration in the range 1.0 × 10-12 to 1.0 × 10-7 moles per litre with a detection limit of 6.5 × 10-13 M. An alternative approach to bacterial DNA sample preparation for a flow-based analysis is also reported. The approach involved application of a thermostable ssDNA binding protein to prevent re-annealing of a heatdenatured target DNA prior to analysis. During analysis, formamide was integrated in the running buffer to denature ET SSB. E. coli DNA corresponding to 10 cells per millilitre of sample was detected in 15 min by this DNA-sensor. The sensor chip could be re-used up to 20 times with RSD of < 6%. The DNA-sensor chip was able to discriminate between Enterobacteriaceae (E. coli) and Lactobacillaceae (L. reuteri) DNAs. The reported DNA-sensor lays the groundwork for incorporating the method into an integrated system for in-field bacteria detection.