DNA based biosensor for the detection of Escherichia coli in water samples

The principal goal of this research was to demonstrate the efficiency and capability of a model biosensor using Escherichia Coli DNA synthetic oligonucleotides for fast and accurate detection E. coli DNA. Molecular biology and cyclic voltammetry (CV) were combined to develop and test a model DNA-based biosensor. The hybridization capability of embedded DNA into polypyrrole (PPY) with complementary DNA samples was determined.; The biosensor platform evaluated was a Platinum (Pt) electrode elctropolymerized with PPY. The recognition elements were oligonucleotides specific for beta-D glucuronidase. The biosensor was capable to generate distinctive CV signals for complementary and non-complementary DNA sequences. Cyclic voltammetry scanning between 0.0 and +0.70 V and 50 mV/s scanning rate were used to generate current vs. potential graphs. A range of DNA concentration of 10-6 g to 10-9 g was used to determine the hybridization signal recognition of the biosensor. Distinctive hybridization signals were obtained after 30 minutes hybridization time. The biosensor platform proved to be effective in the detection of complementary uidA 25 bp oligonucleotide and genomic DNA from E. coli K-12. The biosensor was successful in discriminating for cross hybridization using Salmonella typhimurium and Campylobacter jejuni. Genomic DNA isolated from natural waters demonstrated the capability of the biosensor to detect E. coli from environmental isolates. The total detection time took 40 minutes after sample preparation.