SCREEN-PRINTED ELECTROCHEMICAL HYBRIDIZATION BIOSENSOR FOR THE DETECTION OF DNA-SEQUENCES FROM THE ESCHERICHIA-COLI PATHOGEN

An electrochemical biosensor for the specific detection of short DNA s equences from the E. coli pathogen is described. This hybridization de vice relies on the immobilization of a 25-mer oligonucleotide probe, f rom the E. coli lacZ gene, onto a screen-printed carbon electrode. Chr onopotentiometric detection of the Co(bpy)(3)(+3) indicator is used fo r monitoring the hybridization event. Numerous variables of the assay protocol, including those of the probe immobilization step, the hybrid ization event, and the indicator association/detection, are characteri zed and optimized. Hybridization times of 2- and 30-min are sufficient for detecting 300- and 50 ng/mL, respectively, of the E. coli DNA tar get. Applicability to analysis of untreated environmental water sample s is illustrated. Such single-use electrochemical sensors hold great p romise for decentralized environmental and food testing for the E. col i pathogen.