Fast enzyme-linked electrochemical sensing of DNA hybridization at pencil graphite electrodes. Application to detect gene deletion in a human cell culture

Abstrakt

In this paper we present a rapid electrochemical enzyme-linked DNA hybridization assay using disposable pencil graphite electrodes (PeGE) to detect target DNA (tDNA) sequences in DNA fragments amplified by polymerase chain reaction. The procedure consists of several short (1–2 min) incubation steps, including adsorption of the tDNA at unpretreated PeGE from denaturing medium, surface blocking with milk proteins, hybridization with a biotinylated oligonucleotide probe and binding of streptavidin-alkaline phosphatase conjugate to the biotin tags. Then the PeGE is transferred into background electrolyte solution containing 1-naphthyl phosphate, which is enzymatically dephosphorylated to give electrochemically oxidizable indicator 1-naphthol. The assay, which can be performed within 7–8 min, offers a perfect discrimination between specific and nonspecific DNA amplicons and easy detection of about ~40 femtomoles of tDNA in large excesses of non-complementary DNA. An application on the detection of p53 gene deletion in a human cell culture, featuring a real biological model, is presented. The designed setup has a potential to be applied as one of simple, fast, robust ultralow cost “do-it-yourself “instruments recently introduced as diagnostic tools for third world countries.