Genomagnetic electrochemical assays of DNA hybridization.

An electrochemical genomagnetic hybridization assay has been developed to take advantage of a new and efficient magnetic separation/mixing process, the amplification feature of enzyme labels, and single-use thick-film carbon transducers operated in the pulse-voltammetric mode. It represents the first example of coupling a magnetic isolation with electrochemical detection of DNA hybridization. The new protocol employs an enzyme-linked sandwich solution hybridization, with a magnetic-particle labeled probe hybridizing to a biotinylated DNA target that captures a streptavidin-alkaline phosphatase (AP). The alpha-naphthol product of the enzymatic reaction is quantitated through its well-defined, low-potential (+0.1 V vs. Ag/AgCl) differential pulse-voltammetric peak at the disposable screen-printed electrode. The efficient magnetic isolation is particularly attractive for electrical detection of DNA hybridization which is commonly affected by the presence of non-hybridized nucleic acid adsorbates. The new biomagnetic processing combines such magnetic separation with a low-volume magnetic mixing, and allows simultaneous handling of 12 samples. The attractive bioanalytical behavior of the new enzyme-linked genomagnetic electrical assay is illustrated for the detection of DNA segments related to the breast-cancer BRCA1 gene.