DNA Biosensor: Immunosensor Applications for Anti-DNA Antibody

Two examples of DNA biosensor that respond selectively to anti-DNA antibody are reported. These biosensors comprise a double-stranded DNA as a receptive component and a redox-active, indicator molecule for electrochemical detection. First, a chemical modification with 2-hydroxyethyl disulfide was made on the terminal phosphates of calf thymus DNA and the DNA was immobilized onto Au surface via chemisorption. By taking advantage of the principle of an "ion-channel sensor", the DNA-modified electrode was successfully applied for the detection of anti-DNA antibody (mouse, monoclonal IgM); cyclic voltammetric measurements for [FE(CN)6]4-/3- with the DNA-modified electrode gave reversible current responses in the range of 1 — 100 nM of the IgM while neither mouse IgM nor mouse IgG did not give such responses. Next, the chemoreceptive surface adlayer was improved to a DNA/ferrocene bilayer format to give an analyte-dependent electrochemical signal. The sensor also responded to the anti-DNA antibody in the range of 1 — 10 nM without the use of additional indicator molecules. These DNA biosensors would be useful for monitoring DNA—protein interactions if the immobilized DNA has a specific sequence to the target protein.