A novel electrochemical biosensor was reported for the detection of nucleic acid hybridization and sequence-specific DNAs. A synthesized single stranded DNA (ssDNA-1) was covalently immobilized on gold electrodes, which had been modified by carboxylic group-functionalized carbon nanotubes activated using N-ethyl-N'-(3-dimethylaminopropyl)carbodiimide(EDC) and N-hydroxysuccinimidobiotin (NHS). Differential pulse voltammetry was used to detect DNA with an electroactive indicator of adriamycin which could bind to double stranded DNA. The linear range for the determination of target DNA is from 1.0×10^－6 to 1.0×10^－9 mol/L, and the detection limit is found to be 2.54×10^－10 mol/L.

Key words: carboxylic carbon nanotube, DNA hybridization, adriamycin, differential pules voltammetry