Carbon nanotube-enhanced electrochemical DNA biosensor for DNA hybridization detection

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Abstract
A novel and sensitive electrochemical DNA biosensor based on multi-walled carbon nanotubes functionalized with a carboxylic acid group (MWNTs–COOH) for covalent DNA immobilization and enhanced hybridization detection is described. The MWNTs–COOH-modified glassy carbon electrode (GCE) was fabricated and oligonucleotides with the 5'-amino group were covalently bonded to the carboxyl group of carbon nanotubes. The hybridization reaction on the electrode was monitored by differential pulse voltammetry (DPV) analysis using an electroactive intercalator daunomycin as an indicator. Compared with previous DNA sensors with oligonucleotides directly incorporated on carbon electrodes, this carbon nanotube-based assay with its large surface area and good charge-transport characteristics dramatically increased DNA attachment quantity and complementary DNA detection sensitivity. This is the first application of carbon nanotubes to the fabrication of an electrochemical DNA biosensor with a favorable performance for the rapid detection of specific hybridization.