Carbon nanotube-enhanced DNA biosensor for DNA hybridization detection using manganese(II)-Schiff base complex as hybridization indicator.

A Mn(II) complex, MnL (L=sodium (E)-3-((1-carboxyethylimino)methyl)-4-hydroxybenzenesulfonate), was synthesized and characterized using elemental analysis and IR spectroscopy. Cyclic voltammetry (CV) and fluorescence spectroscopy were used to investigate the interaction between MnL and salmon sperm DNA. It was revealed that MnL presented high electrochemical activity on glassy carbon electrode (GCE), and it could be intercalated into the double helices of double-stranded DNA (dsDNA). Using MnL as the hybridization indicator, a novel and sensitive electrochemical DNA biosensor based on multiwall carbon nanotubes functionalized with carboxyl groups (MWCNTs-COOH, on which DNA probes were covalently immobilized) was prepared. The target single-stranded DNA (ssDNA) could be quantified ranging from 6.7 x 10(-10)M to 8.4 x 10(-9)M with good linearity (r=0.9922). A detection limit of 1.4 x 10(-10)M (3 sigma, n=9) was achieved.