Carbon nanotube-enhanced DNA biosensor for DNA hybridization detection using rutin-Mn as electrochemical indicator

The manganese complex of rutin(R) C54H58MnO32 (abbreviated by MnR2) was synthesized and characterized by elemental analysis and IR spectroscopy. Cyclic voltammetry (CV) and fluorescence spectroscopy were used to investigate the interaction of MnR2 with salmon sperm DNA. It was revealed that MnR2 presented an excellent electrochemical activity on glassy carbon electrode (GCE) and could intercalate into the double helix of double-stranded DNA (dsDNA). A novel and sensitive electrochemical DNA biosensor based on multi-walled carbon nanotubes functionalized with a carboxylic acid group (MWCNTs–COOH) for covalent DNA immobilization and enhanced hybridization detection was described. The MWCNTs–COOH modified glassy carbon electrode was fabricated and oligonucleotides with the 5′-amino group were covalently bonded to the carboxyl group of carbon nanotubes. Compared with DNA sensors with oligonucleotides directly incorporated on glassy carbon electrodes, this carbon nanotube-based assay with its large surface area and good charge-transport characteristics dramatically increased DNA attachment quantity and complementary ssDNA detection sensitivity. The target ssDNA could be quantified ranged from 1.60 × 10−9 M to 4.80 × 10−8 M with good linearity (r = 0.9898) and a detection limit of 3.81 × 10−11 M (3σ, n = 7) was achieved by the constructed electrochemical DNA biosensor.