Preparation of chitosan–dopamine-multiwalled carbon nanotubes nanocomposite for electrocatalytic oxidation and sensitive electroanalysis of NADH

A novel nanocomposite of glutaraldehyde crosslinked chitosan (CS)–dopamine (DA) composite with multiwalled carbon nanotubes (MWCNTs) was synthesized for low-potential and sensitive amperometric sensing of reduced nicotinamide adenine dinucleotide (NADH). The composite was characterized by FT-IR spectrophotometry. The nanocomposite modified Au electrode showed well-defined quinone/phenol redox peaks of the dopamine moieties and was able to effectively mediate the oxidation of NADH in pH 7.0 phosphate buffer, with an overpotential decrease by ca. 450 mV (vs. bare Au). The NADH electrochemical sensor showed a linear range of 0.1–600 μM, a limit of detection of 12 nmol L−1, good antiinterferent ability, and long-term stability. It was also found that the use of acidified MWCNTs showed better performance than that of the nonacidified MWCNTs. Both CS and DA being biomaterials, the CS–DA/MWCNTs system should be of interest and potential for developing in vivo NAD+ (the oxidized form of NADH)-dependent dehydrogenase enzymes based biosensors.