Qingjun Meng

A Nicotinamide Adenine Dinucleotide Dispersed Multi-walled Carbon Nanotubes Electrode for Direct and Selective Electrochemical Detection of Uric Acid

A nanocomposite platform built with multi-walled carbon nanotubes (MWCNTs) and nicotinamide adenine dinucleotide (NAD(+)) via a noncovalent interaction between the large π systems in NAD(+) molecules and MWCNTs on a glassy carbon substrate was successfully developed for the sensitive and selective detection of uric acid (UA) in the presence of ascorbic acid (AA), dopamine (DA). NAD(+) has an adenine subunit and a nicotinamide subunit, which enabled interaction with the purine subunit of UA through a strong π-π interaction to enhance the specificity of UA. Compared with a bare glassy carbon electrode (GCE) and MWCNTs/GCE, the MWCNTs-NAD(+)/GCE showed a low background current and a remarkable enhancement of the oxidation peak current of UA. Using differential pulse voltammetry (DPV), a high sensitivity for the determination of UA was explored for the MWCNTs-NAD(+) modified electrode. A linear relationship between the DPV peak current of UA and its concentration could be obtained in the range of 0.05 - 10 μM with the detection limit as low as 10 nM (S/N = 3). This present strategy provides a novel and promising platform for the detection of UA in human urine and serum samples.

Determination of Reduced Nicotinamide Adenine Dinucleotide with a Protamine Multiwalled Carbon Nanotube Electrode

ABSTRACT A bionanocomposite prepared from multiwalled carbon nanotubes and protamine sulfate is reported for the electrocatalytic determination of dihydronicotinamide adenine dinucleotide. Protamine sulfate was adsorbed via π-π interactions and hydrogen bonds between protonated amines on arginine and surface groups on the multiwalled carbon nanotubes. The multiwalled carbon nanotube protamine composite accumulated dihydronicotinamide adenine dinucleotide on the electrode surface, resulting in high sensitivity and a low limit of detection for dihydronicotinamide adenine dinucleotide. The nanocomposite was employed for dehydrogenase-based biosensing. Alcohol dehydrogenase was allowed to adsorb on the bionanocomposite surface and the sensitivity of the resulting electrode to ethanol was measured. The alcohol biosensor had an excellent sensitivity of 738.5 µA/mM with a low limit of detection of 50 nM.