Construction of an amperometric D-amino acid biosensor based on D-amino acid oxidase/carboxylated mutliwalled carbon nanotube/copper nanoparticles/polyalinine modified gold electrode.

An improved D-amino acid biosensor was constructed based on covalent immobilization of D-amino acid oxidase onto carboxylated mutliwalled carbon nanotube/copper nanoparticles/polyalinine hybrid film electrodeposited on gold electrode. The biosensor exhibited an optimal response within 2s at pH 8.0 and 30°C when polarized at 0.09 V. There was a linear relationship between biosensor response (μA) and D-alanine concentration ranging from 0.001 to 0.7 mM. The sensitivity of the biosensor was 54.85 μA cm(-2) mM(-1) with a lower limit of detection of 0.2 μM (signal/noise=3). The enzyme electrode was used 150 times over a period of 4 months. The biosensor measured the d-amino acid level in fruit juices.