A glucose biosensor based on electrocatalytic oxidation of NADPH at single-walled carbon nanotubes functionalized with poly(nile blue A)

A glucose biosensor based on the electrocatalytic oxidation of reduced nicotinamide adenine dinucleotide phosphate (NADPH) generated by the enzymatic reaction was developed via employing single-walled carbon nanotubes/poly(nile blue A) (PNb-SWNTs) nanocomposite as a mediator and an enzyme immobilization matrix. The cyclic voltammetric results indicated that PNb-SWNTs were able to electrocatalyze the oxidation of NADPH at a very low potential (ca. -30 mV vs. SCE) and led to a substantial decrease in the overpotential by about 750 mV compared with the bare glassy carbon (GC) electrode. The biosensor, which was fabricated by immobilizing glucose dehydrogenase (GDH) on the surface of PNb-SWNTs, exhibited a rapid response (ca. 3 s), a low detection limit (5 mu M), a wide and useful linear range (0.1-8.5 mM), as well as good stability and reproducibility. In addition, the common interfering species, such as ascorbic acid and uric acid, did not cause any interference due to the use of a low operating potential (+50 mV vs. SCE). The biosensor can also be used to quantify the concentration of glucose in real sample. The PNb-SWNTs system represents a simple and functional approach to the integration of dehydrogenase and electrodes, which can provide analytical access to a large group of enzymes for wide range of bioelectrochemical applications including biosensors and biofuel cells. (C) 2008 Elsevier B.V. All rights reserved.