Selective analysis of reduced thiols with a novel bionanomultilayer biosensor based on the inhibition principle

The water-soluble poly(allylamine hydrochloride)-wrapped multiwall carbon nanotubes (MWNT-PAH) can be obtained for the first time relying on the function of barbital, which provides a useful avenue for carbon nanotube application in material science and biosensor technology. The MWNT-PAH/horseradish peroxidase (HRP) bionanomultilayer was prepared via layer-by-layer (LBL) assembly. Atomic force microscopy, scanning electron microscopy and UV–vis spectra were adopted to monitor the uniform LBL assembly of the homogeneous bionanomultilayer. The bionanomultilayer was developed and constructed as a biosensor for the determination of reduced thiols based on the inhibition principle. Under the optimal conditions, the biosensor presented a linear response for glutathione (GSH) and cysteine (CSH) from 0.5 to 41.0 μM (R = 0.9983, n = 12) and 0.4 to 28.8 μM (R = 0.9991, n = 9), respectively. The limits of detection (S/N = 3) for GSH and CSH were 0.09 and 0.06 μM, respectively. A series of reduced thiols such as GSH, CSH, cysteamine, mercaptans and 3-mercapto-1-propanesulfonic acid (MPS) were selectively detected by the bionanomultilayer biosensor, while oxidized thiols showed no effect on the current response of the biosensor.