A highly sensitive biosensor with (Con A/HRP)n multilayer films based on layer-by-layer technique for the detection...

The bilayer of Con A/HRP through the biospecific affinity of concanavalin A (Con A) and glycoprotein horseradish peroxidase (HRP) was prepared on the surface of an Au electrode modified by the precursor film consisted of poly(allylamine hydrochloride) poly(sodium-p-styrene-sulfonate). Atomic force microscopy and electrochemical impedance spectroscopy were adopted to monitor the uniform layer-by-layer assembly of the Con A/HRP bilayers. The amperometric measurement was based on the inhibition of reduced thiols and performed in the presence of the electron mediator hydroquinone in 0.2M phosphate buffer of pH 6.5 at an applied potential of -0.15 V versus Ag/AgCl. Under the optimal conditions, the biosensor presented a linear response for cysteine from 0.1 to 23.5 microM, with a detection limit of 0.02 microM. The biosensor demonstrated high stability and repeatability. A series of reduced thiols were detected by this inhibition biosensor and oxidized thiols showed no effect on the current response of the biosensor.