Amperometric glucose biosensor based on self-assembling glucose oxidase on carbon nanotubes

A flow injection amperometric glucose biosensor based on electrostatic self-assembling glucose oxidase (GOx) on a carbon nanotube (CNT) – modified glassy carbon transducer is described. GOx is immobilized on the negatively charged CNT surface by alternatively assembling a cationic polydiallyldimethylammonium chloride (PDDA) layer and a GOx layer. The unique sandwich-like layer structure (PDDA/GOx/PDDA/CNT) formed by self-assembling provides a favorable microenvironment to keep the bioactivity of GOx and to prevent enzyme molecule leakage. The excellent electrocatalytic activity toward H2O2 of the fabricated PDDA/GOx/PDDA/CNT electrode indicated that the polyelectrolyte-protein multilayer does not affect the electrocatalytic properties of CNT, enabling sensitive determination of glucose. Flow injection amperometric detection of glucose is carried out at −100 mV (vs. Ag/AgCl) in 0.05 M phosphate buffer solution (pH 7.4) with a wide linear response range of 15 μM to 6 mM and a detection limit of 7 μM. The PDDA/GOx/PDDA/CNT/GC biosensor showed excellent properties for the sensitive determination of glucose with good reproducibility, remarkable stability, and freedom of interference from other co-existing electroactive species.