A sensitive and stable biosensor based on the direct electrochemistry of glucose oxidase assembled layer-by-layer at the multiwall carbon nanotube-modified electrode

A novel strategy for fabricating the sensitive and stable biosensor was present by layer-by-layer (LBL) self-assembling glucose oxidase (GOD) on multiwall carbon nanotube (CNT)-modified glassy carbon (GC) electrode. GOD was immobilized on the negatively charged CNT surface by alternatively assembling a cationic poly(ethylenimine) (PEI) layer and a GOD layer. And the direct electrochemistry of GOD in the self-assembled {GOD/PEI}n film was investigated. CNT as an excellent nanomaterial greatly improved the direct electron transfer between GOD in {GOD/PEI}n film and the electrode. And the ultrathin {GOD/PEI}n film on the CNT surface provided a favorable microenvironment to keep the bioactivity of GOD. Moreover, PEI used as an out-layer was adsorbed on the top of the {GOD/PEI}n film to form the sandwich-like structure (PEI/{GOD/PEI}n), improving the stability of the enzyme electrode. On basis of these, the developed PEI/{GOD/PEI}n/CNT/GC biosensor has a high sensitivity of 106.57 μA mM−1 cm−2, and can measure as low as 0.05 mM glucose. In addition, the biosensor has excellent operational stability with no decrease in the activity of enzyme over a 1-week period. Therefore, the developed strategy making use of the advantages of CNT and LBL assembly is ideal for the direct electrochemistry of the redox enzymes and the construction of the sensitive and stable enzyme biosensor.