Fabrication of dual-path electron transfer electrode for electrochemical glucose sensing

A novel type of glucose biosensor was designed based on dual-path electron transfer mechanism. Ferrocenecarboxylic acid (FcCA), the indirect mediator, transfers the electrons of enzymatic reaction from embedded redox active center via redox process. Reduced graphene oxide (rGO) and silver nanoparticles (AgNPs) both are conductive materials, providing fast direct electron transfer path. In this system, ß-cyclodextrin (ß-CD) is of key importance for not only reducing rGO and AgNPs, but providing biocompatible microenvironment for the enzyme as well. At the same time, carboxymethyl-ß-cyclodextrin (CM-ß-CD) formed inclusion complex with FcCA and then covalently bound with the enzyme to immobilize FcCA and GOD. The structure and morphology of modified film were characterized by FTIR, TEM, AFM, XRD, Raman and UV-vis. The rate constant (ks) of modified electrode is calculated to be 4.648 s-1, indicating the fast electron transfer rate on electrode. The glucose biosensor exhibited a wide linear response range from 0.105 to 11.805 mM with a low detection limit of 0.035 mM.