Glucose sensing by a glassy carbon electrode modified with glucose oxidase/chitosan/graphene oxide nanofibers

In this paper, a glassy carbon electrode (GCE) was modified with glucose oxidase (GOx)/chitosan (CS)/graphene oxide (GO) nanofibers for the detection of glucose via the electrospinning method. To do this, GOx was trapped among the two CS/GO nanofibers layers. Respect to electrochemical properties and producing conditions, the optimum amounts for GOx and GO in the deposited layer were 20 mg/mL and 20% w/w, respectively. An investigation on the effects of pH, time of oxygen dissolving in the test solution and scan rate on electrochemical behaviour revealed that the peak current increased with increasing the oxygen dissolving time up to 20 min and scan rate values. However, the redox processes showed more symmetric anodic and cathodic structure at slow scan rates. Also, the highest current was obtained at a pH of 7.4. The result showed that the electrochemical process of GOx occurs through a two-proton and two-electron transformation. Additionally, the sensor exhibited excellent reproducibility and stability properties. It was concluded that the use of nanofibrous structure and the immobilization of the glucose oxidase among the two CS/GO nanofibers layers enhanced significantly the electrochemical properties due to penetration of water-soluble glucose molecules in the porous nanofiber layers, which helped efficiently catalyze the oxidation of glucose and facile direct electron transfer for GOx. The resultant modified electrodes exhibited a high sensitivity of 1006.86 μA mM−1 cm−2 and low detection limit of 0.02 mM with a wide linear range of 0.05–20 mM. The sensing assay did not show interference when glucose co-exists with ascorbic acid, acetaminophen, uric acid and metal ions (Fe3+, Cd2+ and Cu2+).