An amperometric glucose biosensor based on electrostatic force induced layer-by-layer GOD/chitosan/pyrite on a glassy carbon electrode.

Pyrite (PR), as a representative sulfide mineral, possesses the advantages of abundancy, thermodynamic stability, non-toxicity and semi-conductivity. In this study, an amperometric glucose biosensor (GOD/CS/PR/GCE) based on layer-by-layer of glucose oxidase (GOD), chitosan (CS) and pyrite (PR) on a glassy carbon electrode (GCE) was fabricated through electrostatic force. In this research, PR suspension prepared in phosphate buffer (pH 5.5) was first immobilized on the GCE surface, which exhibits a negative charge. Then, positively charged CS was adsorbed on the PR/GCE by electrostatic force. Finally, negatively charged GOD was further modified on the CS/PR/GCE surface through electrostatic force again. The surface morphology and adsorbance mechanism were supported by field emission scanning electron microscopy, quartz crystal microbalance with dissipation and atomic force microscope. The step-by-step procedure gives both strong adhesion ability and good bioelectrocatalytic activity of GOD on the CS- and PR-modified electrode surface. The linear range of this GOD/CS/PR/GCE biosensor was achieved from 0.5 to 60 mM with the linear regression equation of y = 0.897x - 0.3016 (R2 = 0.9996) and a limit of detection value of 50 µM. This approach of using pyrite and chitosan as physically modified GOD to serve as electrostatic glues could be useful for designing better enzyme-based biosensors for a wide variety of practical applications.