Sensitive and selective xanthine amperometric sensors based on calcium carbonate nanoparticles

Using calcium carbonate nanoparticles as enzyme immobilization matrix, the developments of xanthine biosensor were achieved by both electrooxidation and electroreduction of the enzymatic-generated hydrogen peroxide based on xanthine oxidase (XnOx) and horseradish peroxidase (HRP). Amperometric detection of xanthine was evaluated by holding the modified electrode at 0.55 and −0.05 V (versus SCE), for XnOx/Nano-CaCO3 and XnOx/HRP/Nano-CaCO3, respectively. The linear dynamic ranges of anodic and cathodic detections of xanthine were between 2 × 10−6 to 2.5 × 10−4 M and 4 × 10−7 to 5 × 10−5 M, respectively. The detection limits were determined to be of 2 × 10−6 and 1 × 10−7 M with anodic and cathodic processes, respectively. At lower working potential, XnOx/HRP/Nano-CaCO3/GCE bienzymatic system exhibited excellent selectivity; the bienzyme electrode was inert towards ascorbic and uric acid present. Moreover, the permeability of enzyme/Nano-CaCO3 was evaluated by the use of rotating disk electrode voltammetry.