Development of a high analytical performance-xanthine biosensor based on layered double hydroxides modified-electrode and investigation of the inhibitory effect by allopurinol.

The determination of xanthine has considerable importance in clinical and food quality control. Therefore, in this present work, we developed a novel xanthine biosensor based on immobilization of xanthine oxidase (XnOx) by attractive materials layered double hydroxides (LDHs). Amperometric detection of xanthine was evaluated by holding the modified electrode at 0.55V (versus saturated calomel electrode (SCE)). Due to the special properties of LDHs, such as chemical inertia, mechanical and thermal stability, anionic exchange ability, high porosity and swelling properties, XnOx/LDHs-modified electrode exhibited a developed analytical performance. The biosensor provided a linear response to xanthine over a concentration range of 1 x 10(-6)M to 2 x 10(-4)M with a sensitivity of 220 mAM(-1)cm(-2) and a detection limit of 1x10(-7)M based on S/N=3. In addition, the immobilized XnOx layers have been characterized using atomic force microscopy under both air atmosphere and liquid environment, which exhibited the interesting swelling phenomenon of LDHs. The investigation of inhibition of XnOx by allopurinol was carried out using this XnOx/LDHs-modified electrode. The experimental results indicated that inhibitory effect could be achieved by allopurinol with a quasi-reversible competitive type.