Differential type solid-state urea biosensors based on ion-selective electrodes

This work presents a differential solid-state urea biosensor based on an ion-selective membrane. The solid-state urea biosensor comprises three parts—a tin oxide (SnO2) pH electrode, a nonactin-based ammonium ion-selective electrode (ISE) and an ammonium ion-selective membrane-based urea electrode. The enzyme was immobilized by the entrapment method onto an ion-selective membrane. For simplicity of fabrication, a SnO2/indium tin oxide (ITO) glass device was adopted as a basic substrate. Solid-state urea biosensors based on ammonium ion-selective membrane respond rapidly, stably and linearly in the range of urea concentrations between 0.013 mM and 10 mM. Additionally, the voltage response, selectivity, reproducibility and stability are considered. Experimental results indicate that the effect of the interference ions of a solid-state urea biosensor can be improved using the proposed differential urea sensing structure. Additionally, the biosensors exhibit good operational and storage stability.