Microfabricated conductometric urea biosensor based on sol-gel immobilized urease

A conductometric biosensor was constructed with a sol-gel immobilized urease on a microfabricated interdigitated array (IDA) gold electrode. Tetramethoxysilane (TMOS) was used as a sol-gel precursor for the immobilization of the urease and the performance of the resulting urea biosensor was controlled through the water content in the acid-catalyzed hydrolysis of the sol-gel stock solution. The sol-gel-derived urea biosensor showed relatively wide dynamic range of 0.2-50 mM in 5 mM imidazole-HC1 buffer at pH 7.5. Furthermore, the urea biosensor exhibited good sensor-to-sensor reproducibility (6.5 %) and storage stability (50 % of its original activity retained after 3 weeks) when stored in 5 mM imidazole-HC1 buffer at 4 °C. The urea biosensor was successfully applied for the urea determination in urine sample by employing the differential measurement format consisting of an active IDA conductometric sensor containing sol-gel-immobilized urease and a reference IDA conductometric sensor containing bovine serum albumin layer instead of the urease.