An amperometric urea biosensor based on covalently immobilized urease on an electrode made of hyperbranched polyester functionalized gold nanoparticles

Abstract: An amperometric biosensor was fabricated for the quantitative determination of urea in aqueous medium using hematein, a pH-sensitive natural dye. The urease (Urs) was covalently immobilized onto an electrode made of gold nanoparticles functionalized with hyperbranched polyester-Boltron® H40 (H40–Au) coated onto an indium–tin oxide (ITO) covered glass substrate. The covalent linkage between the Urs enzyme and H40–Au nanoparticles provided the resulting enzyme electrode (Urs/H40–Au/ITO) with a high level of enzyme immobilization and excellent lifetime stability. The response studies were carried out as a function of urea concentration with amperometric and photometric measurements. The biosensor based on Urs/H40–Au/ITO as the working electrode showed a linear current response to the urea concentration ranging from 0.01 to 35mM. The urea biosensor exhibited a sensitivity of 7.48nA/mM with a response time of 3s. The Michaelis–Menten constant for the Urs/H40–Au/ITO biosensor was calculated to be 0.96mM, indicating the Urs enzyme immobilized on the electrode surface had a high affinity to urea. [Copyright &y& Elsevier]