Immobilization of uricase on ZnO nanorods for a reagentless uric acid biosensor

A reagentless uric acid (UA) biosensor based on uricase immobilized on ZnO nanorods was developed. Direct electrochemistry and thermal stability of immobilized uricase were studied. The ZnO nanorods derived electrode retained the enzyme bioactivity and could enhance the electron transfer between the enzyme and the electrode. This sensor showed a high thermal stability up to 85°C and an electrocatalytic activity to the oxidation of uric acid without the presence of an electron mediator. The electrocatalytic response showed a linear dependence on the uric acid concentration ranging from 5.0 × 10^-6 to 1.0 × 10^-3 mol L^-1 with a detection limit of 2.0 × 10^-6 mol L^-1 at 3σ. The apparent K_M^app value for the uric acid sensor was estimated to be 0.238 mM, showing a high affinity.