Uric acid enzyme biosensor based on a screen-printed electrode coated with Prussian blue and modified with chitosan-graphene composite cryogel

An amperometric uric acid (UA) biosensor was developed by immobilizing uricase on porous cryogel (cry) platform of graphene-incorporated chitosan (Chi) on top of a Prussian blue layer (PB) electrodeposited on a screen-printed carbon electrode (Uricase/Chi-Gr cry/PB/SPCE). Amperometric detection of UA catalyzed by uricase was based on the change in cathodic current of PB at a potential of 0.00 V in a flow injection system. The UA biosensor showed a linear range between 0.0025 and 0.40 mmol L-1 with a detection limit of 2.5 mu mol L-1 (S/N = 3). In addition, the Uricase/Chi-Gr cry/PB/SPCE provided an excellent stability that enabled reuse up to 175 times (RSD of 3.7%) and a good electrode-to-electrode repeatability (RSDs of 0.53-2.7%, n = 6). A Michaelis-Menten constant (K-M(app)) of 0.23 mmol L-1 indicated the excellent affinity of the immobilized uricase toward UA. The modified electrode showed no effect from the common interferences in human serum samples. When applied to measure UA in human serum samples, the developed UA biosensor achieved recoveries ranging from 98 +/- 2 to 102 +/- 5% and the results obtained were in good agreement with enzymatic colorimetric analysis (P > 0.05).