A sensitive electrochemical detection of xanthine (X), which is an early biomarker of fish meat spoilage, was achieved by a novel biosensor developed via three main steps. The first step is the electropolymerization of a conducting polymer (pyrrole) onto the pencil graphite electrode (PGE). The second step is the entrapment of silver-doped zinc oxide nanoparticles (nano Ag-ZnO) onto PGE, which has already been doped with polypyrrole (PPy). The third step is the immobilization of the enzyme (xanthine oxidase) onto the modified electrode (nano Ag-ZnO/PPy/PGE) surface. The biosensor was characterized by scanning electron microscopy (SEM). The addition of Ag-doped ZnO nanopartides into the conducting polymer structure played an important role in the performance of the biosensor by increasing the porous structure of the conducting polymer surface. The electrochemical behaviour of the biosensor was studied by electrochemical impedance spectroscopy (EIS) and chronoamperometry (CA). This enzyme biosensor showed the maximum response at pH 7.40 when +0.7 V was applied to reach 95% of steady-state current at similar to 3.2 s. The designed biosensor showed high selectivity with a sensitivity of 0.031 mu A/mM and a low detection limit of 0.07 mu M. (C) 2019 Elsevier B.V. All rights reserved.