Au-colloids–polypyrrole nanocomposite film based xanthine biosensor

Stable colloids of Au/polypyrrole (AuPPy) nanocomposites were prepared by oxidizing pyrrole monomer with HAuCl4 in a cetyltrimethylammonium bromide (CTAB) solution and cast on the platinum (Pt) electrode. Xanthine oxidase (XOD) was immobilized onto this nanocomposite film through glutaraldehyde. The AuPPy/Pt electrode was characterized by Fourier transform infrared (FTIR), cyclic voltammetry (CV), X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and electrochemical impedance spectroscopy (EIS) before and after immobilization of XOD. The XOD/AuPPy/Pt as working electrode, Ag/AgCl as reference electrode and Pt wire as auxiliary electrode were connected through a potentiostat to construct a xanthine biosensor. The biosensor exhibited optimum response within 4 s at pH 7.2 and 30 °C and linearity from 0.4 to 100 μM for xanthine with a detection limit 0.4 μM (S/N = 3). The fabricated biosensor was successfully employed for determination of xanthine in fish, chicken, pork, and beef meat. The biosensor showed only 40% loss of its initial activity after its 200 uses over 100 days, when stored at 4 °C.