title: Immobilization of a trienzymatic system in a sol-gel matrix: a new fluorescent biosensor for xanthine.
abstract: In this work we report the development of a highly sensitive fluorescent multienzymatic biosensor for quantitative xanthine detection. This biosensor is built by the simultaneous encapsulation of three enzymes, xanthine oxidase, superoxide dismutase and peroxidase, in a single sol-gel matrix coupled to the Amplex Red probe. The sol-gel chemistry yields a porous, optically transparent matrix that retains the natural conformation and the reactivity of the three co-immobilized proteins. Xanthine determination is based on a sequence of reactions, namely catalytic oxidation of xanthine to uric acid and superoxide radical, and subsequent catalytic dismutation of the radical, resulting in the formation of hydrogen peroxide, which reacts stoichiometrically with non-fluorescent Amplex Red to produce highly fluorescent resorufin. The optimal operational conditions for the biosensor were investigated. Linearity was observed for xanthine concentrations up to 3.5 microM, with a detection limit of 20 nM, which largely improved the sensitivity of the current xanthine biosensors. The developed biosensor is reusable and remains stable for 2 weeks under adequate storage conditions.
authors.affiliation: Instituto de Biología Molecular y Celular, Universidad Miguel Hernández, Elche E-03202, Alicante, Spain.
authors.forename: A
authors.initials: A
authors.lastname: Salinas-Castillo
authors.forename: Isabel
authors.initials: I
authors.lastname: Pastor
authors.forename: Ricardo
authors.initials: R
authors.lastname: Mallavia
authors.forename: C Reyes
authors.initials: CR
authors.lastname: Mateo
mesh_terms: D015374:Biosensing Techniques / Q000295:instrumentation* / Q000379:methods; D004800:Enzymes, Immobilized / Q000737:chemistry; D004867:Equipment Design; D019544:Equipment Failure Analysis; D009097:Multienzyme Complexes / Q000737:chemistry; D009195:Peroxidase / Q000737:chemistry*; D044367:Phase Transition; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D013050:Spectrometry, Fluorescence / Q000379:methods*; D013482:Superoxide Dismutase; D019820:Xanthine / Q000032:analysis*; D014969:Xanthine Oxidase / Q000737:chemistry*
chemical_list: D004800:Enzymes, Immobilized; D009097:Multienzyme Complexes; D019820:Xanthine; D009195:Peroxidase; D013482:Superoxide Dismutase; D014969:Xanthine Oxidase