Highly sensitive and stable laccase based amperometric biosensor developed on nano-composite matrix for detecting pyrocatechol in environmental samples

The present study aims at fabricating a laccase based amperometric biosensor for detection of pyrocatechol in environmental samples. Trametes versicolor laccase was co-immobilized in a nanocomposite matrix comprising of osmium tetroxide on poly 4-vinylpyridine, multiwalled carbon nanotubes, Nafion and carbon black on glassy carbon electrode. The nanocomposite matrix provides a porous structure for easy immobilization of the enzyme as evident from the SEM images and a highly electroactive surface for facile diffusion free electron transfer kinetics as discerned from the cyclic voltametric studies. The heterogeneous electron transfer rate constant (K-s) and surface concentration of the ionic species (F) of the bioelectrode were 0.67 s(-1) and 1.32 x 10(-8) mol cm(-2), respectively. The response of the constructed biosensor was generated at a potential of 0.14 V from the electrocatalyzed reduction of 1,2-benzoquinone formed from the biocatalyzed oxidation of pyrocatechol. The bioelectrode when subjected to differential pulse voltammetry exhibited a linear faradaic current response against pyrocatechol in the concentration range of 3.98 nM-16.71 nM with a minimum detection limit of 2.82 nM and a sensitivity of 3.82 +/- 0.31 nAnM(-1). The bioelectrode also shows high operational stability and optimum storage stability up to 3 weeks. The nanocomposite based fabrication method of the laccase bioelectrode thus shows a great promise for developing a highly sensitive, selective and stable biosensor for detection of pyrocatechol in environmental samples. (C) 2013 Elsevier B.V. All rights reserved.