A phenol biosensor based on immobilizing tyrosinase to modified core-shell magnetic nanoparticles supported at a carbon paste electrode

A phenol biosensor was developed based on the immobilization of tyrosinase on the surface of modified magnetic MgFe2O4 nanoparticles. The tyrosinase was first covalently immobilized to core-shell (MgFe2O4-SiO2) magnetic nanoparticles, which were modified with amino group on its surface. The resulting magnetic bio-nanoparticles were attached to the surface of carbon paste electrode (CPE) with the help of a permanent magnet. The immobilization matrix provided a good microenvironment for the retaining of the bioactivity of tyrosinase. Phenol was determined by the direct reduction of biocatalytically generated quinone species at -150 mV versus SCE. The resulting phenol biosensor could reach 9590 of steady-state current within 20 s and exhibited a high sensitivity of 54.2 mu A/mM, which resulted from the high tyrosinase loading of the immobilization matrix. The linear range for phenol determination was from 1 x 10(-6) to 2.5 x 10(-4) M with a detection limit of 6.0 x 10(-7) M obtained at a signal-to-noise ratio of 3. The stability and the application of the biosensor were also evaluated. (c) 2004 Elsevier B.V. All rights reserved.