Tyrosinase biosensor based on a glassy carbon electrode modified with multi-walled carbon nanotubes and 1-butyl-3-methylimidazolium chloride within a dihexadecylphosphate film

A glassy carbon electrode modified with functionalized multi-walled carbon nanotubes (MWCNT), 1-butyl-3-methylimidazolium chloride (ionic liquid = IL) and tyrosinase (Tyr) within a dihexadecylphosphate (DHP) film for the development of a biosensor is proposed. MWCNT, IL and Tyr were efficiently immobilized in the film using 1-ethyl-3-(3-dimethylaminopropyl) carbodiimide/N-hydroxysuccinimide (EDC/NHS) as crosslinking agents, and which was characterized by cyclic voltammetry (CV) in the presence of catechol. The IL-MWCNT nanocomposite showed good conductivity and biocompatibility with Tyr enzyme, since the biosensor presented biocatalytic activity toward the oxidation of catechol to o-quinone which was electrochemically reduced to catechol at a potential of 0.04 V. The analytical curve ranged from 4.9 × 10−6 to 1.1 × 10−3 mol L−1 with a detection limit of 5.8 × 10−7 mol L−1. The developed Tyr-IL-MWCNT-DHP/GCE biosensor showed a wide linear range, good reproducibility, sensitivity and stability and the biosensor was successfully applied to the determination of catechol in natural water samples, with satisfactory results compared with a spectrophotometric method, at the 95% confidence level.