Extradiol dioxygenase-SiO₂ sol-gel modified electrode for catechol and its derivatives detection.

A feasible and sensitive biosensor for catechol and its derivatives using 2,3-dihydroxybiphenyl 1,2-dioxygenase (BphC)-modified glassy carbon electrode was successfully constructed by polyvinyl alcohol-modified SiO₂ sol-gel method. The as-prepared biosensor was characterized by electrochemical impedance spectroscopy, and the surface topography of the film was imaged by atomic force microscope. Liquid chromatography-tandem mass spectrometry was applied to reveal the catalytic mechanism. BphC embedded in SiO₂ gel maintained its bioactivity well and exhibited excellent eletrocatalytical response to both catechol and some of its derivatives (such as 3-methylcatechol and 4-methylcatechol). The biosensor showed a linear amperometric response range between 0.002 mM and 0.8 mM catechol. And the sensitivity was 1.268 mA/(mM cm²) with a detection limit of 0.428 μM for catechol (S/N = 3). Furthermore, the BphC biosensor exhibited perfect selectivity for catechol in the mixtures of catechol and phenol. It was suggested that this flexible protocol would open up a new avenue for designing other ring-cleavage enzyme biosensors, which could be widely used for monitoring various kinds of environmental pollutants.