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Laccase Biosensor Based on Graphene-Chitosan Composite Film for Determination of Hydroquinone

A novel laccase biosensor was fabricated by entrapping laccase in graphene–chitosan composite materials and applied to determine hydroquinone. The graphene–chitosan composite had good conductivity, high stability, and good biocompatibility. Laccase was firmly embedded into the composite without other cross-linking reagents. The morphology and electrical conductivity of graphene-chitosan film were measured by scanning electron microscopy and electrochemical impedance spectroscopy. This biosensor catalyzed the oxidation of hydroquinone to p-quinone and the reduction back to hydroquinone. The cathodic peak current of hydroquinone increased significantly with concentration in the range of 2.0 × 10−6 to 1.0 × 10−4 mol · L−1 (r = 0.9975) with a limit of detection of 2.6 × 10−7 mol · L−1. The response time of the biosensor to reach 95% of its steady-state current was less than 10 s. Moreover, the biosensor exhibited good stability, reproducibility, and selectivity.