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• The performance of a laccase biosensor is improved by using LbL films as substrate. • LbL films contain chitosan, an ionic liquid and a copper phthalocyanine derivative. • The combination of their complementary functionalities improves the performance. • Improvement is due to their electrocatalytic and immobilization properties. • Biosensors with laccase on LbL layers show a LOD of 9.98·10−9 M towards catechol. The performance of electrochemical laccase-based biosensors can be improved by immobilizing the enzyme on composite Layer-by-Layer (LbL) supports in which materials with complementary functions are combined. LbL films are formed by layers combining an electrocatalytic material which favors electron transfer (sulfonated copper phthalocyanine, CuPcS(−)), an ionic liquid which enhances the electrical conductivity of the layers (1-butyl-3-methylimidazolium tetrafluoroborate, IL(+)) and a material able to promote enzyme immobilization (chitosan, CHI(+)). Composite films with different structures have been demonstrated to be efficient electrocatalysts, producing an increase in the magnitude of the responses towards catechol. The most intense and reproducible electrocatalytic effect was observed when a layer of the CuPcS(−) was placed on top of a layer formed by a mixture of CHI(+) + IL(+) to obtain [CHI(+) + IL(+)|CuPcS(−)] 2 films. Biosensors with laccase immobilized on the surface of the LbL layers [CHI(+) + IL(+)|CuPcS(−)] 2 |Lac showed mediated electron transfer between the redox enzyme and the film and a reproducibility of device-to-device performance of 4.1%. The amperometric biosensor showed a sensitivity of 0.237 A·M−1 and a linear detection range from 2.4 μM to 26 μM for catechol. The excellent Limit of detection (LOD) of 8.96·10−10 M (3·σ /m) is one order of magnitude lower than that obtained in similar studies. A Michaelis-Menten constant of 3.16 μM confirms excellent enzyme-substrate affinity. [ABSTRACT FROM AUTHOR]

The electron mediator properties of three subphthalocyanines (SubPcs) [hexa-chloro boron subphthalocyanine (ClSubPc), tri- tert -butyl boron subphthalocyanine ( t- BuSubPc) and hexa-phenoxy boron subphthalocyanine (PhOSubPc)] in Tyrosinase and Laccase biosensors (deposited on ITO glass) for the detection of catechol and hydroquinone were evidenced. A particularly remarkable performance was observed in the PhOSubPc-Tyr sensor, which takes account of the π-π interactions between subphthalocyanine rings and the active sites of the enzymes. Mediated electron transfer between redox enzymes and the ITO electrode improved the limits of detection by one order of magnitude, reaching 10 −7 mol·L −1 values. Studies at increasing scan rates confirmed the improvement of the charge transfer rates caused by the presence of the SubPcs. A bioelectronic tongue formed by an array of the SubPc based biosensors has been able to discriminate red wines according to their Total Polyphenol Index. [ABSTRACT FROM AUTHOR]