Développement d’un biocapteur optique à tyrosinase de truffe (Terfezia leonis Tul.) immobilisée sur gel de silice pour le dosage du catéchol en solution

Abstract

Catechol is widely used in many manufacturing industry, but has been recognized as a toxic and carcinogenic to humans and animals. Therefore, it is necessary to have a sensitive, less expensive, simple and reproducible analytical method for catechol detection. Conventional analytical methods such as spectrophotometry, capillary electrophoresis, voltammetry, chromatography and chemiluminescence have several disadvantages thus limiting their use for the determination of this pollutant. Actually, immobilized tyrosinase biosensors have received a great attention in the analytical field for the determination of phenols in solution. This work aims to develop an optical biosensor using a crude extract of desert truffle (Terfezia leonisTul.) as an enzymatic source of tyrosinase. The biosensor is constructed by the immobilization of tyrosinase crude extract in a bi-layered silica gel film prepared by dip-coating of an alkoxide/colloidal silica solution containing the enzyme on glass slide. Encapsulation has a moderate effect of the enzyme optimal pH stability but largely increases its thermal stability. Immobilized enzymes have a higher substrate affinity towards catechol (KMapp = 0,3mM) but smaller maximum conversion velocity (VMaxapp). The optical biosensor showed a good reproducibility and provides a linear response for catechol in the concentration range of 50–400 μM with a limit of detection 52 μM. AFM studies show that the enzymes affect the silica gel structure, preventing further deposition of additional layers. The optical biosensor with desert truffle tyrosinase can be considered as a promising tool for catechol analysis in pharmaceutical and environmental fields.