Tyrosinase Modified Poly(thionine) Electrodeposited Glassy Carbon Electrode for Amperometric Determination of Catechol

Abstract

A stepwise strategy of mediator-free amperometric biosensor for the detection of catechol was developed based on the covalent bonding of tyrosinase (TYR) onto thionine (TN)-electrodeposited glassy carbon (GC) surface via glutaraldehyde (GA). Prior to the TYR-immobilization, poly(thionine) was prepared on a GC electrode surface by an electrooxidative polymerization of thionine. The TYR/GA/pTN modified electrode was evaluated by SEM and EIS measurements. The terminal amino groups (-NH2) which electrodeposited on the GC surface were cross-linked with protein lysine group (or cysteine group) by GA. The resulting TYR/GA/pTN-immobilized GCE was utilized as a working electrode unit of a catechol-detect biosensor. Catechol was used as model analyte for the evaluation of catecholase activity, and the signal based on the electro-reduction of the enzymatically produced o-quinone species were monitored at −0.05 V vs. Ag/AgCl. The resulting TYR/GA/pTN/GCE biosensor exhibited rapid and sensitive response to catechol (100% response time: ≈5 s, sensitivity: 5.04 µA/mM, detection limit: 6.0 µM. The TYR/GA/pTN/GCE retained 71% of original activity for catechol oxidation after 1 month storage.