Development of an amperometric biosensor based on covalent immobilization of tyrosinase on a boron-doped diamond electrode

An amperometric enzyme electrode based on direct covalent immobilization of tyrosinase on a boron-doped diamond (BDD) electrode has been developed for the detection of phenolic compounds. Combined chemical and electrochemical modifications of the BDD film with 4-nitrobenzenediazonium tetrafluoroborate, an aminophenyl-modified BDD (AP–BDD) surface was produced, and then the tyrosinase was covalently immobilized on the BDD surface via carbodiimide coupling. The response dependences of the enzyme electrode (Tyr–AP–BDD electrode) on pH of solution, applied potential, oxygen level and phenolic compounds diffusion were studied. The Tyr–AP–BDD electrode shows a linear response range of 1–200, 1–200 and 1–250 μM and sensitivity of 232.5, 636.7 and 385.8 mA M−1 cm−2 for phenol, p-cresol and 4-chlorophenol, respectively. 90 percent of the enzyme activity of the Tyr–AP–BDD electrode is retained for 5 weeks storing in 0.1 M PBS (pH 6.5) at 4 °C.