Tyrosinase - Based Biosensor for Determination of Tyrosine Using Cysteine and Chitosan Immobilization at Glassy Carbon Electrode

For determination of tyrosine a tyrosinase – based biosensor fabricated. For biosensor making, a glassy carbon electrode modified by gold nanoparticle electrodeposition. Then, cysteine, chitosan, and tyrosinase successively immobilized at the modified electrode surface. To evaluate biosensor performance, cyclic voltammetry separately carried out in the presence of different concentrations of tyrosine. All cyclic voltametry experiments performed in the potassium buffer phosphate, pH 7 and 25 ºC and voltammograms considered as responses of constructed biosensor. Voltammograms showed that peak currents remarkably increased with rising concentrations of tyrosine. At next stage, the analytical parameters investigated using calibration curve. According to calibration curve, the linear range of biosensor determined from 30 μM to 50 μM. Detection limit and sensitivity determined 2.77 μM and 0.158 μA/μM, respectively. In addition, long-term stability 14th Annual Electrochemistry Seminar of Iran Materials and Energy Research Center (MERC), 12- 13 Dec, 2018 69 study indicated that biosensor response reduced from – 0.7 μA at beginning of the study to – 0.4 μA after two months. As a result, if this biosensor utilizes in human samples, some correction coefficient will be necessary to obtain precise results.