Determination of phenolic compounds with tyrosinase biosensor based on gold nanoparticle

In this thesis, development of a gold nanoparticle (AuNP) modified tyrosinase biosensor which brings a new and original perspective to biosensor technology indeed for epinephrine determination. AuNP was synthesized by Turkevich method and it was characterized with zeta potential counter. In this biosensor system, carbon paste was prepared with AuNP and graphite mixed. KP/AuNP/Tyrosinase/Nafion modified system formed by dropping a Tyrosinase enzyme and dried then dropping a Nafion solution again dried on surface of carbon paste. Epinephrine measurement were done cathodic region with using differential pulse method between from (+0.8) to (-0.8) potentials by developed biosensor system. In the optimization studies of the biosensor firstly such as optimum tyrosinase enzyme activity and gold nanoparticles amount, were carried out. In the optimization working condition; optimum pH and oxygen gas time were also investigated. Afterwards in characterization studies of the biosensor some parameters such as linearity, storage stability were determined. From the results of the optimization studies optimum gold nanoparticles amount and optimum tyrosinase enzyme activity were determined 40 μL and 313.087 U/mL respectively. From the experiments the phosphate buffer (50 mM, pH 7.5) were chosen to be optimum working conditions for the tyrosinase biosensor. It was determined at the characterization studies on the biosensor that linear curves were obtained between the ranges of 5-500 μM epinephrine concentrations. At the repeability experiments (n= 7), the average value, standard deviation (SD) and coefficient of variation (CV) were calculated to be 218.56±3.53 and 1.61 percent for 200 μM EP concentration. Also determination of epinephrine were carried out in real adrenalin ampule samples by developed biosensor.