Selective ElectrochemicalBiosensors for Tyrosinaseand Tyramine via Enzyme-Mediated Oxidation Reaction

Tyrosinase, a copper-containing oxidase, holds promise as a critical biomarker for diverse skin-related infections and vitiligo and melanoma tumors. Beyond its role as a critical biomarker and in biological pigmentation, tyrosinase is also involved in the oxidation of biogenic amines such as tyramine. Tyramine as a tyrosinase substrate serves as a precursor in the synthesis of various neurotransmitters such as dopamine and norepinephrine and contributes to significant neurological processes. It is well-stated that tyrosinase could oxidize tyramine in the presence of oxygen to give dopamine as a product. The oxidation of tyramine by tyrosinase to produce dopamine has been widely applied in colorimetric and fluorimetric assays of tyramine and tyrosinase. Herein, we optimized and utilized this oxidation reaction for the effective electrochemical detection of tyramine and tyrosinase without any electrode modification for the first time. We achieved the selective detection of tyrosinase and tyramine via selective detection of dopamine in situ, generated from the enzymatic conversion of tyramine by tyrosinase. Tyrosinase and tyramine were detected by using cyclic voltammetry (CV) and square wave voltammetry (SWV). Both electrochemical biosensors demonstrated excellent analytical performance. CV offered linear detection ranges of 0.7–10 μg/mL and 5.0–100 μM for tyrosinase and tyramine, respectively, while SWV exhibited a notably low signal-to-noise ratio, resulting in enhanced sensitivity for the detection of tyrosinase (0.3–10 μg/mL and LOD of 0.29 μg/mL) and tyramine (1.0–100 μM and LOD of 0.69 μM). The simple and convenient biosensors successfully detected tyrosinase in human serum samples and tyramine in yogurt and human urine samples and are very promising for the detection of real samples.