Disposable Amperometric Biosensor Based on Poly‐L‐lysine and Fe 3 O 4 NPs‐chitosan Composite for the Detection of Tyramine in Cheese

An amperometric tyramine biosensor based on poly‐L‐lysine (PLL) and Fe 3 O 4 nanoparticles (Fe 3 O 4 NP) modified screen printed carbon electrode (SPCE) was developed. PLL was formed on the SPCE by the electropolymerization of L‐lysine. Subsequently, Fe 3 O 4 NP suspension prepared in chitosan (CH) solution was casted onto the PLL/SPCE. Tyrosinase (Ty) enzyme was immobilized onto the modified Fe 3 O 4 −CH/PLL/SPCE and the electrode was coated with Nafion to fabricate the Ty/Fe 3 O 4 −CH/PLL/SPCE. Different techniques including scanning electron microscopy, chronoamperometry ( i –t curve), cyclic voltammetry and electrochemical impedance spectroscopy were utilized to study the fabrication processes, electrochemical characteristics and performance parameters of the biosensor. The analytical performance of the tyramine biosensor was evaluated with respect to linear range, sensitivity, limit of detection, repeatability and reproducibility. The response of the biosensor to tyramine was linear between 4.9×10 −7 –6.3×10 −5 M with a detection limit of 7.5×10 −8 M and sensitivity of 71.36 μA mM −1 (595 μA mM −1 cm −2 ). The application of the developed biosensor for the determination of tyramine was successfully tested in cheese sample and mean analytical recovery of added tyramine in cheese extract was calculated as 101.2±2.1 %. The presented tyramine biosensor is a promising approach for tyramine analysis in real samples due to its high sensitivity, rapid response and easy fabrication.