An amperometric biosensor based on laccase immobilized onto Fe3O4NPs/cMWCNT/PANI/Au electrode for determination of phenolic content in tea leaves extract

A method is described for the construction of an amperometric biosensor for detection of phenolic compounds based on covalent immobilization of laccase onto iron oxide nanoparticles (Fe3O4NPs) decorated carboxylated multiwalled carbon nanotubes (cMWCNTs)/polyaniline (PANI) composite electrodeposited onto a gold (Au) electrode. The modified electrode was characterized by scanning electron microscopy (SEM), Fourier transform infrared (FTIR) spectroscopy, cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). The biosensor showed optimum response within 3 s at pH 6.0 (0.1 M sodium acetate buffer) and 35 °C, when operated at 0.3 V vs. Ag/AgCl. Linear range, detection limit were 0.1–10 μM (lower concentration range) and 10–500 μM (higher concentration range), and 0.03 μM respectively. The sensor measured total phenolic content in tea leaves extract. The enzyme electrode lost 25% of its initial activity after its 150 uses over a period of 4 months, when stored at 4 °C.

► Constructed an amperometric polyphenol biosensor based on Fe3O4NP/cMWCNT/PANI/Au electrode.
► Biosensor showed optimum response within 3 s at 0.32 V, pH 6.0 and 35 °C.
► Working range and detection limit of biosensor were 0.1–500 μM and 0.03 μM respectively.
► Biosensor measured phenolic content in tea leaves extract.
► Electrode lost 25% activity after 150 uses over a period of 4 months.