An amperometric biosensor based on laccase immobilized onto nickel nanoparticles/carboxylated multiwalled carbon nanotubes/polyaniline modified gold electrode for determination of phenolic content in fruit juices

A method is described for construction of an enzyme electrode for detection of phenolic compounds based on covalent immobilization of laccase onto nickel nanoparticles (NiNPs) decorated carboxylated multiwalled carbon nanotubes (cMWCNTs)/polyaniline (PANI) composite electrodeposited onto gold (Au) electrode. The modified electrode was characterized at different stages of its construction by scanning electron microscopy (SEM), Fourier transform infrared (FTIR) spectroscopy, cyclic voltam-mograms and electrochemical impedance spectroscopy (EIS). An amperometric biosensor for phenolic compounds was fabricated by connecting enzyme electrode (Lac/NiNPs/cMWCNTs/PANI/AuE) as working electrode, with Ag/AgCl as reference electrode and Pt wire as auxiliary electrode through potentiostat. The biosensor showed optimum response at pH 5.5 (0.1 M acetate buffer) and 35 degrees C, when operated at a scan rate of 20 mV s(-1). Linear range, response time, detection limit and sensitivity of biosensor were 0.1-10 mu M (lower concentration range) and 10-500 mu M (higher concentration range), 8s, 0.05 mu M and 0.694 mu A mu M-1 cm(-2) respectively. The biosensor measured total phenolic content in fruit juices. The enzyme electrode was used 200 times over a period of four months, when stored at 4 degrees C. (C) 2012 Elsevier B.V. All rights reserved.