A novel tyrosinase biosensor based on hydroxyapatite-chitosan nanocomposite for the detection of phenolic compounds

A novel tyrosinase biosensor based on hydroxyapatite nanoparticles (nano-HA)-chitosan nanocomposite has been developed for the detection of phenolic compounds. The uniform and size controlled nano-HA was synthesized by hydrothermal method, and its morphological characterization was examined by transmission electron microscope (TEM). Tyrosinase was then immobilized on a nano-HA-chitosan nanocomposite-modified gold electrode. Electrochemical impedance spectroscopy and cyclic voltammetry were used to characterize the sensing film. The prepared biosensor was applied to determine phenolic compounds by monitoring the reduction signal of the biocatalytically produced quinone species at -0.2 V (vs. saturated calomel electrode). The effects of the pH, temperature and applied potential on the biosensor performance were investigated, and experimental conditions were optimized. The biosensor exhibited a linear response to catechol over a wide concentration range from 10 nM to 7 microM, with a high sensitivity of 2.11 x 10(3) microA mM(-1) cm(-2), and a limit of detection down to 5 nM (based on S/N=3). The apparent Michaelis-Menten constants of the enzyme electrode were estimated to be 3.16, 1.31 and 3.52 microM for catechol, phenol and m-cresol, respectively. Moreover, the stability and reproducibility of this biosensor were evaluated with satisfactory results.