Direct monitoring of pollutants based on an electrochemical biosensor with novel peroxidase (POX1B)

A biosensor for the monitoring of phenolic compounds based on a new protein named POX1B purified from garlic which demonstrates similar biochemical properties to peroxidase is investigated. The enzyme was immobilized into chitosan microspheres with covalent link. The properties of the biosensor were analyzed with Fourier transform-infrared spectroscopy (FT-IR), scanning electron microscopy (SEM) and cyclic voltammetry (CV). FT-IR demonstrates the covalent attachment of POX1B into chitosan and SEM shows high dispersion of the POX1B into the chitosan microspheres. The redox potential of POX1B in chitosan is 147 mV vs. SCE, which is much higher than reported works using HRP, demonstrating excellent direct electrochemical behaviour of the POX1B. The electrocatalytic activity of the obtained biosensor towards chlorophenols derivatives in a large range from 10 pM to 10 μM was demonstrated. The mediator free POX1B-based biosensor exhibited high sensitivity towards 2,6-dichlorophenol, 4-chlorophenol and pentachlorophenol. A detection limit of 1 pM in the case of 4-chlorophenol was demonstrated with kinetic constant Km,app of 0.42 μM with high rapidity of electrochemical response of the biosensor of 1 s.