Hydrogen peroxide - sensitive enzyme sensor based on phthalocyanine thin film

An enzyme biosensor specific for hydrogen peroxide was developed using a ne w conductometric transducer based on tetra-tert-butyl copper phthalocyanine (ttb-CuPc) thin films and horseradish peroxidase as sensitive element. Thi s analytical system is based on detection of molecular iodine produced as a result of the oxidation of the iodide ions by hydrogen peroxide in the pre sence of horseradish peroxidase. For the detection of the peroxidase-initia ted reaction the ability of the ttb-CuPc thin film to change its conductivi ty in response to the appearance of molecular iodine is used. To minimise t he interfering effect of the aqueous electrolyte on the conductometric resp onse of the ttb-CuPc thin film itself. gold interdigitated electrodes beari ng ttb-CuPc layer were covered with a hydrophobic gas-permeable membrane. T hermally evaporated calixarene or plasma polymerised hexamethyldisiloxane w as used as a gas-permeable membrane material. In order to assess the optimu m sensor technology as well as the operating regime, impedance spectroscopy data were analysed. For biosensor creation horseradish peroxidase was depo sited on the sensitive part of the electrodes in a cross-linked bovine seru m albumin matrix. The possibility of hydrogen peroxide detection with the b iosensor proposed in the range 5-300 mu M was demonstrated. The operational stability of biosensor was at least 7 h and the relative standard deviatio n did not exceed 10%. When stored at +4 degrees C the sensor response was s table for more than 90 days. The dependencies of the sensor response on pH, buffer and NaCl concentrations were investigated. (C) 1999 Elsevier Scienc e B.V. All rights reserved.