Hydrogen peroxide – sensitive enzyme sensor based on phthalocyanine thin film

Abstract

An enzyme biosensor specific for hydrogen peroxide was developed using a new conductometric transducer based on tetra- tert-butyl copper phthalocyanine (ttb-CuPc) thin films and horseradish peroxidase as sensitive element. This 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 presence of horseradish peroxidase. For the detection of the peroxidase-initiated reaction the ability of the ttb-CuPc thin film to change its conductivity in response to the appearance of molecular iodine is used. To minimise the interfering effect of the aqueous electrolyte on the conductometric response of the ttb-CuPc thin film itself, gold interdigitated electrodes bearing ttb-CuPc layer were covered with a hydrophobic gas-permeable membrane. Thermally evaporated calixarene or plasma polymerised hexamethyldisiloxane was used as a gas-permeable membrane material. In order to assess the optimum sensor technology as well as the operating regime, impedance spectroscopy data were analysed. For biosensor creation horseradish peroxidase was deposited on the sensitive part of the electrodes in a cross-linked bovine serum albumin matrix. The possibility of hydrogen peroxide detection with the biosensor proposed in the range 5–300 μM was demonstrated. The operational stability of biosensor was at least 7 h and the relative standard deviation did not exceed 10%. When stored at +4°C the sensor response was stable for more than 90 days. The dependencies of the sensor response on pH, buffer and NaCl concentrations were investigated.