Amperometric Biosensors for Detection of L- and D-Amino Acids on Co-Immobilized Peroxidase and L- and D-Amino Acid Oxidases in Carbon Paste Electrodes

Abstract

An apparent direct electron transfer between various electrode materials and peroxidases immobilized on the surface of the electrode has been reported in the last few years. An electrocatalytic reduction of hydrogen peroxide promoted by the immobilized peroxidase starts already at about +600 mV vs SCE at neutral pH. The efficiency of the electrocatalytic current increases as the applied potential is made more negative and starts to level off at about -200 mV vs SCE. Amperometric biosensors for hydrogen peroxide can be constructed with these kind of peroxidase modified electrodes. By co-immobilizing a hydrogen peroxide producing oxidase with the peroxidase, amperometric biosensors can be made responding for the substrate of the oxidase within a potential range essentially free of interfering electrochemical reactions. Sensors for L- and D-amino acids are shown with preliminary results obtained for L- and D-phenylalanine, respectively.