Amperometric pH-sensing biosensors for urea, penicillin, and oxalacetate

The possibility of constructing a biosensor exploiting amperometric pH-sens ing was investigated. The principle is based on the use of pH-sensitive red ox-active probe molecules. The selected probe molecules applied in various forms, e.g. dissolved hematein, electrode bulk lauryl gallate, adsorbed met hylene blue poly(o-phenylenediamine) film, were used for the construction o f penicillin (with penicillinase), urea (with urease), and oxalacetate (wit h oxalacetate decarboxylase) biosensors. Platinum, gold and solid composite electrodes were used as transducers. The biosensors exhibited low detectio n limits, from 2 to 10 mu M, linear responses up to 2 mM, insensitivity to a small variation in the ion concentrations, a good accuracy and storage st ability. The present, new concept could extend the range of analytes detect able using the amperometric transduction technology, such as substrates of decarboxylases, amidohydrolases, esterases and other hydrolases. (C) 2000 E lsevier Science B.V. All rights reserved.