Amperometric pH-sensing biosensors for urea, penicillin, and oxalacetate Original Research Article

The possibility of constructing a biosensor exploiting amperometric pH-sensing was investigated. The principle is based on the use of pH-sensitive redox-active probe molecules. The selected probe molecules applied in various forms, e.g. dissolved hematein, electrode bulk lauryl gallate, adsorbed methylene blue poly(o-phenylenediamine) film, were used for the construction of penicillin (with penicillinase), urea (with urease), and oxalacetate (with oxalacetate decarboxylase) biosensors. Platinum, gold and solid composite electrodes were used as transducers. The biosensors exhibited low detection limits, from 2 to 10 μM, linear responses up to 2 mM, insensitivity to a small variation in the ion concentrations, a good accuracy and storage stability. The present, new concept could extend the range of analytes detectable using the amperometric transduction technology, such as substrates of decarboxylases, amidohydrolases, esterases and other hydrolases.