Design of enzyme electrodes for extended use and storage life

A novel design for an extended-life amperometric enzyme electrode is presented. The enzyme electrode is fabricated by arranging the three components of a biosensor (an electrode material, an enzyme, and a stabilizer) on a shapable electroconductive (SEC) film (a polyanion-doped polypyrrole film) surface by a layer-after-layer approach. First, a thin and compact Pt black layer is prepared onto the SEC film by the heat-press method. Then, an ultrathin layer of L-lactate oxidase (LOx) is cast on the platinized SEC film, and after drying, a thin gelatin layer is prepared on the LOx-cast SEC film. Finally, the dried layer assembly is cross-linked by exposing it to a diluted glutaraldehyde solution for a very short time. The performance of the developed sensor is evaluated by a FIA system at 37 degrees C and under continuous polarization at 0.4 V (vs Ag/AgCl). The developed sensor shows remarkably improved performance. The sensor produces a large response current with a wide linear dynamic range. The sensor shows an extended working life of more than 2 months and a shelf life of about 2 years when it is stored dry in a freezer at -18 degrees C and about 1 year when it is stored at room temperature.