Stabilization of lactate oxidase in screen-printed enzyme electrodes

Lactate oxidase was freeze-dried and stored in DEAE-dextran/ lactitol for 355 days at 25 degrees C. By this time the activity of the enzyme had fallen to about 64% of its initial activity, whereas that stored without polymer had fallen to about 2%. The enzyme was also incorporated into electrodes with various polymers: hydroxyethyl cellulose, DEAE-dextran/lactitol, a neutral form of Gafquat, a cationic form and a mixture of the cationic form and lactitol, the electrodes being stored at 25 degrees C for 172 days. The highest currents at the end of the storage period were developed by those electrodes based on the cationic form of Gafquat, either by itself or mixed with lactitol. This work indicates that lactate oxidase may be stabilized by readily available polymers for periods approaching commercially feasible shelf-lives. (C) 1996 Elsevier Science Limited