Fabrication and characterization of disposable type lactate oxidase sensors for dairy products and clinical analysis

Disposable transducers having a working electrode made of a polymer disk sp utter-coated with platinum, a screen-printed graphite basal track and an al uminum foil as a contact pad were fabricated for the development of L-lacta te oxidase biosensors. Uncoated electrodes were characterized by cyclic vol tammetry. A mixture of lactate oxidase with polyethyleneimine (PEI) and pol y(carbamoyl)sulphonate (PCS) hydrogel was used for enzyme immobilization on to the platinum disk of the transducers. A two-electrode configuration set up in an amperometric mode was used to measure the current generated due to the enzymatically generated hydrogen peroxide. The sensors capable of sens itive L-lactate determination were fabricated with different settings of Na fion(R) layers to exclude electroactive interferents. Lactate oxidase senso rs were characterized with respect to linear range, sensitivity, response r ime and recovery time. The effects of ascorbic acid and temperature on the sensor performance were investigated. The continuous operation and the stab ility of sensors were also evaluated. The performance of sensors coated wit h larger numbers of small amounts of Nafion(R) was found to be more advanta geous than that of sensors coated with fewer numbers of larger amounts of N afion(R). The sensors were also tested with diluted dairy products and huma n whole blood and serum. Good agreement was found between the results obtai ned by the newly developed disposable sensors and other well established an alytical methods. (C) 2000 Elsevier Science S.A. All rights reserved.