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 sputter-coated with platinum, a screen-printed graphite basal track and an aluminum foil as a contact pad were fabricated for the development of l-lactate oxidase biosensors. Uncoated electrodes were characterized by cyclic voltammetry. A mixture of lactate oxidase with polyethyleneimine (PEI) and poly(carbamoyl)sulphonate (PCS) hydrogel was used for enzyme immobilization onto 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 sensitive l-lactate determination were fabricated with different settings of Nafion® layers to exclude electroactive interferents. Lactate oxidase sensors were characterized with respect to linear range, sensitivity, response time and recovery time. The effects of ascorbic acid and temperature on the sensor performance were investigated. The continuous operation and the stability of sensors were also evaluated. The performance of sensors coated with larger numbers of small amounts of Nafion® was found to be more advantageous than that of sensors coated with fewer numbers of larger amounts of Nafion®. The sensors were also tested with diluted dairy products and human whole blood and serum. Good agreement was found between the results obtained by the newly developed disposable sensors and other well established analytical methods.