Disposable amperometric biosensor based on lactate oxidase immobilised on platinum nanoparticle-decorated carbon nanofiber and poly(diallyldimethylammonium chloride) films.

A novel biosensor for lactate has been developed, using screen-printed carbon electrodes (SPCE) and lactate oxidase (LOx). The active surface of the electrodes was modified using a dispersion of platinum nanoparticle decorated carbon nanofibers (PtNp-CNF) in poly(diallyldimethylammonium) chloride (PDDA) solution. In this way, sensitive, disposable, low cost and reliable hydrogen peroxide sensors were obtained. The immobilisation of LOx on top of these PtNp-CNF-PDDA/SPCEs resulted in amperometric biosensors with high operational stability. The sensitivity of the optimised lactate biosensor was 36.8 (mA/Mcm(2)) with a linear range of 25-1500 µM. The limit of detection was 11 µM (S/N=3). Reproducibility, selectivity and storage stability were also evaluated. Additionally, the stability of the biosensor was also predicted by a model based on thermal degradation. Finally, lactate in sweat and blood samples was determined in a sport test using LOx/PtNp-CNF-PDDA/SPCEs and commercial biosensors respectively. Based on these data, the validity of the sweat lactate for the determination of the lactate threshold is discussed.