Development of a bioelectrode fabricated with a multilayer thin film of poly(diallyldimethylammonium)/gold-nanoparticle/lactate oxidase for analysis of L-lactate in food samples

Abstract

Multilayer films made of poly(diallyldimethylammonium) (PDDA), gold nanoparticles (AuNP) of 10 nm diameter and lactate oxidase (LOx), were built for the first time, by layer-by-layer (LBL) assembly technique onto both quartz and gold substrates. The surface plasmon resonance (SPR) band of AuNP was used for monitoring the film growth and adsorption kinetics on PDDA monolayer supported onto quartz substrate. In the case of polycrystalline gold surfaces, electrochemical characterization was performed by means of cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). The latter system was used as bioelectrode for L-lactate quantification, showing a short time response (<10 s) with high sensitivity of 63 ± 3 μA mM−1cm−2, detection limit of 0.47 μM and linear range between 0.001 mM and 0.25 mM. This bioelectrode was also tested for L-lactate analysis in yogurt and fermented milk, and it was checked that typical interfering as glucose and citric, acetic and ascorbic acids do not play a role. Present results indicate that self-assembled multilayers made of PDDA/AuNP/LOx are suitable thin films for electroanalytical determination of L-lactate in real samples.