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

[Display omitted] •Multilayers made of PDDA/gold-nanoparticle/lactate oxidase are stable and suitable for bioelectrode preparation.•Bioelectrode sensitivity is one of the highest among those reported for similar systems.•The bioelectrode was fast and accurate for lactic acid quantification in dairy products. Multilayer films made of poly(diallyldimethylammonium) (PDDA), gold nanoparticles (AuNP) of 10nm 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 (