title: Reagent-Less and Robust Biosensor for Direct Determination of Lactate in Food Samples.
abstract: Lactic acid is a relevant analyte in the food industry, since it affects the flavor, freshness, and storage quality of several products, such as milk and dairy products, juices, or wines. It is the product of lactose or malo-lactic fermentation. In this work, we developed a lactate biosensor based on the immobilization of lactate oxidase (LOx) ontoN,N'-Bis(3,4-dihydroxybenzylidene) -1,2-diaminobenzene Schiff base tetradentate ligand-modified gold nanoparticles (3,4DHS-AuNPs) deposited onto screen-printed carbon electrodes, which exhibit a potent electrocatalytic effect towards hydrogen peroxide oxidation/reduction. 3,4DHS-AuNPs were synthesized within a unique reaction step, in which 3,4DHS acts as reducing/capping/modifier agent for the generation of stable colloidal suspensions of Schiff base ligand-AuNPs assemblies of controlled size. The ligand-in addition to its reduction action-provides a robust coating to gold nanoparticles and a catalytic function. Lactate oxidase (LOx) catalyzes the conversion of l-lactate to pyruvate in the presence of oxygen, producing hydrogen peroxide, which is catalytically oxidized at 3,4DHS-AuNPs modified screen-printed carbon electrodes at +0.2 V. The measured electrocatalytic current is directly proportional to the concentration of peroxide, which is related to the amount of lactate present in the sample. The developed biosensor shows a detection limit of 2.6 μM lactate and a sensitivity of 5.1 ± 0.1 μA·mM-1. The utility of the device has been demonstrated by the determination of the lactate content in different matrixes (white wine, beer, and yogurt). The obtained results compare well to those obtained using a standard enzymatic-spectrophotometric assay kit.
authors.affiliation: Departamento de Química Analítica y Análisis Instrumental, Universidad Autónoma de Madrid, Cantoblanco, 28049 Madrid, Spain. iria.bravo@uam.es.|Instituto Madrileño de Estudios Avanzados en Nanociencia (IMDEA-Nanociencia), Faraday, 9, Campus UAM, Cantoblanco, 28049 Madrid, Spain. iria.bravo@uam.es.
authors.forename: Iria
authors.initials: I
authors.lastname: Bravo
authors.affiliation: Departamento de Química Analítica y Análisis Instrumental, Universidad Autónoma de Madrid, Cantoblanco, 28049 Madrid, Spain. monica.revenga@uam.es.|Instituto Madrileño de Estudios Avanzados en Nanociencia (IMDEA-Nanociencia), Faraday, 9, Campus UAM, Cantoblanco, 28049 Madrid, Spain. monica.revenga@uam.es.|Institute for Advanced Research in Chemical Sciences (IAdChem), Universidad Autónoma de Madrid, 28049 Madrid, Spain. monica.revenga@uam.es.
authors.forename: Mónica
authors.initials: M
authors.lastname: Revenga-Parra
authors.affiliation: Departamento de Química Analítica y Análisis Instrumental, Universidad Autónoma de Madrid, Cantoblanco, 28049 Madrid, Spain. felix.pariente@uam.es.|Institute for Advanced Research in Chemical Sciences (IAdChem), Universidad Autónoma de Madrid, 28049 Madrid, Spain. felix.pariente@uam.es.
authors.forename: Félix
authors.initials: F
authors.lastname: Pariente
authors.affiliation: Departamento de Química Analítica y Análisis Instrumental, Universidad Autónoma de Madrid, Cantoblanco, 28049 Madrid, Spain. encarnacion.lorenzo@uam.es.|Instituto Madrileño de Estudios Avanzados en Nanociencia (IMDEA-Nanociencia), Faraday, 9, Campus UAM, Cantoblanco, 28049 Madrid, Spain. encarnacion.lorenzo@uam.es.|Institute for Advanced Research in Chemical Sciences (IAdChem), Universidad Autónoma de Madrid, 28049 Madrid, Spain. encarnacion.lorenzo@uam.es.
authors.forename: Encarnación
authors.initials: E
authors.lastname: Lorenzo
mesh_terms: D015374:Biosensing Techniques; D004566:Electrodes; D004800:Enzymes, Immobilized; D006046:Gold; D019344:Lactic Acid; D053768:Metal Nanoparticles
chemical_list: D004800:Enzymes, Immobilized; D019344:Lactic Acid; D006046:Gold
keywords: Schiff base tetradentate ligand modified gold nanoparticles; enzymatic biosensor; gold nanoparticles; lactate determination; lactate oxidase biosensor