Departamento de Química Analítica y Análisis Instrumental, Universidad Autónoma de Madrid, Cantoblanco, 28049 Madrid, Spain.
Instituto Madrileño de Estudios Avanzados en Nanociencia (IMDEA-Nanociencia), Faraday, 9, Campus UAM, Cantoblanco, 28049 Madrid, Spain.
Sensors (Basel). 2017 Jan 13;17(1):144. doi: 10.3390/s17010144.
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) onto ,'-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. 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.
乳酸是食品工业中的一个相关分析物，因为它影响了许多产品的风味、新鲜度和储存质量，如牛奶和乳制品、果汁或葡萄酒。它是乳糖或苹果酸-乳酸发酵的产物。在这项工作中，我们开发了一种基于乳酸氧化酶（LOx）固定在 ，'-双（3,4-二羟基苄叉）-1,2-二氨基苯希夫碱四齿配体修饰的金纳米粒子（3,4DHS-AuNPs）上的乳酸生物传感器，该传感器对过氧化氢氧化/还原表现出强大的电催化作用。3,4DHS-AuNPs 是在独特的反应步骤中合成的，其中 3,4DHS 作为还原/封端/修饰剂，用于生成稳定的希夫碱配体-AuNPs 组装体的胶体悬浮液，其尺寸得到控制。配体-除了其还原作用外-还为金纳米粒子提供了坚固的涂层和催化功能。乳酸氧化酶（LOx）在氧气存在下催化 L-乳酸转化为丙酮酸，产生过氧化氢，该过氧化氢在 3,4DHS-AuNPs 修饰的丝网印刷碳电极上在 +0.2 V 处被催化氧化。测量的电催化电流与过氧化物的浓度成正比，而过氧化物的浓度与样品中存在的乳酸量有关。所开发的生物传感器显示出 2.6 μM 乳酸的检测限和 5.1 ± 0.1 μA·mM 的灵敏度。该装置的实用性已通过在不同基质（白葡萄酒、啤酒和酸奶）中测定乳酸含量得到证明。获得的结果与使用标准酶分光光度测定试剂盒获得的结果相当。
