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) onto N,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.

Recent developments in penta-, hexa- and heptadentate Schiff base ligands and their metal complexes

“…Schiff bases are among the most widely used organic compounds, exhibiting a broad range of applications, such as intermediates in organic synthesis [4][5][6][7], chemosensors [8][9][10] and polymer stabilisers [11][12][13], in food industry [14,15], as dye [16][17][18] and pigments [19][20][21], catalysis [22,23] and others [24][25][26]. Schiff bases also present a broad range of biological activities [27][28][29][30] for which the azomethine or imine group present in their structures, seems to play a critical role [31][32][33].…”

Spectroscopic studies, DFT calculations, cytotoxicity activity, and docking stimulation of novel metal complexes of Schiff base ligand of isonicotinohydrazide derivative

“…[1][2][3][4][5][6][7] Schiff bases have attracted a lot of concern because of their ease of synthesis, 8 in which the aldehyde or ketone containing the carbonyl group (C=O) has been replaced by an imine or azomethine group (>C=N-) and they are synthesized by condensing primary amines and carbonyl compounds. 9 Schiff bases are among the most widely used organic compounds, with applications ranging from organic synthesis intermediates to chemosensors and polymer stabilizers, 10,11 dyes and pigments, 12 and catalysis 13 Condensation reactions between two molecules to produce a new Schiff base are frequently used in drug development to create compounds with novel biological properties. 14,15 The significant role of Schiff base is in the formation of stable metal complexes due to its capability to stabilize metal ions with several oxidation states and use in different industrial and biological actions.…”

Synthesis, Spectral, Thermal and Biological Studies of Some Transition and Inner Transition Schiff base Metal Complexes

“…Schiff bases were distinguished by an imine group HC=N which helped to elucidate the mechanism of Schiff transamination and racemization reaction in biological systems [1,2]. Among the most extensively used organic compounds, the Schiff bases were exhibiting a broad range of applications, such as intermediates in organic synthesis [3][4][5][6], polymer stabilizers [7][8][9], catalysis [10,11], chemosensors [12][13][14], in food industry [15,16], and others [17][18][19].…”