RESUMEN
This work addresses a technological advance applied to the construction of a magnetogenoassay with electrochemical transduction for the maize taxon-specific (HMGA gene) detection using gold-coated magnetic nanoparticles as nanosized platform. Superparamagnetic core-shell Fe3O4@Au nanoparticles (10.4⯱â¯1.7â¯nm) were used to assemble the genoassay through the covalent immobilization of HMGA DNA probes onto carboxylated self-assembled monolayers at the nanoparticles surface. A hybridization reaction using sandwich format was selected to prevent inefficient hybridization connected with stable secondary DNA structures using also fluorescein isothiocyanate as DNA signaling tag. The labelling of the hybridization reaction with enzymes allowed the chronoamperometric measurement of the peroxidase activity linked to the nanoplatform located on gold surface. Using this electrochemical magnetogenoassay a linear concentration range from 0.5 to 5â¯nM and a LOD of 90 pM with a RSD <1.2% was calculated. Certified maize was evaluated without further purification after PCR amplification. This work highlights the efficacy of the electrochemical magnetogenoassay for the HMGA detection, showing its potential as alternative procedure for the verification of the compliance of the legislation.
Asunto(s)
Técnicas Biosensibles/métodos , Genes de Plantas , Oro/química , Proteínas HMGA/genética , Nanopartículas de Magnetita/química , Zea mays/genética , Secuencia de Bases , Sondas de ADN/química , Sondas de ADN/genética , ADN de Plantas/química , ADN de Plantas/genética , ADN de Cadena Simple/química , ADN de Cadena Simple/genética , Técnicas Electroquímicas/métodos , Ácidos Nucleicos Inmovilizados/química , Ácidos Nucleicos Inmovilizados/genética , Límite de Detección , Hibridación de Ácido Nucleico , Proteínas de Plantas/genética , Plantas Modificadas Genéticamente/genéticaRESUMEN
An on-surface isothermal helicase-dependent amplification is devised for simple, point-of-need quantification of bacterial genomes. The method relies on the enzyme-extension of a thiol-modified reverse primer anchored to indium tin oxide electrodes, which shows strikingly high thermal and storage stability. Amplification and electrochemical detection of only 10 genomes are thus performed on the same platform without thermal cycling.
Asunto(s)
ADN Helicasas/metabolismo , Técnicas Electroquímicas , Enzimas Inmovilizadas/metabolismo , Técnicas de Amplificación de Ácido Nucleico , Oligonucleótidos/química , Salmonella/aislamiento & purificación , Compuestos de Estaño/química , Electrodos , Salmonella/genéticaRESUMEN
To counteract and prevent the deleterious effect of free radicals the living organisms have developed complex endogenous and exogenous antioxidant systems. Several analytical methodologies have been proposed in order to quantify antioxidants in food, beverages and biological fluids. This paper revises the electroanalytical approaches developed for the assessment of the total or individual antioxidant capacity. Four electrochemical sensing approaches have been identified, based on the direct electrochemical detection of antioxidant at bare or chemically modified electrodes, and using enzymatic and DNA-based biosensors.
Asunto(s)
Antioxidantes/análisis , Técnicas Biosensibles/instrumentación , Conductometría/instrumentación , Análisis de los Alimentos/instrumentación , Análisis de Secuencia por Matrices de Oligonucleótidos/instrumentación , Estrés Oxidativo , Diseño Asistido por Computadora , Diseño de Equipo , Análisis de Falla de EquipoRESUMEN
Reactive oxygen species (ROS) are produced as a consequence of normal aerobic metabolism and are able to induce DNA oxidative damage. At the cellular level, the evaluation of the protective effect of antioxidants can be achieved by examining the integrity of the DNA nucleobases using electrochemical techniques. Herein, the use of an adenine-rich oligonucleotide (dA(21)) adsorbed on carbon paste electrodes for the assessment of the antioxidant capacity is proposed. The method was based on the partial damage of a DNA layer adsorbed on the electrode surface by OH radicals generated by Fenton reaction and the subsequent electrochemical oxidation of the intact adenine bases to generate an oxidation product that was able to catalyze the oxidation of NADH. The presence of antioxidant compounds scavenged hydroxyl radicals leaving more adenines unoxidized, and thus, increasing the electrocatalytic current of NADH measured by differential pulse voltammetry (DPV). Using ascorbic acid (AA) as a model antioxidant species, the detection of as low as 50 nM of AA in aqueous solution was possible. The protection efficiency was evaluated for several antioxidant compounds. The biosensor was applied to the determination of the total antioxidant capacity (TAC) in beverages.
