title: Challenging genosensors in food samples: The case of gluten determination in highly processed samples.
abstract: Electrochemical genosensors have undergone an enormous development in the last decades, but only very few have achieved a quantification of target content in highly processed food samples. The detection of allergens, and particularly gluten, is challenging because legislation establishes a threshold of 20 ppm for labeling as gluten-free but most genosensors expresses the results in DNA concentration or DNA copies. This paper describes the first attempt to correlate the genosensor response and the wheat content in real samples, even in the case of highly processed food samples. A sandwich-based format, comprising a capture probe immobilized onto the screen-printed gold electrode, and a signaling probe functionalized with fluorescein isothiocyanate (FITC), both hybridizing with the target was used. The hybridization event was electrochemically monitored by adding an anti-FITC peroxidase (antiFITC-HRP) and its substrate, tetramethylbenzidine. Binary model mixtures, as a reference material, and real samples have been analyzed. DNA from food was extracted and a fragment encoding the immunodominant peptide of α2-gliadin amplified by a tailored PCR. The sensor was able to selectively detect toxic cereals for celiac patients, such as different varieties of wheat, barley, rye and oats, from non-toxic plants. As low as 0.001% (10 mg/kg) of wheat flour in an inert matrix was reliably detected, which directly compete with the current method of choice for DNA detection, the real-time PCR. A good correlation with the official immunoassay was found in highly processed food samples.
authors.affiliation: Sección Departamental de Química Analítica, Facultad de Farmacia, Universidad Complutense de Madrid, Pz. Ramón y Cajal s/n, 28040 Madrid, Spain. Electronic address: bealopru@ucm.es.
authors.forename: Begoña
authors.initials: B
authors.lastname: Martín-Fernández
authors.affiliation: Departamento de Química Física y Analítica, Universidad de Oviedo, Av. Julián Clavería 8, 33006 Oviedo, Spain. Electronic address: santosnoemi@uniovi.es.
authors.forename: Noemí
authors.initials: N
authors.lastname: de-los-Santos-Álvarez
authors.affiliation: Departamento de Biotecnología - Biología Vegetal, Escuela Técnica Superior de Ingenieros Agrónomos, Universidad Politécnica de Madrid, Ciudad Universitaria s/n, 28040 Madrid, Spain. Electronic address: juanpedro.martin@upm.es.
authors.forename: Juan Pedro
authors.initials: JP
authors.lastname: Martín-Clemente
authors.affiliation: Departamento de Química Física y Analítica, Universidad de Oviedo, Av. Julián Clavería 8, 33006 Oviedo, Spain. Electronic address: mjlc@uniovi.es.
authors.forename: María Jesús
authors.initials: MJ
authors.lastname: Lobo-Castañón
authors.affiliation: Sección Departamental de Química Analítica, Facultad de Farmacia, Universidad Complutense de Madrid, Pz. Ramón y Cajal s/n, 28040 Madrid, Spain. Electronic address: bealopru@quim.ucm.es.
authors.forename: Beatriz
authors.initials: B
authors.lastname: López-Ruiz
mesh_terms: D001483:Base Sequence; D015374:Biosensing Techniques / Q000379:methods*; D002523:Edible Grain / Q000737:chemistry; D004563:Electrochemistry; D005433:Flour / Q000032:analysis; D005504:Food Analysis / Q000379:methods*; D005506:Food Contamination / Q000032:analysis; D005511:Food Handling; D005983:Glutens / Q000032:analysis* / Q000737:chemistry; D015345:Oligonucleotide Probes / Q000737:chemistry / Q000235:genetics; D014908:Triticum / Q000737:chemistry
chemical_list: D015345:Oligonucleotide Probes; D005983:Glutens
keywords: Celiac disease; Disposable electrodes; Electrochemical genosensor; Gluten quantification; Highly processed food; Wheat