Vargas Orgaz, EvaPovedano Muñumel, EloyRuiz Valdepeñas Montiel, VíctorTorrente Rodríguez, Rebeca MagnoliaZouari, MohamedMontoya Miñano, Juan JoséRaouafi, NoureddineCampuzano Ruiz, SusanaPingarrón Carrazón, José Manuel2023-06-172023-06-172018-03-151424-822010.3390/s18030863https://hdl.handle.net/20.500.14352/12648This work reports an amperometric biosensor for the determination of miRNA-21, a relevant oncogene. The methodology involves a competitive DNA-target miRNA hybridization assay performed on the surface of magnetic microbeads (MBs) and amperometric transduction at screen-printed carbon electrodes (SPCEs). The target miRNA competes with a synthetic fluorescein isothiocyanate (FITC)-modified miRNA with an identical sequence for hybridization with a biotinylated and complementary DNA probe (b-Cp) immobilized on the surface of streptavidin-modified MBs (b-Cp-MBs). Upon labeling, the FITC-modified miRNA attached to the MBs with horseradish peroxidase (HRP)-conjugated anti-FITC Fab fragments and magnetic capturing of the MBs onto the working electrode surface of SPCEs. The cathodic current measured at −0.20 V (versus the Ag pseudo-reference electrode) was demonstrated to be inversely proportional to the concentration of the target miRNA. This convenient biosensing method provided a linear range between 0.7 and 10.0 nM and a limit of detection (LOD) of 0.2 nM (5 fmol in 25 μL of sample) for the synthetic target miRNA without any amplification step. An acceptable selectivity towards single-base mismatched oligonucleotides, a high storage stability of the b-Cp-MBs, and usefulness for the accurate determination of miRNA-21 in raw total RNA (RNAt) extracted from breast cancer cells (MCF-7) were demonstrated.engAtribución 3.0 Españahttps://creativecommons.org/licenses/by/3.0/es/journal articlehttps://doi.org/10.3390/s18030863https://www.mdpi.com/1424-8220/18/3/863open accessmiRNAscreen-printed electrodeamperometrycompetitive assaymagnetic beadscancer cellsQuímica analítica (Química)2301 Química Analítica