Electrochemical affinity biosensors for fast detection of gene-specific methylations with no need for bisulfite and amplification treatments

This paper describes two different electrochemical affinity biosensing approaches for the simple, fast and bisulfite and PCR-free quantification of 5-methylated cytosines (5-mC) in DNA using the anti-5-mC antibody as biorecognition element. One of the biosensing approaches used the anti-5-mC as capture bioreceptor and a sandwich type immunoassay, while the other one involved the use of a specific DNA probe and the anti-5-mC as a detector bioreceptor of the captured methylated DNA. Both strategies, named for simplicity in the text as immunosensor and DNA sensor, respectively, were implemented on the surface of magnetic microparticles and the transduction was accomplished by amperometry at screen-printed carbon electrodes by means of the hydrogen peroxide/hydroquinone system. The resulting amperometric biosensors demonstrated reproducibility throughout the entire protocol, sensitive determination with no need for using amplification strategies, and competitiveness with the conventional enzyme-linked immunosorbent assay methodology and the few electrochemical biosensors reported so far in terms of simplicity, sensitivity and assay time. The DNA sensor exhibited higher sensitivity and allowed the detection of the gene-specific methylations conversely to the immunosensor, which detected global DNA methylation. In addition, the DNA sensor demonstrated successful applicability for 1 h-analysis of specific methylation in two relevant tumor suppressor genes in spiked biological fluids and in genomic DNA extracted from human glioblastoma cells.The financial support of the Spanish Ministerio de Economía y Competitividad CTQ2015-64402-C2-1-R and SAF2014-53209-R Research Projects, the PI17CIII/00045 research project from AESI and the NANOAVANSENS Program from the Comunidad de Madrid (S2013/MT-3029) and predoctoral contracts from the Spanish Ministerio de Economía y Competitividad (R.M. Torrente-Rodríguez and E. Povedano) and Universidad Complutense de Madrid (V. Ruiz-Valdepeñas Montiel) are also gratefully acknowledged.S