Femtomolar level detection of RASSF1A tumor suppressor gene methylation by electrochemical nano-genosensor based on Fe3O4/TMC/Au nanocomposite and PT-modified electrode

The alterations in DNA methylation pattern have been identified as one of the most frequent molecular phenomenon in human cancers. The RASSF1A tumor suppressor gene was shown to be often inactivated by hypermethylation of its promoter region. In the present study, a novel chip format sandwich electrochemical genosensor has been developed for the analysis of gene-specific methylation using Fe3O4/Ntrimethyl chitosan/gold (Fe3O4/TMC/Au) nanocomposite as tracing tag to label DNA probe and polythiophene (PT) as immobilization platform of sensing element. However, no attempt has yet been made to conjugate DNA probe to Fe3O4/TMC/Au nanocomposite as electrochemical label for strip-based genosensing. Cyclic voltammetric (CV) analysis indicated that modification procedure was well performed. Differential pulse voltammetry (DPV) was employed for quantitative assessment of RASSF1A DNA promoter methylation. The electrochemical measurements accomplished using non-specific DNA fragments mixed with samples, revealed the high specificity and selectivity in methylation analysis by means of this DNA nanobiosensor. With the linear range of concentration from 1 x 10(-14) M to 5 x 10(-9) M and the detection limit of 2 x 10(-15) M, this new strategy has shown such a promising application to be used for universal analysis of any DNA sequence. (C) 2015 Elsevier B.V. All rights reserved.