Ultrasensitive detection of cancer biomarkers using conducting polymer/electrochemically reduced graphene oxide-based biosensor: Application toward BRCA1 sensing

Breast Cancer (BRCA) is the most common threat in women worldwide. Increasing death rate of diagnosed cases is the main leading cause of designing specific genosensors for BRCA-related cancer detection. In the present study, an ultrasensitive label-free electrochemical DNA (E-DNA) sensor based on conducting polymer/reduced graphene-oxide platform has been developed for the detection of BRCA1 gene. An electrochemical method was applied as a simple and controllable technique for the electrochemical reduction of graphene oxide and also, electro-polymerization of pyrrole-3-carboxylic acid monomer. The results of the present work show that the polymer-coated reduced graphene-oxide provide more active sites compare to polymer-coated glassy carbon electrode for the DNA probe immobilization. The fabricated signal-off E-DNA sensor employs Cyclic Voltammetry (CV), Differential Pulse Voltammetry (DPV) and Electrochemical Impedance Spectroscopy (EIS) techniques for monitoring the electrochemical behavior of the redox probe. To survey the morphological pattern and surface structural characterizations, the Atomic Force Microscopy (AFM) and Scanning Electron Microscopy (SEM) have been applied, respectively. The applicability of the modified surface layer toward DNA sensing was evaluated by both DPV and EIS measurements. This platform permits quantitative determination of BRCA1 in the range of 10 fM-0.1 mu M with a limit of detection as low as 3 fM. The proposed genosensor showed a perfect discriminatory power between complementary, non-complementary and mismatched DNA sequences. The described method combined the outstanding features in terms of selectivity, sensitivity, repeatability, reproducibility and remarkable reusability, without demanding for labor-intensive labeling steps. Moreover, the modified electrode was successfully used for accurate determination of trace amounts of DNA target in blood plasma samples. (C) 2018 Elsevier B.V. All rights reserved.