A label-free electrochemical DNA biosensor based on thionine functionalized reduced graphene oxide

In this paper, a transducing interface was designed on a glassy carbon electrode (GCE) to construct a label-free DNA biosensor. The interface was consisted of capture DNA sequence (CP), gold nanoparticles (AuNPs), and thionine functionalized reduced graphene oxide (Thi-rGO). The signal transduction induced directly from redox reaction of thionine because of the excellent electrochemical activity of Thi in the Thi-rGO nanocomposite. However, the redox reaction will be hindered by the biomolecules that immobilized subsequently onto the surface of GCE. Therefore, the determination of target sequence (tDNA) can be realized by monitoring the voltammetric response current of Thi before and after the hybridization between CP and tDNA. Under the optimal conditions, the peak current decreased linearly with the logarithm of concentration of tDNA in the range from 1.0 x 10(-17) to 1.0 x 10(-12) M with a detection limit of 4.28 x 10(-19) M(S/N = 3). The DNA biosensor showed the advantage of acceptable selectivity, good stability and fabrication reproducibility. The proposed DNA biosensor was applied for tDNA detection in a real biological sample, and good recoveries were obtained from 95.61 to 101.8%. (C) 2017 Elsevier Ltd. All rights reserved.