Sensitivity enhancement of graphene/zinc oxide nanocomposite-based electrochemical impedance genosensor for single stranded RNA detection

Publication date: 15 August 2017
Source:Biosensors and Bioelectronics, Volume 94
Author(s): Sze Shin Low, Hwei-San Loh, Jian Sheng Boey, Poi Sim Khiew, Wee Siong Chiu, Michelle T.T. Tan
An efficient electrochemical impedance genosensing platform has been constructed based on graphene/zinc oxide nanocomposite produced via a facile and green approach. Highly pristine graphene was synthesised from graphite through liquid phase sonication and then mixed with zinc acetate hexahydrate for the synthesis of graphene/zinc oxide nanocomposite by solvothermal growth. The as-synthesised graphene/zinc oxide nanocomposite was characterised with scanning electron microscopy (SEM), transmission electron microscopy (TEM), Raman spectroscopy and X-ray diffractometry (XRD) to evaluate its morphology, crystallinity, composition and purity. An amino-modified single stranded DNA oligonucleotide probe synthesised based on complementary Coconut Cadang-Cadang Viroid (CCCVd) RNA sequence, was covalently bonded onto the surface of graphene/zinc oxide nanocomposite by the bio-linker 1-pyrenebutyric acid N-hydroxysuccinimide ester. The hybridisation events were monitored by electrochemical impedance spectroscopy (EIS). Under optimised sensing conditions, the single stranded CCCVd RNA oligonucleotide target could be quantified in a wide range of 1.0×10^–11M to 1.0×10⁻⁶ with good linearity (R =0.9927), high sensitivity with low detection limit of 4.3×10^–12M. Differential pulse voltammetry (DPV) was also performed for the estimation of nucleic acid density on the graphene/zinc oxide nanocomposite-modified sensing platform. The current work demonstrates an important advancement towards the development of a sensitive detection assay for various diseases involving RNA agents such as CCCVd in the future.



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