R. Wang, W. Liu
Missouri University of Science and Technology,
Keywords: electrochemical biosensor, DNA origami, label-free
Summary:MicroRNAs (miRNAs) have emerged as the promising molecular biomarkers for early diagnosis, and enhanced understanding of the molecular pathogenesis of cancers as well as certain diseases. Here, a facile, label-free, and amplification-free electrochemical biosensor was developed to detect miRNA by using DNA origami nanostructure-supported DNA probes, with methylene blue (MB) serving as the hybridization redox indicator. In this design, DNA origami was utilized, for the first time, as the miRNA sensing platform to provide a large number of free-standing DNA probes for capturing target nucleic acids with enhanced probe accessibility. In addition, the DNA origami probes were immobilized on the working electrode surface via electrostatic adsorption between a cationic and biodegradable chitosan film and negatively charged DNA origami nanostructures. This method offered the advantage of, not only providing a simple, yet stable attachment of DNA origami on the electrode surface, but also avoiding the use of modified thiol-DNA or biotin-DNA. With a facile fabrication method that does not require laborious labeling, probe immobilization, and signal amplification, our strategy promises the aforementioned advantages in determining the concentration of miRNA. The successful immobilization of DNA probes (ss-DNA) and its hybridization with targeted miRNA-21 molecules were confirmed by electrochemical impedance spectroscopy (EIS) and cyclic voltammetry (CV) methods. This strategy employed for determination of target miRNA-21 in cancer exhibited high sensitivity. Its linear detection range was from 0.1pm to 10nM with a lower detection limit of 78.3 fM. The selectivity of the miRNA biosensor was also studied by observing the discrimination ability of a non-complementary target. Overall, this strategy has demonstrated great potential for sensitive, selective and label-free determination of miRNA in cancer diagnosis at the early stage, and prognosis of certain diseases.