Title
Ligand-Induced G-Quadruplex Polymorphism: A DNA Nanodevice for Label-Free Aptasensor Platforms
Author
Prashant S. Deore, Micaela D. Gray, Andrew J. Chung, Richard A. Manderville
Year
2019
Journal
JACS
Abstract
G-Quadruplexes (GQs) serve as popular recognition elements for DNA aptasensors and are incorporated into a DNA nanodevice capable of controlled conformational changes to activate a sensing mechanism. Herein we highlight the utility of a GQ–GQ nanodevice fueled by GQ-specific ligands as a label-free aptasensor detection strategy. The concept was first illustrated utilizing the prototypical polymorphic human telomeric repeat sequence (H-Telo22, d[AG3(T2AG3)3]) that can undergo ligand-induced topology changes between antiparallel, parallel, or hybrid GQ structures. The H-Telo22−ligand interactions served as a model of the GQ–GQ nanodevice. The utility of the device in a real aptasensor platform was then highlighted utilizing the ochratoxin A (OTA) binding aptamer (OTABA) that folds into an antiparallel GQ in the absence and presence of target OTA. Three cationic fluorogenic ligands served as GQ-specific light-up probes and as potential fuel for the GQ–GQ nanodevice by producing an inactive GQ topology (parallel or hybrid) of OTABA. Our findings demonstrate efficient OTA-mediated dye displacement with excellent emission sensitivity for OTA detection when the fluorogenic dyes induce a topology change in OTABA (parallel or hybrid). However, when the fluorogenic dye fails to induce a conformational change in the antiparallel fold of OTABA, subsequent additions of OTA to the aptamer–dye complex results in poor dye displacement with weak emission response for OTA detection. These results are the first to exemplify a ligand-induced GQ–GQ nanodevice as an aptasensor mechanism and demonstrate diagnostic applications for topology-specific GQ binders.
Full Article
Instrument
J-815
Keywords
Circular dichroism, G-quadruplex structure, Ligand binding, Thermodynamics, Nanostructures, Materials, Biochemistry