Self-assembled functional DNA Nanostructures as intracellular biosensors in single live human cells

In the last decade, in vivo studies have revealed that even subtle differences in size, concentration of components, or cell-cycle stage, make genetically-identical cells in a population respond differently to the same stimulus. In order to characterize such complexity of behavior and shed more light on the functioning and communication amongst cells, researchers are developing strategies to study single live cells in a population. Self-assembled DNA nanostructures can be introduced in live cells, even without the aid of transfecting agents or by altering the membrane permeability otherwise. Recently, we have worked on the methods to design and prepare DNA-based fluorescent tetrahedral nanostructures, to deliver them to live cells and characterize such cells with fluorescence microscopy [3]. We have designed two types of sensitive DNA nanostructures (nanobiosensors). These are variation on the DNA tetrahedron motif introduced by the Turberfield group. Sensing of the desired target leads to a significant conformational change in the nanostructure that can be visualized (in solution or in the cells) via the spectroscopic properties of a FRET pair. For example, by exploiting and tuning the properties of an intramolecular CT-motif triple helix, we designed and tested a nanostructure that can undergo a conformational transition driven by a change in pH, in a physiologically-relevant range. We showed the functioning of such functional nanostructures and their internalization in live cultured cells.