DNA Nanostructures as Intracellular Biosensors in Single Live Human Cells

No two genetically-identical human cells are exactly the same. In the last decade, in vivo studies have revealed that even subtle differences in size, concentration of components, cell cycle stage, make the 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. As it was first shown by the group of Turberfield [1], and then mastered also by other [2], self-assembled DNA nanostructures can be introduced in live cells, even without the aid of transfecting agents (such as lipids) or by altering the membrane permeability otherwise. We describe the methods to design and prepare DNA-based fluorescent tetrahedral nanostructures, to deliver them to live cells and characterize such cells with epifluorescence microscopy. We report that HeLa cells internalize these nanostructures spontaneously with a higher efficiency with respect to single-stranded or double-stranded oligonucleotides. These type of findings clearly suggest that DNA tetrahedra can serve as a platform for the realization of a series of multifunctional intracellular biosensors for the study of single live cells. It is conceivable that a variety of biosensors nanostructures can be realized in the future and these will help towards the elucidation of the intimate clockwork of cells' functioning.