Reversible Supra‐Folding of User‐Programmed Functional DNA Nanostructures on Fuzzy Cationic Substrates

Abstract

We report that user‐defined DNA nanostructures, such as two‐dimensional (2D) origamis and nanogrids, undergo a rapid higher‐order folding transition, referred to as supra‐folding, into three‐dimensional (3D) compact structures (origamis) or well‐defined μm‐long ribbons (nanogrids), when they adsorb on a soft cationic substrate prepared by layer‐by‐layer deposition of polyelectrolytes. Once supra‐folded, origamis can be switched back on the surface into their 2D original shape through addition of heparin, a highly charged anionic polyelectrolyte known as an efficient competitor of DNA‐polyelectrolyte complexation. Orthogonal to DNA base‐pairing principles, this reversible structural reconfiguration is also versatile; we show in particular that 1) it is compatible with various origami shapes, 2) it perfectly preserves fine structural details as well as site‐specific functionality, and 3) it can be applied to dynamically address the spatial distribution of origami‐tethered proteins.

Magnesium-Free Immobilization of DNA Origami Nanostructures at Mica Surfaces for Atomic Force Microscopy

“…We then turned to polyelectrolyte adsorption for modifying the mica surface. The most prominent polyelectrolyte in the present context is probably PLL, which has been used to immobilize dsDNA molecules [ 54 ], DNA-coated nanoparticles [ 55 ], and DNA origami [ 56 , 57 ]. The latter, however, was always performed in the presence of millimolar concentrations of Mg 2+ ions [ 56 , 57 ].…”

“…The most prominent polyelectrolyte in the present context is probably PLL, which has been used to immobilize dsDNA molecules [ 54 ], DNA-coated nanoparticles [ 55 ], and DNA origami [ 56 , 57 ]. The latter, however, was always performed in the presence of millimolar concentrations of Mg 2+ ions [ 56 , 57 ]. As can be seen in Figure 5 a, PLL adsorption at mica resulted in a rather smooth surface topography with an average RMS roughness S q below 0.8 Å, which is slightly lower than for the Ni 2+ -treated surface shown in Figure 3 a.…”