Reversible Self‐Assembly of Nucleic Acids in a Diffusiophoretic Trap

The steep salt gradient generated by an electrolyte-filled micropipette can be utilized for diffusiophoretic trapping of charged colloids and molecules. The trap can localize, concentrate and promote hybridization between complementary DNA strands, and facilitate the self-assembly of DNA nanostructures into DNA gels. Assembly of the gel only occurs under non-equilibrium conditions, when the salt gradient is present.

Abstract

The formation and dissociation of duplexes or higher order structures from nucleic acid strands is a fundamental process with widespread applications in biochemistry and nanotechnology. Here, we introduce a simple experimental system—a diffusiophoretic trap—for the non-equilibrium self-assembly of nucleic acid structures that uses an electrolyte gradient as the driving force. DNA strands can be concentrated up to hundredfold by a diffusiophoretic trapping force that is caused by the electric field generated by the electrolyte gradient. We present a simple equation for the field to guide selection of appropriate trapping electrolytes. Experiments with carboxylated silica particles demonstrate that the diffusiophoretic force is long-ranged, extending over hundreds of micrometers. As an application, we explore the reversible self-assembly of branched DNA nanostructures in the trap into a macroscopic gel. The structures assemble in the presence of an electrolyte gradient, and disassemble upon its removal, representing a prototypical adaptive response to a macroscopic non-equilibrium state.

Zum Volltext