(794d) The Role of Spacers On the Self-Assembly of ssDNA Aptamer-Amphiphiles Into Micelles and Nanotapes

Biopolymers formed from nucleic and amino acid building blocks have been used to create functional supramolecular and multi-dimensional structures that rely on extensive intermolecular interactions to produce biocompatible materials with structural order on the nanometer scale for applications in electronics, biosensing, and tissue engineering. Single-stranded DNA (ssDNA) is often used to create these materials as the DNA bases provide an intrinsic molecular code that can be exploited to allow for programmed assembly of structures based upon Watson-Crick base-pairing. However, engineering complex materials and devices from biopolymers alone requires careful design to ensure that the intrinsic forces responsible for organizing them are capable of creating the desired products. Additional control over supramolecular assembly can be achieved by chemically modifying the biopolymers with hydrophobic moieties to create amphiphilic molecules, which adds the hydrophobic effect to the list of contributing forces that help dictate the self-assembly process. This strategy has been widely utilized to form peptide-amphiphiles consisting, typically, of hydrocarbon chains conjugated to hydrophilic peptide headgroups. But despite widespread research utilizing ssDNA for bionanotechnology applications, ssDNA-amphiphiles have not been studied as thoroughly as peptide-amphiphiles. In this work we created a set of ssDNA aptamer-amphiphiles composed of hydrophobic tails, hydrophilic ssDNA aptamer headgroups and different spacer molecules linking these groups together. Through the use of cryo-transmission electron microscopy (cryo-TEM), small angle x-ray scattering (SAXS), and circular dichroism (CD), we found that the aptamer-amphiphiles can assemble into a variety of structures depending on the spacer used. For the first time we demonstrate the presence of self-assembled aptamer-amphiphile nanotapes, and show that the choice of the spacer used in the design of aptamer-amphiphiles influences the self-assembly and secondary structure of the aptamer-amphiphiles.