High Throughput Exploration of Nanoparticle Assemblies using Physically-Tethered DNA Bonds

DNA is a powerful tool to assemble nanoparticles due to its programmability and ability to bond to nanoparticle surfaces using chemical modifications. In this work, a single-stranded DNA molecule modified with cholesterol functional groups is physically tethered to nanoparticles using a lipid layer, which allows for increased DNA mobility over the surface of the nanoparticle, and the ability to bond over several types of nanoparticle surfaces (e.g. silica, gold, clay). First, we used high-throughput experimentation to optimize the formation of lipid bilayers over the surface of nanoparticles using specially formulated lipid mixtures. The formation of the desired structure was then confirmed with dynamic light scattering (DLS), SAXS, and zeta-potential measurements. To induce the assembly of the nanoparticles coated with lipid bilayers, single-stranded DNA modified with cholesterol functional groups is first added followed by NaCl to reduce the electrostatic repulsion, allowing for a higher grafting density of DNA on the surface of the nanoparticle. A DNA ‘linker’ molecule is added with complementary nucleotides to the two particle-tethered DNA on each end. A controlled thermal cycling protocol is used to induce controlled hybridization and form DNA-guided nanoparticle assemblies. Using automated liquid handling tools, the assemblies can be created in high throughput and rapidly characterized using small angle x-ray scattering. This allows for the efficient exploration of the large experimental design space (e.g. reagent concentrations, thermal history, solution conditions). Finally, we explore the effect of fluctuations by comparing the extent of organization in nanoparticles functionalized by saturated and unsaturated lipid bilayers leading to different extents of lateral fluctuations.