Optimized Assembly and Covalent Coupling of Single-Molecule DNA Origami Nanoarrays

Artificial DNA nanostructures, such as DNA origami, have great potential as templates for the bottom-up fabrication of both biological and nonbiological nanodevices at a resolution unachievable by conventional top-down approaches. However, because origami are synthesized in solution, origami-templated devices cannot easily be studied or integrated into larger on-chip architectures. Electrostatic self-assembly of origami onto lithographically defined binding sites on Si/SiO₂ substrates has been achieved, but conditions for optimal assembly have not been characterized, and the method requires high Mg²⁺ concentrations at which most devices aggregate. We present a quantitative study of parameters affecting origami placement, reproducibly achieving single-origami binding at 94 ± 4% of sites, with 90% of these origami having an orientation within ±10° of their target orientation. Further, we introduce two techniques for converting electrostatic DNA–surface bonds to covalent bonds, allowing origami arrays to be used under a wide variety of Mg²⁺-free solution conditions.