Dynamic wireframe DNA structures have gained significant attention in recent years, with research aimed toward using these architectures for sensing and encapsulation applications. For these assemblies to reach their full potential, however, knowledge of the rates of strand displacement and hybridization on these constructs is required. Herein, we report the use of single-molecule fluorescence methodologies to observe the reversible switching between double- and single-stranded forms of triangular wireframe DNA nanotubes. Specifically, by using fluorescently labeled DNA strands, we were able to monitor changes in intensity over time as we introduced different sequences. This allowed us to extract detailed kinetic information on the strand displacement and hybridization processes. Due to the polymeric nanotube structure, the ability to individually address each of the three sides, and the inherent polydispersity of our samples as a result of the step polymerization by which they are formed, a library of compounds could be studied independently yet simultaneously. Kinetic models relying on mono-exponential decays, multi-exponential decays, or sigmoidal behavior were adjusted to the different constructs to retrieve erasing and refilling kinetics. Correlations were made between the kinetic behavior observed, the site accessibility, the nanotube length, and the structural robustness of wireframe DNA nanostructures, including fully single-stranded analogs. Overall, our results reveal how the length, morphology, and rigidity of the DNA framework modulate the kinetics of strand displacement and hybridization as well as the overall addressability and structural stability of the structures under study.
Keywords: dynamic DNA nanotechnology; single-molecule fluorescence; size-dependent kinetics; stimuli-responsive nanomaterials; structural cooperativity.