Cyanine-Mediated DNA Nanofiber Growth with Controlled Dimensionality.

Supramolecular one-dimensional (1D) architectures are of high interest in drug delivery and templation of complex linear arrays due to their high aspect ratio and rigidity. A particular desire is the access of 1D nanostructures with high functionality and biorelevance, which opens the door to  their applications in materials science and nanomedicine. Here we report the discovery that the site-specific introduction of a cyanine (Cy3) dye unit in sequence-defined DNA amphiphiles causes a complete shift of the overall structure from spheres to 1D DNA nanofibers in aqueous media. We show that the generation of DNA nanofibers is dependent on the presence of cyanine units and their position within the DNA-polymer hybrid. We further demonstrate an example of stimuli-responsive shape-shifting DNA nanofibers to highlight the role of the dye in the overall assembly. Notably, we show the preparation of fibers with controlled length by seeded-growth mechanism. Additionally, the DNA nanofibers exhibit a change in Cy3 dye optical properties upon assembly, typical of cyanine dye aggregation, which can be used to monitor the fiber growth process. To demonstrate the functionality of these structures, we show the templation of gold nanoparticles (AuNP) along the fiber length and demonstrate the directional templation of DNA nanofibers on rectangular DNA origami. Our findings provide a method for generating functional nanomaterials and hierarchical complex architectures and show promise as a platform for biosensing and targeted drug delivery.