Dynamic metallization of spherical DNA via conformational transition into gold nanostructures with controlled sizes and shapes

Despite the reversible condensation properties of DNA, DNA metallization during controlled conformational transitions has been rarely investigated. We perform dynamic metallization of spherically condensed DNA nanoparticles (DNA NPs) via a globule-to-coil transition. A positively charged new Au³⁺ reagent is prepared via ligand-exchange of conventional complex Au³⁺ ions, which was used to synthesize spherically condensed DNA NPs simply based on the fundamental electrostatic and coordinative interactions between DNA and Au³⁺ ions. Interestingly, the size of the Au³⁺-condensed DNA NPs (Au³⁺-DNA NPs) and the type of reducing agents lead to the formation of different Au nanostructures with unprecedented morphologies (cracked NPs, bowl-shaped NPs, and small NPs), owing to the controlled conformational changes in the Au³⁺-DNA NPs during metallization. The condensed DNA NPs play significant roles for Au nanostructures as (1) the dynamic template for the synthesis, (2) the reservoir and supply of Au³⁺ for the growth, and (3) the surface stabilizer. The synthesized Au nanostructures are remarkably stable against high ionic strength and exhibit catalytic activities and excellent SERS properties. This is the first study on the morphological control and concomitant dynamic metallization of spherically condensed DNA, proposing new synthetic routes for bioinorganic nanomaterials.