Hybridization on DNA-Coated Ultrasmall Gold Nanoparticles (2 nm)

Ultrasmall gold nanoparticles were functionalized with covalently attached DNA strands of 20 or 30 nucleotides. This was achieved via click chemistry with alkyne-terminated DNA and azide-terminated gold nanoparticles. The particles were characterized by high-resolution transmission electron microscopy, UV-Vis spectroscopy, fluorescence spectroscopy, and small-angle X-ray scattering. The DNA strands were fluorescently labelled with either FAM or Cy3, permitting their detection and quantification on the nanoparticle surface. Complementary DNA strands were attached to the nanoparticles via hybridization. The connection of gold nanoparticles by complementary DNA strands was also demonstrated. In-situ fluorescence spectroscopy confirmed the hybridization at ambient temperature and the melting of the DNA strands at elevated temperature. The hybridization was confirmed by fluorescence spectroscopy with the FRET effect. This opens broad possibilities for the noncovalent functionalization of ultrasmall nanoparticles.