G4-DNA-coated gold nanoparticles: synthesis and assembly

Here, we describe the preparation of stable 15 nm gold nanoparticles (Au-NPs) coated with parallel-stranded G-quadruplexes (G4-DNA), comprising phosphorothioate residues on both sides of the DNA. Phosphorothioate residues located on the surface of the coated particles can anchor them to noncoated ones. Their incubation with more than 20-fold excess of 15 nm citrate-stabilized Au-NPs leads to the formation of flower-shaped structures comprising a central noncoated particle and five to six G-quadruplex-coated ones at the periphery, as revealed by TEM imaging analysis. The absorption band of the structures is shifted toward long wavelengths compared to individual particles not connected to each other. We show a strong dependence of plasmon coupling strength on the length of the DNA connecting Au-NPs.