Site-selective immobilization of gold nanoparticles functionalized with DNA oligomers

The organization of metal and semiconductor nanoparticles to form micro- and nanostructured assemblies is currently of tremendous interest. This communication reports on the utilization of DNA molecules as positioning elements for generating microstructured surface architecture from gold nanoparticles. Citrate-passivated 40 nm gold colloids were modified by chemisorptive coupling with a 5′-thiol-derivatized DNA oligomer. The nucleic acid was used as a molecular handle for the specific immobilization on solid supports, previously functionalized with capture DNA oligomers, complementary to the nanoparticle-bound DNA. As a consequence of the enormous specificity of nucleic acid hybridization, the DNA-directed immobilization (DDI) allows, to site-specifically target the hybrid nanoparticles to microlocations which contain the complementary oligomers. The site-selectivity of the surface adsorption is demonstrated by immobilizing the gold colloids on a DNA microarray on a glass cover slide. Moreover, scanning force microscopy (SFM) analysis, used to characterize the intermediate steps of the DDI on a gold substrate, provided initial insights into the specificity and efficiency of this technique. The application of the DDI to fabricate complex colloidal micro- and nanostructures is anticipated. Received: 26 July 2000/Accepted: 5 October 2000