Controlling the number and positions of oligonucleotides on gold nanoparticle surfaces.

We describe a new method to immobilize a given number of oligonucleotides (ODNs) on gold nanoparticles (AuNPs) in a specific arrangement directed by a geometrical template made of DNA. The basic strategy is as follows. First, a set of thiolated ODNs for immobilization and a nonthiolated template are hybridized to make a DNA nanostructure. Next, the DNA nanostructure is reacted with AuNPs via the thiol groups to form a complex of the AuNP and the DNA nanostructure. Finally, the intended AuNP/ODN conjugate is obtained by removing the template from the complex. The above strategy enables us to make various formats of AuNP/ODN conjugates simply by changing the design of the DNA nanostructure. We demonstrate proof-of-concept experiments using a linear design of the DNA nanostructure.