Science 334, 204–208 (2011)

The shape of building blocks and the interactions between them often determine the structure the blocks self-assemble into. Except for the simplest lattices — such as the face-centred cubic — designing the building blocks that spontaneously assemble into the desired ordered structure is difficult. Robert Macfarlane and colleagues now report six design rules that can be used to obtain nine specific superlattices from gold nanoparticles functionalized with DNA linkers. The rules provide relationships between three design parameters for the superlattices — crystallographic symmetry, lattice parameters and nanoparticle size within a lattice — and the variables that control the assembly of the DNA–nanoparticle conjugates: hydrodynamic radii, number of linkers and the number of possible hybridizations between linkers. In fact, the authors find that nanoparticles with the same hydrodynamic radius show no differences in their self-assembly. Furthermore, the linkers' rehybridization rate can be used to select between two lattices of similar thermodynamic stability. The synthesis of desired crystal structures by using programmable linker interactions should now be easier, provided one plays by the rules.