DNA-guided crystallization of colloidal nanoparticles

Abstract

The idea that DNA base pairing could direct the crystallization of useful materials is a tempting one for nanotechnologists. Now — over ten years after it was first shown that DNA attached to nanoparticles can influence their assembly — two groups have put this concept into practice. Park et al. demonstrate that the DNA molecules attached to gold nanoparticles, and DNA molecules used to link them, can be selected to ensure that the nanoparticles self-assemble into either face-centred cubic or body-centred cubic crystals. The cover graphic, by Cole Krumbholz, is a close-up of the latter. Nykypanchuk et al. identify the requirements for DNA design and the crystallization conditions that allow the reversible formation of body-centred cubic crystals, with nanoparticles occupying just a few percent of a lattice volume. As discussed in News & Views, these developments might make it possible to create ordered and tunable 3D nanoscale architectures relevant for photonic and magnetic applications, biomedical sensing, and information or energy storage. This paper demonstrates that the interactions between complementary DNA strands attached to nanoparticle surfaces can be tuned to drive the reversible formation of three-dimensional crystals with an open structure. The hope now is that the approach might be extended further, to provide easy access to new classes of ordered multicomponent materials with useful properties. Many nanometre-sized building blocks will readily assemble into macroscopic structures. If the process is accompanied by effective control over the interactions between the blocks and all entropic effects1,2, then the resultant structures will be ordered with a precision hard to achieve with other fabrication methods. But it remains challenging to use self-assembly to design systems comprised of different types of building blocks—to realize novel magnetic, plasmonic and photonic metamaterials3,4,5, for example. A conceptually simple idea for overcoming this problem is the use of ‘encodable’ interactions between building blocks; this can in principle be straightforwardly implemented using biomolecules6,7,8,9,10. Strategies that use DNA programmability to control the placement of nanoparticles in one and two dimensions have indeed been demonstrated11,12,13. However, our theoretical understanding of how to extend this approach to three dimensions is limited14,15, and most experiments have yielded amorphous aggregates16,17,18,19 and only occasionally crystallites of close-packed micrometre-sized particles9,10. Here, we report the formation of three-dimensional crystalline assemblies of gold nanoparticles mediated by interactions between complementary DNA molecules attached to the nanoparticles’ surface. We find that the nanoparticle crystals form reversibly during heating and cooling cycles. Moreover, the body-centred-cubic lattice structure is temperature-tuneable and structurally open, with particles occupying only ∼4% of the unit cell volume. We expect that our DNA-mediated crystallization approach, and the insight into DNA design requirements it has provided, will facilitate both the creation of new classes of ordered multicomponent metamaterials and the exploration of the phase behaviour of hybrid systems with addressable interactions.