Solid colloids with surface-mobile DNA linkers.

Surface functionalization with bioinspired binding groups is increasingly used to steer nano- and microscale self-assembly processes, with complementary DNA "sticky ends" as one of the most notable examples. The fabrication of well-organized structures is complicated, however, by the sharp association/dissociation transitions and the slow rearrangement kinetics intrinsic to collections of discrete, surface-immobilized binding groups and is aggravated by natural nonuniformities in the surface coating. Here, we demonstrate a novel system of solid microparticles functionalized with specific binding groups-in this case DNA linkers-that are fully mobile along the particle surface. These colloids display qualitatively new behavior and circumvent many of the commonly encountered issues. Importantly, the association/dissociation transition, and thereby the temperature window for equilibrium self-assembly, is much broader. We further find that the linkers are uniformly distributed above the DNA melting temperature, while visibly accumulating at the interparticle contacts below this temperature. The unique combination of binding group mobility with nondeformability, monodispersity, and facile manipulation of solid particles should have a profound impact on DNA-mediated and other bioinspired self-assembly approaches. Moreover, our highly tunable experimental system enables detailed model investigations that will also deepen our fundamental understanding of other systems with surface-mobile binding groups, for instance, biological ligand-receptor interactions.