Protein-Mediated Colloidal Assembly.

Programmable colloidal assembly enables the creation of mesoscale materials in a bottom-up manner. Although DNA oligonucleotides have been used extensively as the programmable units in this paradigm, proteins, which exhibit more diverse modes of association and function, have not been widely used to direct colloidal assembly. Here we use protein-protein interactions to drive controlled aggregation of polystyrene microparticles, either through reversible coiled-coil interactions or through intermolecular isopeptide linkages. The sizes of the resulting aggregates are tunable and can be controlled by the concentration of immobilized surface proteins. Moreover, particles coated with different protein pairs undergo orthogonal assembly. We demonstrate that aggregates formed by association of coiled-coil proteins, in contrast to those linked by isopeptide bonds, are dispersed by treatment with chemical denaturants or soluble competing proteins. Finally, we show that protein-protein interactions can be used to assemble complex core-shell aggregates. This work illustrates a versatile strategy for engineering colloidal systems for use in materials science and biotechnology.