Construction of superlattice structures via controlled assembly of individual nanoparticles is an area of significant interest because such materials have the potential for exhibiting collective behaviors and properties different from those of the individual particles. Cage-like proteins such as virus-like particles (VLPs) are promising building blocks for constructing protein-based superlattice materials because they can encapsulate various functional cargo molecules, such as enzymes, within their interior cavities. We demonstrated the one-pot self-assembly of multilayered face-centered cubic (FCC) superlattices from a mixed population of VLP building blocks derived from bacteriophage P22, where each layer is composed of the same type of building blocks (Figure). This selective, spatially segregated assembly is achieved by modulating two material attributes: the surface charge of the building blocks and the ionic strength of the sample solution. The surface charge of P22 VLP was tuned systematically by introducing two repeats of heptapeptides at the C-terminus of the P22 coat protein, which is exposed on the exterior of the P22 VLP. The ionic strength of the sample solution was gradually altered through step-by-step dialysis to facilitate the assembly process. Furthermore, we recently demonstrated temperature-dependent reversible assembly of VLP superlattices. An FCC superlattice disassembled into individual VLPs at 4 °C and reversibly reassembled at higher temperatures. Together, our studies are a step toward designing stimuli-responsive superlattice materials via controlled assembly of protein-based building blocks.

Super-resolution fluorescence microscope observation of P22 VLP superlattices formed in a mixture of four types of VLPs after a step-by-step dialysis from I = 823 mM to 41 mM. P22-E3₂, P22-E₂, P22-Q₂, and P22-K₂ were labeled with Alexa-488 (green), Texas Red (red), and CF405M (blue), and Alexa-488 (green) fluorescent dyes, respectively.

Nathasha Hewagama

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