Development of Toroidal Nanostructures by Self-Assembly: Rational Designs and Applications

Abstract

Toroidal nanostructures are symmetrical ring-shaped structures with a central internal pore. Interestingly, in nature, many transmembrane proteins such as β-barrels and α-helical bundles have toroidal shapes. Because of this similarity, toroidal nanostructures can provide a template for the development of transmembrane channels. However, because of the lack of guiding principles for the construction of toroids, researchers have not widely studied the self-assembly of toroidal nanostructures as compared with the work on other supramolecular architectures. In this Account, we describe our recent efforts to construct toroidal nanostructures through the self-assembly of rationally designed building blocks. In one strategy for building these structures, we induce interfacial curvatures within the building blocks. When we laterally graft a bulky hydrophilic segment onto a p-oligophenyl rod or β-sheet peptides, the backbones of the self-assembled structures can bend in response to the steric effect of these large side groups, driving the p-oligophenyl rod or β-sheet peptides to form nanosized toriods. In another strategy, we can build toroids from bent-shaped building blocks by stacking the macrocycles. Aromatic segments with an internal angle of 120° can associate with each other in aqueous solution to form a hexameric macrocycle. Then these macrocycles can stack on top of each other via hydrophobic and π-π interactions and form highly uniform toroidal nanostructures. We provide many examples that illustrate these guiding principles for constructing toroidal nanostructures in aqueous solution. Efforts to create toroidal nanostructures through the self-assembly of elaborately designed molecular modules provide a fundamental approach toward the development of artificial transmembrane channels. Among the various toroids that we developed, a few nanostructures can insert into lipid membranes and allow limited transport in vesicles.

Frame‐Guided Assembly of Amphiphiles

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Computational simulation of palm kernel oil-based esters nano-emulsions aggregation as a potential parenteral drug delivery system

“…The pore inducing peptides are amphipathic because the peptides are located at the water-lipid interface in the polar headgroups throughout the channel. The toroid with hydrophilic exterior functions as proton channels across a lipid bilayer (Kim et al, 2013).…”

Photoresponsive, Water‐Soluble Supramolecular Dendronized Polymer with Specific Lysosome‐Targetable Bioimaging Application in Living Cells

“…Although various responsive side/main chain SDPs responding to external temperature, solvents, and anions have been developed for functional materials, there are only few reports referring to photoresponsive SDPs . Specifically, main chain SDPs are usually constructed by non‐covalent forces such as multiple hydrogen bonding, metal coordination, and π–π interaction . Nevertheless, little attention has been paid to main chain SDP by host–guest interaction .…”