Cyclodextrin-covered organic nanotubes derived from self-assembly of dendrons and their supramolecular transformation

Abstract

The dendritic building blocks with a focal pyrene unit self-organize into vesicles in aqueous phase. The in situ inclusion of the focal pyrene units into the cavity of ␤-or ␥-cyclodextrin (CD) induces self-assembled organic nanotubes with an average outer diameter of Ϸ45 nm and inner diameter of 22 nm. The surface of the nanotube is covered with CD. Therefore, the functional group on the surface of the nanotube is controlled simply by modifying the functionality of CD. The removal of CD from the nanotube with poly(propylene glycol) reversibly generates vesicles. This work provides an efficient methodology not only to create an additional class of CD-covered organic nanotubes but also to exhibit reversible transformation of nanotubes and vesicles triggered by the motifs of dendron self-assembly, CD inclusion, and pseudorotaxane formation.vesicle ͉ amphiphile S elf-assembly and transformation of biological or synthetic macromolecules in a wide range of scientific fields are crucial subjects for the achievement of well defined nanostructures and the precise control of the function of supramolecules at the molecular level (1)(2)(3)(4)(5)(6)(7)(8)(9)(10)(11)(12)(13)(14). A multitude of biological or chemical assemblies including vesicle, tubule, fibril, and viral helical coats perform numerous biochemical operations in nature. In particular, vesicular and tubular assemblies are of much interest because of their unique characteristics as a biomimetic system, carrier for drug or gene, biochemical sensor, electronic or photonic material, nanoreactor, and template for hybrid structure (9-18). Therefore, in these viewpoints, self-assembly of synthetic building blocks by noncovalent interactions is expected to provide a unique methodology for creating supramolecular functional materials (5)(6)(7)(8)(9)(10)(11)(12)(13)(14)(15)(17)(18)(19)(20)(21)(22)(23)(24)(25)(26)(27).Self-organization of dendrons (6) into supramolecular assemblies has been demonstrated in a thermotropic fashion (19,27), in aqueous phase (21-25), in organic media (20,22,23,26), and at solid-liquid interface (26). Recently, we reported that the amide dendrons can self-organize in various conditions to exhibit a multiplicity of architectures and functions (22-26). For the preparation of self-assembling nanomaterials, we designed the amide dendritic building blocks consisting of amide branches for hydrogen bonding, carboxyl functionality at the focal point, and alkyl tails for the stabilization of assembled structures by van der Waals interaction (22). Particularly, it was suggested that the dimeric form of the amide dendron, induced by secondary interactions such as hydrogen bonding and -interaction at the focal functional units, is the primary building block in the self-aggregation process in organic media (22,23,26). In addition, the amphiphilic nature of these amide dendritic building blocks provides an opportunity for the formation of various self-assembled nanostructures in aqueous phase. For example, we reported that the transition of the self-organiz...

Biodegradable nanospheres self-assembled from complementary hydrophilic dextran macromers

“…Nanomaterials with diverse morphologies, such as vesicles, fibers, and tubules, have been fabricated through bottom-up molecular self-assembly (Antonietti & Förster, 2003;Park et al, 2006;Yan, Zhou, & Hou, 2004;Yokoi, Kinoshita, & Zhang, 2005). Zhang and Eisenberg (1995) even self-assembled a polystyrene-poly-(acrylic acid) block copolymer into six different morphological yet stable aggregates.…”

Self‐Assembly Vesicles Made from a Cyclodextrin Supramolecular Complex

“…The mechanism of vesicle formation and transition is discussed along with the data obtained from induced circular dichroism (ICD) and UV/visible spectroscopy, polarized optical microscopy (POM), and 1 sions. [9] However, great challenges exist for assembling CD vesicles from natural CD and some other small segments by using noncovalent interactions.…”

Hydrogenated and Fluorinated Host–Guest Surfactants: Complexes of Cyclodextrins with Alkanes and Fluoroalkyl‐Grafted Alkanes

“…[6] They are inherent in capturing appropriate guest molecules into their cavity through host-guest interactions. Nowadays, most "supramolecular amphiphiles" composed of CD/guest molecules [7] or the other couples of complexation are focused on their supramolecular assemblies in solution, for example, vesicles [8] or nanotubes, [9] which are expected to be promising candidates in drug delivery, cell modeling, nanocontainers, and nanoreactors. However, work dealing with the effect of reducing water surface tension, that is, the supramolecular surfactant indeed, are almost in blank.…”