Supramolecular Nanotube Hosts for Encapsulation of 10-nm-Scale Objects
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0922-U05-01
Supramolecular Nanotube Hosts for Encapsulation of 10-nm-Scale Objects Toshimi Shimizu1,2 1 Nanoarchitectonics Research Center, National Institute of Advanced Industrial Science and Technology (AIST), Tsukuba Central 5, 1-1-1 Higashi, Tsukuba, Ibaraki, 305-8565, Japan 2 SORST, Japan Science and Technology Agency (JST), Tsukuba Central 5, 1-1-1 Higashi, Tsukuba, Ibaraki, 305-8565, Japan
ABSTRACT Supramolecular nanotube hosts with precisely controlled inner or outer diameters have been synthesized by self-assembly of cardanol-based glycolipids, glucopyranosylamide lipids, or glucose-based unsymmetrical bolaamphiphiles. Time-resolved fluorescent measurement using 8anilinonaphtahalene-1-sulfonate (ANS) as a probe revealed that the water confined in a cardanolbased glycolipid nanotube has relatively lower solvent polarity than bulk water, which corresponds to that of 1-propanol. Extensively developed hydrogen bond networks also characterize the confined water in comparison to the case in bulk water. Encapsulation ability of the glucopyranosylamide lipid nanotube, which depends on capillary action, has been examined by filling the lyophilized lipid nanotubes with aqueous dispersions of gold or silver nanocrystals, ferritin, or magnetic crystals. We have also succeeded in filling the unsymmetrical bolaamphiphile nanotube, which possesses positively charged inner surfaces, with negatively charged polymer beads or ferritin without depending on capillary action. INTRODUCTION Lipid nanotubes (LNTs) with 10−100-nm-scale hollow cylinders have been again receiving much interest because of their resemblance to carbon nanotubes in size dimensions, their unique shapes, and prospective technological applications [1]. In particular, cylindrical hollows of the LNTs with high-axial ratios have many potential applications as nanochannels for nanofluidic devices, templates for metal nanowire formation, and size-selective pores for analytical and/or storage devices. Though a limited number of synthetic lipid monomers have been well documented to self-assemble into tubular structures, there have been no definitive guiding principles to manipulate the nanotube morphologies. Discrete, organic, hollow cylinder architectures are also of great interest in nanomaterials science owing to the continuing interest in nano-space-specific fundamental phenomena [2]. However, filling the inner core of the LNTs with high axial ratios with a foreign constituent has never been addressed although we can refer to one example of the metal deposition inside tobacco mosaic virus [3]. Here we describe chiral self-assembly of synthetic glycolipid monomers into uniform hollow cylinder structures in approximately 100% yields, which has been achieved by optimizing the introduction position of a cis-double bond in the unsaturated hydrocarbon chains in a series of glucopyranosylamide lipids [4]. In addition, we have for the first time succeeded in the confined organization of gold nanocrystals [5,6] or ferritin [7] at room temperature by filling a vacant
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