Self-assembly of a cholesteryl-modified nucleoside into tubular structures from giant unilamellar vesicles

Luisa Losensky,Anna Arbuzova,Gudrun Holland,Anca Petran,Jürgen Liebscher,Michael Laue,Salvatore Chiantia

doi:10.1039/c4ra11289j

Abstract

Phosphatidylcholine-assisted self-assembly of cholesterylaminouridine into hollow needle-like structures was observed at room temperature.

Highlights

We have previously reported the self-assembly of CholAU with a phospholipid into nano- and microtubules containing about 80–90 mol% of CholAU starting from 30 : 70 CholAU : DOPC multilamellar vesicles.[25]
Incubation of the CholAU : DOPC mixture at 70 C, presumably supporting the solubilization of CholAU in the DOPC membrane, and cooling to room temperature was reported to be essential for the formation of the tubular structures
We report that the nanotubules were formed even at room temperature when using solubilized CholAU and DMoPC giant unilamellar vesicles, indicating that the limiting factor is the degree of incorporation of the conjugate into the lipid bilayer

Summary

Introduction

Self-assembly of amphiphilic molecules into micelles, vesicles, sheets, or tubular structures are governed by an interplay of hydrophobic interactions, hydrogen bonding, stacking, structure (form, chirality) of the molecules, and interaction with the solvent.[1,2,3,4,5] The pseudo one-dimensional needle-like and tubular structures are of particular interest, as they are found in nature, e.g. cholesterol (Chol) needle-like crystals in bile and atherosclerotic plaques,[6,7] but can be used for different applications, e.g. as templates for inorganic nanotubules and wires, drug-delivery systems, single-molecule sensing, cleaning of water,[8,9,10] and for structuring of edible oils to margarine.[11]Different mechanisms were suggested for the formation of the tubular structures: rolling of membrane sheets, fusion of vesicles, growth of helical structures in width or decreasing pitch.[12,13] the mechanism of the tubular structure assembly is still not well understood; especially as different assembly mechanisms were found in binary systems depending on the molar ratio of the components.[14]Both cholesterol and nucleoside derivatives were reported to self-assemble into needles, helices, tubular structures, orWe have reported on the micro- and nano-tubule formation from 20-N-(2-(cholesteryl)-succinyl)-20-deoxy-20-aminouridine (CholAU, Fig. 1A) with 1,2-dioleoyl-sn-glycero-3-phosphocholine (DOPC) upon cooling of a 30 : 70 CholAU : DOPC (mol%) aqueous suspension from 70 C to room temperature.[25]. Similar rupture of vesicles caused by lysozyme crystals growth was reported previously.[54] One day a er mbCD– CholAU addition, predominantly needle-like structures with some GUVs were observed (Fig. 2B and C).

Results

Conclusion