Solubilisation and transformation of amphipathic lipidic dendron vesicles (dendrisomes) into mixed micelles

Abstract

A novel lipidic peptide dendron was synthesised using solid-phase techniques. To a third-generation polylysine dendron were coupled eight α-amino tetradecanoic acid (C14) molecules to the eight Nα and Nε of the terminal lysines and three pendant C14 chains were coupled to the C-terminal of the starting lysine. This novel dendron was found to self-assemble in water into vesicular structures or "dendrisomes". These dendrisomes were prepared using a reverse-phase evaporation (REV) technique and visualised by transmission electron microscopy (TEM). The interaction of these second order structures with the non-ionic surfactant iso-octyl phenyl poly(10)oxyethylene ether (Triton X-100) was studied by turbidimetry, photon correlation spectroscopy (PCS) and TEM. Quantitative estimation of the solubilised peptide dendron was carried out by the bicinchoninic acid (BCA) assay. The dendrisomes are transformed into surfactant-dendron mixed micelles. The dispersion became optically clear at a concentration 8 mM (13.4:1 Triton X-100:dendron molar ratio). When the concentration of the surfactant was increased up to 60-100 mM (100-170:1 Triton X-100:dendron molar ratio) the aggregate diameter decreased to the micellar range, namely 12-50 nm. At a 100:1 Triton X-100:dendron molar ratio, the BCA assay showed complete dendron solubilisation. This suggests that the cationic lipidic dendron and their assemblies can be solubilised by amphipathic non-ionic moieties when the surfactant-dendron interaction is more energetically favourable than dendron-dendron and surfactant-surfactant interactions. © 2005 Elsevier B.V. All rights reserved.