Self-assembled amphiphiles

Gompper G and Schick M 1994 Self-assembling amphiphilic systems Transitions and Critical Phenomena vol 16, ed C Domb and J L Lebowitz (New York Academic)... 

Hawker C J, Seville P M and White J W 1994 The synthesis and characterization of a self-assembling amphiphilic fullerene J. Org. Chem. 59 3503-5... 

G. Gompper, M. Schick. In C. Domb, J. L. Lebowitz, eds. Phase Transitions and Critical Phenomena, Vol. 16, Self-assembling Amphiphilic Systems. London Academic Press, 1994. 

The formation of polymeric capsules can also be achieved by the cross-linking of self-assembled amphiphilic block copolymers [85]. The hydrophobic section of the polymer in an aqueous solution will tend to aggregate on the interior of the micelle, whereas the hydrophilic ends will form the outer shell of the micelle. If the hydrophilic end is appropriately functionalized, it can be cross-linked, giving a polymeric shell. The overarching concept is shown in Figure 5.10. 

Micelles formed by self-assembled amphiphilic polymers (such as PEG-phosphatidyl ethanolamine) can also be loaded with amphiphilic PL-based chelates carrying diagnostically important metal ions such as In and Gd [20]. The final preparations are quite stable and serve as fast and efficient agents for scintigraphy or MR imaging. 

Martinez JS, Zhang GP, Flolt PD, Jung FIT, Carrano CJ, Haygood MG, Butler A (2000) Self-assembling Amphiphilic Siderophores from Marine Bacteria. Science 287 1245... 

Hakanpaa J, Paananen A, Askolin S, Nakari-SetalaT, Parkkinen T, Penttila M, Linder MB, Rouvinen J, Atomic resolution structure of the HFBII hydrophobin, a self-assembling amphiphile, /Biol Chem 279 534—539, 2004. 

Dworkin, J. D., Deamer, D. W., Sandford, S., and Allmandola, L. (2001). Self-assembling amphiphilic molecules synthesis in simulated interstellar/precometary ices. Proc. Natl. Acad. Sci., 98, 815-19. 

Liposomes and micelles are lipid vesicles composed of self-assembled amphiphilic molecules. Amphiphiles with nonpolar tails (i.e., hydrophobic chains) self-assemble into lipid bilayers, and when appropriate conditions are present, a spherical bilayer is formed. The nonpolar interior of the bilayer is shielded by the surface polar heads and an aqueous environment is contained in the interior of the sphere (Figure 10.3A). Micelles are small vesicles composed of a shell of lipid the interior of the micelle is the hydrophobic tails of the lipid molecules (Figure 10.3B). Liposomes have been the primary form of lipid-based delivery system because they contain an aqueous interior phase that can be loaded with biomacromolecules. The ability to prepare liposomes and micelles from compounds analogous to pulmonary surfactant is frequently quoted as a major advantage of liposomes over other colloidal carrier systems. 

G. Gompper, M. Schick, Self-assembling Amphiphilic Systems, Academic Press, London, 1994. 

Fig. 4 Stability and permeability of self-assembled amphiphilic structures. Amphiphilic molecules such as fatty acids having carbon chain lengths of 9 or more carbons form bilayer membranes when sufficiently concentrated, a Pure bilayers of ionized fatty acid are relatively unstable but become markedly more stable as long chain alcohols are added, b Dimensions of the amphiphile also play a role. Shorter chain amphiphiles (9-10 carbons) are less able to form bilayers, while those of intermediate chain length (12-14 carbons) produce stable bilayers that also are permeable to ionic and polar solutes. Longer chain lengths (16-18 carbons) produce bilayers that are increasingly less permeable to solutes [48]...

The first self-assembling block copolymers were PS-fe-PMPS- -PS synthesised by Matyjaszewski and Moller. They observed micellar aggregates by ATM after casting dilute dioxane solutions (a solvent selective for the PS block) of the copolymer. The observed micelles were taken to have internal PMPS cores and were measured at 25-30nm in diameter [73], The hrst self-assembling amphiphilic polysilane block copolymers to be investigated was the PMPS-PEO multi-block copolymer with normal distribution PMPS blocks and uniform low polydispersity PEO blocks. After dialysis aqueous dispersions of this copolymer formed micellar as well as vesicular structures [78, 79] as shown in Eig. 19. 

Gompper M, Schick M (1994). Self-Assembling Amphiphilic Systems, Academic Press, New York. 

Fig. 7.11. Schematic representation of a silica membrane material exhibiting an ordered porous texture. Template effect obtained from self-assembled amphiphilic systems, (a) Wet gel ccmfeiining a hexagonal liquid crystal phase and the corresponding X ray diagram. G ) Heat-treated gel with residual ordered porosity and the corresponding X-ray diagram [68].

The size of the self-assembled amphiphilic structures varies from about 10 nm to a micron scale. Micelles are smaller than the vesicles, because they do not have internal aqueous core, and the wall is monolayer, not bilayer like in the liposomes. 

R462 Y. Morishima, Self-Assembling Amphiphilic Polyelectrolytes and their Nanostructures , Chin. J. Polym. Sci., 2000,18, 323... 

Martinez J.S., Zhang G.P., Holt P.D., Jung H.-T., Carrano C.J., HaygoodM.G., Butler A. (2000) Self-assembling amphiphilic siderophores from marine bacteria. Science 287, 1245-7. 

In order to prepare the micelles using self-assembling amphiphilic block copol3rmers, it is very important to determine the hydrophilic/hydrophobic balance. This is because... 

Norman LL, Barrett CJ. 2002. Solution properties of self assembled amphiphilic copoly mers determined by isomerization spectroscopy. J Phys Chem B 106(34) 8499 8503. 

Wang, Y Donsi, R Huang, Q., Self-assembling amphiphilic system for curcumin delivery, in preparation (2011). 

The preparation of nanogels from polymer precursor is based on the simply locking of self-assembled amphiphilic copolymers. This versatile methodology is discussed in detail based on cross-linking reaction types employed to fix the self-assembled polymer in this entry. 

This last example confirmed the usefulness of this novel approach for producing particles of hydrophilic shell and hydrophobic core that indeed consisted of self-assembled amphiphilic block copolymers. However, for the strategy to be successful, the authors underlined the prerequisite of avoiding monomer droplets and thus advised the use of slowly feeding the hydrophobic monomer. 

G. Gompper and M. Schick, Self-Assembling Amphiphilic Systems, Academic, London, 1994. K.-V. Schubert and E. W. Kaler, Ber. Bunsenges. Phys. Chem. 700 190 (1996). 

Incorporation of self-assembly amphiphilic copolymer into polyethersulfone (PES)-based membrane has also been widely studied by several research groups. For instance, Loh et al. [12] performed a study by adding Pluronic into PES-based membrane matrix. At optimum concentration of Pluronic (10 wt%) and PEO mass content in copolymer (70 wt%), optimized membrane properties with molecular weight cutoff (MWCO) of 9 kDa and flux of 113 L/m h bar could be produced. It must be pointed out that membrane flux tended to decline upon addition of higher Pluronic concentration into membrane matrix, owing to the formation... 

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