Vesicles polymers

Uchegbu and coworkers have studied the complexation and delivery of DNA using a unique poly(amino acid)-based polymer vesicle. A polymer of either poly (L-lysine) or poly(L-omithine) was functionalized with methoxy-poly(ethylene glycol) (mPEG) and hydrophobic palmitic acid chains to synthesize an amphiphilic triblock of either mPEG-6-poly(L-lysine)-6-palmitoyl or mPEG-Z>-poly(L-omithine)-6-palmitoyl. Vesicles formed from these polymers were complexed with DNA and showed improved transfection in vitro over poly(amino acid) complexed with DNA or DNA alone [82]. 

Polymerization in Bilayers. Upon irradiation with UV light the monomer vesicles are transferred to polymer vesicles (Figure 12.). In the case of the diyne monomers (2,5-9,12,13,14) the polyreaction can again be followed by the color change via blue to red except phospholipids (5,6), which turn red without going through the blue intermediate as observed in monolayers. The VIS spectra of these polymer vesicle dispersions are qualitatively identical to those of the polymer monolayers (Figure 13.). 

Polymer formation from monomeric butadiene lipid vesicles is demonstrated by the decrease of the monomer absorption at 260 nm as well as by GPC of the residue of a freeze dried polymer vesicle dispersion. The latter method was also used for proving the formation of polymeric vesicles from the methacryloyl lipids. 

The great stability of polymerized vesicles can be demonstrated by several experiments (9) dilution of polymer vesicle solutions with 50% of ethanol does not result in a precipitation. Turbidity measured at 300 nm remains the same (28), whereas monomer vesiclesare destroyed under these conditions followed by a considerable decrease of turbidity. A precipitation of stabilized vesicles can, however, be achieved by the addition of salts (KC1), but again it has to be pointed out that the polymeric vesicles... 

Vesicles for use as materials can be divided into two categories naturally occurring vesicles, or liposomes, which are composed of natural amphiphiles, usually phospholipids and polymer vesicles, which are generally composed of block copolymers. 

Sacrificial photosensitized water reduction has been extensively investigated both in homogeneous solutions and in the presence of organized assemblies (micelles, microemulsions, polyelectrolytes, polymers, vesicles and... 

Pochan DJ, Chen Z, Cuii H, Hales K, Qi K, Wooley KL (2004) Science 306 94 FOrster S (2005) Polymer vesicles. In Encyclopedia of polymer science and technology. WUey, New York... 

Kukula, H. Schlaad, H. Antonietti, M. Porster, S. The formation of polymer vesicles or peptosomes by polybuta-diene-fcocfc-poly(L-glutamate)s in dilute aqueous solution. Journal of the American Chemical Society 2002, 124, 1658-1663. 

Zhou, Y.F. and Yan, D.Y. (2005) Real-time membrane fusion of giant polymer vesicles. Journal cf the American Chemical Society, 127 (30), 10468-10469. 

Membrane properties of polymer vesicles reflect the chemical composition, the block length ratio and the molecular weight of the block copolymers from which they are formed. 

In polymersomes with thicker membranes the limited mobility of high MW polymer chains is the reason for the better resistance to dissolution. Thus, while liposomes would normally be destroyed when exposed to SDS (sodium dodecyl sulfate) or other strong detergents, polymer vesicles would be more resistant to detergents since this process is obstructed by the restricted chain mobility. Combination of experimental data and theoretical modeling suggests that polymer vesicle dissolution is mediated by the diffusion of detergent molecules across the membrane [132],... 

Real-time monitoring of fusion and fission has been reported for polymer vesicles generated from an amphiphilic multiarm copolymer with a hyperbranched poly(3-ethyl-3-oxetanemethanol) core and many oligo(ethylene oxide) arms (HBPO-star-PEO) [152,153], Sonication could partly break the hydrogen bonds and give rise to molecular packing defects on the membrane, which triggers the membrane fusion. 

Interestingly, Forster and coworkers reported the use of inkjet printing technology to produce directly unilamellar polymer vesicles with a narrow size distribution. The average size of the vesicles depended on the initial polymer concentration in the organic (water-miscible) phase and the type of nozzle used [166],... 

Related thermo-sensitive, cross-linked polymer vesicles were also formed by self-assembly of poly(2-cinnamoylethyl methacrylate)-W< cfc-poly((V-isopropylacry-lamide) (PCEMA61 — fc—PNIPAM22) copolymer and subsequent photo-crosslinking of the PCEMA shells [228]. The vesicles can load a large amount of 4-aminopyridine (Apy) and release the compound at a tunable rate depending on temperature. 

Many of the polymer vesicles present in the literature are addressed to drug delivery applications. To achieve their potential as effective delivery vehicles, polymer-somes must efficiently encapsulate therapeutic agents. Their ability to encapsulate molecules into either the aqueous lumen [144,229,234] of the vesicle (e.g., doxorubicin) or the hydrophobic core of the membrane (e.g., taxol (TAX)) has been... 

Encapsulation and delivery of DNA has also been investigated with poly(amino acid) (poly(AA)) based polymer vesicles. Brown and coworkers synthesized an amphiphilic triblock copolymer from methoxy-poly(ethylene glycol) (mPEG), hydrophobic palmitic acid chains in block segments along a poly-L-lysine (PLL) or... 

Another possibility for therapeutic application of polymer vesicles has been presented recently [242], Superoxide dismutase, an antioxidant enzyme, was encapsulated in the vesicular cavity and shown to remain functional in neutralizing superoxide radicals in situ. The polymer membranes were proven permeable to superoxide radicals by pulse radiolysis, and the encapsulation of the enzyme prolongs its lifetime (which is only minutes in the bloodstream, when non-shielded). 

To bring the nanocontainer to a specific place where it should release its pay-load, targeting is a required approach. Hence, much work has been carried out to attach ligands or antibodies to the hydroxyl end-group of PEG-based assemblies [150,181,243], Biotinylated nondegradable block copolymer assemblies have been shown to attach to surfaces coated with the biotin receptor avidin [146,147, 150,244], Coupling chemistry has been applied to conjugate either an antihuman IgG, or antihuman serum to PEG-carbonate- or PEG-polyester-assembled polymer vesicles [149,245], HIV-derived Tat peptide attached to PEG-PBD polymersomes enhanced the cellular delivery of nanoparticles [246] and increased dendritic cell uptake in vitro [181]. 

Two membrane proteins were used in polymer vesicles for ATP production. In this very complex system, bacteriorhodopsin inserted in the polymer membranes pumped protons from the outside to the inside of vesicles when illuminated by light [260], Next, those protons would turn on the ATP-ase (also inserted in the membrane), and when ADP is present, ATP production could be monitored in solution [261], From the academic point of view, such platforms are excellent model systems for understanding the protein function. 

Polymer vesicles are also suitable to transport and target imaging agents such as fluorescent dyes and paramagnetic contrast agents. Hammer and coworkers encapsulated porphyrin-based near-infrared (NIR) fluorophores into PBD-PEO... 

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