Vesicles entrapment

Shek, P.N., and Sabiston, B.H. (1982b) Immune response mediated by liposome-associated protein antigens. II. Comparison of the effectiveness of vesicle-entrapped and surface-associated antigens in immu-nopotentiation. Immunology 47, 627. 

Fig. 4 Elution profiles for (A) propranolol (a), promethazine (b), and chlorprom-azine (c) applied separately on a 5-mm ILC column containing cytoskeleton-depleted red blood cell membrane vesicles entrapped in dextran-grafted agarose gel beads (1.4 /amol phospholipid, 0.5 mL/min) and (B), from left to right, acetylsalicylic acid, salicylic acid, warfarin, and pindolol on a capillary continuous bed containing liposomes immobilized by use of C4 ligands (1.0 /xmol phospholipid, 10 /xl./min). The elution volumes in the absence of lipid are shown (a0, b0, and c0, and the arrow, respectively). (Part A is reprinted with permission, with slight modification, from Ref. 26. Copyright 1999 Elsevier Science. Part B is reprinted with permission from Ref. 23. Copyright 1996 Elsevier Science.)...

Vesicle-entrapped or isolated Pt were used as 564 catalysts for ethylene and cyclohexane hydrogenation... 

In addition to enzymatic hydrolysis of natural lipids in polymeric membranes as discussed in chapter 4.2.2., other methods have been applied to trigger the release of vesicle-entrapped compounds as depicted in Fig. 37. Based on the investigations of phase-separated and only partially polymerized mixed liposomes 101, methods to uncork polymeric vesicles have been developed. One specific approach makes use of cleavable lipids such as the cystine derivative (63). From this fluorocarbon lipid mixed liposomes with the polymerizable dienoic acid-containing sulfolipid (58) were prepared in a molar ratio of 1 9 101115>. After polymerization of the matrix forming sulfolipids, stable spherically shaped vesicles are obtained as demonstrated in Fig. 54 by scanning electron microscopy 114>. 

Nomura, Shin-ichirou, Giant Phospholipid Vesicles Entrapping Giant DNA,... 

Similarly, significantly higher humoral responses were obtained after s.c. administration of either a lipid and/or a nonionic-based vesicle-entrapped plasmid for the nucleoprotein of H3N2 influenza virus in comparison to the naked DNA alone [226],... 

Block copolymer vesicles, or polymersomes, are of continued interest for their ability to encapsulate aqueous compartments within relatively robust polymer bilayer shells (Fig. 7) [66, 67]. Eisenberg and coworkers were the first to report the formation of block copolymer vesicles from the self-assembly of polystyrene-h-poly(acrylic acid) (PS-h-PAA) block copolymers. They also have described the formation of a wide range of vesicle architectures in solution from the self-assembly of five different block copolymers PS-h-PAA. PS-h-PMMA, PB-h-PAA, polystyrene-h-poly(4-vinyIpyridinium methyl iodide), and polystyrene-h-(4-vinylpyridinium decyl iodide) [68]. Small uniform vesicles, large polydisperse vesicles, entrapped vesicles, hollow concentric vesicles, onions, and vesicles with hollow tubes in the walls have been observed and the formation mechanism discussed. Since vesicles could be prepared with low glass transition polymers such as PB [69, 70] and PPO [71], it has been established than these structures are thermodynamically stable and not trapped by the glassy nature of the hydrophobic part. 

Figure 4.20 Vesicle entrapped organic ions react slowly with each other. ...

Upon sonication, an a,co-disulfone macrocycle (Figure 4.25) produces extremely long-lived, electroneutral vesicles which were perforated with various PEG derivatives, but these synthetic pores could not be efficiently sealed. An oligoamino pore with anionic head groups turned out to be more controllable. It allowed vesicle entrapped calcein to be fully accessible to Fe ions which quenched its fluorescence. Taurine and several other bulky anions closed the amino pore completely and pH-reversibly. It was also possible to suck the entrapped iron ions out of the vesicle with external EDTA (Figure 4.25). So far, the synkinetic pores have proved to be much more controllable than the covalent ones. 

Surfactant vesicles entrap electrolytes and polyelectrolytes. Only protons and hydroxide ions move freely across the mono- and bilayers of vesicles. However, in vesicles which contain cholesterol a pH gradient may stay stable for up to an hour (see also page 80 and Figure 4.23). 

Jurima-Romet M, Bather RF, Shek PN (1992) Liposomes and hronchoalveolar lavage fluid release of vesicle-entrapped glutathione. Int J Pharm 88 201-210... 

Quinones play an important role in both covalent (synthetic) and nonco-valent (synkinetic) assemblies, which are supposed to allow electron transport through membranes and light-induced charge separation processes. With respect to their ability to carry electrons through lipid membranes, quinones with a side chain of more than two isoprene units are far more efficient than homologs with shorter chains. In the reduction of vesicle-entrapped ferricyanide ions by external dithionite, for example, the long side chain may act as the rod of a pendulum (Fig. 7.2.2) leading to fast electron transfer. Tocopherol and other branched-chain hydrocarbons (e.g., phytol,) also disturb egg lecithin... 

Polymersomes are polymer-based bilayer vesicles, also termed as nanometer-sized bags by scientists. The bilayer structure displayed is similar to liposomes and niosomes as shown in Figure 48.7. They can be considered as liposomes but of nonbiological origin. Amphiphilic block copolymers can form various vesicular architectures in solution. They can have different morphologies such as uniform common vesicles, large polydisperse vesicles, entrapped vesicles, or hollow concentric vesicles. ... 

The diffusion of OH /H through the membrane of (DODA)B and Lecithin vesicles was determined incorporating a water soluble positively charged pH probe, 2-hydroxy-5-(2-trimethyl-ammonium) acetyl benzoate (2-HTAB, pKa = 10.5) (Scheme 3) in both preparations. If OH diffusion in, or probe leakage out, were fast, no kinetics of probe dissociation could be observed in the time-scale of these experiments (several seconds). With both (DODA)B and lecithin vesicles the half life for deprotonation was approximately 7 min, in the range of the half-life observed for MCP hydrolysis in the internal aqueous compartment of the same vesicles (Fig. 3C). These result indicate that slow OH diffusion through the membrane is responsible for the difference observed in the rate of MCP hydrolysis in the outer and inner aqueous compartments. The vesicle-entrapped dissociated probe can be... 

Surfactants have recently been used as models for membranes. Didodecyl-dimethylammonium bromide aggregates extensively in aqueous solutions into stable bilayer structures which further form vesicles and lamellae. Single compartment bilayer dioctadecyldimethylammonium chloride vesicles entrap and retain a number of substrates. Similar aggregation occurs with anionic amphiphiles with two normal alkyl groups as the hydrophobic residue. The hydrolysis of esters catalysed by a hydrophobic imidazole derivative occurs faster (up to 20-fold) in the intravesicle compared with the intervesicle reaction with didodecyldimethylammonium bromide. ... 

CapUlary inner Flow rate Mean vesicle Entrapment... 

Barber, R. K Shek, P. N. Liposomes and tear fluid. I. Release of vesicle-entrapped carboxyfluorescein. Biochim. Biophys. Acta, Lipids Lipid Metab. 1986, 879, 157-163. 

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