Immobilized Vesicles

Shim et al. 2004). When the NHS ester-containing liposomes are polymerized prior to immobilization on the glass, the blue liposomes turn red upon contact with the slide. However, if the liposomes are immobilized prior to polymerization and subsequently irradiated, the immobilized vesicles are blue and can undergo a subsequent chromatic transition in response to heat (Fig. 12.11). 

Chemical reactions occurring in geometries resembling those found in a cell can be investigated with the help of nanotube-vesicle networks (NVNs, Fig. 23.3 [fO]). NVNs are highly flexible lipid bilayer structures in which the main building blocks are surface-immobilized vesicles connected by nanotubes. 

Lipid bilayers and surface immobilized vesicles provide an alternative architecture for the micro- and nanofabrication of bioreactive and biocompatible platforms [63-67]. In recent years, the modification of solid surfaces with biological molecules has been widely studied as a means to obtain biomimetic interfaces for biomedical and environmental applications. Among the various formats of functionalized interfaces investigated, substrate-supported lipid bilayers have received considerable attention. Proteins have been successfully... 

In conclusion, this novel method of lipid vesicle immobilization on substrate-supported lipid bilayers in a spatially confined manner may serve as a platform for research on proteins incorporated in the lipid bilayers comprising the vesicles. Owing to their structural similarities to the cell membrane, lipid bilayers and substrate-immobilized vesicles provide interesting platforms for studies of incorporated proteins, an area that will see progressive growth in the near future. 

Fig. 11 Confocal laser sceinning microscopy images (a) immobilized vesicles containing a membrane-encapsulated dye, tmd (b) eifter Pluronic addition to the immobilized vesicles. Reprinted from [148] with permission. Copyright 2008 American Chemical Society...

Figure 6.14 (A) Scheme of an immobilized vesicle on a surface. LSM images of structurally immobilized nanoreactors (B) before and (C) after incubation (20 minutes) with ELF 97 substrate.

Preparation of Enzyme Immobilized Vesicles. Polymerizable lipid 1 (9 mg) was... 

The interaction with myosin motors enables F-actin to transport molecules as well as to change or maintain the shape of the cell by exerting tension. Thus, myosin-I motors move to the barbed end and can transport cargoes such as vesicles. When immobilized at the cargo site... 

Bioencapsulation is a technology aimed toward the immobilization and incorporation (entrapping) of a biologically active compound on or inside solid particles (microspheres) or liquid vesicles in order to stabilize, stracture, and protect the active compound and allow control of its release. 

Fig. 9 Surface modification of cells with ssDNA-PEG-lipid. (a) Real-time monitoring of PEG-lipid incorporation into a supported lipid membrane by SPR. (r) A suspension of small unilamellar vesicles (SUV) of egg yolk lecithin (70 pg/mL) was applied to a CH3-SAM surface. A PEG-lipid solution (100 pg/mL) was then applied, (ii) Three types of PEG-lipids were compared PEG-DMPE (C14), PEG-DPPE (C16), and PEG-DSPE (C18) with acyl chains of 14, 16, and 18 carbons, respectively, (b) Confocal laser scanning microscopic image of an CCRF-CEM cell displays immobilized FITC-oligo(dA)2o hybridized to membrane-incorporated oligo(dT)20-PEG-lipid. (c) SPR sensorigrams of interaction between oligo(dA)2o-urokinase and the oligo (dT)2o-PEG-lipid incorporated into the cell surface, (i) BSA solution was applied to block nonspecific sites on the oligo(dT)20-incorporated substrate, (ii) Oligo(dA)20-urokinase (solid line) or oligo(dT)20-urokinase (dotted line) was applied...

Biotinylated liposomes usually are created by modification of PE components with an amine-reactive biotin derivative, for example NHS-LC-Biotin (Chapter 11, Section 1). The NHS ester reacts with the primary amine of PE residues, forming an amide bond linkage (Figure 22.19). A better choice of biotinylation agent may be to use the NHS-PEG -biotin compounds (Chapter 18), because the hydrophilic PEG spacer provides better accessibility in the aqueous environment than a hydrophobic biotin spacer. Since the modification occurs at the hydrophilic end of the phospholipid molecule, after vesicle formation the biotin component protrudes out from the liposomal surface. In this configuration, the surface-immobilized biotins are able to bind (strept)avidin molecules present in the outer aqueous medium. 

H.S. Jung, J.M. Kim, J.W. Park, H.Y. Lee, and T. Kawai, Amperometric immunosensor for direct detection based upon functional lipid vesicles immobilized on nanowell array electrode. Langmuir 21, 6025-6029 (2005). 

Vandegriff KD, Wallach DF, Winslow RM. Encapsulation of hemoglobin in non-phospholipid vesicles. Artif Cells Blood Substit Immobil Biotechnol 1994 22 849. 

The basic principle is shared by several methods In chromatographic or electrophoretic systems where the liposomes (vesicles) are immobilized, pseudostationary, or carried by an electroendosmotic flow, migrating amphiphilic drug molecules partition between the water outside the liposomes, the lipid bilayer of the liposome, and the aqueous compartment within the liposome (Fig. 3). In all cases the migration rate basically reflects the par-... 

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.)...

M Sandberg, P Lundahl, E Greijer, M Belew. Immobilization of phospholipid vesicles on alkyl derivatives of agarose gel beads. Biochim Biophys Acta 924 185-192, 1987. 

Q Yang, M Wallsten, P Lundahl. Immobilization of phospholipid vesicles and protein-lipid vesicles containing red cell membrane proteins on octyl derivatives of large-pore gels. Biochim Biophys Acta 938 243-256, 1988. 

Falten et al. recently reported that phospholipid membrane vesicles can be con-stmcted on a filter scaffold without any organic solvent [57-60]. In this system, the phospholipid vesicle occupies the filter pores to form a permeation barrier. This is more relevant to the cellular membrane than PAMPA membranes with organic solvent. The membrane can be stored up to two weeks without significant change and is stable at pH 2-8. The Fa% predictability was compared with BM-PAMPA, DS-PAMPA, Caco-2 and immobilized liposome chromatography, resulting in promising predictability. 

Haneskog, L., Zeng, C.-M., Lundqvist, A., and Lundahl, P, Biomembrane affinity chromatographic analysis of inhibitor binding to the human red cell nucleoside transporter in immobilized cells, vesicles and proteoliposomes. Biochim. Biophys. Acta, 1371, 1-4, 1998. 

A variety of methods for immobilizing polymerized liposomes have been reported. Multiple layers of vesicles were deposited on quartz slides by layer-by-layer assembly (Su 2005). The slides were first coated with a layer of poly(ethylene imine), a... 

A related system is that of the lipid-bilayer corked capsule membranes which are formed from ultrathin (about 1 pm thick), spongy, 2.0- to 2.5-mm-diameter, more-or-less spherical nylon bags in which multiple bilayers are immobilized (Fig. 43) [343-345]. They were considered to combine the advantages of mechanical and chemical stabilities of polymeric membranes with the controllable permeabilities of surfactant vesicles. Polymerization of the bilayers, in situ,... 

Controlled evaporation of SUVs and MLVs on substrates has been shown to result in the formation of ultrathin films which retained the regular bilayer structure of vesicles [69, 425-427]. These immobilized bilayers, termed as cast multibilayers , cast multibilayers , or ordered cast (ultrathin) films , have provided an alternative to LB films [425-446]. Alkylammonium surfactants with azobenzene (33) and glutamate (34) functionalities have been used, for example, in the preparation of cast-film-forming SUVs. X-ray diffraction... 

At least two additional types of acetylcholine receptors are found within the neuromuscular apparatus. One type is located on the presynaptic motor axon terminal, and activation of these receptors mobilizes additional transmitter for subsequent release by moving more acetylcholine vesicles toward the synaptic membrane. The second type of receptor is found on perijunctional cells and is not normally involved in neuromuscular transmission. However, under certain conditions (eg, prolonged immobilization, thermal burns), these receptors may proliferate sufficiently to affect subsequent neuromuscular transmission. 

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