Liposomes interaction

Fig. 11 Schematic representation of liposome interactions at a membrane surface.

Depending on their size and surface charge, parenterally administered liposomes interact with the reticuloendothelial system (RES) and provoke an immune response. 

Jaaskelainen, I., Monkkonen, J., Urtti, A. (1994). Oligonucleotide-cationic liposome interactions. A physicochemical study. Biochim. Biophys. Acta., 1195, 115-123. 

Cationic liposomes are a relatively new development in liposomal therapeutics, which demonstrate considerable potential for improving the delivery of genetic material. The cationic lipid components of the liposomes interact with, and neutralize, negatively charged DNA, thereby condensing the DNA into a more compact structure. Depending on the preparation method used, the complex may not be a simple aggregate, but an intricate structure in which the condensed DNA is surrounded by a lipid bilayer. These systems are discussed further in Chapter 14. 

Avdeef A, Box KJ, Comer EA et al. (1998) pH metric logP 10. Determination of liposomal membrane-water partition coefficients of ionizable drugs. Pharm Res 15 209-215 Baird CL, Courtenay ES, Myszka DG (2002) Surface plasmon resonance characterization of drug/liposome interactions. Anal Biochem 310 93-99... 

Extensive research on the attempts to overcome the bilayer membrane barrier has resulted in the emergence of several different methodologies for partial and temporary cell membrane permeabilization. The prominent among them are chemical permea-bilizers, liposomal interactions, ultrasonication, ionizing radiation, and electroporation. 

Depending on their size and surface charge, parenter-ally administered liposomes interact with the reticulo endothelial system (RES) and provoke an immunological response. After being marked by the adsorption of certain serum proteins, called opsonins, they are identified as an invader and destroyed by specific immune cells mainly in the liver, spleen, and bone marrow. 

Liposomes are vesicles composed of naturally occurring or synthetic phopholipids. The bilayer structure can be single- or multicompartment. The size can also vary from smaller than 1pm to larger than 10 pm. When negatively charged lipid molecules, which form liposomes, interact with divalent cations, a solid, multilayered, crystallaine structure called cochleate is formed. Because liposomes and cochleates can protect antigens from the GI tract and deliver them to the Peyer s patches, they have been exploited as an effective delivery system for oral vaccination. 

Ivanov, A.S. Molnar, A.A. Petrov, V.V. Popov, A.M. Anisimov, M.M. In Liposomes. Interaction with cells and tissues. Proclaims of All-Union symposium-, Nauka Moskow, 1981 pp. 115-123. 

In terms of structural chemistry, liposomes are supramolecular aggregates. A drug will also associate with the liposome by via non-covalent binding. With modified and unmodified ODNs, liposomes have become a particularly promising approach, aided by the fact that specific ODN-modifications may also be used specifically to influence drug-liposome interaction. Thus, base-modified cholesterol derivatives have been developed to act as specific anchor points for ODNs in liposomal formulations [397-408], Application of pH-sensitive liposomes made from DOPE/OA [409] or DOPE/OA/CHOL [410] has also been suggested. As a first important effect of liposome formulation, protection of ODNs from extracellular nucleases has been observed [411-413]. Use of such formulations has proven to be a valid method for cellular internalization in cultured cell lines, an effect which has been reviewed by a number of authors [414,415]. 

Elhissi AMA, O Neill MAA, Roberts SA, Taylor KMG. A calorimetric study of dimyristoylphosphatidylchoUne phase transitions and steroid-liposome interactions for hposomes prepared by thin fihn and proliposome methods. Int J Pharm 2006 320 124-30. 

These preliminary microcalorimetric measurements suggest that there is apparently no interaction between the homopolymer and the liposomes, since the LCST transition is unaffected by the presence of liposomes. However the signal corresponding to the LCST of the hydrophobically-modified polymers is altered in the presence of liposomes, in terms of both intensity and broadness. This observation is taken as a clue that these polymers interact with the liposomes. Particularly revealing is the fact that for liposomes in their fluid state (DMPC) an LCST transition can still be detected, but this transition seems to disappear for liposomes in their solid-analogous state (DSPC). This dependence of the polymer/liposome interactions on the membrane phase will be put on much firmer grounds by the fluorescence experiments described next. Indeed further microcalorimetric measurements with fully coated liposomes systems need to be... 

We can rationalise these differences assuming that when in liposomal complex, the apoHBD interacts with the polar head and with the proximal part of the hydrophobic chains (may be up to 4-6 carbon atoms) which is the region less modified by the gel-to-liquid-crystalline phase transition (Hubbell Me Connell, 1970 Levine et al., 1972 Barton Gunstone, 1975) therefore the enzyme-liposome interaction and, consequently, the HBD activity of these complexes is not sensitive to phase transitions. Conversely, in the diC14 substituted membranes (and may be in the original mitochondria) the apoHBD could be deeply inserted in the lipid matrix and would... 

Glycosteroids in vesicles and liposomes, interactions with membranes, drug transport and solubilization... 

Weinstein, J. N. Blumenthal, R. Klausner, R. D. Carboxyfluorescein leakage assay for lipoprotein-liposome interaction. Methods Enzymol. 1986,128, 657-668. 

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