Liposome chemical structure

Figure 1 Chemical structures of some amphipathic weak bases that have been loaded and stabilized in liposomes using trialkylammonium salts of polyanionic trapping agents in our lab. (A) Doxorubicin, (B) epirubicin, (C) vinorelbine, (D) vincristine, (E) vinblastine, (E) topotecan, (G) irinotecan, (H) swainsonine, (I) 2-diethylami-noethyl-ellipticinium, (J) 6-(3-aminopropyl)ellipticine, and (K) LAQ824.

Despite the fact that many different cationic lipids have been synthesized and tested for transfection (25 34), relatively few systematic structure activity TE-relationship studies have been performed (35 39). As a result, no general relationship between chemical structure and TE could be drawn from these studies. One reason for this is that the chemical structure of a cationic lipid is not directly responsible for TE. TE rather depends on the biophysical characteristics of the cationic lipid aggregate (e.g., liposomes and lipoplexes), which, for its part, is dependent on the chemical structure of the lipids. In a previous study with analogs of the transfection lipid A-[l-(2,3-dioleoyloxy) propyl]-A,A,A-trimethylammoniumchloride (DOTAP) (40) which differ in their nonpolar hydrocarbon chains, it could be shown that the TE strongly depended on the biophysical properties of the resulting liposomes and lipoplexes (35). Minimal alterations of biophysical properties by using lipids with different hydrocarbon chains or by mixing the lipid with different neutral helper lipids could completely allow or prevent transfection. 

Liposomes are useful as carrier systems for therapeutic or diagnostic drugs. Depending on the chemical structure of the loaded compound, it can either be incorporated into the membrane layer as is observed for lipophilic drugs or stored in the aqueous compartment at the centre of the vesicle (hydrophilic substances). 

Phospholipids, when dispersed in water, may exhibit self-assembly properties (either as micellar self-assembly aggregates or larger structures). This may lead to aggregates that are called liposomes or vesicles. Liposomes are structures that are empty cells and that are currently being used by some industries. They are microscopic vesicles or containers formed by the membrane alone, and are widely used in the pharmaceutical and cosmetic fields because it is possible to insert chemicals inside them. Liposomes may also be used solubilize (in its hydrophobic part) hydro-phobic chemicals (water-insoluble organic compounds) such as oily substances so that they can be dispersed in an aqueous medium by virtue of the hydrophilic properties of the liposomes (in the alkyl region). 

Liposomes are microscopic vesicles consisting of one or more phospholipid membranes surrounding a discrete water compartment. The lipid layer is composed of amphipathic phospholipids whose hydrophobic tails associate, while the polar hydrophihc heads align toward the bulk of the water phase. A variety of hposomes with unique physical and chemical structure can be manufactured by altering non-polar and polar groups. Excellent reviews have been recently pubhshed... 

Neoglycoproteins, liposomes, and glycopolymers have been successfully used to demonstrate that multivalency does indeed amplify carbohydrate-protein binding interactions by factors as high as thousands. However, by their very nature, these neoglycoconjugates have ill-defined chemical structures. They are heterogeneous in size and carbohydrate contents. Additionally, neoglycoproteins have been shown to... 

Although they are a chemically diverse assortment of compounds, lipids share a number of properties. The amphipathic nature of lipid molecules encourages the formation of more complex structnres such as micelles, bilayers, and liposomes. These structures, as well as the actual lipid substances themselves, affect all aspects of cell biology, see also Fats and Fatty Acids Lipid Bilayers Membrane Phospholipids. 

Dendrimers have been investigated as a vector for nucleic acid-based therapies for nearly 20 years, and PAMAM and PPI dendrimers are the two most commonly used kinds that are commercially available.[113-115] Their unique chemical architecture with all primary, secondary, and tertiary amines enabling the proton-sponge effect described above make dendrimers one of the ideal platforms for gene delivery. Furthermore, the close-to-monodispersed chemical structure of dendrimers allows the precise control over their functionalities, which can minimize the unpredictable transfection efficiencies observed in the cases of heterogeneous liposomes and other polymer-based systems.[l 16]... 

Figure 5 Chemical structure of Ghadiri s cyclic peptide 18 which undergoes self-association in phosphatidylcholine liposomes to form nanotubes that transport glucose across the membrane.

Fig. 4 Chemical structure of sodium 2-mercaptoethanesulfonate (4) (MESNA) used to catalyze the native chemical ligation on the liposome surface, as described by Reulen et al. [109]...

Fig. 5 Chemical structure of cyanur chloride (5) used to introduce the cyanur functionality into liposomes by acylation of DPPE-PEG-OH, as described by Brendas et al. [21]...

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