fluorochrome acridine orange. Method of fluorescence microscopy (1250-fold magnification). Various types of phosphatidylcholine<unk> s in suspension. Method of phase-contrast microscopy (1000-fold magnification). The following types of<unk> s are visible: small monolamellar vesicles, large monolamellar vesicles, multilamellar vesicles, oligolamellar vesicles. A<unk>  has an aqueous solution core surrounded by a hydrophobic membrane, in the form of a lipid bilayer; hydrophilic solutes dissolved in the core cannot readily pass through the bilayer. Hydrophobic chemicals associate with the bilayer. A<unk>  can be hence loaded with hydrophobic and/or hydrophilic molecules. To deliver the molecules to a site of action, the lipid bilayer can fuse with other bilayers such as the cell membrane, thus delivering the<unk>  contents; this is a complex and non-spontaneous event, however, that does not apply to nutrients and drug delivery. By preparing<unk> s in a solution of DNA or drugs (which would normally be unable to diffuse through the membrane) they can be (indiscriminately) delivered past the lipid bilayer.<unk> s are used as models for artificial cells.<unk> s can also be designed to deliver drugs in other ways.<unk> s that contain low (or high) pH can be constructed such that dissolved aqueous drugs will be charged in solution (i.e., the pH is outside the drug's pI range). As the pH naturally neutralizes within the<unk>  (protons can pass through some membranes), the drug will also be neutralized, allowing it to freely pass through a membrane. These<unk> s work to deliver drug by diffusion rather than by direct cell fusion. However, the efficacy of this pH regulated passage depends on the physiochemical nature of the drug in question (e.g. pKa and having a basic or acid nature), which is very low for many drugs. A similar approach can be exploited in the biodetoxification of drugs by injecting empty<unk> s with a transmembrane pH gradient. In this case the vesicles act as sinks to scavenge the drug in the blood circulation and prevent its toxic effect. Another strategy for<unk>  drug delivery is to target endocytosis events.<unk> s can be made in a particular size range that makes them viable targets for natural macrophage phagocytosis. These<unk> s may be digested while in the macrophage's phagosome, thus releasing its drug.<unk> s can also be decorated with opsonins and ligands to activate endocytosis in other cell types. The use of<unk> s for transformation or transfection of DNA into a host cell is known as lipofection. In addition to gene and drug delivery applications,<unk> s can be used as carriers for the delivery of dyes to textiles, pesticides to plants, enzymes and nutritional supplements to foods, and cosmetics to the skin.<unk> s are also used as outer shells of some microbubble contrast agents used in contrast-enhanced ultrasound.
Liposome
Glycol nucleic acid
Cementicle
Endosome
Protelean
Dendrosome
Polysome
Matrix-core