Liposome
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A liposome is a small artificial
Liposomes are most often composed of
Based on vesicle structure, there are seven main categories for liposomes: multilamellar large (MLV), oligolamellar (OLV), small unilamellar (SUV), medium-sized unilamellar (MUV), large unilamellar (LUV), giant unilamellar (GUV) and multivesicular vesicles (MVV).[6] The major types of liposomes are the multilamellar vesicle (MLV, with several lamellar phase lipid bilayers), the small unilamellar liposome vesicle (SUV, with one lipid bilayer), the large unilamellar vesicle (LUV), and the cochleate vesicle. A less desirable form is multivesicular liposomes in which one vesicle contains one or more smaller vesicles.
Liposomes should not be confused with lysosomes, or with micelles and reverse micelles.[8] In contrast to liposomes, micelles typically contain a monolayer of fatty acids or surfactants.[9]
Discovery
The word liposome derives from two Greek words: lipo ("fat") and soma ("body"); it is so named because its composition is primarily of phospholipid.
Liposomes were first described by British hematologist
Bangham, with colleagues Jeff Watkins and Standish, wrote the 1965 paper that effectively launched what would become the liposome "industry."Around that same time, Weissmann joined Bangham at the Babraham. Later, Weissmann, then an emeritus professor at New York University School of Medicine, recalled the two of them sitting in a Cambridge pub, reflecting on the role of lipid sheets in separating the cell interior from its exterior milieu. This insight, they felt, would be to cell function what the discovery of the double helix had been to genetics. As Bangham had been calling his lipid structures "multilamellar smectic mesophases," or sometimes "Banghasomes," Weissmann proposed the more user-friendly term liposome.[16][17]
Mechanism
Encapsulation in liposomes
A liposome has an aqueous solution core surrounded by a
Delivery
To deliver the molecules to a site of action, the lipid bilayer can fuse with other bilayers such as the
A similar approach can be exploited in the biodetoxification of drugs by injecting empty liposomes 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.[25] Another strategy for liposome drug delivery is to target
Certain anticancer drugs such as doxorubicin (Doxil) and daunorubicin may be administered encapsulated in liposomes. Liposomal cisplatin has received orphan drug designation for pancreatic cancer from EMEA.[26]
The use of liposomes for transformation or
In addition to gene and drug delivery applications, liposomes can be used as carriers for the delivery of dyes to textiles,[27] pesticides to plants, enzymes and nutritional supplements to foods, and cosmetics to the skin.[28]
Liposomes are also used as outer shells of some microbubble contrast agents used in contrast-enhanced ultrasound.
Dietary and nutritional supplements
Until recently, the clinical uses of liposomes were for
The term nutraceutical combines the words nutrient and pharmaceutical, originally coined by Stephen DeFelice, who defined nutraceuticals as “food or part of a food that provides medical or health benefits, including the prevention and/or treatment of a disease”.[32] However, currently, there is no conclusive definition of nutraceuticals yet, to distinguish them from other food‐derived categories, such as food (dietary) supplements, herbal products, pre‐ and probiotics, functional foods, and fortified foods.[33] Generally, this term is used to describe any product derived from food sources which is expected to provide health benefits additionally to the nutritional value of daily food. A wide range of nutrients or other substances with nutritional or physiological effects (EU Directive 2002/46/EC) might be present in these products, including vitamins, minerals, amino acids, essential fatty acids, fibres and various plants and herbal extracts. Liposomal nutraceuticals contain bioactive compounds with health-promoting effects. The encapsulation of bioactive compounds in liposomes is attractive as liposomes have been shown to be able to overcome serious hurdles bioactives would otherwise encounter in the gastrointestinal (GI) tract upon oral intake.[34]
It is important to note that certain factors have far-reaching effects on the percentage of liposome that are yielded in manufacturing, as well as the actual amount of realized liposome entrapment and the actual quality and long-term stability of the liposomes themselves.[35] They are the following: (1) The actual manufacturing method and preparation of the liposomes themselves; (2) The constitution, quality, and type of raw phospholipid used in the formulation and manufacturing of the liposomes; (3) The ability to create homogeneous liposome particle sizes that are stable and hold their encapsulated payload. These are the primary elements in developing effective liposome carriers for use in dietary and nutritional supplements.
Manufacturing
The choice of liposome preparation method depends, i.a., on the following parameters:[36][37]
- the physicochemical characteristics of the material to be entrapped and those of the liposomal ingredients;
- the nature of the medium in which the lipid vesicles are dispersed
- the effective concentration of the entrapped substance and its potential toxicity;
- additional processes involved during application/delivery of the vesicles;
- optimum size, polydispersity and shelf-life of the vesicles for the intended application; and,
- batch-to-batch reproducibility and possibility of large-scale production of safe and efficient liposomal products
Useful liposomes rarely form spontaneously. They typically form after supplying enough energy to a dispersion of (phospho)lipids in a polar solvent, such as water, to break down multilamellar aggregates into oligo- or unilamellar bilayer vesicles.[5][24]
Liposomes can hence be created by
Prospect
Further advances in liposome research have been able to allow liposomes to avoid detection by the body's immune system, specifically, the cells of
Liposomes are used as models for artificial cells.
Liposomes can be used on their own or in combination with traditional antibiotics as neutralizing agents of bacterial toxins. Many bacterial toxins evolved to target specific lipids of the host cells membrane and can be baited and neutralized by liposomes containing those specific lipid targets.[48]
A study published in May 2018 also explored the potential use of liposomes as "nano-carriers" of fertilizing nutrients to treat malnourished or sickly plants. Results showed that these synthetic particles "soak into plant leaves more easily than naked nutrients", further validating the utilization of nanotechnology to increase crop yields.[49][50]
and to predict the particle size and theSee also
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