Liposomes as drug carriers: Difference between revisions
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Cholesterol is important for liposomes as it is used as a membrane additive to fill up the empty spaces between the phospholipids. Cholesterol increases the fluidity of the cell’s membrane and provides an increase in the order of the bilayer as it anchors the components of the bilayer more strongly. This increases the transition temperature of the system and provides stability.                  
Cholesterol is important for liposomes as it is used as a membrane additive to fill up the empty spaces between the phospholipids. Cholesterol increases the fluidity of the cell’s membrane and provides an increase in the order of the bilayer as it anchors the components of the bilayer more strongly. This increases the transition temperature of the system and provides stability.                  
Depending on the molecule that is intended for use, it can either be introduced into an aqueous space or intercalated into the lipid bilayer. Logically, this depends on whether the molecule is hydrophobic or hydrophilic. Unilamellar vesicles, which are liposomes with one lipid bilayer, are the most optimally used with water soluble drugs as they contain the largest aqueous core. However, when lipid soluble drugs are introduced, a multilamellar vesicle is used, as it can passively entrap the drug between its multiple lipid bilayers structured like an onion skin.                   
A liposome containing a certain drug, or genetic material, can be delivered past the cellular lipid bilayer by fusing with the cell’s bilayer. To do this both membranes need to come in very close contact of each other. The liposome fuses with the outer layer of the plasma membrane, then the two fused membranes unite as the inner layers of both membranes get closer to each other as the drug is delivered as both layers fuse.

Revision as of 13:15, 7 December 2015

Liposomes as a drug delivery system

Basic structure

Liposomes are microscopic spherical vesicles. The outer part, the membrane, is composed of a phospholipid bilayer enclosing in an aqueous volume.

Cholesterol in a conventional liposome

Phospholipids are the main building block of liposomes. They have tubular shape and have two acyl chains attached to a polar head, which with hydration results in a bilayer, with a hydrophilic head and two hydrophobic tails. This combination means that liposomes are amphiphilic. Liposomes can either be naturally derived phospholipids or of pure surfactant components like DOPE for example.

Cholesterol is important for liposomes as it is used as a membrane additive to fill up the empty spaces between the phospholipids. Cholesterol increases the fluidity of the cell’s membrane and provides an increase in the order of the bilayer as it anchors the components of the bilayer more strongly. This increases the transition temperature of the system and provides stability.                  

Depending on the molecule that is intended for use, it can either be introduced into an aqueous space or intercalated into the lipid bilayer. Logically, this depends on whether the molecule is hydrophobic or hydrophilic. Unilamellar vesicles, which are liposomes with one lipid bilayer, are the most optimally used with water soluble drugs as they contain the largest aqueous core. However, when lipid soluble drugs are introduced, a multilamellar vesicle is used, as it can passively entrap the drug between its multiple lipid bilayers structured like an onion skin.                   

A liposome containing a certain drug, or genetic material, can be delivered past the cellular lipid bilayer by fusing with the cell’s bilayer. To do this both membranes need to come in very close contact of each other. The liposome fuses with the outer layer of the plasma membrane, then the two fused membranes unite as the inner layers of both membranes get closer to each other as the drug is delivered as both layers fuse.