Over the past several years, there has been an increase in the use of liposomes particularly when it comes to injectable nutrition and medications. So, what exactly is a liposome?
Liposomes are microscopic vesicles composed of one or more lipid membranes surrounding discreate aqueous compartments. These vesicles can encapsulate water-soluble nutrients and/or drugs in their aqueous spaces and lipid-soluble drugs within the membrane itself. Liposomes release their contents by interacting with cells in one of four ways: adsorption, endocytosis, lipid exchange, or fusion. Liposome-entrapped drugs and nutrients are distributed within the body much differently than free drugs or nutrients. Liposomes also accumulate preferentially at the sites of inflammation and infection and in some solid tumors; however, the reason for this accumulation is not clear (we will discuss this more in another blog post).
Four major factors influence liposomes' in vivo behavior and biodistribution: (1) liposomes tend to leak if cholesterol is not included in the vesicle membrane, (2) small liposomes are cleared more slowly than large liposomes, (3) the half-life of a liposome increases as the lipid dose increases, and (4) charged liposomal systems are cleared more rapidly than uncharged systems.
Terms to know:
Lipids: fats
Liposome: fatty acids
Aqueous: water
Vesicles: a small fluid-filled bladder, sac, or cyst
In Vivo: (of a process) performed or taking place in a living organism