Liposomes are spherical engineered particles made of phospholipids used in the pharmaceutical and cosmetic industries. The size and surface charge of liposomes are important characteristics which require measurement and monitoring. Dynamic light scattering (DLS) is the most common analytical technique used for measuring the size of submicron liposomes. Single particle optical sizing (SPOS) is used to measure the size of liposomes greater than one micron. The Entegris Nicomp® DLS system and AccuSizer® SPOS system are used in laboratories around the world for the accurate measurement of the size and charge (zeta potential) of liposomes.
Liposomes are bilayer vesicles routinely used in the pharmaceutical industry as a drug delivery system for transport of chemotherapeutic drugs to the tumor area. They are composed of phospholipids which have a polar end attached to a nonpolar chain that self assembles into bilayer vesicles with the polar ends facing the aqueous medium and nonpolar ends forming a bilayer. In pharmaceutical applications the active pharmaceutical ingredient (API) is usually incorporated into the liposome, either into the hydrophilic pocket or sandwiched between the bilayers depending on the hydrophilicity of the API.