ABSTRACT
The physiologists used liposomes as models to investigate ionic flow across cell membranes, and the biophysicists used them to study the phase behavior of lipids under precisely controlled conditions. This chapter describes two steps that are involved in the preparation of liposome for parenteral formulation, namely aseptic filtration and lyophilization of the liposome. The interaction mechanisms of liposomes with cells: adsorption, endocytosis, lipid exchange, and fusion. Liposomes are unique as drug carriers in that they can encapsulate drugs with widely varying polarities. Liposome membranes, like biological membranes, are semipermeable. Mechanical dispersion methods are used in the production of the laboratory scale liposomes. In the freezing step, the aqueous liposomal formulation is filled into vials and then the vials are loaded onto temperature-controlled shelves in a large chamber. The chapter discusses the mechanical dispersion, organic solvent dilution, dialysis, freezing-drying, pH-gradient, and gas-bubbling for solubilization. Compared with other solubilization techniques for water-insoluble drugs, liposome technology is a superior choice in many cases.
