Pulsatile Release from Microencapsulated Liposomes

Abstract

Ideally, release profiles of drugs from drug delivery systems should be designed to meet specific demands, such as release at a specific time points and predetermined doses; however most systems lack these capabilities. Liposomes are an example of a delivery system that generally release its contents in a continuous fashion. We have pursed two approaches of pulsatile release- that is, release of bursts of incorporated drug at specific time points- with microencapsulated liposomes. In the first approach our studies revealed that the encapsulation of certain liposomes within alginate-poly (L-lysine) microcapsules produce systems that release their contents in a pulsatile manner. In the second approach, enzymatically controlled pulsatile release from microencapsulated liposomes was achieved by incorporating phospholipase A₂ into the systems. In both systems, the number of pulses and duration between the pulses could be regulated by selecting lipid composition, enzyme concentration and type, and other parameters, such as polyelectrolyte (alginate, poly(L-lysine)) and calcium ion concentrations.