ECHOGENIC LIPSOMES FOR TARGETED DRUG DELIVERY

Echogenic immunoliposomes (ELIP) are under development to enable ultrasound-controlled drug delivery. Mechanistic studies in vitro have revealed that stable cavitation is correlated with enhanced recombinant tissue Plasminogen Activator (rt-PA) thrombolysis, yet strategies to optimize the occurrence of such bubble activity and avoid potential harmful bioeffects have yet to be identified. Stable cavitation is characterized by bubbles pulsating gently in response to the time-varying acoustic pressure in an ultrasound field. A review of in vitro sonothrombolysis studies utilizing commercial US contrast agent or echogenic liposomes loaded with rt-PA to nucleate stable cavitation will be presented. Strategies for the development of ultrasound-enhanced thrombolysis and drug delivery will be discussed. Targeted echogenic immunoliposomes (ELIP) are under development to highlight thrombus or atheroma components. Liposomes, or phospholipid bilayer vesicles enclosing gas and fluid, are novel agents that may permit evaluation of vasoactive and pathologic endothelium. Since first examined by Bangham et al. [1], liposomes have been developed for a wide range of technical and medical applications. Echogenic liposomal dispersions can be prepared b