AIR-CONTAINING LIPOSOMES

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This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. Primary support for the subproject and the subproject's principal investigator may have been provided by other sources, including other NIH sources. The Total Cost listed for the subproject likely represents the estimated amount of Center infrastructure utilized by the subproject, not direct funding provided by the NCRR grant to the subproject or subproject staff. Liposomes are self-forming lipid bilayer arrays separating an aqueous internal compartment from the bulk aqueous phase with clearly separated hydrophilic and hydrophobic regions. Initially, liposomal preparations were modified to permit gas encapsulation in order to be used as a targetable contrast agent for ultrasound imaging enhancement. These preparations have been termed "echogenic liposomes (ELIP)". When a gas is encapsulated into a liposome, the gas can be presumed, for thermodynamic reasons, to reside between the two monolayers of the liposome bilayer or as a monolayer covered air bubble within the aqueous compartment of liposomes. Our samples are liposomes in 0.32 M mannitol solution. The size distribution of of the liposomes falls into two primary populations, 100 nm and 1,000 nm, with the average size at 800nm. In our previous research, we have successfully co-encapsulated drugs and genes into ELIP and have imaged our ELIP using freeze fracture electron microscopy. The highly acoustic liposomes have demonstrated a spherical structure with the acoustic formulation.