Abstract: This invention features in vitro methods of determining the rate and extent to which test compounds, such as drug candidates, enter, move within, and traverse lipid-associated barriers. This invention also features method that measure the accumulation, that is the partition coefficient, of test compounds in lipid structures relative to, e.g., an aqueous phase, as well as the rate of accumulation of test compounds in the lipid structures. In addition, the invention features lipid vesicles that contain fluorophores localized within the aqueous interior that can be employed in the methods described herein.

Abstract: This invention features in vitro methods of determining the rate and extent to which test compounds, such as drug candidates, enter, move within, and traverse lipid-associated barriers. This invention also features method that measure the accumulation, that is the partition coefficient, of test compounds in lipid structures relative to, e.g., an aqueous phase, as well as the rate of accumulation of test compounds in the lipid structures. In addition, the invention features lipid vesicles that contain fluorophores localized within the aqueous interior that can be employed in the methods described herein.

Abstract: Phospholipid liposomes are provided having a lipid bilayer surrounding a confined composition which includes a gas or a gas precursor. The liposomes can be administered to a patient and can be detected in vivo by ultrasound techniques which permit organ imaging.

Abstract: Phospholipid liposomes are provided having an outer layer including a cholesterol derivative such as a cholesterol ester and an aqueous medium confined by the layer which includes a tracer agent, a cytoxic agent or a therapeutic agent. The liposomes are adapted for specific organ targeting.