Patent ID: 6403057
Filing Date: 2002-06-11
Classification: A61K

Abstract:
A process of making a solid microcapsule for use in ultrasound echography with a mean size from a fraction of micrometer to 1000 micrometers, the microcapsule having a biodegradable, 50 to 500 nm thick membrane encapsulating air or a gaseous core, wherein the membrane is obtained from:(1) one or more biodegradable, water insoluble and at room temperature solid lipids selected from di-glycerides, tri-glycerides, fatty acids having at least 12 carbon atoms, sterols, waxes and mixtures thereof, and (2) up to 75% by weight of biodegradable polymers, said process comprising the steps of: (a) dissolving the biodegradable lipid and optionally a biodegradable polymer in an organic solvent or a solvent mixture, (b) admixing the solution of step (a) with an aqueous phase, (c) emulsifying the mixture of step (b) to form oil-in-water emulsion, (d) adding a redispersing agent, (e) freezing the emulsion, (f) lyophilizing the frozen product of step (e) to form a powder containing semi-spherical or spherical air or gas filled microcapsules, (g) dispersing the lyophilized powder in an aqueous carrier, (h) separating the air or gas containing microcapsules from any debris by decantation, and (i) drying the recovered microcapsules.