Production of sustained released system
AssigneeDamon Biotech, Inc.
InventorFranklin Lim
Life of this patent
Estimating the term…
Abstract
Permeable capsules are loaded with a reservoir of the substance to be dispensed at a concentration sufficient to provide an osmotic pressure above threshold level, and the pore size of the capsule membrane is controlled so that the passage of the substance through the membrane becomes the rate-limiting factor in dispensing. Shape-retaining spheres are formed from a water-soluble polymer containing plural anionic or cationic groups and cross-linking surface layers of the spheres by contact with a polymer having plural groups of charge opposite that of the water-soluble polymer. After loading, the capsules are again treated with the same or a different cross-linking polymer to reduce the dimensions of the pores.
Claims12
A process for producing a dispensing system capable of releasing a substance at a substantially constant rate in an environment that depletes said substance, said process comprising the steps of:
- A. forming a capsule which defines an intracapsular volume and comprises a membrane defining a multiplicity of pores of a size sufficient to permit passage of molecules of said substance, said capsule being formed by first preparing a shape-retaining sphere comprising a water-soluble polymer comprising plural cationic or anionic groups and subsequently contacting said sphere with a first polymer comprising plural groups having a charge opposite that of said water-soluble polymer;
- B. placing said capsule in a solution containing a concentration of said substance for a time sufficient to permit said solution and said substance to diffuse into said intracapsular volume to produce a capsule loaded with said substance;
- and
- C. reducing the dimensions of the pores defined by the membrane of said loaded capsule to a degree sufficient to limit the rate at which molecules of said substance pass therethrough by exposing the capsule to a second polymer comprising a multiplicity of groups having a charge opposite that of said water-soluble polymer.
Dependencies are inferred from the claim text.