Multivesicular liposomes with controlled release of encapsulated biologically active substances

A multivesicular liposome having multiple non-concentric chambers with internal membranes distributed as a network throughout, produced by a method comprising the steps of:

• (a) forming a water-in-oil emulsion from two immiscible components, the two immiscible components being:
• 1) a lipid component comprising at least one organic solvent, at least one amphipathic lipid, and at least one neutral lipid lacking a hydrophilic head group, and
• 2) a first aqueous component;
• said water-in-oil emulsion further comprising:
• 3) non-hydrohalic acid in a concentration range from about 0.1 mM to about 0.5 M, wherein the concentration is selected to provide controlled release of the biologically active substance in 4) from the liposome, and
• 4) at least one biologically active substance;
• said non-hydrohalic acid and said biologically active substance being independently incorporated into the lipid component, the first aqueous component, or both;
• (b) mixing the water-in-oil emulsion containing the non-hydrohalic acid with a second aqueous component to form solvent spherules;
• and thereafter
• (c) removing the organic solvent from the solvent spherules to form multivesicular liposomes.