System for delayed and pulsed release of biologically active substances

A method for making a microencapsulated system for controlled release of entrapped biologically active substances comprising:

• providing a first biologically active substance,
• entrapping the first substance within liposomes, wherein the liposomes have a predetermined rigidity, permeability, stability, and sensitivity to stimuli selected from the group consisting of pH, sonication, temperature, high ionic strength solutions, bivalent metals, detergents, phospholipases, and light, such that exposure to a stimulus effects release of the entrapped substance from the liposomes, and,
• encapsulating the substance-containing liposomes within microcapsules, wherein the microcapsules are permeable to solutions and the substance to be released but impermeable to scavenging components of the reticuloendothelial system, have a predeterined diameter, rigidity, stability, and are non-toxic to the encapsulated liposomes and host if implanted.

A method for controlled release of an entrapped biologically active substance comprising:

• releasing by exposure to a specific stimuli a first biologically active substance entrapped within encapsulated liposomes having a predetermined rigidity, permeability, stability, and sensitivity to specific stimuli selected from the group consisting of pH, sonication, temperature, high ionic strength solutions, bivalent metals, detergents, phospholipases, and light, such that exposure to a stimulus effects release of the entrapped substance from the liposomes, wherein the permeability of the liposomes has been disrupted after encapsulation within microcapsules that are permeable to solutions and the substance to be released but impermeable to scavenging components of the reticuloendothelial system, having a predetermined diameter, rigidity, stability, and non-toxicity to the encapsulated liposomes and host if implanted.