| abstract |
Novel controlled-release compositions are disclosed. These compositions comprise: (1) an agent suitable for use in a selected environment; and (2) a membrane surrounding this agent. The membrane is substantially inert to the agent and permeable to the environment, its thickness and permeability comprising a means for controlling diffusion of the environment therethrough. The membrane thickness is substantially uniform due to the presence of a quantity of submicron particles therein, these particles being substantially inert to the membrane and the agent. The membrane comprising the submicron particles is capable of releasing the agent to the selected environment at a predetermined time by a variety of mechanisms. The release mechanisms that may be selected for use with a composition will depend in part on the choices of agent, membrane, and submicron particle materials, as well as on the choice of environment into which the composition is to be introduced. |