Importance

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Abstract

A device for the dispensing of a biologically active material into the surrounding environment is disclosed which consists of at least one wall enclosing a compartment which contains a swollen stimuli sensitive hydrogel in which the biologically active material is entrained in solution. The hydrogel deswells or shrinks in response to contact by external physical or chemical stimuli releasing the biologically active material into the portion of the compartment previously occupied by the swollen hydrogel. The wall enclosing the compartment is rigid and contains means allowing the passage of the biologically active material from the compartment to the surrounding environment and also for transmitting the external stimuli to the swollen hydrogel in said compartment. The wall may contain orifices or be permeable to the active material and external stimuli depending upon the drug and the stimuli to be used. The hydrogel reversibly deswells, shrinks or contracts in response to stimuli, such as temperature, pH, ionic strength, glucose concentration or metabolites in the body and then reswells and reentrains active material not diffused from the compartment when the stimuli is removed. The wall may consist of one or more layers which, in combination, provide for the expeditious delivery of the active substance either through permeation through the wall or through orifices in the wall and also for the conducting of the external stimuli through the wall into the compartment to trigger the deswelling of the hydrogel.

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First Claim