Abstract: Terpolymers which are sensitive to pH and temperature are useful carriers for conducting bioactive agents through the gastric juices of the stomach in protected form. Such terpolymers swell at the higher physiologic pH of the intestinal tract causing release of the bioactive agents into the intestine. The terpolymers are linear and are made up of 35 to 99 wt % of a temperature sensitive component, which imparts to the terpolymer LCST (lower critical solution temperature) properties below body temperatures, 1 to 30 wt % of a pH sensitive component having a pK.sub.a in the range of from 2 to 8 which functions through ionization or deionization of carboxylic acid groups to prevent the bioactive agent from being lost at low pH but allows bioactive agent release at physiological pH of about 7.4 and a hydrophobic component which stabilizes the LCST below body temperatures and compensates for bioactive agent effects on the terpolymers.

Abstract: A drug delivery device is described which utilizes gas pressure from free oxygen and hydrogen derived from the electrolysis of water at the electrodes in negatively charged polymeric hydrogels by electro-osmosis. The gas pressure forces the infusion of the drugs through appropriate means into the body. The rate of electrolysis which produces the oxygen and hydrogen is controlled by an electric current. Therefore the rate of drug delivery can be predetermined and precisely controlled. The current is activated and controlled by an electronic timer or a biomedical control system. The negatively charged hydrogel polymers have mechanical strength and rigidity and allow water to flow through the polymer network toward the cathode ensuring a continuous water supply to the electrodes inside the hydrogel system by electro-osmosis. The hydrogels may be recharged (reswollen) with water or simply replaced.

Abstract: An artificial pancreas system which minimizes the volume of the artificial pancreas by not encapsulating each islet is taught wherein the islets are separated and held within a polymeric matrix which is soluble in an aqueous solution below body temperature but insoluble in aqueous solutions at or above body temperature. The polymer-islet mixture is contained in a pouch having access means such as entry and exit ports. The solubility makes it possible to replace the contents of the pouch by solubilizing the matrix simply by lowering the temperature below the LCST. The pouch is constructed of a biocompatible material permeable to insulin and other substances of similar or lesser molecular weight but is impermeable to cellular and humoral components of the body immune system. The islet-polymer matrix can be functionalized to stimulate insulin secretion from the islets using insulinotropic agents such as sulfonylurea.

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.

Abstract: A heterogeneous interpenetrating polymer network is provided for use in the controlled release of drugs. The network is a heterogeneous matrix that is formed from a hydrophilic component such as polyethylene oxide or poly(N,N'-dimethyl acrylamide-co-styrene) and a hydrophobic component such as styrene, an alkyl methacrylate, or polytetramethylene ether glycol. The relative amounts of the two components, or "domains", can be varied, as can the diffusivities and solubilities of the drug combinations to be loaded therein, to control and change as desired the timed release profile of incorporated drug. Prolonged pseudo-zero order release can be obtained where one domain acts as a diffusion barrier layer to the release of drug from the other domain.