ABSTRACT
The new type of hydrogel system (which is known under the trademark HYPAN), is described in some detail here, emphasizing its grades and those properties potentially useful in controlled drug delivery systems. HYPAN hydrogels are distinguished by a physical network of crystalline clusters which fully replace the covalent network typical of other hydrogels. As a result, HYPAN hydrogels can be processed by a number of methods unusual for hydrogels, such as extrusion, injection molding and the like. The crystalline network also provides HYPAN with improved mechanical properties at higher water contents, which in turn allows for higher permeabilities of aqueous solutes. The combination of improved mechanical properties and permeabilities with improved processability and good biocompatibility is believed to open some new possibilities in targeted and controlled drug delivery. This paper is written as an overview of the compositions, structures and essential properties of HYPAN materials. It will soon be followed by more detailed studies in selected areas.
Subject(s)
Acrylic Resins , Delayed-Action Preparations , Absorption , Adsorption , Biocompatible Materials , Chemistry, Pharmaceutical , Materials Testing , Models, Molecular , Molecular Structure , Permeability , Polymers , Proteins/pharmacokineticsABSTRACT
Topical sustained release of various medications by a subdurally implantable device at the site of spinal cord injury is considered advantageous in the treatment of early symptoms of tissue damage. A typical case is the interference with collagenous scar by beta-aminopropionitrile, inhibiting collagen polymerization. Four materials, silicone, polyethylene, polytetrafluoroethylene (PTFE), and polyacrylonitrile-based hydrogel were evaluated for biocompatibility in subcutaneous implantations. The hydrogel, the least reactive, was then compared with silicone sheets as subcural implants. The histology favored the hydrogel as the most inert material, which was then used for the construction of soft, pliable pouches, releasing the drug through the hydrated wall at a rate controlled by an osmotic pump.
Subject(s)
Aminopropionitrile/analogs & derivatives , Aminopropionitrile/administration & dosage , Spinal Cord Injuries/drug therapy , Aminopropionitrile/metabolism , Aminopropionitrile/therapeutic use , Animals , Biocompatible Materials , Dogs , Drug Implants , Male , Membranes, Artificial , Permeability , Polyethylenes , SiliconesSubject(s)
Abortion, Induced/methods , Acrylic Resins , Adult , Dilatation/methods , Evaluation Studies as Topic , Female , Humans , Laminaria , PregnancyABSTRACT
Measurements of the permeability coefficients of various compounds up-to a molecular weight of about 70,000 have shown clearly that membranes prepared from hydrolyzed polyacrylonitrile are about 10 times more permeable than those made of poly(2-hydroxyethyl) methacrylate. The higher permeability is probably due more to the higher water content (about 75%) than to the type of network. The high mechanical strength of the membranes and their good permeability to compounds possessing a comparatively high molecular weight seem to designate the material for some new applications in medicine.
