Abstract
A design and construction of new type of drug delivery systems having signal responsive controlled release function was studied using semiconductor material and the fabrication technique. A silicone wafer was fabricated by a lithographyetching to make chips with 5×5 mm wells and a pitch to connect the chips, The chips were covered with a pyrex glass plate. Holes for drug release were penetrated in the cover glass lid (Type A) or in the bottom of silicone well (Type B). A crosslinked poly acrylic acid layer was formed on the holes as the pH-responsive sensor-gate by a monomer coating and the photo-polymerization. Release of methylene blue as a model drug by natural stream was investigated. The release was promoted with the increases of numbers of chip and hole. Then the pH change responsive releases of methylene blue were studied. The drug release was remarkably promoted under acidic conditions and retarded under alkaline conditions owing to reversible volume changes of polyacrylic acid layer between shrinkage and expansion. It was proved that the system having polyacrylic acid sensor-gate carried out the pulsatile releases of methylene blue in response to the on-off switching of pH changes between acidic and alkaline pHs. Further studies would be done on the independent release design from each indivisual chip and the networked and programmed release design from the integrated chip systems, using the silicone semiconductor and the fabrication techniques.
