Synthesis of Starch-g-poly (acrylic Acid-co-2-hydroxy Ethyl Methacrylate) as Potential pH-sensitive Hydrogel-based Drug Delivery System

The present work focused on the design of drug delivery system (DDS) based on a pH-sensitive hydrogel. The hydrogels were prepared via graft copolymerization of mixtures of acrylic acid (AA) and 2-hydroxy ethyl methacrylate (HEMA) onto starch backbones by a free radical polymerization technique. Sodium bicarbonate (NaHCO3) was added to function as a foaming agent under acidic conditions, rendering the hydrogels to be porous. Porous structure of hydrogel was essential in this system to yield a large surface area so that 5-fluorouracil (5-FU) release could be facilitated. The hydrogel thus prepared possessed a porous structure as determined by scanning electron microscopy. Due to the reversible swelling behavior of the hydrogels, the synthesized networks can sense the environmental pH change and achieve an oscillatory release pattern. Using drug 5-FU as a model molecule, the in vitro controlled drugrelease behaviors of these hydrogels were investigated. The results indicate that the main parameter affecting the drug-release behavior of hydrogels is the pH of the solution. The release rate of 5-FU from hydrogel at pH 7.4 was faster than that at pH 1.2 due to the shrinkage of the hydrogel at pH 1.2.These results suggest that a porous hydrogel could potentially be a useful local delivery system to release drugs primarily at a specific site of body.