Synthesis of starch-g-poly (acrylic acid-co-2-hydroxy ethyl methacrylate) as potential pH-sensitive hydrogelbased drug delivery system

Mohammad Sadeghi

doi:10.17485/ijst/2011/v4i9.11

Abstract

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.

Highlights

Drug release from solid matrix systems, made of polymer(s) and drug(s), is a basic concept for studies on controlled drug delivery
A general reaction mechanism for starch- g -poly(AA-co-hydroxy ethyl methacrylate (HEMA)) hydrogel formation is shown in the Scheme
A novel biopolymer-based superabsorbent hydrogel, starch-g -poly(AA-co-HEMA), was synthesized through simultaneous crosslinking and graft polymerization of acrylic acid and 2-hydroxy ethyl methacrylate mixtures onto starch

Summary

Introduction

Drug release from solid matrix systems, made of polymer(s) and drug(s), is a basic concept for studies on controlled drug delivery. Hydrogels are special soft and pliable polymeric materials that can absorb large quantities of water, saline, or physiological solutions while the absorbed solutions are not removable even under pressure. 1 Stimuli-responsive smart hydrogels that can respond to environmental physical and chemical stimuli, such as temperature, 2 pH, 3 light, 4 magnetic field, 5 and substance species, 6 have attracted great interest in recent years due to their versatile applications such as controlled drug and gene delivery systems, 7−11 chemical-/bio-separations, 12 and sensors and/or actuators. The main reason for this is that delivery systems based on biodegradable polymers do not require removal of the polymers from the body at the end of the treatment period, as they degrade into physiologically occurring compounds that can be readily excreted from the body. The main reason for this is that delivery systems based on biodegradable polymers do not require removal of the polymers from the body at the end of the treatment period, as they degrade into physiologically occurring compounds that can be readily excreted from the body. 14 polymeric hydrogels are of considerable interest as biomaterials in drug delivery research. 15−19

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