Synthesis, characterization and in vitro application of pH/temperature sensitive superabsorbent hydrogel of phosphated co-polymer of methacrylic acid and methyl methacrylate ester

Abstract

This study presents an efficient functionalization method of methacrylic polymers such as Eudragit L100. The incorporation of phosphate groups results in pH/temperature-sensitive superabsorbent hydrogels. They are characterized spectroscopically by 1H-, 13 C- 31P-NMR and FT-IR. Thermal analyses, powder X-ray diffractometry and scanning electron microscopy are also carried out. The swelling experiments of the hydrogels take place in phosphate buffer of different pH values at various temperatures and it is found that the hydrogels follow second order kinetics. The swelling percents are in the range of 5200 and 2160 % at 37 °C and pH 7.2, and up to 7130 % at 55 °C and pH 8.0. The matrices of the hydrogels show bimodal curves on the dissolution study which correlate the drug release with the swelling results. The release of the drug achieves values from 12 to 24 times slower than those obtained with Eudragit L100. The synthesized hydrogels respond to changes in pH and temperature and show a collapsing to swelling phase behavior not reported before. These properties make them useful to be studied as potential in site-specific delivery systems.