Authors: Ionela Asmarandei Gheorghe Fundueanu Mariana Cristea Valeria Harabagiu Marieta Constantin
Publish Date: 2013/10/26
Volume: 20, Issue: 11, Pages: 293-
Abstract
Interpenetrating polymer networks IPN consisting of pHsensitive carboxymethyl pullulan CMP and thermosensitive polyNisopropylacrylamide PNIPAAm were synthesized through a twostep procedure by chemical crosslinking of NIPAAm in the presence of CMP followed by additional reticulation of the polysaccharide The hydrogels were characterized by Fourier transform infrared spectroscopy scanning electron microscopy and swelling measurements Swelling properties of the hydrogels were studied at equilibrium by investigating pH and temperaturedependence dynamic swelling ratio and pulsatile swellingdeswelling kinetics It was found that IPN hydrogels responded to both temperature and pH changes and such stimuliresponsiveness was reversible At pH 12 and temperature values lower than VPTT the swelling ratios of IPN hydrogels are smaller than that of pure PNIPAAm because most of the carboxylic groups are protonated forming hydrogen bonds with other carboxylic or amide groups of PNIPAAm Conversely in phosphate buffer solutions at pH 74 the swelling ratios of IPN hydrogels are higher than that of pure PNIPAAm In this case the carboxylic groups of CMP are ionized therefore the hydrogen bonds are broken and the electrostatic repulsions lead to a more expanded network The loading and release profiles of a model drug namely diphenhydramine DPH were also evaluated The results showed that the release rate of DPH was higher at pH 10 buffer solution than at pH 74 and 12 at 37 °C In pseudo physiological conditions DPH was quickly released from the hydrogel at 20 °C and showed a sustained release profile at 37 °C
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