Drug release behaviors of a pH/thermo-responsive porous hydrogel from poly(N-acryloylglycinate) and sodium alginate

A pH/thermo-responsive hydrogel with porous structure (HME), composed of poly(N-acryloylglycine methyl ester), poly(N-acryloylglycine ethyl ester) and sodium alginate (SA) was prepared for the controllable drug carrier. The resultants, CO₂ and CaCl₂ from the reaction of CaCO₃ particles and HCl act as pore-forming and crosslinking of SA, respectively. The porous HME was characterized by differential scanning calorimetry, scanning electron microscopy (SEM), Fourier transform infrared spectroscopy and surface area and porosity analysis. The sheet, porous structure was clearly observed by the SEM measurement and the specific surface area of HME was evidently increased with an increase of CaCO₃ content. At pH 2.1 phosphate buffered saline (PBS), the release amount of caffeine at room temperature was only 7.2 % within 600 min, while this value approached to 65.3 % at pH 7.4 PBS. Additionally, the cumulative release at 37 °C is much higher than that at room temperature due to the thermo-sensitivity of HME. The experimental results indicated that porous HME has a potential to be used as the promising release-controlled drug carrier in the biomedical fields.