pH-Responsive composite based on prednisone-block copolymer micelle intercalated inorganic layered matrix: Structure and in vitro drug release

Amphiphilic block copolymer, poly(tert-butyl acrylate-co-ethyl acrylate-co-methacrylic acid), was well established as building block for the preparation of negatively charged micelle, which contains hydrophobic drug prednisone (PNS) in the core. The micelle was further intercalated into galleries of magnesium–aluminum layered double hydroxide (LDH) for the study of drug carrier and release behavior. Powder X-ray diffraction (XRD), Fourier transform infrared (FT-IR) and UV–vis spectroscopy indicate a successful intercalation of PNS-containing micelle between the LDH layers. The scanning electron microscope (SEM) image shows that the as-synthesized drug/polymer–LDH composite exhibits compact microspheres morphology. The release behavior at different pH values was studied in detail, and it was found that the release rate increases with the increase of pH value. Studies on mathematical modeling of drug release show that the system approaches a release mechanism described by approximately Fickian diffusion at pH 7.2 and exhibits anomalous transport at pH 6.4, while it shows the combination of diffusion through the matrix and degradation of the micelle at pH 4.8. The controlled release formulations in this work indicate that this drug-containing composite has potential application in the field of site-specific drug delivery to the colon (pH 7.2), taking advantage of the long transit time and almost complete release.