Application of Taguchi Method to Investigate the Drug Release Behavior of Poly(Acrylamide-co-Maleic Acid)/Montmorillonite Nanocomposite Hydrogels

The pH-sensitive poly(acrylamide-co-maleic acid)/montmorillonite (P(AAm-MA)/MMT) nanocomposite hydrogels were synthesized through in situ polymerization. The chemical structure and morphology of nanocomposites were characterized by Fourier transform infrared spectroscopy, X-ray diffraction, and transmission electron microscopy. The resulted disks were then loaded by caffeine, a moderately soluble model drug, using soaking method. The swelling and the drug release experiments were carried out in enzyme-free simulated gastric and intestinal fluids. The release experiments showed that with the addition of MMT, the burst effect is well controlled, and the barrier property of nanocomposite hydrogels is improved. The effects of some compositional parameters including maleic acid to acrylamide (MA/AAm) molar ratio (MA(R)), weight percent of MMT (MMT%), cross-linker/AAm molar ratio (C-R), and also the influence of pH of medium on the equilibrium swelling ratio (Q) as well as caffeine release behavior of disks were studied by Taguchi method. The results indicated that shifting the pH value from 1.2 to 7.4 leads to a greater Q. The Q value and the release percentage (P%) increased with increasing the MA(R) in the structure of disks at pH 7.4. The amounts of P% and Q in both external media decreased with increasing both MMT% and C-R. Mathematical behavior of release process was well represented by Peppas Power law model (at short times) and a two-dimensional Fickian mass transfer model (at long times). The caffeine release behavior in both media was corresponded to the non-Fickian transport mechanism.