Novel pH-sensitive blend microspheres for controlled release of nifedipine--an antihypertensive drug

Water-soluble acrylamide (AAm)-grafted-chitosan (CS) copolymer (AAm-g-CS) was synthesized using potassium persulfate (PPS) initiator from which interpenetrating polymer network (IPN) microspheres were prepared by water-in-oil (w/o) emulsion that are cross-linked with glutaraldehyde (GA) and used for encapsulating nifedipine (NFD). Microspheres were coated with sodium alginate (NaAlg) to enhance their pH-sensitivity for extending the release time of NFD up to 14 h, releasing with 93% of NFD. The coated and uncoated microspheres were characterized by Fourier transform infrared spectra (FTIR) and differential scanning calorimetry (DSC) to understand chemical interactions and blend compatibility. Morphology and particle size of the microspheres were assessed by scanning electron microscopy (SEM) and particle zeta analyzer, respectively. Swelling and in vitro release experiments were performed in pH 1.2 and 7.4 buffer media, which showed a dependence on IPN blend composition, extent of cross-linking and amount of AAm used. Empirical analysis of drug patterns suggested the differences between NaAlg coated and uncoated microspheres.