Semi-interpenetrating network of acrylamide-grafted-sodium alginate microspheres for controlled release of diclofenac sodium, preparation and characterization

• The sodium alginate was successfully modified by grafting with acrylamide.
• The graft copolymer, AAm-g-NaAlg was then crosslinked with GA to form MPs by water in oil (w/o) emulsification method.
• The diffusion coefficient (D) was found to be dependent on the amount of crosslinking agent (GA) and amount of grafting ratio in the matrix.
• The values of diffusional exponent, n ranged from 1.27 to 1.47, suggesting that the drug release mechanism from MPs follows the super Case II transport.

The semi-interpenetrating networks (semi-IPNs) of acrylamide grafted sodium alginate (AAm-g-NaAlg) microspheres (MPs) were prepared by emulsion-crosslinking method using glutaraldehyde (GA) as a crosslinking agent. The grafting of acrylamide onto sodium alginate was prepared by free-radical graft polymerization using ceric ammonium nitrate (CAN) as initiator at three acrylamide concentrations with monomer to polymer ratio of 1:1, 2:1 and 3:1, respectively. The grafting efficiency was found to be 91%. The produced MPs are almost spherical in nature with smooth surfaces. Diclofenac sodium (DS), an anti-inflammatory drug was successfully encapsulated into the MPs. The encapsulation efficiency was found to vary between 83% and 95%. The MPs were characterized by differential scanning calorimetry (DSC), scanning electron microscopy (SEM) and Fourier transform infrared (FTIR) spectroscopy. The diffusion coefficient (D) was dependent upon the amount of crosslinking agent (GA) and amount of grafting ratio in the matrix. The rate of release was found to be dependent on the amount of GA, AAm:NaAlg grafting ratio and % drug loading in the MPs. The release data have been fitted to an empirical equation to investigate the diffusional exponent (n), which indicated that the release mechanism from MPs follows the super Case II transport.

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