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A novel type of pH-sensitive hydrogel blend of poly(vinyl alcohol) with acrylic acid-graft-guar gum has been prepared. Microspheres with a size of ∼10 µm were produced by the water-in-oil (w/o) emulsification method for investigating the controlled release of an antituberculosis drug, isoniazid. These novel carriers were analyzed for surface morphology, size, effect of pH, swelling, drug loading, and in vitro release of isoniazid in pH 1.2 and 7.4 media. The kinetics of drug release was analyzed using empirical equations. Release times of the drug were increased to 8 h from its nascent plasma half-life of 0.5-1.6 h.

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Acrylamide-grafted-guar gum (pAAm-g-GG) was prepared and blended with chitosan (CS) to form interpenetrating polymer network (IPN) hydrogel microspheres by the emulsion cross-linking method using glutaraldehyde (GA) as a cross-linker. The microspheres encapsulated up to 74% of ciprofloxacin (CFX), an antibiotic drug, having a plasma half-life of 4 h and the release of CFX was extended up to 12 h. Scanning electron microscopy (SEM) confirmed their spherical structure with smooth surfaces; Fourier transform infrared spectroscopy (FTIR) confirmed the grafting reaction as well as chemical stability of CFX in the blend IPN hydrogel microspheres. Differential scanning calorimetry (DSC) and X-ray diffraction (XRD) techniques confirmed the molecular level dispersion of CFX in the matrix. Swelling of microspheres performed in pH 7.4 buffer media was used to understand the drug release kinetics. In vitro release of CFX in pH 1.2 and 7.4 media showed a dependence on blend composition of the IPN, extent of cross-linking as well as initial drug loading. In vitro release data was analyzed using empirical equations, namely, KorsmeyerÀPeppas, to compute the diffusion exponent (n), whose value ranged between 0.19 and 0.33, indicating non-Fickian transport of CFX through the blend IPN hydrogel microspheres.

Semi-interpenetrating polymer network (semi-IPN) hydrogel blend microspheres of gelatin and hydroxyethyl cellulose were prepared by a water-in-oil (w/o) emulsion technique and used to investigate the controlled release (CR) of theophylline (THP), an antiasthamatic drug. About 74% encapsulation of THP was achieved, and the drug release profiles were analyzed in terms of gelatin and hydroxyethyl cellulose blend composition, amount of cross-linking agent, and percentage drug loading. Fourier transform infrared (FTIR) spectroscopy confirmed the formation of the IPN blend matrix, as well as chemical stability of the drug in the microsphere. The physical state of the drug in the IPN matrix as evaluated by differential scanning calorimetry (DSC) and X-ray diffraction (XRD) remained undisturbed. The size of the microspheres varied from 98 to 144 μm as measured by laser light scattering. Scanning electron microscopy (SEM) indicated the smooth surface morphology of the microspheres. Equilibrium and dynamic swelling of the microspheres in distilled water were measured to compute the diffusion coefficient (D v) of the drug solution through the microspheres. The in vitro cumulative release data were analyzed using an empirical equation to compute the diffusion exponent (n), whose values suggest a non-Fickian mode of transport.

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Novel pH-sensitive stearic acid-coated interpenetrating polymer network (IPN) blend microspheres of chitosan and gelatin were prepared by the emulsion cross-linking method using glutaraldehyde for the controlled release (CR) of isoniazid (INH), an antituberculosis drug. Coated as well as uncoated microspheres were developed and characterized by Fourier transform infrared (FTIR) to understand the chemical interactions and formation of the IPN blend structure as well as to confirm successful coating with the stearic acid. X-ray diffraction (XRD) indicated the distribution of INH, while differential scanning calorimetry (DSC) was used for investigating the thermal stability of the IPN blend matrices. Scanning electron microscopy (SEM) was used to distinguish between the morphologies of coated and uncoated microspheres. Coated microspheres were produced in the size range of 52 μm down to 502 nm with encapsulation efficiencies of 65−78%. Equilibrium swelling was studied in pH 1.2 and pH 7.4 buffer media, and the in vitro drug release showed the dependence of drug release on the cross-linking, blend ratio of the IPN matrix as well as stearic acid coating. The variations in the IPN blend ratio and cross-link density controlled the drug release up to 30 h, but the coated microspheres could reduce the burst release in the gastric stomach media, while enhancing in intestinal pH 7.4 media.