Stearic Acid-Coated Chitosan-Based Interpenetrating Polymer Network Microspheres: Controlled Release Characteristics

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 mu m 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.