Preparation and Characterization of <scp>pH</scp> ‐Responsive Kaolin‐Containing Pectin/Poly(Acrylic Acid) <scp>IPN</scp> Hydrogel for Potential Colon‐Targeted Drug Delivery

ABSTRACT Diclofenac sodium (DS) is a widely used non‐steroidal anti‐inflammatory drug with a short biological half‐life, necessitating frequent dosing. In this study, a pH‐responsive kaolin‐containing pectin/poly(acrylic acid) interpenetrating polymer network (IPN) hydrogel was developed for controlled, colon‐targeted delivery of DS. The hydrogels were characterized by attenuated total reflectance–Fourier transform infrared spectroscopy (ATR‐FTIR), scanning electron microscopy (SEM), thermogravimetric analysis (TGA), and X‐ray diffraction (XRD). Swelling behavior, gel content, and degradation were also evaluated. ATR‐FTIR analysis confirmed the presence of the characteristic functional groups associated with the hydrogel constituents. SEM observations demonstrated enhanced porosity in kaolin‐containing hydrogel and XRD analysis revealed that the hydrogel network was amorphous. Kaolin incorporation contributed to a more stable network structure and improved gel content while maintaining pH‐responsive swelling. In vitro release studies showed minimal DS release at pH 1.2, followed by enhanced release at pH 7.4, with kaolin‐containing hydrogels exhibiting a more gradual and sustained profile. At pH 7.4, the kaolin‐containing pectin/poly(acrylic acid) IPN hydrogel achieved nearly 97% cumulative release at 25 h. Kinetic analysis at pH 7.4 showed good agreement with the zero‐order, Higuchi, and Korsmeyer–Peppas models. Overall, the developed pH‐sensitive IPN hydrogels show strong potential for prolonged and site‐specific drug delivery to the colon.