| Summary: | The aim of the current study was to prepare pH-sensitive chondroitin sulfate-co-poly(acrylic acid) hydrogels (CSPAA-hydrogels) for controlled release of diclofenac sodium. CSPAA-hydrogels were prepared by free radical polymerization technique where chondroitin sulfate (CS) was used as polymer; ethylene glycol dimethylacrylate (EGDMA) and acrylic acid (AA) were used as cross-linker and monomer. Various structural features of hydrogels were evaluated by FTIR, XRD, TGA, DSC, and SEM, which confirmed the synthesis and stability of developed structures. FTIR studies confirmed the successful grafting of acrylic acid on the backbone of chondroitin sulfate. XRD results showed that the high intensity crystalline peaks of drug were reduced by developed hydrogel, thus no interaction of drug and hydrogel contents was observed. Thermal analysis revealed that the developed hydrogel network was more stable thermally than its basic ingredients (chondroitin sulfate). Sporous structure of CSPAA hydrogels was confirmed by SEM, corresponding to high swelling of hydrogels. Dynamic swelling indicated high swelling of hydrogels at pH 7.4 as compared to pH 1.2, as a result, high in-vitro drug release was shown at pH 7.4. Similarly, the drug release rate in pH 7.4 medium was significantly higher than that pH 1.2 medium. Kinetic modelling including zero order, first order, Higuchi and Korsmeyer–Peppas models were applied to know the release mechanism of drug from fabricated hydrogels.
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