Tacrolimus-Loaded Superabsorbent Hydrogels: Formulation, Evaluation, and Therapeutic Potential

Background: Tacrolimus belongs to the BCS class-II drug family and exhibits poor water solubility, which leads to poor bioavailability. Furthermore, since tacrolimus is an immunosuppressant, it is essential to maintain its therapeutic concentration for a greater period of time to confirm its effectiveness against transplant rejection. Therefore, to achieve the objective of the sustained release of the drug with a suitable amount of entrapment efficiency, pH-sensitive tacrolimus-loaded superabsorbent hydrogels using chitosan have been prepared. Methodology: The free-radical polymerization technique has been used to develop the hydrogel formulation, where chitosan served as the polymer, acrylamide served as the monomer, n,n'-methylenebis-(acrylamide) served as the cross-linker, and potassium persulfate served as the initiator. The prepared formulations were evaluated for their swelling behavior, entrapment efficiency, porosity, in vitro drug release, and kinetics. The formulation design and optimization have been carried out using a statistical tool, i.e., Design Expert. Results: A good swelling capacity and porosity of the hydrogel have been observed, advocating a well-interconnected network structure suitable for drug entrapment and release. The porosity of the prepared hydrogel was found to be 77.7-232.16%, while the sol-gel fraction ranged between 4.65 and 17.71 and 82.29 and 95.35%, respectively. Furthermore, the release of 59.9% of the drug over 8 h of the studies has assured a good sustained behavior of the formulation. Conclusions: The outcomes of the studies have been advocating the successful execution of the research work, where the prepared hydrogel has demonstrated a good entrapment efficiency, followed by a suitable sustained-release behavior. Conclusively, the selected combination of the drug and excipients, the adopted method of hydrogel preparation, and the evaluation process were quite efficient for the delivery of a drug like tacrolimus.