Hydrogel as advance drug delivery system

Hydrogels three-dimensional, hydrophilic polymer networks capable of absorbing large amounts of water have emerged as versatile platforms for advanced drug delivery. This review synthesizes foundational concepts, materials and fabrication methods, mechanisms of drug loading and release, stimuli-responsive and multifunctional hydrogel systems, and translational considerations including biocompatibility, sterilization, regulatory perspectives, and commercialization challenges. Emphasis is placed on injectable, in situ-forming hydrogels, hydrogel–nanoparticle hybrids, and applications in cancer therapy, wound healing, ocular delivery, and RNA/biologic delivery. The review concludes with critical gaps and future directions to accelerate clinical translation.