Hydrogel-Based Drug Delivery: From Traditional Formulations to Advanced Applications

Hydrogels—three-dimensional, water-rich polymer networks—have become pivotal in drug delivery research owing to their biocompatibility, tunable properties, and capacity for controlled release. Early hydrogel systems provided steady, sustained drug release but offered limited targeting and responsiveness. Recent advances in polymer science, nanotechnology, and fabrication methods have resulted in “smart” hydrogels with environmental triggers, improved mechanical stability, and site-specific targeting. This review outlines the evolution of hydrogels from traditional sustained-release platforms to advanced, stimuli-responsive formulations. Key topics include fundamental hydrogel chemistry, drug-loading methods, classifications by source and responsiveness, and mechanisms of drug release. The discussion then moves to exemplary applications, including cancer therapy, wound healing, ocular treatments, and neurological disorders. Safety, toxicity, and regulatory perspectives are also addressed, along with current challenges—such as manufacturing scale-up—and future directions in personalized medicine and integrated bioelectronic systems. Collectively, this review underscores the growing significance of hydrogel-based drug delivery for improving treatment efficacy and patient quality of life.