Hydrogels for Drug Delivery

Hydrogels, three-dimensional hydrophilic polymer networks capable of retaining large amounts of water, have become pivotal platforms for advanced drug delivery systems due to their unique physicochemical properties, including biocompatibility, tunable degradation, and mechanical characteristics. This chapter comprehensively explores the design, functionalization, and applications of hydrogels in delivering diverse therapeutic agents such as small molecules, proteins, nucleic acids, and living cells with controlled release profiles aligned to clinical needs. Emphasizing the interplay of materials science, biology, and medicine, hydrogels are presented as biomimetic environments that replicate the extracellular matrix, facilitating protective and targeted delivery. This chapter highlights stimulus-responsive mechanisms like pH, temperature, enzymatic, redox, and light triggers, which enable spatiotemporal control over drug release. Detailed discussions cover natural and synthetic polymers, including alginate, chitosan, hyaluronic acid, polyethylene glycol, polyvinyl alcohol, and PNIPAAm, detailing their biodegradability, mechanical properties, and clinical translation. Advanced platforms incorporating nanocomposites, multicompartmental structures, and smart features such as self-healing and shape-memory are also reviewed. The overview concludes with current challenges in formulation, manufacturing, and regulatory approval, while projecting future directions involving AI-guided design and personalized medicine. Collectively, this chapter underscores hydrogels’ transformative potential to revolutionize therapeutic delivery across diverse medical applications.