Hydrogels are three-dimensional polymeric networks that retain large amounts of water and, due to their soft and tissue-like properties, are considered one of the most promising classes of biomaterials. Their unique advantage lies in the ability to provide mechanical support while simultaneously storing and gradually releasing bioactive compounds. By mimicking the natural extracellular environment, hydrogels are increasingly used as carriers for the targeted delivery of therapeutics, particularly macromolecules that are sensitive to degradation. This work emphasizes the physicochemical mechanisms underlying hydrogel performance, including the Flory-Huggins and Flory-Rehner theories as well as the concept of free volume. These parameters are closely linked to diffusion and drug-release dynamics, enabling the design of materials with finely tuned release profiles. Special attention is given to glass transition temperature, mesh size, and their impact on controlled release. Recent advances have introduced a new generation of hydrogels, such as stimuli-responsive, self-assembling peptide-based, nanocomposite, and hybrid systems that combine the strengths of different material classes. Alongside traditional approaches involving chemical and physical crosslinking, modern techniques such as 3D bioprinting are gaining importance, offering precise fabrication of customized, functionally graded structures and thus bridging the gap between conceptual design and real-world application. The biomedical relevance of hydrogels is illustrated through applications in regenerative medicine and pharmaceutical delivery, ranging from neuro- and cardiac tissue regeneration to targeted drug release within the gastrointestinal tract or across the skin barrier. More broadly, the work includes a review of the literature and demonstrates how the interplay of chemistry, physics, and engineering strategies can give rise to "smart" hydrogel systems that pave the way toward safer, more effective, and patient-friendly therapeutic solutions.
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