From molecular architecture to clinical translation: Structure-property-performance relationships in alginate-based nanostructured hydrogels.

Alginate-based hydrogels have emerged as versatile biomaterials because of their biocompatibility, high water content, mild aqueous processing, and tunable network architecture. However, their performance is strongly dependent on molecular characteristics, including molecular weight, mannuronic-to-guluronic acid (M/G) ratio, block distribution, degree of functionalization, and crosslinking density. This review critically examines how these parameters govern the physicochemical, mechanical, biological, and translational performance of alginate-based nanostructured hydrogels. Particular emphasis is placed on ionotropic gelation, covalent functionalization, oxidation, sulfation, grafting, and hybrid covalent-ionic crosslinking, together with nanocomposite reinforcement and advanced biofabrication strategies. Recent studies demonstrate that controlling network architecture and nanoscale organization can substantially improve mechanical stability, degradation behavior, drug-loading and release characteristics, cellular interactions, and tissue-regeneration performance. For example, re-cent alginate systems have achieved optimized pore dimensions in the ∼100-200 μm range for cell-supporting scaffolds, drug encapsulation efficiencies approaching or exceeding 90% in selected nanostructured systems, and high cell viability (>95%) in representative double-network hydrogel platforms. The review further identifies persistent challenges involving source-to-source variability, batch reproducibility, ion exchange, insufficient intrinsic bioactivity, controlled degradation, sterilization, and clinical translation. Finally, future opportunities are discussed in stimulus-responsive networks, hierarchical biofabrication, multifunctional nanocomposites, sustainable alginate extraction, and data-driven structure-property optimization. The review establishes a structure-processing-property-biological performance framework for the rational design of next-generation alginate-based nanostructured hydrogels.