Polyvinyl alcohol (PVA)-based hydrogels have attracted significant attention due to their excellent biocompatibility, tunable mechanical properties, and ability to form stable three-dimensional networks. This comprehensive review explores the recent advancements in PVA-based hydrogels, focusing on their unique properties, fabrication strategies, and multifunctional applications. Firstly, it discusses various facile synthesis techniques, including freeze/thaw cycles, chemical cross-linking, and enhancement strategies, which have led to enhanced mechanical strength, elasticity, and responsiveness to external stimuli. These improvements have expanded the applicability of PVA-based hydrogels in critical areas such as biomedical, environmental treatment, flexible electronics, civil engineering, as well as other emerging applications. Additionally, the integration of smart functionalities, such as self-healing capabilities and multi-responsiveness, is also examined. Despite progress, challenges remain, including optimizing mechanical stability under varying conditions and addressing potential toxicity of chemical cross-linkers. The review concludes by outlining future perspectives, emphasizing the potential of PVA-based hydrogels in emerging fields like regenerative medicine, environmental sustainability, and advanced manufacturing. It underscores the importance of interdisciplinary collaboration in realizing the full potential of these versatile materials to address pressing societal challenges.

Alginate-based hydrogels, derived from brown seaweed, represent biocompatible and biodegradable materials whose properties are systematically controlled through molecular structure (M/G composition), crosslinking strategy, and compositional modification. This review synthesizes recent advances in alginate hydrogel design, encompassing fundamental structural properties, three primary crosslinking approaches—ionic coordination with divalent cations (Ca²⁺, Ba²⁺, Sr²⁺), covalent chemical linkages, and hybrid multi-crosslinking systems—and strategic modification strategies including chemical derivatization, polymer blending, and nanoparticle incorporation. These modifications address inherent limitations of native alginate, namely insufficient mechanical strength and biological inertness, thereby expanding applicability. The review examines applications across biomedical domains (drug delivery, tissue engineering, wound healing), environmental remediation, food industry systems, and emerging technologies including flexible electronics and soft robotics. Advanced fabrication techniques—3D/4D printing, microfluidics, and electrospinning—enable improved architectural control. Current evidence from preclinical and clinical studies demonstrates feasibility in specific applications, while important challenges persist, including predictable degradation kinetics, mechanical property optimization, standardization of characterization protocols, regulatory compliance, and manufacturing scalability. This review aims to provide a systematic assessment of alginate-based hydrogel development and identify areas requiring further investigation to advance clinical translation.