Toward sustainable, smart, and multifunctional Carrageenan bio(nano)composites: Mechanistic insights, physicochemical properties, biomedical interfaces, and AI-driven design perspectives.

Carrageenan (CG), a sulfated galactan derived from red seaweed, has emerged as a versatile biopolymer for developing sustainable, smart, and multifunctional biomaterials. This review critically surveys recent advances in CG bio(nano)composites, emphasizing their structural design, crosslinking mechanisms, and performance across biomedical and environmental interfaces. Ionic (K+, Ca2+), covalent, and polyelectrolyte complexation strategies are compared in terms of mechanical reinforcement, swelling behavior, and controlled drug release, highlighting CG's tunable viscoelasticity and physicochemical adaptability. Integration with metallic, polymeric, and biodegradable nanofillers has expanded its functionality to include antimicrobial, antioxidant, and regenerative applications. Despite these advances, systematic evaluation of parameters such as modulus, mesh size, ion leaching, and cytotoxicity remains inconsistent across studies. This review underscores the need for standardized characterization and predictive modeling frameworks. Finally, emerging artificial intelligence and machine learning approaches are discussed for data-driven optimization of kappa carrageenan (κ-CG) formulation, structure-property correlation, and performance prediction. Together, these insights position κ-CG bio(nano)composites as next-generation, sustainable platforms bridging carbohydrate chemistry with intelligent material design.