Harnessing the power of brown seaweed: The science and applications of alginate

Abstract

Alginate is a polysaccharide derived from the sea, with a tunable structure and mild ionic gelation property, which has allowed it to move from a conventional hydrocolloid to an advanced biomaterial platform. This review addresses progress in alginate development from brown seaweed, emphasising the relationship between feedstock, extraction, molecular framework, processing, and end performance. The main extraction methods, traditional acid-alkali extraction and novel ultrasound, microwave, enzyme, extrusion, pressure and subcritical-water-assisted methods, are analysed, focusing on the effect of processing conditions on molecular weight, mannuronic acid/guluronic acid (M/G) ratio, purity, viscosity and gel-forming behaviour. Alginate material architecture is linked to physicochemical properties such as water interaction, rheology, ionic gelation, swelling, film- and fibre-forming ability, mechanical properties, biocompatibility, and chemical modifiability. Conventional beads, hydrogels, films, and fibres are discussed alongside microfluidic spinning, electrospinning, pressurised spinning, and 3D/4D bioprinting. The review critically discusses applications in drug delivery, wound care, tissue engineering, cell encapsulation, regenerative medicine, food and packaging, agriculture, and environmental remediation. It places special emphasis on sustainability, highlighting energy- and water-intensive processing, feedstock variability, scale-up constraints, and the need to evaluate alginate across its entire value chain. The review emphasizes green extraction, structure–property optimisation, multifunctional composites, scalable manufacturing, standardized characterization, life-cycle assessment, techno-economic analysis, and integrated seaweed biorefineries as major directions for translation. Overall, the future of alginate lies not only in expanding its applications but also in developing predictable, application-specific, sustainably manufactured materials that can move from laboratory innovation to industrial and biomedical implementation.