Cross-Linking the Blue: Trends in Marine-Based Hydrogels

Marine-derived natural polymers have attracted increasing interest as sustainable, high-value biomaterials for hydrogel development, owing to their biocompatibility, biodegradability, and tunable physicochemical properties. This study maps publication retrieval and patent trends related to marine-derived biopolymers and hydrogel cross-linking technologies between 2000 and 2024, based on keyword searches of four bibliographic databases combining “marine”, the biopolymer name and “cross-linking”, with or without a specific cross-linking type, and individually screened patent records. Retrieval counts increased overall in all four databases with all search categories reaching their highest counts in 2020–2024, and the number of patents rose sharply in 2020–2024. Over the study period, alginate and chitosan were the most frequently retrieved algae- and animal-derived biopolymers in each database, while patents were concentrated in health and medical applications, with collagen represented in the highest number of patents. Among the cross-linking type terms, “chemical” returned the most records in every database, and no records were retrieved for the enzymatic cross-linking of most algae-derived biopolymers. Fucoidan, hyaluronic acid and carrageenan occupied an intermediate position, whereas ulvan, laminarin, agarose and chondroitin sulfate were rarely retrieved and had limited or no patent data. The main rankings were consistent across all four databases and the individually screened patent records showed similar temporal and biopolymer patterns. Based on these data, marine-derived polymers were classified into three development tiers, and the barriers and opportunities for their further development are discussed.