The relationship between the mechanisms of animal polysaccharides and their structural and conformational features.

This review characterizes the mechanisms of action of animal polysaccharides (chitin, chitosan, hyaluronan, chondroitin sulfate, dermatan sulfate, keratan sulfate, heparin/heparan sulfate) based on their structural and conformational features. A systematic search was conducted in PubMed, Scopus, Web of Science, and the Russian Citation Index (2015-2026). The review organizes polysaccharides according to three structure-dependent targeting paradigms: (1) charge-mediated targeting (chitosan, dermatan sulfate), where cationic or anionic density determines electrostatic interactions; (2) molecular weight-dependent receptor selection (hyaluronan, chitosan), where chain length dictates receptor engagement and signaling outcomes; and (3) sulfation pattern-directed protein recognition (heparin/heparan sulfate, chondroitin sulfate, keratan sulfate), where specific O- and N-sulfation codes enable selective protein binding. Key findings reveal that biological activity depends largely on molecular weight, sulfation pattern, and charge density, with concentration-dependent reversal of immunomodulatory effects - low doses elicit anti-inflammatory while high doses induce pro-inflammatory activation - representing a critical consideration for therapeutic design. Recent methodological advances (UPLC-MS/MS, chemical synthesis, chemoenzymatic synthesis) now enable detailed structure-activity studies, particularly for keratan sulfate, though knowledge gaps remain. The convergence of mechanisms across polysaccharide classes - particularly NF-κB pathway modulation - suggests common principles underlying bioactivity. The review also addresses major obstacles to clinical translation, including polydispersity, batch variability, and characterization challenges, and proposes future research directions to overcome these limitations.