Functional activity features of lactoferrin-fucoidan complexes in model systems in vitro

Fucoidan, an anionic polysaccharide from brown algae, demonstrates anticoagulant, antioxidant, anti-inflammatory, antitumor, and antiviral activities. It can form polyelectrolyte complexes with various proteins, including the therapeutically important protein lactoferrin. The aim of this study was to investigate the physicochemical and functional properties of a fucoidan-lactoferrin complex formed by mixing their solutions at physiological pH. The complex, detected using atomic force microscopy, had a negative charge and a hydrodynamic diameter of 382 nm. Interaction with lactoferrin changed the IR spectrum of fucoidan in the absorption band in the range of 1220-1260 cm-1, corresponding to vibrations of the sulfate group. It increased the total antioxidant activity of biopolymers in the Fenton reaction and reduced the anticoagulant activity of fucoidan, assessed by determining the activated partial thromboplastin time. Fucoidan reduced luciferase activity in a luciferin-luciferase model system, and complex formation with lactoferrin attenuated the inhibitory capacity of fucoidan. These results demonstrate the possibility of targeted influence on the functional activity of biopolymers during complex formation and prospects for using fucoidan and lactoferrin as a complex in the development of new drugs and drug delivery systems.