Therapeutic agents target delivery may enhance the effectiveness of drug action and at the same time reduce a number of side effects. Therefore, the development of drug delivery systems using natural polymers is a burning problem. A high-molecular-weight polymer, fucoidan in particular, along with magnetic particles was used for the research. The hydrodynamic radius of the obtained biocomposites was studied using the dynamic light scattering. The results show that with the increase in magnetic nanoparticles in specimens, electrokinetic potential grows. High prop