FIELD : chemical-pharmaceutical industry.SUBSTANCE : invention relates to the chemical and pharmaceutical industry and is a suspension of magnetic polymer long-term stable micro- and submicroparticles for labeling cells of the system of mononuclear phagocytes, consisting of iron oxyhydroxide cores, a polymer based on dextran and a silicon containing shell, such as silicon dioxide, in which : the polymer simultaneously connects several magnetic cores in the composition of the particle and emerges onto the surface of the particle, while the solid silicon-containing shell is formed around the magnetic cores and fixes the polymer in its structure.EFFECT : invention makes it possible to obtain magnetic polymeric particles that retain their magnetic, biochemical, and colloidal properties for a long time, which can be effectively absorbed by tissue macrophages in the body.11 cl, 2 dwg, 6 ex