The necessity of obtaining new sorbents with medico-biological functions causes the urgency of new methods creation, by which the synthesis of magnetocarried nanocomposites with selective sorbing agent’s features may be held. Nanosized magnetic particles coverage by highly effective chelating agent allows the purification of biosystems by nanostructures with functions of nanorobots of the first generation. In order to form polymeric layer on the surface of magnetic nanoparticles, which may act as a ligand, contain free tiol groups, cause transmission of nanoparticles from organic phase to an aqua one and provide for biostability, meso-2,3-dimercaptosuccinic acid (DMSA) was taken. The new technique of chemical modification of the monodomain magnetite surface by DMSA was developed to create nanocomposites for microbiological objects recognition in biological environment. The characteristics of obtained nanocolloid magnetic suspensions were analized. Zeta-potential (-40,3 mV) and average size (40,5 nm) of the magnetic particles suspension was measured by the method of dynamic light scattering. Methods of RPhS and IR spectroscopy were used to prove the the presence of disulfide bridges and –SH groups on the modified surface, while the method of iodometric titration the quantitive content of –SH functional groups was determined.