Surface modifi cation of magnetic nanoparticles (MNPs) with tetramethylorthosilicate and 3-aminopropyltrimethoxysilane was studied. The use of N-phosphonomethyliminodiacetic acid for the stabilization of the initial MNPs can signifi cantly increase the coating thickness and specifi c surface area of SiO2/APS-modifi ed (APS is 3-aminopropylsilane) MNPs. The possibility of sorption of antitumor drug doxorubicin (DOX) on the synthesized nanoparticles was studied. The degree of sorption of DOX increases with an increase in the specifi c surface area of the particles.