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Fe3O4 nanoparticles were coated with a layer of citric acid, forming coordination bonds between citrate ions and iron ions. The resulting aqueous citrate ferrite colloid was used as a T2-weighted MRI negative contrasting agent. Sequential i.v. doses of citrate ferrite and Magnevist led to increases in MRI image contrast for 40 h and brightness for 30 min; scanning using a Bruker Biospec BC 70/30 USR biospectrotomograph yielded enhanced MRI images. This enhancement of MRI images was used to monitor oncogenesis during magnetohydrodynamic thermochemotherapy (MT) of mammary adenocarcinoma Ca 755 in female C57Bl/6j mice. Dextran ferrite colloid containing cyclophosphamide was tested as a magnetically directed antitumor agent using MT. Treatment of non-infiltrating tumors of volume ≈ 30 mm3 with six sessions of MT each lasting 30 min at 46°C led to 40% tumor regression and 300% increases in survival time. Treatment of infiltrating tumors of volume ≈ 300 mm3 in the same conditions yielded a 200% increase in survival time.

Water-based dextran-ferrite (DF) magnetic fluids for magnetic field hyperthermia were prepared and characterised. Magnetic properties, toxic effects, and mechanisms of magnetic nanoparticles assimilation were investigated. The effective Curie temperature was proved to be too high for self-regulation of heat release. DF based magnetic fluids demonstrate low toxicity and are well tolerable by living organisms.