Diffusion of functionalized magnetite nanoparticles forced by a magnetic field studied by EPR method

•Synthesis of TEMPO-functionalized magnetite nanoparticles with different coating.•Diffusion of magnetite nanoparticles forced by an inhomogeneous magnetic field investigated by EPR method.•Small gradients of magnetic field used to move the nanoparticles.•Proposition of a new software for calculation of distribution of nanoparticles in a sample.

The article shows the influence of time of the inhomogeneous magnetic field application and the type of coverage on the behavior of functionalized magnetite nanoparticles. TEMPO-functionalized and polymer-coated nanoparticles (Fe3O4@PEG) in water solution were subjected to a magnetic field for 1, 2 and 4 min, while the same nanoparticles mixed with bovine serum for 1 and 2 min. TEMPO-functionalized and silane-coated nanoparticles (Fe3O4@Silane) diluted in water, human blood or human serum were subjected to a magnetic field for 4 min. For each sample before and after its placement in an inhomogeneous magnetic field the electron paramagnetic resonance (EPR) spectra were recorded using an X-band (9.4 GHz) EPR spectrometer. On the basis of EPR spectra we developed a new method and software to study the effect of external magnetic field on the changes in nanoparticles distribution in the samples studied. It has been observed that the placement of the sample with the nanoparticles in the inhomogeneous magnetic field causes them to diffusion, wherein the speed of diffusion depends on the time during which the sample is hold in a magnetic field, the kind of coverage and the type of solvent.