New superparamagnetic fluorescent Fe@C-C$_5$ON$_2$H$_{10}$-Alexa Fluor 647 nanoparticles for biological applications

The structure and physical properties of superparamagnetic Fe@C nanoparticles (Fe@C NPs) as well as their uptake by living cells and behavior inside the cell were investigated. Magnetic capacity of Fe@C NPs was compared with Fe$_7$C$_3$@C NPs investigated in our previous work, and showed higher value of magnetic saturation, 75 emu.g$^{-1}$ (75 Am$^2\cdot$ kg$^{-1}$), against 54 emu.g$^{-1}$ (54 Am$^2\cdot$ kg$^{-1}$) for Fe$_7$C$_3$@C. The surface of Fe@C NPs was alkylcarboxylated and further aminated for covalent linking to the molecules of fluorochrome Alexa Fluor 647. Fluorescent Fe@C-C$_5$ON$_2$H$_{10}$-Alexa Fluor 647 NPs (Fe@C-Alexa NPs) were incubated with HT1080 human fibrosarcoma cells and investigated using fluorescent, confocal laser scanning and transmission electron microscopy. No toxic effect on the cell physiology was observed. In a magnetic field, the NPs became aligned along the magnetic lines inside the cells.