b2815 Tissue Engineering and Nanotheranostics “9.61x6.69”112 Tissue Engineering and Nanotheranostics
decomposition of iron oleate and then phospholipid–polyethylene gly-
col (PL–PEG–COOH) was used to transfer the phase from hydro-
phobic to hydrophilic providing the –COOH functional group on
the surface. A layer of poly-L-histidine (PLH), positively charged
peptide, is adsorbed onto the external surface of MNPs–PEG via
charge interaction and the gold shell is developed by the reduction of
gold. The organic molecules around the surface of MNPs present
constrain direct gold growth on iron oxide nanoparticles and the gap
can be seen in the TEM picture (Fig. 5(e)).
Recently, iron carbides (Fe 3 C, Fe 5 C 2 , and Fe 7 C 3 ) have attained
significant attraction in both applied engineering and fundamental
science. Iron carbide nanostructures have demonstrated high stability
because of carbon atoms on the surface and high saturation magneti-
zation (~140 emu/g) which are promising characteristics for mag-
netic storage and bioimaging applications.^39 A facile synthesis method
provided by Ma et al. is shown in Fig. 6.40,41
Fig. 6. (a) and (b) Graphical representation of the synthesis mechanism of Fe 5 C 2 NPs,
black spots are carbon, silver are Fe and brown are oxygen, (c) TEM, (d) HRTEM images,
and (e) magnetic hysteresis loops for Fe 5 C 2 NPs after surface modification and (blue
line) exposed in water for six months. Reprinted with permission from Refs. 40 and 41.