Carbon-coated FeCo nanoparticles as sensitive magnetic-particle-imaging tracers with photothermal and magnetothermal properties

The low magnetic saturation of iron oxide nanoparticles, developed primarily as contrast agents for magnetic resonance imaging, limits the sensitivity of their detection via magnetic particle imaging. Here, we show that FeCo nanoparticles 10 nm in core diameter bearing a graphitic carbon shell decorated with poly(ethylene glycol) provide a signal intensity for magnetic particle imaging that is about 6-fold and 15-fold higher than the signals from the superparamagnetic iron oxide tracers Vivotrax and Feraheme at the same molar concentration of iron. We also show that the nanoparticles have photothermal and magnetothermal properties and can thus be used for tumour ablation in mice, and that they have high optical absorbance in a broad near-infrared region spectral range (700–1200 nm in wavelength), which also makes them suitable as tracers for photoacoustic imaging. As sensitive multifunctional and multimodal imaging tracers, carbon-coated FeCo nanoparticles may confer advantages in cancer imaging and hyperthermia therapy.