Cobalt nanoparticles coated with graphitic shells as localized radio frequency absorbers forcancer therapy

Abstract

Graphitic carbon-coated ferromagnetic cobalt nanoparticles (C–Co-NPs) with diameters ofaround 7 nm and cubic crystalline structures were synthesized by catalytic chemical vapordeposition. X-ray diffraction and x-ray photoelectron spectroscopy analysis indicated thatthe cobalt nanoparticles inside the carbon shells were preserved in the metallic state.Fluorescence microscopy images and Raman spectroscopy revealed effective penetrationsof the C–Co-NPs through the cellular plasma membrane of the cultured HeLacells, both inside the cytoplasm and in the nucleus. Low radio frequency (RF)radiation of 350 kHz induced localized heat into the metallic nanoparticles, whichtriggered the killing of the cells, a process that was found to be dependent on theRF application time and nanoparticle concentration. When compared to carbonnanostructures such as single-wall carbon nanotubes, these coated magnetic cobaltnanoparticles demonstrated higher specificity for RF absorption and heating.DNA gel electrophoresis assays of the HeLa cells after the RF treatment showed astrong broadening of the DNA fragmentation spectrum, which further proved theintense localized thermally induced damages such as DNA and nucleus membranedisintegration, under RF exposure in the presence of C–Co-NPs. The data presentedin this report indicate a great potential of this new process for in vivo tumorthermal ablation, bacteria killing, and various other biomedical applications.