We report the development of a self-assembling protein nanocage as a contrast agent for magnetic resonance imaging (MRI). The protein nanocage is derived from genetically engineered ferritin from

GaP/GaO x core-shell nanowires and nanochains have been synthesized in a large quantity by thermal evaporation of mixture of GaP and Ga powders at high temperature. The as-synthesized products were characterized by X-ray diffraction, scanning electron microscopy, and transmission electron microscopy. Microstructure analysis indicates that both products are composed of GaP nanowires and GaO x amorphous shells. Their growth directions are along face-centered-cubic (fcc) GaP <11 j 1> direction with high density twins. The transport properties were also investigated by patterning the core-shell nanowires and nanochains on Si/SiO 2 substrates. The characteristic I-V curves demonstrated good conductivity for the core-shell nanowires and nanochains, but a field-effect property was only observed in the core-shell nanowires. A distinct response between the core-shell nanowire and nanochain devices was observed under an illumination of an ultraviolet light, which might be attributed to the nature of the nanowires and nanochains.