Gold nanotags for combined multi-colored Raman spectroscopy and x-ray computed tomography.

Multi-color gold-nanoparticle-based tags (nanotags) are synthesized for combined surface-enhanced Raman spectroscopy (SERS) and x-ray computed tomography (CT). The nanotags are synthesized with quasi-spherical gold nanoparticles encoded with a reporter dye (color), each with a unique Raman spectrum. A library of nanotags with six different colors were synthesized for a range of gold nanoparticle sizes and an optimum size has been established to yield the largest SERS intensity and x-ray attenuation that is higher than the iodinated CT contrast agents used in clinics. Proof-of-principle in vivo imaging results with nanotags are presented that, for the first time, demonstrates the combined in vivo dual modality imaging capability of SERS and CT with a single nanoparticle probe.