Near-infrared fluorescent silica-coated gold nanoparticle clusters for x-ray computed tomography/optical dual modal imaging of the lymphatic system.

Lymph nodes (LNs) are often removed to prevent the spread of cancer because they are frequently the first site of metastases. However, the enucleation of LNs requires difficult operative techniques and lymphedema can result as a complication. Although lymphedema can be cured by anastomosis of a lymph vessel (LV) to a vein, the operative procedure is extremely difficult because LNs and LVs are too small and indistinct to be identified. Therefore, visualization of LNs and LVs is important. The combination of X-ray computed tomography (CT) and fluorescence imaging, CT/fluorescence dual modal imaging, enables the visualization of LNs and LVs before and during surgery. To accomplish this, near-infrared fluorescent silica-coated gold nanoparticle clusters (Au@SiO2) with a high X-ray absorption coefficient are synthesized. Both fluorescence imaging and CT show that the Au@SiO2 nanoparticles gradually accumulate in LNs through LVs. CT determines the location and size of the LNs and LVs without dissection, and fluorescence imaging facilitates their identification. The Au@SiO2 nanoparticles have neither hepatotoxicity nor nephrotoxicity. The results demonstrate that CT/fluorescence dual modal imaging using Au@SiO2 nanoparticles provides anatomical information, including the location and size of LNs and LVs for determining a surgery plan, and provides intraoperative visualization of LNs and LVs to facilitate the operation.