In Vivo Imaging of Sentinel Nodes Using Fluorescent Silica Nanoparticles in Living Mice

We examine the feasibility of fluorescent imaging system for sentinel lymph node detection by using functionalized silica nanoparticles. We developed a functionalized RITC-SiO2 nanoparticles containing fluorescent dye, C28H31N2O3Cl (rhodamine B isothiocyanate) inside, and subsequently synthesized Ga-68-NOTA-RITC-SiO2 nanoparticles. At 5 min after RITC-doped silica nanoparticles injection, fluorescent signals were shown in both right axillary lymph node (ALN) and injection site of living mice. Fluorescent signals were also observed at these locations in a biodistribution study. In addition, fluorescence was detected in frozen ALN sections microscopically. The percentages of doses injected per gram of tissue of axillary and brachial lymph nodes near footpad treated with Ga-68-NOTA-RITC-SiO2 nanoparticles were 308.3 +/- 3.4 and 41.5 +/- 6.1, respectively. Little Ga-68 radioactivity was found in other organs. Our data provide strong evidence that functionalized silica nanoparticles has a promising potential as organic lymphatic tracer in biomedical imaging such as pre- and intraoperative surgical guidance.