Development and in vivo imaging of a PET/MRI nanoprobe with enhanced NIR fluorescence by dye encapsulation

Aim: To monitor cells in vivo or to detect the sentinel lymph node, we developed a PET/MRI silica nanoprobe with an enhanced near-infrared fluorescence signal. Methods: We developed enhanced near-infrared fluorescent (NIRF) magnetic silica nanoparticles, MNP-SiO2(NIR797), that encapsulate NIRF dye in the silica. We applied this probe to visualizing cells in the deep tissue of mice using NIRF imaging. After labeling with a radioisotope, 68Ga, on the surface of MNP-SiO2(NIR797), we injected it into the forepaw of mice to visualize the sentinel lymph node. Results: This encapsulated nanoprobe showed enhancement of fluorescent intensity and stability compared with the nanoprobe, which had the same dyes on the surface of the silica nanoparticles. We also obtained multimodal in vivo imaging of 68Ga-{MNP-SiO2(NIR797)} applied to sentinel lymph node detection of mice using PET/MRI/NIRF images. Conclusion: This multimodal nanoprobe with enhanced fluorescence may provide a useful tool for imaging diagnostics and cell tracking.