In vivo NIR imaging of nanoparticle lymphatic migration: (Top) IR-813 encapsulated eNP are seen migrating from the site of injection (arrow) to a regional draining lymph node (arrowhead) through a discrete lymphatic channel. Shown are representative color (left), NIR fluorescence (middle), and a pseudocolored (red) merged (right) images, 24 hours after injection. Scale bar = 1 cm.(Bottom) Using real-time, intraoperative NIR image guidance, the specific draining lymph node is identified and distinguished from adjacent non-draining LNs. Shown are representative images of the dissected, fluorescent LN (right) and an adjacent non-draining node (left). Arrowhead marks sinus entry point. Scale bar = 0.5 cm.