Two-color lymphatic mapping using Ig-conjugated near infrared optical probes.

To map the drainage patterns of the lymphatic system, multicolor optical probes must be developed, which can be interstitially administered. These agents must be of sufficient size to be retained by the lymphatic system and permit the conjugation or incorporation of fluorescent probes with varying emission wavelengths. Quantum dots fulfill these criteria, but their potential toxicity limits their application to research settings. Here, we describe the synthesis of lymphatic optical probes based on Igs conjugated with Cy5.5 and Cy7 and demonstrate in animal models that these agents can map the lymphatic drainage patterns within axillary nodes draining both the breast and upper extremity, cervical nodes draining both the ear and upper extremity, and sentinel lymph nodes draining different anatomic locations. The ability to separately and simultaneously visualize the drainage patterns from two separate lymphatic vessels may have implications for the preoperative mapping of lymph nodes before lymph node resection. The biocompatibility of fluorescently labeled Igs in comparison to other nanoparticulate fluorophores improves the chances of clinical translation. This noninvasive and biocompatible multicolor method of optical lymphangiography may elucidate the complex human lymphatic system and reduce the risk of lymphedema after surgery for melanoma and other cancers.