Fluorescence Imaging and Whole-Body Biodistribution of Near-Infrared-Emitting Quantum Dots after Subcutaneous Injection for Regional Lymph Node Mapping in Mice

Purpose: This study compares fluorescence imaging to mass spectroscopy (inductively coupled plasma mass spectroscopy, ICP-MS) for detection of quantum dots (QDs) in sentinel lymph node (LN) mapping of breast cancer. Procedures: We study the accumulation of near-infrared-emitting QDs into regional LNs and their whole-body biodistribution in mice after subcutaneous injection, using in vivo fluorescence imaging and ex vivo elemental analysis by ICP-MS. Results: We show that the OD accumulation in regional LNs is detectable by fluorescence imaging as early as 5 min post-delivery. Their concentration reaches a maximum at 4 h then decreases over a 10-day observation period. These data are confirmed by ICP-MS. The QD uptake in other organs, assessed by ICP-MS, increases steadily over time; however, its overall level remains rather low. Conclusions: Fluorescence imaging can be used as a non-invasive alternative to ICP-MS to follow the QD accumulation kinetics into regional LNs.