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

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Abstract
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 QD 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.