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 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.