Biodistribution of near-infrared emitting CuInS2/ZnS quantum dots by mass spectroscopy and fluorescence imaging of axillary lymph node in healthy mice
Résumé
Background : The biopsy of the sentinel lymph node is now widely used for the breast cancer. Although this approach has strong advantages, it has its own limitations (manipulation of radioactive products and possible anaphylactic reactions to the dye). As recently proposed, these limitations could in principle be by-passed if semiconductor nanoparticles (quantum dots or QDs) were used as fluorescent contrast agents for the in vivo imaging of sentinel lymph nodes. QDs are fluorescent nanoparticles with unique optical properties like strong resistance to photobleaching, size dependent emission wavelength, large molar extinction coefficient, and good quantum yield. Materiel and Methods : 20 μL of 1 μM CuInS2/ZnS core/shell QD solution were injected subcutaneously in the right anterior paw of healthy balb/c mice. Animals were sacrificed at different time points after QDs injection. Organs, blood and excretions were collected and analysed by ICP-MS. Right axillary lymph nodes (RALNs) and right lateral thoracic lymph nodes (RLTLNs) were removed and weighed for histological analysis to visualize inflammatory changes Results : CuInS2/ZnS QDs were observed in RALN, studied organs and blood as soon as 5 min and up to 10 days after the injection by ICP-MS and in vivo fluorescence imaging. The maximum amount of QDs in the RALN was detected 24 h after injection and corresponded to 5 % of the injected dose. Histological sections of RALNs dissected 7 days post-injection have shown that the RALN of mice injected with 20 pmol of CuInS2/ZnS showed no appreciable difference with control lymph nodes. Conclusion : Effective and rapid detection of RALN using fluorescence imaging of NIR emitting CuInS2/ZnS QDs in living animals was demonstrated. Nevertheless, the improvement of their surface chemistry are required to allow their excretion, and therefore, to eliminate any risk of toxicity.