P2-09-04: Near Infra Red Quantum Dots as Novel Probes for Sentinel Lymph Node Biopsy.

Abstract

Abstract Background: Sentinel Lymph Node Biopsy (SLNB) is a standard procedure in breast cancer surgery. The current tracers for SLNB including the blue dye and radiocolloid, have various limitations like anaphylactic reaction to the dye and exposure of radioactivity to both patients and staff. Quantum dots (QDs) are fluorescent nanoparticles (2-10nm in diameter), with unique photophysical properties like enhanced photostability and size tunable emission wavelengths, that can potentially replace the current tracers for SLNB. QDs emitting in the Near Infra Red (NIR) range of the electromagnetic spectrum can be tracked in deep tissues as biological tissues are transparent to NIR wavelengths (700-2000nm). We have developed Near Infra Red emitting Quantum Dots (NIR QDs) as alternative probes for SLNB and set up a live NIR imaging system to track them in deep tissues. Materials and Methods: NIR emitting QDs based on CdTeHg were synthesized by a one pot aqueous method and characterized using Transmission Electron Microscopy (TEM), UV-V is*** spectrometry and photoluminescence studies. 100μl of QDs (1mg/ml) were co-injected intradermally with blue dye into the hind legs of rat models (n=4) and compared to controls (n=4) which were injected with blue dye only. The procedure was conducted under inhalational anaesthesia using isofluorane and rats were monitored for hemodynamic instability for a period of 2 hrs after injection. QDs were tracked using a live NIR imaging system including an excitation light of 630nm, emission filter of 850nm and a Hamamatsu Orca 2 UV-Vis-NIR thermoelectrically cooled CCD camera. Results: NIR QDs had a core diameter of 7nm on TEM and emitted at 860nm upon excitation with a 630nm light source. Within 3 minutes of an intradermal injection QDs entered the lymphatic tracts. The lymphatics converged to the groin and a small surgical incision at this site revealed the underlying sentinel lymph node with minimal dissection. The rats remained hemodynamically stable throughout the duration of the procedure with no significant difference in comparison with the controls. Conclusion: NIR emitting QDs can be used for accurate localisation of the SLN prior to surgical incision, making this an even more minimally invasive procedure and possibly an office based procedure in the future. The nanosize, surface chemistry and deep tissue visibility of these novel nanoprobes allow relentless possibilities for in vitro and in vivo molecular and cellular imaging. NIR QDs can be conjugated to biomolecules for cancer localisation, detection of micrometastasis and image guided targeted drug delivery of chemotherapeutic agents. Further studies to investigate their in vivo biodistribution are in progress to take this technology one step closer to clinical application. Citation Information: Cancer Res 2011;71(24 Suppl):Abstract nr P2-09-04.