Synthesis and evaluation of Cy5.5-Rit tracer for specific near-infrared fluorescence imaging of sentinel lymph node

Sentinel lymph nodes biopsy (SLNB) is a critically important technique to determine the metastatic status of primary breast cancer. Here we reported the new use of a conjugate, Cy5.5-Rituximab (Cy5.5-Rit), which is specific toward the CD20 receptor, as an imaging agent for non-invasive near-infrared fluorescence (NIRF) imaging of sentinel lymph nodes (SLN). The conjugate, Cy5.5-Rit, was synthesized with the ratio of dye to Rituximab close to 1.0. Both gel electrophoresis and mass spectrometry analysis confirmed the molecular integrity of Cy5.5-Rit. For in vivo NIRF imaging, the conjugate stayed in SLN as long as 9 days post injection. The in vivo imaging results of SLN targeting were also confirmed by in vitro HE stain. In addition, the direct fluorescence signal of dissected lymph node demonstrated that Cy5.5-Rit binds to the surface of lymph node cells. All of these results showed that the conjugate Cy5.5-Rit has potential for non-invasive optical imaging of SLN. (C) 2016 Elsevier Ltd. All rights reserved.