Fluorescent molecular imaging of metastatic lymph node using near-infrared emitting low molecular weight heparin modified nanoliposome based on enzyme-substrate interaction

Tumor metastatic lymph node mapping has been widely used to predict the metastatic spread of primary tumor and guide the lymph node dissection in clinical practice. In this research, a new near-infrared (NIR)-emitting low molecular weight heparin (LMWHEP)-modified Cy7-loaded nanoliposome (LMWHEP-NLips/Cy7) was developed and had the particle size of about 80nm and the fluorescence intensity of about 2300, which is optimal for metastatic lymph node uptake and imaging. The NIR-emitting nanoliposomes were designed by LMWHEP coating on the surface of Cy7-loaded nanoliposome (NLips/Cy7) according to electrostatic attraction. The LMWHEP-NLips/Cy7 with negligible cytotoxicity for Hela and RAW264.7 cells and was found to be fluorescent stability compared with the Cy7-free dye at room temperature. The BALB/c nude mice bearing tumor lymphatic metastasis was established at eighth week post-injection by subcutaneously injecting Hela cells suspension. Heparanase (HPA) expression concentrations quantitatively measured by ELISA kit respectively were 237.42U/mL, 214.82U/mL and 128.45U/mL in the extracellular Hela cells, metastatic popliteal and iliac lymph node. LMWHEP-NLips/Cy7 successfully increased fluorescence signal in the metastatic lymph node compared with normal lymph node and achieve in vivo and ex vivo high fluorescence signal within 10min and retention time up to 4h post-injection. Maximum mean fluorescence intensity of the LMWHEP-NLips/Cy7 group was significantly more than NLips/Cy7 group (increase 2-fold in the metastatic popliteal lymph node and 4.8-fold in the metastatic iliac lymph node, p<0.05). The experimental results demonstrating LMWHEP-NLips/Cy7 have the potential utility as specific, biosafe and stable near-infrared imaging contrast agents for HPA-expression tumor metastatic lymph node mapping. Copyright (c) 2016 John Wiley & Sons, Ltd.