Quantum dots-bevacizumab complexes for in vivo imaging of tumors.

BACKGROUND/AIM The basic role of vascular endothelial growth factor (VEGF) in cancer is underscored by the approval of bevacizumab for first-line treatment of cancer patients. Recent anticancer therapeutics based on active tumor targeting by conjugating tumor-specific antibodies has become of great interest in oncology. Current progress in nanomedicine has exploited the possibility of designing tumor-targeted nanocarriers able to deliver specific molecule payloads in a selective manner to improve the efficacy and safety of cancer imaging and therapy. We herein aimed to determine the targeting ability of bevacizumab-conjugated quantum dots (QDs) in vitro and in vivo. MATERIALS AND METHODS We used QDs labeled with bevacizumab, in various in vitro experiments using cell lines derived from colorectal cancer (CRC) and breast cancer (BC). For a competition study of QD-bevacizumab complex and bevacizumab, the cells were pre-treated with bevacizumab (100 nmol/L) for 24 h before exposure to the QD-bevacizumab complex. The breast cancer cells (MDA-MB-231) were injected to 9 nude mice to make the xenograft tumor model. The QD-bevacizumab complex was injected into the tumor model and fluorescence measurements were performed at 1, 12, and 24 h post-injection. RESULTS Immunocytochemical data confirmed strong and specific binding of the QD-bevacizumab complex to the cell lines. The cells pre-treated with an excess of bevacizumab showed absence of QD binding. The in vivo fluorescence image disclosed that there was an increased signal of tumor after the injection of QDs. Ex vivo analysis showed 3.1 ± 0.8%, 28.6 ± 5.4% and 30.8 ± 4.2% injected dose/g accumulated in the tumors at 1, 12 and 24 h respectively. Tumor uptake was significantly decreased in the animals pretreated with excess of bevacizumab (p=0.001). CONCLUSION In conclusion, we could successfully detect the VEGF-expressing tumors using QDs-bevacizumab nanoprobes in vitro and in vivo, opening new perspectives for VEGF-targeted non-invasive imaging in clinical practice.