Dual-function Small Molecule Fluorescent Probe For Tumor-targeted Bio-imaging And The Detection Of Nitric Oxide

Molecular imaging technology has become the most development potential of multi-disciplinary field of research in recent years. The discovery of new molecular tumor markers is the key to the development of tumor imaging. Tumor-targeted probes will not only help us in early diagnosis of cancer, but also contribute to the objective evaluation of tumor medical response and to optimal therapeutic strategies.Recent studies have found that integrin plays an indispensable role in tumor angiogenesis. According to the cyclic RGD peptide affinity with integrin, someone prepared the RGD modified tumor-targeted imaging probes and the imageing results were good. Nitric oxide (NO) has a very important role in tumor occurrence and migration as a signal molecule. Our laboratory synthesized a NO fluorescent probe, it could be used for the direct detection and imaging of NO. But the fluorescent probe with the dual function of NO determination and tumor targeting has still not been reported.This paper firstly designed and synthesized N-{3-(2-phenyl imidazole)-4-hydroxyphenyl}maleimide(HMPB). This compound reacted with thiol group of cyclic RGD (RGDfC-SH) and generated a strong fluorescent probe RGDfC-HMPB at room temperature. The expression of integrin receptors of MDA-MB-231cells are more than MCF-7cells. In the cell integrin receptor affinity experiment, RGDfC-HMPB was added in these cells, and the results of fluorescence microscopy observation indicated that the probe binded to MDA-MB-231cells significantly more than MCF-7 cells. Further research founded that the affinity of RGDfC-HMPB with MDA-MB-231cells could be competitively inhibited by RGD. The result fully showed that the probe targeted to the integrin receptors in the cells mediated through the RGD motif. In4T1and S180tumor-bearing mice, the distribution of the probe in vivo showed that72h after tail vein injection, RGDfC-HMPB probe fluorescence intensity in the tumor tissue reached maximum, suggested that the probe well targeted to tumor blood vessels.RGDfC-HMPB probe and Cu2+were prepared for copper (II) complexes RGDfC-HMPB-Cu, fluorescence spectroscopy characterization results showed that the fluorescence of copper(Ⅱ) complexes extracted off, and it restored after reacting with NO, suggested that copper(Ⅱ) complexes could be used for the detection of NO. Experimental results showed that copper(II) complexes directly detected NO produced by LPS stimulated RAW264.7cells. Finally, the tumor tissue distribution and determination of NO of copper (II) complexes in4T1tumor-bearing mouse, indicated that the copper (II) complexes not only targeted tumor blood vessels but also detected NO effectively. The dual-function fluorescent probe provides a new way for the development of tumor imaging probes, expected to be a powerful tool for early diagnosis of cancer.