~(99m)Tc/Gd Rapidly Labeled Functionalized NGO Lymph Node And Tumor Multimodal Molecular Imaging

Nanographene oxide(NGO),a new type of two-dimensional carbon nanomaterials,contains a large number of active chemical groups,such as hydroxyl,carboxyl and epoxy,enabling easy multi-functional modification on its surface to improve its biocompatibility.NGO has exhibited great application potential in the field of molecular imaging,especially in cancer multimodal molecular imaging.In this paper,we covalently modified folic acid(FA)on the surface of polyethylene glycol(PEG)functionalized NGO,and then directly labeled 99 mTc and Gd on the surface of NGOPEG and NGO-PEG-FA to prepare single photon emission computed tomography(SPECT)molecular imaging probe(NGO-PEG@99mTc,NGO-PEG-FA@99mTc)and magnetic resonance(MR)contrast agent(NGO-PEG@Gd,NGO-PEG-FA@Gd).Moreover,we covalently modified NGO-PEG with Cy5.5 to prepare near-infrared fluorescence(NIRF)molecular imaging probe(NGO-PEG-Cy5.5).The mapping and surgical removal of lymph nodes,tumor-targeted imaging and biological behaviors in vivo were investigated by multimodal molecular imaging via SPECT/CT,MRI and NIRF.The full text is divided into four chapters.The first chapter is the introduction.This chapter mainly summarized NGO-based single-modality molecular imaging and multi-modality molecular imaging,and finally proposed the research idea of this paper.In the second chapter,we directly labeled 99 mTc and Gd with NGO-PEG to form NGO-PEG@99mTc and NGO-PEG@Gd,and studied their application on SPECT/CT and MR imaging of lymph node.First,the preparation of NGO-PEG@Gd by direct Gd3+ chelating,and gadolinium-saturated modification and amino-density measurement were studied.Subsequently,99 mTc radiolabeled molecular imaging probe NGO-PEG@99mTc was prepared,and its radiochemical properties and SPECT/CT imaging of lymph nodes were explored.The results showed that it presented good radiolabeling yield and stability,and produced clear SPECT/CT imaging of lymph nodes.For NGO-PEG@Gd,it had high in vitro stability and relaxation rate,low biotoxicity,and yielded clear MR imaging of popliteal lymph nodes via subcutaneous injection.Then,we prepared NIRF molecular imaging probe NGO-PEG-Cy5.5,investigated NIRF imaging of lymph node and NIRF-guided lymph node dissection.Finally,the toxicity of MR contrast agent NGO-PEG@Gd in vivo was studied by tissue distribution(H&E staining),which indicated it had no significant toxicity in vivo and had good biocompatibility.The experimental results above proved that direct labeling of 99 mTc and Gd with NGO-PEG facilitated to rapidly prepare NGO-based multimodal molecular imaging probes,both of which provided high-contrast imaging of lymph nodes,showing great application potential of NIRF-guided surgery of lymph node dissection.In the third chapter,by using the direct labeling of 99 mTc and Gd,we prepared NGO-PEG-FA@99mTc and NGO-PEG-FA@Gd,and investigated the SPECT/CT and MR imaging of 4T1 tumor model.Firstly,on the PEGylated NGO was modified with the target molecule folic acid(FA),and further labeled with Gd and 99 mTc directly,to yield folate receptor(FR)-targeted SPECT molecular imaging probe NGO-PEGFA@99mTc and MR contrast agent NGO-PEG-FA@Gd.In vitro cell experiments showed that the probes had low cytotoxicity,and laser confocal microscopy experiments found that they significantly target to 4T1 cells with high FR expression,whereas no obvious targeting to MCF-7 cells with negative FR expression.Then,NGOPEG-FA@99mTc and NGO-PEG-FA@Gd were injected into the tumor-bearing mice via the tail vein,and SPECT/CT and MR imaging of tumors were performed respectively.The results showed that NGO-PEG-FA@99mTc and NGO-PEG-FA@Gd exhibted high tumor uptake in the active targeting group,whereas no obvious uptake of 4T1 tumor in the passive and blocking groups,which indicated that the prodes had high tumor targeting,facilitating tumor-targeted multimodality molecular imaging.The biodistribution of NGO-PEG-FA@99mTc and NGO-PEG-FA@Gd found they shared similar uptake and change trend in the major organs and tumor,which were consistent with the imaging results.Therefore,the FA-functionalized nanographene oxide had evident FR targeting,and the direct labeling of Gd and 99 mTc facilitated to rapidly prepare tumor-targeted multimodal molecular imaging probes,showing great potential of cancer diagnosis via multimodality molecular imaging.The fourth chapter summarized the experimental data and results in this study,and outlooked the development and application of NGO-based multimodality molecular imaging probes.