蛙皮素样肽t-BBN与肿瘤细胞高表达的胃泌素释放肽受体GRPR具有高度亲和力，t-BBN可作为肿瘤特异性标记物用于分子影像学研究。申请者拟在前期研究的基础上，采用迭代还原法将Au3+逐次还原在Fe2O3表面，通过控制Au3+还原次数和金壳层厚度，制备同时符合CT和MRI增强成像要求的金磁性纳米粒Fe2O3@Au。通过Fmoc多肽固相合成法合成t-BBN短肽，在肽链氨基端定点修饰HS-PEG-COOH，再利用Au-S共价键作用，将复合物连接于Fe2O3@Au表面，制备GRPR靶向的CT和MRI双模态分子探针Fe2O3@Au-PEG-t-BBN。将人乳腺癌T47-D细胞（高表达GRPR）和MCF-7细胞（不表达GRPR）移植于裸鼠皮下，引入分子探针后CT和MRI成像研究它对高表达GRPR乳腺癌的靶向识别作用、体内分布和药代动力学，为高表达GRPR肿瘤的CT和MRI双模态成像提供一条新途径。

Bombesin like peptide (truncated bombesin, t-BBN) has high binding affinity with gastrin releasing peptide receptor (GRPR), which is extensively expressed in tumor cells. So t-BBN can be used as a specific biomarker for molecular imaging of tumor. Based on the research fundament, the applicant wants to use iterative reduction method to reduce Au3+ onto Fe2O3 surface to synthesis core-shell structure Fe2O3@Au nanoparticles. By regulating the reduction cycles and the gold nanoshell thickness, to insure the nanoparticles can satisfy the demands of CT and MRI contrast imaging. The t-BBN peptide can be synthesized by Fmoc solid phase peptide synthesis method, and site-specifically modificated by HS-PEG-COOH of the N-terminal amino acid. After that, the molecular probe Fe2O3@Au-PEG-t-BBN can be synthesized by coupling of Fe2O3@Au nanoparticles with PEG-t-BBN via Au-S covalent bond. The human breast cancer cell lines of T47-D cells (GRPR+) and MCF-7 cells (GRPR–) are selected to build mouse xenografts models. After intravenous injection of Fe2O3@Au-PEG-t-BBN, CT and MR imaging will be performed to study the target recognition effect, biodistribution and pharmacokinetics of the molecular probe. The study would provide a new method to image tumors with high GRPR expression by CT and MRI dual-mode imaging.