如何实现对胰岛移植物数量及功能变化的实时、准确评估是目前胰岛移植临床及研究领域仍未解决的难点。既往采用的移植前简单标记并不能准确反映移植物的状态。项目组前期合成出靶向胰岛细胞表面GLP-1受体的磁共振造影剂-SPIO-exendin4，可良好实现胰岛细胞瘤的靶向显像。本项目延续前期工作基础，拟采用SPIO-exendin4实现胰岛移植物的靶向示踪，并利用基于10Fn3蛋白骨架及mRNA展示技术，筛选可与GLP-1R特异性高效结合的抗体类似蛋白质（AMPs）作为靶向物质，以克服exendin-4短肽的不足，并通过造影剂反复、多次靶向成像以建立信号强度与移植物数量及功能状态的相关性。同时，我们利用SPIO-exendin4及SPIO-AMPs对胰岛的靶向性，实现胰岛保护剂C3G在体内对移植物区域的靶向输送及治疗，最大程度保护胰岛移植物，改善移植效果。

How to timely and accurately evaluate the number and function of islet grafts is still an unsolved problem which hampered the progress of clinical islet transplantation. The procedure of simply islet labeling before transplantation and subsequent imaging in vivo does not exactly reflect the functional status of grafts. In our previous study, we synthesized islet-targeted MRI contrast agent-SPIO-exendin4 (with GLP-1 receptor as target). We found that SPIO-exendin4 could idealy track islet and insulnoma in vivo. Based on there results, we here try to track islet grafts using SPIO-exendin4. To overcome the shortage of small peptide exendin-4, we will adopt 10Fn3 protein scaffold-based mRNA display technology to screen and synthesize antibody mimic protein with high specificity and affinity to GLP-1 receptor. By multiple islet graft-targeted imaging with SPIO-exendin4 and SPIO-AMPs, we want to establish the relationship between signal intensity and graft number/function status. Besides, we further use islet-targeting properity of these two contrast agents to transport an islet protective agent-C3G to graft area. In such situation, we can greatly protect the islet graft and improve the outcome of islet transplantation.