基于窄分子量分布壳聚糖基衍生物的多功能成像探针研究

Multifunctional imaging probe (MIP) for early diagnosis of incurable diseases is a novel emerging tool in recent years, which involve interdisciplinary cross including chemistry, biological materials, life sciences, etc, is one of the hotspots either domestic or international research. However, how to achieve the high efficiency and low toxicity in clinical is one of the difficult problem at this research field. In this subject, we will firstly, prepare different degrees (DP) norrow molecular weight distribution chitosan(NOCSn). Secondly, bond the diethylenetriaminepentaacetic acid anhydride with NOCS by covalent bond, obtain the low-toxic parent ligand which could chelateded different paramagnetic metal ions (the ligand, NOCSn-DTPA). Thirdly, link one or more fluorescent groups and iodine- containing amino acid to the remaining free amino groups by covalent bond at the ligand (NOCSn-DTPA-O/I*), respectively. Fourthly, chelat the paramagnetic metal ions to obtain the complexes with three functions, which containing magnetic resonance imaging (MRI), fluorescence and isotope iodine tracer, that are multifunctional imaging probes (MIP, NOCSn-DTPA-O/I*-M). Fifthly, characterize the structures of these products, probe into the rule of the ring formation between NOCS and diethylenetriaminepentaacetic acid anhydride and the existence diversity of topological structural.Then study the physical and chemical properties (magnetic/ fluorescent/ isotope-labeled) and explore the effect of MIP in vitro/in vivo, screen the excellent candidates though repeated practices. Finally, explore the in vivo safety, including the distribution and the residue of the metal ions in animals, acute toxicity and teratogenicity tests, etc. Accumulate early data for the further use of a safe MIP in clinical.

利用多功能成像探针（MIP）对疑难病症进行早期诊断，是近年来发展的一种新兴手段，涉及化学、生物材料和生命科学等交叉学科，是当今国内外研究的重点热点之一。怎样做到临床高效低毒又是这一领域难点，本课题将采用二乙三胺五乙酸酸酐与不同聚合度的窄分子量分布低聚壳聚糖（NOCS）键合得到可螯合金属离子的低毒母本配体，再在这些配体壳聚糖链剩余自由氨基上分别键接一至多个荧光性基团和含碘类氨基酸，进而螯合顺磁性金属离子，获得具有磁共振成像造影、荧光与同位素碘示踪三项功能的金属配合物，即多功能成像探针（MIP）。表征产物结构，探明NOCS与二乙三胺五乙酸酸酐成环规律，及存在拓扑结构多样性。研究其理化性质（磁学/荧光/同位素标记），探索体外/内MIP效果，反复实践筛出优良候选物。进而观察其体内安全性，包括金属离子在动物体内的分布与残留、急性毒性与致畸试验等，为下一步研究临床安全实用型MIP积累前期数据。

利用多功能成像探针对疑难疾病进行早期诊断，克服了单一成像模式的固有局限性，提高了临床诊断的准确性，这也是目前本领域研究的热点之一。本项目以不同聚合度的窄分子量分布低聚壳聚糖修饰的二乙三胺五乙酸作为基础配体，再在其剩余的自由氨基上链接不同类别的功能荧光分子，进而络合顺磁性金属离子，得到兼具MRI成像功能和荧光成像功能的双功能成像探针。通过不同的表征方法对合成的双功能成像探针的结构、理化性能等进行了研究。研究结果显示，制备得到的几种成像探针的弛豫率均高于传统的商用造影剂Gd-DTPA，且在降低用量的条件下，能够达到与Gd-DTPA同等的成像效果，有利于提高体内安全性。与牛血清白蛋白(BSA)的作用结果表明，虽然成像探针对BSA所处的微环境有所影响，但是BSA的结构依然以α螺旋为主。几种成像探针与BSA的结合均是自发的，且与BSA的结合力大于Gd-DTPA与BSA的结合强度，有效延长了成像探针在体内的作用时间，为临床成像提供了充足的扫描时间。本项目的研究为实现多功能成像和成像治疗一体化提供了新的方法，同时为临床实验提供了可靠的数据参考。