小分子重金属诊疗荧光探针的研发

This project aims to develop small molecule-based novel theranostic fluorescent agents for convenient detection and detoxification treatment of heavy metal poisoning. The design rule is to integrate heavy metal detoxifying drugs such as meso-2,3-dimercaptosuccinic acid (DMSA) and D-penicillamine with fluorescent chemodosimeters. These novel theranostic fluorescent probes will be synthesized and tested for their heavy metal detection and differentiation abilities as well as detoxification effects. Not only their fluorescence changes upon reacting with different heavy metals and mechanisms behind will be studied in details, but also their imaging applications in model cell lines and small animals for heavy metal tracking will be performed. Moreover, their detoxification effects will be evaluated. Besides, further addition of targeting groups to improve detoxification treatment for specific tissues such as brain is also proposed. This project would change the current parallel research situation in the field of diagnosis and detoxifying treatment related to heavy metal poisoning by providing potential novel first-line theranostic protocols, which would certainly have positive impact to the heavy-metal poisoning surveillance and theranostic program in our country and also benefit the health of our people.

本项目以诊疗一体化为设计理念，将重金属荧光检测探针与传统小分子重金属解毒药物 如：二巯基丁二酸和青霉胺等结合起来，设计合成兼有诊断和解毒功能的小分子重金属诊疗荧光探针，对其检测和解毒性能与机制进行深入研究，并通过细胞和动物模型进行初步的荧光成像和解毒应用研究。在此基础上，进一步发展针对富集重金属的特定组织（如脑组织）靶向的小分子重金属诊疗荧光探针。本项目将改变目前重金属离子的诊断和治疗相对独立的现状，发展新的重金属中毒治疗诊疗一线方案，对改善我国重金属污染健康危害监测与诊疗系统，提高人民生活健康具有深远的意义。

本项目将癌症治疗中的诊疗一体化理念用于重金属荧光探针的开发上，以重金属螯合解毒药物为识别基团与荧光团相连，设计合成兼有荧光检测和螯合解毒功能的小分子重金属诊疗荧光探针。以前期发展的C-DMSA诊疗荧光探针为先导分子，通过改变螯合解毒药物（二巯基丁二酸、D-青霉胺、二巯基丙醇等）、荧光团（香豆素、萘酰亚胺等）、连接基团和靶向基团、以及对分子亲疏水性的调控，发展了17个荧光探针分子, 其中10个有重金属离子荧光响应和螯合解毒活性。项目新发展了因分子内氢键稳定的四氢噻唑啉连接基团，对诊疗荧光探针中可近红外激发的荧光团进行了拓展，合成了首个酯酶靶向激活的重金属离子荧光探针，并在荧光探针设计上提出了待测物再生型荧光探针、多样化荧光响应、依次激活双位点荧光探针和荧光给体等新概念。发展的探针3可以以三种不同的多样化荧光响应来实现对汞离子、铜离子、以及银离子的区分检测，且对三种重金属离子引起的细胞损伤都具有与D-青霉胺相类似的解毒保护作用。它对铜离子的荧光响应表现为探针浓度依赖性，推测其机制为探针分子中存在依次激活的双铜离子结合位点。此外，项目通过构建维生素E-枝接壳聚糖和壳寡糖混合纳米胶束给药体系实现了对诊疗探针分子C-DMSA的加载和肝脏靶向功能，并在大鼠的汞离子中毒模型中进行了各器官分布研究和解毒性能研究，发现诊疗荧光探针分子能有效逆转汞离子引起的肝损伤，降低血液中肝损伤标志物丙氨酸转氨酶和天冬氨酸转氨酶。本项目发展的重金属诊疗荧光探针在反应设计中有效的结合了荧光团的配位位点和荧光响应机制来实现重金属离子检测的选择性，在解毒药物的释放上，体现了荧光探针和荧光给体的结合，并在细胞和初步的动物实验中初步验证了探针对重金属离子的荧光检测和解毒功能。但本项目发展的小分子荧光诊疗荧光探针仍存在检测模态和治疗解毒模块剂量不相匹配和荧光团潜在毒性等难以克服的问题，临床应用还需要进一步研究。