肿瘤细胞的靶向识别是癌症诊断及治疗的关键。脑部肿瘤，如脑胶质瘤等，生理环境精细复杂，且受到血脑屏障的保护，因此，实现其靶向识别更具挑战性。来源于蝎子毒液的环状多肽氯毒素对脑胶质瘤细胞有特异的选择性和血脑屏障穿透性，已在相关癌症的荧光成像和术中导航等方面展现出极大的应用前景。然而，氯毒素的靶向机制（与受体蛋白质MMP-2的作用机制）尚未阐明，严重地限制了基于其结构修饰的药物设计研究。考虑到MMP-2分子量较大，本项目拟分别对其各结构域进行表达与研究，揭示其与氯毒素作用的关键氨基酸残基信息。在此基础上，发展化学修饰新方法，实现氯毒素的选择性、均一修饰，获得更为安全有效的多肽—药物偶联复合物。本项目的研究结果将有助于阐明氯毒素的肿瘤靶向机制这一基础性问题，并为研究氯毒素成为多用途靶向分子及相关药物发现奠定基础。

Selective targeting of tumor cells is the key of cancer diagnosis and therapy. Brain tumor, such as glioma, surrounds by delicate and complicated environment, and is protected by the blood-brain barrier, which makes it extremely challenge to achieve selective targeting. Chlorotoxin, a cyclic peptide from the venom of scorpion, shows very high selectivity towards glioma and has the ability to cross the blood-brain barrier. As such, it is a promising molecule, when conjugated with fluorescent molecules, in areas like fluorescent tumor imaging and guided surgeon. The targeting mechanism (towards the receptor MMP-2), however, is largely unknown, which severely limits the related structure modification and drug design. MMP-2 is a relatively large protein molecule, in the proposal, we will try to express and study its domains independently. The key interacting residues in chlorotoxin will be identified via biophysical methods. Next, site-selective modification of chlorotoxin will be investigated to obtain safer and more effective peptide-drug conjugates. The proposed research will help to elucidate the tumor targeting mechanism of chlorotoxin; it sets the stage for developing chlorotoxin towards a useful targeting molecule and related drug development.