靶向MMP-2/9的双模态纳米探针构建及其预测腹主动脉瘤扩张和破裂风险的分子影像学研究

Abdominal aortic aneurysm (AAA) has the risk of intermittent expansion and rupture. No imaging modality is now available to effectively predict its expansion and rupture. Inflammation associated with MMP-2/9 activation and destructive remodeling of extracellular matrix are the essential mechanism for the occurrence and progression of AAA. Activated MMP-2/9-targeted molecular imaging promises to be an effective modality for risk monitoring of AAA. In this study, we will use activatable cell penetrating peptide linked with polyamidoamine dendrimers as a template with gold nanoparticles entrapped and 99mTc labeled to construct a MMP-2/9-targeted SPECT/CT dual-modality nanoprobe ACPP-G5@Au-99mTc. The cell toxicity, target ability and metabolic kinetics will be systemically assessed. By establishing the intra-renal AAA model in mice, then undergoing the dual-modality SPECT/CT imaging using the probe, the value of the probe for diagnosing and predicting AAA expansion and rupture risk will be evaluated. The implementation of this project will provide an experimental foundation for the risk prediction of AAA and provide the basis for the evaluation of therapy response.

腹主动脉瘤(abdominal aortic aneurysm，AAA)有间断扩张进而破裂的风险，目前尚无成熟的影像学方法有效预测其扩张和破裂。与MMP-2/9活化相关的炎症反应和细胞外基质破坏性重构是导致AAA发生和发展的重要机制，靶向MMP-2/9活性的分子影像学显像有望成为AAA风险监测的有效手段。本研究拟以可激活细胞穿膜肽偶联PAMAM树状大分子为模板包裹金纳米颗粒，并进行99mTc标记，构建靶向MMP-2/9的SPECT/CT双模态纳米探针ACPP-G5@Au-99mTc；系统评价探针的细胞学毒性、细胞靶向摄取能力及代谢动力学特性；并建立AngⅡ诱导的小鼠肾上型AAA模型，运用Micro SPECT/CT双模态显像，评价探针在AAA诊断及其扩张和破裂风险预测中的价值。本课题的实施将为AAA的风险预测提供实验基础，并为其临床疗效评估提供依据。

腹主动脉瘤（abdominal aortic aneurysm，AAA）具有间断扩张进而破裂的风险，破裂后死亡率高，靶向MMP-2/9活性的分子显像有望实现AAA的监测和风险评估。根据课题执行中遇到的实际情况，对课题进行了部分更改。首先，由于PET比SPECT具有更高的敏感性，MR比CT对软组织的分辨率更高，所以将基于SPECT/CT的双模态探针结构ACPPn-G5@Au-99mTc改善为基于PET/MR的双模态探针结构89Zr-DFO-Fe3O4@ACPP。其次，本研究组根据文献方法无法高效构建小鼠的AAA模型，所以采用HCT116人肠癌细胞小鼠进行了活体内MMP-2/9的靶向显像评价，后续将继续构建AAA模型并进行显像研究。本研究成功构建了靶向MMP-2/9的PET/MR双模态显像的分子探针89Zr-DFO-Fe3O4@ACPP，通过radio-iTLC检测了探针放化纯和稳定性，并对其生物学分布及药代动力学特性进行评估，最后通过microPET对小鼠进行了MMP-2/9的活体内靶向显像。89Zr-DFO-Fe3O4@ACPP放化纯为98.10%，室温放置2小时后放化纯为96.53%，具有较高的稳定性。探针静脉注射后快速从血液中清除，主要通过肝脏和肾脏排泄。肿瘤有较高的摄取，在注射后2小时达（2.16±0.68）%ID/g，与肌肉组织的摄取靶本比（T/NT）为3.3，至6小时摄取达峰值（2.75±0.54）%ID/g， T/NT为5.6，肿瘤摄取随时间延长缓慢降低。microPET显像可清晰显示肿瘤，6小时摄取达到峰值。本研究证实了靶向MMP-2/9的PET/MR双模态探针89Zr-DFO-Fe3O4@ACPP可用于活体内活化MMP-2/9的分子显像，有望为MMP-2/9高表达相关疾病的诊治提供有效的分子影像学方法。