CNA35胶原靶向氟碳纳米粒检测心肌纤维化的超声分子显像研究

Myocardial fibrosis is the result of the exaggerated deposition of collagen types I and III fibers，ultrasound molecular imaging technique with collagen-targeted ultrasound microbubbles is a novel and promising noninvasive method for the detection of myocardial fibrosis. Currently, ultrasound molecular imaging technique has been limited by the defects of microbubbles: Firstly, the large size of conventional microbubble gives low penetrability, which can’t pass through the endothelial gaps and restricts their targeting efficiency. Secondly, nanoparticles can easily pass through the endothelial gaps, but their ability of enhancing ultrasound imaging is dissatisfied. The development of appropriate probes for achieving both excellent targeting and imaging effects is the key and critical problems of ultrasound molecular imaging. . Based on our previous research, we plan to use the following techniques including thin film hydration、high-speed disperse homogeneous、ultrasonic vibration、high pressure homogenization and film dispersion-filtration, and use collagen binding domain CNA35 as the collagen targeting probe, to develop collagen type I targeted, liquid-gas phase transition perfluorocarbon nanoparticles. The perfluorocarbon nanoparticles can generate phase transition with the application of low intensity focus ultrasound. The targeted molecular imaging effect will be studied in-vitro and vivo with infarction induced myocardial fibrosis rabbit model. . The results from the project will resolve the key scientific question of targeting and imaging in the field of ultrasound molecular imaging of myocardial fibrosis, and which may provide a novel imaging technique for the detection of myocardial fibrosis.

心肌纤维化时心脏间质胶原纤维增生，基于胶原靶向的超声分子成像技术有望为心肌纤维化提供一种全新的检测方法。但当前的超声分子成像技术存在较大的缺陷：①常规超声微泡粒径大，无法穿透血管内皮间隙，组织内的靶向能力差；②纳米微泡的超声显影能力弱。实现靶向性和显影效果的统一，是心肌纤维化分子显像的重点和难点。. 本课题基于前期研究基础，通过已经掌握的薄膜水化、高速分散均质法、声振法、高压均质法、薄膜挤压等技术手段，采用磷脂作为成膜材料、包裹相变型液态氟碳、并连接Ⅰ型胶原特异性结合蛋白（CNA35）作为胶原检测的分子探针，研制一种靶向心肌Ⅰ型胶原的液-气相变氟碳纳米粒，并联合低功率聚焦超声及诊断超声在心肌梗死致心肌纤维化模型上研究其靶向显影效果。本研究可解决当前心肌纤维化超声分子成像技术中难以实现靶向性与显影效果统一的关键科学问题， 为心肌纤维化的检测提供一种新型的检测方法。

心肌纤维化在心力衰竭及恶性心律失常的发生发展过程中起着重要的作用，严重的心肌纤维化可增加心脏性猝死的发生率。因此，心肌纤维化的早期检测对评价患者的预后，制定相应的治疗策略具有重要意义。钆剂延迟增强磁共振成像（LGE-MRI）可显示心肌纤维化及瘢痕的部位及程度，被认为是无创性检测心肌纤维化的主要影像学手段。但磁共振检查的空间分辨率较差，对图像采集条件要求较高，且部分患者因各种原因无法进行磁共振检查。本项目成功制备了液态氟碳脂质纳米粒（PFP NPs）以及I型胶原靶向纳米粒(CNA35-PFP NPs), 经过体外观察，证实其稳定性好，可在37.5℃下稳定超过60min。体外实验阐明了CNA35-PFP NPs加热相变及声致相变的条件。进行细胞及活体内的毒性试验，证实CNA35-PFP NPs对培养细胞及机体各脏器均无明显的毒性作用。通过建立兔心肌梗死动物模型，在体外及体内实验证实CNA35-PFP NPs具有I型胶原靶向性。经静脉注射CNA35-PFP NPs至心肌梗死兔体内，再采用低功率超声辐照心肌梗死部位，触发纳米粒发生液气相变，通过诊断超声检测提示梗死部位心肌显影增强，实现了心肌纤维化的超声分子显像，建立了超声分子显像检测心肌纤维化的方法学。为心肌纤维化的影像学检测提供了一种实时的超声检测新方法，并为心肌纤维化的治疗研究提供了新的技术方案和平台。