纳米靶向磁共振探针的构建及对周围神经显像的动物实验研究

Peripheral nerve imaging is still a difficult clinical problem which is of great significance in localizable diagnosis and function evaluation. Our previous study revealed that there exist different pathological changes in proximal and distal site after peripheral nerve injury, especially for some myelin associated proteins(P0 and PMP22), which are neural-specific proteins expressed specificly in peripheral nerve system, and are totally degraded in distal site of injury point, while less degraded in the proximal segment. Using the 5th generation poly(amidoamine) dendrimers(G5PAMAM), we prepared acetylated dendrimer-entrapped gold nanoparticles (Au DENPs), which are modified and connected to target protein by the superficial amino-group in order to conduct targeted CT molecular imaging of tumors. Based on these findings, we supposed that in the light of the changes of neural-specific proteins, the targeted peripheral nerve imaging in vivo can be fulfilled by using high-field MR scanner with targeted nanometer magnetic resonance probe. Therefore, this research will make P0 and PMP22 as targets and construct neural-targeted and high-paramagnetism nanometer magnetic resonance probe by using acetylated dendrimer-entrapped ultrasmall superparamagnetic iron oxide particles whose free amino-group can be coupled with functionalized anti-P0 and PMP22 segment. After characterization, the probe is evaluated in biocompatibility and applied to the peripheral nerve imaging in animal models with peripheral nerve injury. The final aim is to realize the targeted peripheral nerve imaging in animal models and lay the ground work for the subsequent clinical research.

周围神经显像对临床定位诊断及功能评估具重要意义但仍是临床难题。课题组前期研究发现：周围神经损伤位点的远近端发生不同的病理改变，特别是髓鞘相关蛋白(P0、PMP22) 这一周围神经特异表达蛋白在远端被降解，但近端的降解十分有限。用第5代树状大分子（G5PAMAM）包裹纳米金颗粒，经修饰后将其表面氨基藉化学键与靶向蛋白质分子链接，实现了肿瘤的靶向CT分子成像。由此推测，针对神经特异蛋白的变化，构建纳米靶向磁共振(MR)探针，通过高场强MR仪可实现周围神经靶向显像。为此，本项目以P0、PMP22为靶点，用G5PAMAM包被超小超顺磁纳米铁微粒并利用前者提供的游离氨基，偶联功能化的抗P0、PMP22片段，构建具神经靶向、高顺磁性特性的MR探针，对其表征及生物相容性评价，并在周围神经损伤动物模型进行周围神经MR成像，实现动物模型的靶向周围神经显像，为后续临床探索提供依据。

周围神经显像对临床定位诊断及功能评估具重要意义但仍是临床难题，迫切需要一种无创、早期定位和评价的方法，分子影像学方法为其提供了可行性。本项目执行期间，采用不同的制备、优化方法制备了纳米铁、纳米金等纳米颗粒，并运用叶酸、RGD肽、a-TOS等作为靶向分子合成功能化的纳米颗粒，完成了其表征、不同成像属性测定和体内、外实验，结果显示不同的纳米颗粒具有良好的稳定性及成像特性。构建了偶联辣根过氧化物酶的功能化的纳米铁颗粒，初步验证了其可标记细胞且标记细胞可体外磁共振成像和监测，建立了标记细胞MRI成像的参数。运用3.0 T高场强磁共振仪，在新西兰兔上成功进行了坐骨神经成像及掌握了相关成像技术，并在动物模型上建立、优化和验证了MRI成像参数设定及定量分析，为实现动物模型的靶向周围神经显像和后续临床探索提供了依据。.本项目基本按原计划顺利完成，发表标准本项目资助的SCI论文20篇，获得省部级科技进步二等奖2次，出版专著1部，授权专利3项，毕业博士4名，毕业硕士2名，在读博士生1名，培养博士后1名，主办国内学术会议3次，参加国际学术会议9次。