化学学报 ›› 2019, Vol. 77 ›› Issue (2): 172-178.DOI: 10.6023/A18090410 上一篇    下一篇

研究论文

124I原位标记有机黑色素纳米粒子的制备及初步分子影像研究

夏雷a, 程震b, 朱华a, 杨志a   

  1. a 北京大学肿瘤医院暨北京市肿瘤防治研究所核医学科 恶性肿瘤发病机制及转化研究教育部重点实验室 北京 100142;
    b Molecular Imaging Program at Stanford (MIPS) and Bio-X Program, Department of Radiology, School of Medicine, Stanford University, Stanford, California, 94305
  • 投稿日期:2018-09-29 发布日期:2018-11-01
  • 通讯作者: 朱华,E-mail:zhuhuananjing@163.com,Tel:010-88196192; 杨志,E-mail:pekyz@163.com E-mail:zhuhuananjing@163.com;pekyz@163.com
  • 基金资助:

    项目受国家自然科学基金(Nos.81671733,81501519,81571705)和北京市科技新星计划(No.Z171100001117020)项目资助.

Preparation and Preliminary Molecular Imaging Study of 124I in-situ Labeled Organic Melanin Nanoparticles

Xia Leia, Cheng Zhenb, Zhu Huaa, Yang Zhia   

  1. a Key Laboratory of Carcinogenesis and Translational Research(Ministry of Education/Beijing), Department of Nuclear Medicine, Peking University Cancer Hospital & Institute, Beijing 100142;
    b Molecular Imaging Program at Stanford(MIPS) and Bio-X Program, Department of Radiology, School of Medicine, Stanford University, Stanford, California, 94305
  • Received:2018-09-29 Published:2018-11-01
  • Contact: 10.6023/A18090410 E-mail:zhuhuananjing@163.com;pekyz@163.com
  • Supported by:

    Project supported by the National Natural Science Foundation of China (Nos. 81671733, 81501519 and 81571705) and Beijing Nova program (No. Z171100001117020).

探索了有机黑色素纳米粒子对一种目前最有潜力的新型PET成像核素的原位标记方法,制备出新型多功能纳米探针,并进行初步的分子影像研究.以自然存在的黑色素(Melanin)为原料,利用超声破碎法制备超微粒径(5.5 nm)黑色素纳米粒子(MNPs),并使用两端具有氨基的PEG3500对其表面进行修饰,获得具有较好水分散性和氨基活性基团的新型PEG-MNP纳米载体.采用动态光散射(DLS)、透射电镜(TEM)、红外光谱(FTIR)以及核磁氢谱(1H NMR)对纳米粒子进行充分形貌表征.而后使用溴代琥珀酰亚胺(NBS)作为氧化剂进行长半衰期核素124I的原位标记,获得了相应的具有PET成像功能的124I-PEG-MNP纳米载体.而后使用游离124I、124I-PEG-MNP分别进行正常昆明小鼠Micro-PET成像对比研究,同时构建胰腺癌荷瘤鼠模型BxPC3,并进行124I-PEG-MNP肿瘤成像研究.结果显示,长半衰期核素124I对PEG-MNP的标记率可达99%以上,且体外稳定性良好.Micro-PET图像显示,124I-PEG-MNP在小鼠体内未见脱标现象,体内放射性分布与游离124I成像差异明显.通过基于选定甲状腺及肝脏感兴趣区(Region of Interest,ROI)的半定量分析表明,经过124I标记后的PEG-MNP纳米粒子,与原有124I的代谢学行为具有显著的统计学差异(P<0.001).同时,124I-PEG-MNP利用自身的实体瘤高通透性和滞留效应(EPR)在肿瘤部位有明显的富集,并在肿瘤部位滞留超过48 h.上述研究表明,有机纳米粒子PEG-MNP具备标记单质长半衰期核素的能力,并可用于肿瘤模型PET显像,为其进一步构建长循环多模态成像探针提供实验依据.

关键词: 黑色素纳米粒子, 核素标记, 原位标记, 分子影像, 小动物PET成像

Developing biocompatible, multifunctional and in-situ labeling nanoplatform is high challenging for molecular imaging. Organic derivates melanin nanoparticles (MNPs) holds great potential to be multimodal contrast agents, and have been used for photoacoustic imaging, magnetic resonance imaging, and 64Cu PET imaging with simple modifications. In order to extend MNPs application in molecular imaging, here a novel radio-nuclide was applied to in-situ labeling of MNPs. Large numbers of active dihydroxyindole/indolequinone groups and natural binding ability of MNPs enabled them to have the ability to label different types of radionuclides which have unique half-life and functions, especially long-life elemental nuclide. This project explored the in-situ labeling methods of organic melanin nanoparticles with a promising diagnostic radionuclides named Iodine-124 (124I), and using this novel multifunctional organic nanoparticles for preliminary molecular imaging studies. Generally, ultrafine particle size melanin nanoparticles (5.5 nm in diameter) were prepared by ultrasonication method using naturally occurring melanin, then PEG3500 which had amino group at both ends was used as a stabilizer agent to obtain PEG-MNP nanocarriers (7.5 nm in diameter) with better water solubility and stability. The nanoparticles were full characterized by dynamic light scattering (DLS), transmission electron microscope (TEM) and 1H NMR, respectively. Then, one kind of elemental nuclide was labeled. Classic iodine labeled method with N-Bromo Succinimide (NBS) was used as oxidant to oxidize active dihydroxyindole/indolequinone ring of PEG-MNP for electrophilic substitution reaction labeling 124I (100.8 h). This reaction rate is extremely fast (60 s reaction time) and high labelling yield (>99%). The 124I was labeled successfully and in-situ labeled PEG-MNP nanocarriers were obtained. After that, 124I and 124I-PEG-MNP were used to further preclinical evaluation by micro-PET imaging. Micro-PET images were collected at 2 h, 24 h and 48 h after intravenous injection 7.4 MBq 124I and 124I-PEG-MNP in normal Kunming mice (n=3). The ROI target area of heart, liver and thyroid were delineated for semi-quantitative analysis. Then, in order to verify the imaging ability of 124I-PEG-MNP in solid tumor. We built human pancreatic cancer BxPC3 xenograft model (n=3), and Micro-PET scans were performed at different time points. Results showed that the labeling rate of 124I on PEG-MNP was 99.9%. And the radiochemical purity in vitro stability of 124I-PEG-MNP in 96 h was more than 90%. Micro-PET images showed that 124I-PEG-MNP had no obvious thyroid uptake which indicated no de-marking in mice. The radio-distribution of 124I and 124I-PEG-MNP was substantially different in liver and thyroid (P<0.001). In vivo semi-quantitative analysis showed that the radio uptakes of organs were consistent with the distribution of nanoparticles. And the PET imaging of xenograft mice showed that 124I-PEG-MNP can utilize the enhanced permeability and retention effect (EPR) to be significantly enriched at the tumor and retained in the tumor site for more than 48 h. PEG-MNP has the ability to label long half-life nuclide 124I. This research provides an experimental basis for further construction of long-circulation multimodal imaging probes.

Key words: melanin nanoparticles, polynuclear labeled, molecular imaging, in-situ labeling, Micro-PET