新型核素~(64)Cu标记D-脱氧葡萄糖及其小动物正电子发射断层扫描显像

为拓展脱氧葡萄糖(DG)在肿瘤代谢显像中的应用,以新型核素64Cu标记葡萄糖胺-1,4,7,10-四氮杂环十二烷-1,4,7,10-四乙酸(DOTA-DG).通过优化反应条件,于25℃反应30 min后得到高放化纯度和高比活度的标记化合物64Cu-DOTA-DG,标记产物经放射性高效液相色谱(Radio-HPLC)检测.体外稳定性实验结果表明,64Cu-DOTA-DG有良好的稳定性.将64Cu-DOTA-DG通过尾静脉注射入荷瘤肝癌细胞(Hep-G2)裸鼠体内,分别于注射后1和3 h进行小动物正电子发射断层扫描(Micro-PET)显像.结果表明,其在肿瘤部位有所富集.64Cu-DOTA-DG的合成及分子显像研究拓宽了以18F-氟代脱氧葡萄糖为代表的肿瘤代谢类显像剂的应用范围,为新型核素标记肿瘤代谢显像剂提供一种新途径.     

64Cu放射性药物化学

64Cu半衰期为12.7 h,其衰变过程既发射β+粒子(β+,0.655 MeV,17.8%),又发射β-粒子(β-,0.573 MeV,38.4%)。近20年来,随着铜配位化学的发展,新型配体不断出现(如DOTA、TETA、NOTA、CB-TE2A、C3B-DO2A等)。Cu(Ⅱ)的络合物在生物体内/外的稳定性不断提高,64Cu已经成功标记在氨基酸、多肽、蛋白、核酸等分子以及纳米颗粒上。64Cu可制成正电子显像药物用作诊断,同时也有发展为放射性治疗药物的潜力。新型铜配体和标记方法以及新的药物靶标的研究已经成为64Cu放射性药物研究的热点,至今已研制出了多种64Cu标记的放射性药物,如64Cu-ATSM是有效的肿瘤乏氧显像剂,64Cu-PTSM是优良的血流示踪剂等。本文旨在介绍64Cu(Ⅱ)几种主要类型的含氮配体以及64Cu标记的放射性药物在显像和治疗方面的最新研究进展,并展望其发展趋势。     

Tc标记的叶酸肿瘤显像剂

叶酸受体在许多源于上皮组织的恶性肿瘤中高度表达,是目前肿瘤放射性显像研究的一个新的靶点。由于叶酸对于叶酸受体具有很高的亲和性,作为重要的特异性靶向介导分子,^99mTc标记叶酸肿瘤显像剂已成为当前放射性药物的研究热点之一。本文对不同类型的^99mTc标记的叶酸类放射性肿瘤显像剂的研究进展、应用情况和存在的问题进行了评述,探讨了^99mTc标记叶酸显像剂的一般设计方法,并对其未来发展方向进行了展望。     

诊疗一体化探针~(64)Cu-DOTA-TATE的制备、质量控制及分子影像

采用放射性核素~(64)Cu标记生长抑素类似物DOTA-3-酪氨酰基-奥曲肽(DOTA-TATE),制备了生长抑素受体显像分子探针~(64)Cu-DOTA-TATE;分别测试了其在5%(体积分数)的人血清白蛋白(HSA)和0.9%(体积分数)生理盐水中的稳定性.将~(64)Cu-DOTA-TATE经尾静脉注射入荷胰腺癌细胞裸鼠体内,并分别于注射后1,4和10 h进行小动物正电子发射断层(Micro-PET)显像.结果表明,经固相萃取小柱(Sep-Pak)分离纯化后,~(64)Cu-DOTA-TATE的放射化学纯度99%,且40 h内在5%HSA和0.9%生理盐水中有良好的稳定性.Micro-PET显像结果表明,随着时间延长,肿瘤区域对~(64)Cu-DOTA-TATE放射性摄取增加.~(64)Cu-DOTA-TATE有望成为较好的生长抑素类似物的PET显像剂.     

~(64)Cu-NOTA-Herceptin的设计、活性测定及肿瘤靶向分子显像研究

利用双功能螯合剂2-[(4-异硫氰基苯基)甲基]-1,4,7-三氮杂环九烷-1,4,7-三乙酸(NCS-Bz-NOTA)对Herceptin单抗表面的氨基进行修饰获得了NOTA-Herceptin,通过基质辅助激光解吸电离飞行时间质谱(MALDI-TOF)对该偶联物进行了表征.利用酶联免疫吸附测定了偶联前后Herceptin抗体效价的改变.利用新型正电子核素~(64)Cu标记,获得可用于肿瘤放射靶向精准诊疗的~(64)Cu-NOTA-Herceptin探针,其标记率为90%,放化纯度98%,比活度185 MBq/nmol.分别进行了该探针在HER2过表达胃癌细胞NCI-N87及HER2低表达胃癌细胞BGC823等肿瘤细胞中的摄取实验,测定了该探针的肿瘤特异性.建立了荷人胃癌BGC823裸鼠模型,通过微型正电子断层显像(Micro-PET)设备观察了探针在模型动物体内的代谢情况:在静脉注射7.4 MBq~(64)Cu-NOTA-Herceptin探针后,分别于4和60 h进行正电子断层显像(PET)的显像,观察到其在肿瘤部位的摄取有所富集,且随着代谢时间的延长,肝脏部位摄取得到明显降低.研究结果表明,~(64)Cu-NOTAHerceptin探针有望应用于肿瘤放射性靶向诊疗.     

两种新型99mTcN核标记的甲硝唑类乏氧显像剂的制备及生物性能评价

为研制新的肿瘤乏氧显像剂, 设计合成了2-(2-甲基-5-硝基咪唑基)乙基氨荒酸钾(MNIE-DTC)和4-(2-甲基-5-硝基咪唑基)丁基氨荒酸钾(MNIB-DTC)两种氨荒酸盐配体, 并制得了相应的99mTcN核配合物99mTcN(MNIE-DTC)2和99mTcN(MNIB-DTC)2. 所获得的两种99mTcN核配合物均为电中性, 具有较高的体外稳定性. 在荷乳腺癌的TA-2小鼠体内分布实验结果显示, 两种配合物均具有一定的肿瘤摄取, 给药1 h后, 99mTcN(MNIE-DTC)2和99mTcN(MNIB-DTC)2的肿瘤摄取率分别为(0.50±0.01)%ID/g和(0.64±0.10)%ID/g. 注入肼苯哒嗪后, 两种配合物的肿瘤摄取明显增高, 表明这两种配合物都具有对乏氧肿瘤的选择性.     

羟基磷灰石负载放射性18F作为分子影像纳米探针在生物医学中的应用

采用简便有效的方法,制备了生物兼容性强、放射性标记羟基磷灰石(HAp)纳米粒子的正电子发射计算机断层显像(PET)纳米探针。在合成HAp纳米粒子的过程中,放射性的~(18)F作为掺杂剂,占据HAp晶格中羟基位置,在短时间内牢固地标记到HAp上。~(18)F不仅标记在纳米粒子的表面,而且还通过强的化学键标记在纳米颗粒的内部。以达到提高标记量并防止辐射泄漏的目的。设计的高标记量的放射性纳米探针应用于动物实验并靶向到达脏器器官。     

99mTc(Ⅳ)标记双膦酸配合物的制备及其在动物体内骨显像性能

以2-乙基咪唑、5-溴戊酸乙酯和PCl3为原料,合成了一种唑来膦酸衍生物:1-羟基-5-(2-乙基-1H-咪唑-1-基)戊烷-1,1-双膦酸(EIPeDP),将其与放射性元素99mTc(Ⅳ)进行标记形成配合物,研究了EIPeDP用量和反应体系pH值对标记率的影响。结果表明,当pH值为5～6、EIPeDP为5 mg、SnCl2.2H2O为100μg和Na99mTcO4为92.5 MBq时,可获得满意的标记率和放化纯(均大于97%)。标记物99mTc-EIPeDP具有良好的体外稳定性。动物体内实验表明,兔经注射99mTc-EIPeDP 1 h后获得的骨显像图质量明显优于99mTc-ZL和99mTc-MDP。表明99mTc-EIPeDP是一种制备简便、稳定性好和骨显像性能优异的新型放射显像剂。     

新型PET核素68Ga标记D-脱氧葡萄糖的合成及生物学评价

以2-氨基-2-脱氧-D-葡萄糖为原料,通过微波加热法合成得到可用于核素标记的葡萄糖胺-1,4,7,10-四氮杂环十二烷-1,4,7,10-四乙酸(DOTA)前体化合物.产物通过IR,1H NMR,HPLC-MS,ESI-HRMS表征.通过标记条件的优化设计,在微波作用下,与新型正电子显像核素Ga-68进行放射性标记,高产率得到68Ga-DOTA-DG.而后对该标记化合物进行了K-562,Hela,A431等肿瘤细胞摄取实验,测定了对肿瘤的特异性.68Ga-DOTA-DG的合成,拓宽了以18F-FDG为首的肿瘤代谢类显像剂的新应用,为PET(Positron emission tomography)显像肿瘤代谢情况提供了一种新的途径.     

走近放射性药物化学——学习和认识正电子核素标记的放射性药物

正电子核素标记的放射性药物是正电子发射计算机断层显像(positron emission computed tomography,PET)发挥功能的关键因素,其开发和临床转化是PET诊断技术发展的核心技术之一。简要介绍PET显像原理及其安全性、PET与其他医学影像技术的区别,阐述放射性药物合成、标记及其临床应用等相关内容,旨在普及放射性药物及其PET显像技术的相关知识。可供教师选用于教学参考,拓展学生化学应用视野,提升学生科学素养。     

Strained Cyclooctyne as a Molecular Platform for Construction of Multimodal Imaging Probes

Small‐molecule‐based multimodal and multifunctional imaging probes play prominent roles in biomedical research and have high clinical translation ability. A novel multimodal imaging platform using base‐catalyzed double addition of thiols to a strained internal alkyne such as bicyclo[6.1.0]nonyne has been established in this study, thus allowing highly selective assembly of various functional units in a protecting‐group‐free manner. Using this molecular platform, novel dual‐modality (PET and NIRF) uPAR‐targeted imaging probe: ⁶⁴Cu‐CHS1 was prepared and evaluated in U87MG cells and tumor‐bearing mice models. The excellent PET/NIRF imaging characteristics such as good tumor uptake (3.69 %ID/g at 2 h post‐injection), high tumor contrast, and specificity were achieved in the small‐animal models. These attractive imaging properties make ⁶⁴Cu‐CHS1 a promising probe for clinical use.     

Efficient Uptake of 177Lu‐Porphyrin‐PEG Nanocomplexes by Tumor Mitochondria for Multimodal‐Imaging‐Guided Combination Therapy

The benefits to intracellular drug delivery from nanomedicine have been limited by biological barriers and to some extent by targeting capability. We investigated a size‐controlled, dual tumor‐mitochondria‐targeted theranostic nanoplatform (Porphyrin‐PEG Nanocomplexes, PPNs). The maximum tumor accumulation (15.6 %ID g^?1, 72 h p.i.) and ideal tumor‐to‐muscle ratio (16.6, 72 h p.i.) was achieved using an optimized PPN particle size of approximately 10 nm, as measured by using PET imaging tracing. The stable coordination of PPNs with ¹⁷⁷Lu enables the integration of fluorescence imaging (FL) and photodynamic therapy (PDT) with positron emission tomography (PET) imaging and internal radiotherapy (RT). Furthermore, the efficient tumor and mitochondrial uptake of ¹⁷⁷Lu‐PPNs greatly enhanced the efficacies of RT and/or PDT. This work developed a facile approach for the fabrication of tumor‐targeted multi‐modal nanotheranostic agents, which enables precision and radionuclide‐based combination tumor therapy.     

A pH-Sensitive Zwitterionic Iron Complex Probe with High Biocompatibility for Tumor-Specific Magnetic Resonance Imaging

Accurate diagnosis of tumor characteristics, including its location and boundary, is of immense value to subsequent therapy. Activatable magnetic resonance imaging (MRI) contrast agents that respond to tumor-specific microenvironments, such as the redox state, pH, and enzyme activity, enable better mapping of tumor tissue. However, the practical application of most reported activatable agents is hampered by problems including potential toxicity, inefficient elimination, and slow activation. In this study, we developed a zwitterionic iron complex (Fe-ZDS) as a positive MRI contrast agent for tumor-specific imaging. Fe-ZDS could dissociate in weakly acidic solution rapidly, accompanied by clear longitudinal relaxivity (r₁) enhancement, which enabled the complex to act as a pH-sensitive contrast agent for tumor-specific MR imaging. In vivo experiments showed that Fe-ZDS rapidly enhanced the tumor-to-normal contrast ratio by >40 %, which assisted in distinguishing the tumor boundary. Furthermore, Fe-ZDS circulated freely in the bloodstream and was excreted relatively safely via kidneys owing to its zwitterionic nature. Therefore, Fe-ZDS is an ideal candidate for a tumor-specific MRI contrast agent and holds considerable potential for clinical translation.     

A chelator-free multifunctional [64Cu]CuS nanoparticle platform for simultaneous micro-PET/CT imaging and photothermal ablation therapy

We synthesized and evaluated a novel class of chelator-free [(64)Cu]CuS nanoparticles (NPs) suitable both for PET imaging and as photothermal coupling agents for photothermal ablation. These [(64)Cu]CuS NPs are simple to make, possess excellent stability, and allow robust noninvasive micro-PET imaging. Furthermore, the CuS NPs display strong absorption in the near-infrared (NIR) region (peak at 930 nm); passive targeting prefers the tumor site, and mediated ablation of U87 tumor cells occurs upon exposure to NIR light both in vitro and in vivo after either intratumoral or intravenous injection. The combination of small diameter (～11 nm), strong NIR absorption, and integration of (64)Cu as a structural component makes these [(64)Cu]CuS NPs ideally suited for multifunctional molecular imaging and therapy.     

Applications of “Hot” and “Cold” Bis(thiosemicarbazonato) Metal Complexes in Multimodal Imaging

The applications of coordination chemistry to molecular imaging has become a matter of intense research over the past 10 years. In particular, the applications of bis(thiosemicarbazonato) metal complexes in molecular imaging have mainly been focused on compounds with aliphatic backbones due to the in vivo imaging success of hypoxic tumors with PET (positron emission tomography) using ⁶⁴CuATSM [copper (diacetyl‐bis(N4‐methylthiosemicarbazone))]. This compound entered clinical trials in the US and the UK during the first decade of the 21^st century for imaging hypoxia in head and neck tumors. The replacement of the ligand backbone to aromatic groups, coupled with the exocyclic N's functionalization during the synthesis of bis(thiosemicarbazones) opens the possibility to use the corresponding metal complexes as multimodal imaging agents of use, both in vitro for optical detection, and in vivo when radiolabeled with several different metallic species. The greater kinetic stability of acenaphthenequinone bis(thiosemicarbazonato) metal complexes, with respect to that of the corresponding aliphatic ATSM complexes, allows the stabilization of a number of imaging probes, with special interest in “cold” and “hot” Cu(II) and Ga(III) derivatives for PET applications and ¹¹¹In(III) derivatives for SPECT (single‐photon emission computed tomography) applications, whilst Zn(II) derivatives display optical imaging properties in cells, with enhanced fluorescence emission and lifetime with respect to the free ligands. Preliminary studies have shown that gallium‐based acenaphthenequinone bis(thiosemicarbazonato) complexes are also hypoxia selective in vitro, thus increasing the interest in them as new generation imaging agents for in vitro and in vivo applications.     

Dual-Emissive Platinum(II) Metallacage with a Sensitive Oxygen Response for Imaging of Hypoxia and Imaging-Guided Chemotherapy

Imaging of hypoxia in vivo helps with accurate cancer diagnosis and evaluation of therapeutic outcomes. A Pt^II metallacage with oxygen-responsive red phosphorescence and steady fluorescence for in vivo hypoxia imaging and chemotherapy is reported. The therapeutic agent and diagnostic probe were integrated into the metallacage through heteroligation-directed self-assembly. Nanoformulation by encapsulating the metallacage into nanoparticles greatly enhanced its stability the in physiological environment, rendering biomedical applications feasible. Apart from enhanced red phosphorescence upon hypoxia, the ratio between red and blue emissions, which only varies with intracellular oxygen level, provides a more precise standard for hypoxia imaging and detection. Moreover, in vivo explorations demonstrate the promising potential applications of the metallacage-loaded nanoparticles as theranostic agents for tumor hypoxia imaging and chemotherapy.     

Molecular Imaging of Hypoxia: Strategies for Probe Design and Application

Tumor hypoxia is a negative prognostic factor and its precise imaging is of great relevance to therapy planning. The present review summarizes various strategies of probe design for imaging hypoxia with a variety of techniques such as PET, SPECT and fluorescence imaging. Synthesis of some important probes that are used for preclinical and clinical imaging and their mechanism of binding in hypoxia are also discussed.     

64Cu radiolabeled nanomaterials for positron emission tomography (PET) imaging

The prevalence of positron emission tomography (PET) imaging has advanced biomedical applications for its ultrahigh sensitivity, deep tissue penetration and quantitative visualization of diseases in vivo. ⁶⁴Cu with ideal half-life and decay characteristics has been designed as radioactive probes for disease diagnosis. The currently reported ⁶⁴Cu-labeled nanomaterials have the advantages of long circulation time in serum, good biocompatibility and mature preparation methods, and have been used in vivo PET imaging, biodistribution and pharmacokinetic monitoring, and imaging guided therapy. At the same time, suitable carrier characteristics and radiolabeling strategies are particularly important in the ⁶⁴Cu PET imaging process. In this review, we summarize different imaging probe designs and ⁶⁴Cu radiolabeling strategies, as well as their eventual applications in biomedicine. The potential challenges and prospects of ⁶⁴Cu labeled nanomaterials are also described, which provides broad prospects for radiolabeling strategies and further applications.