Due to its ideal physical properties, fluorine-18 turns out to be a key radionuclide for positron emission tomography (PET) imaging, for both preclinical and clinical applications. However, usual biomolecules radiofluorination procedures require the formation of covalent bonds with fluorinated prosthetic groups. This drawback makes radiofluorination impractical for routine radiolabeling, gallium-68 appearing to be much more convenient for the labeling of chelator-bearing PET probes. In response to this limitation, a recent expansion of the 18F chemical toolbox gave aluminum [18F]fluoride chemistry a real prominence since the late 2000s. This approach is based on the formation of an [18F][AlF]2+ cation, complexed with a 9-membered cyclic chelator such as NOTA, NODA or their analogs. Allowing a one-step radiofluorination in an aqueous medium, this technique combines fluorine-18 and non-covalent radiolabeling with the advantage of being very easy to implement. Since its first reports, [18F]AlF radiolabeling approach has been applied to a wide variety of potential PET imaging vectors, whether of peptidic, proteic, or small molecule structure. Most of these [18F]AlF-labeled tracers showed promising preclinical results and have reached the clinical evaluation stage for some of them. The aim of this report is to provide a comprehensive overview of [18F]AlF labeling applications through a description of the various [18F]AlF-labeled conjugates, from their radiosynthesis to their evaluation as PET imaging agents.

/pdf/a-comprehensive-review-of-non-covalent-radiofluorination-1kxkq5ngb2.pdf

A Comprehensive Review of Non-Covalent Radiofluorination Approaches Using Aluminum [ 18 F]fluoride: Will [ 18 F]AlF Replace 68 Ga for Metal Chelate Labeling?

// Zelai He 1, 3, * , Xiangyu Zhang 4, * , Jingwen Huang 1, 3, * , Yufeng Wu 5 , Xuanzhang Huang 1 , Jie Chen 1 , Junyong Xia 6 , Hao Jiang 3 , Jing Ma 2 , Jian Wu 1 1 The Second Affiliated Hospital and Yuying Children’s Hospital of Wenzhou Medical University, Wenzhou, China 2 Ultrasonic Department, Shanghai Songjiang Center Hospital, Shanghai, China 3 The First Affiliated Hospital of Bengbu Medical College, Bengbu, China 4 Department of Pathology, Jining No.1 Peoples’ Hospital, Jining, China 5 Department of Internal Medicine, Affiliated Cancer Hospital of Zhengzhou University, Henan Cancer Hospital, Zhengzhou, China 6 Department of Nuclear Medicine, The Affiliated Provincial Hospital of Anhui Medical University, Hefei, China * These authors contributed equally to this work Correspondence to: Junyong Xia, email: xiabingbing@126.com Hao Jiang, email: jianghao1223@163.com Jing Ma, email: majing0709@163.com Jian Wu, email: wzzjian@hotmail.com Keywords: K237, folate, PEG-PLGA, nanoparticles, biodistribution Received: July 29, 2016      Accepted: October 12, 2016      Published: October 24, 2016 ABSTRACT In a previous study, amphiphilic copolymer, polypeptide K237 (HTMYYHHYQHHL) and folic acid (FA) modified poly(ethylene glycol)-poly(lactic-co-glycolic acid) (K237/FA-PEG-PLGA) nanoparticles were developed and studied as a drug carrier. To further promote the clinical application of K237/FA-PEG-PLGA nanoparticles and provide guidance for future research, we need to examine their specific biodistribution in vivo . In this study, K237/FA-PEG-PLGA nanoparticles were effectively labeled by a direct method with Technetium-99m ( 99m Tc) using stannous chloride as a reducing agent. The optimal stability of the labeled nanoparticles was determined by evaluating their radiochemical purity in serum, physiological saline, diethylenetriaminepentaacetic acid (DTPA) and cysteine solutions. The affinity of ligands and receptors was elicited by cell binding and blocking experiments in KDR/folate receptor high expressing SKOV-3 ovarian cancer cells. The nanoparticles biodistribution was studied after intravenous administration in healthy mice xenografted with SKOV-3 cells. A higher percent injected dose per gram of tissue (% ID/g) was observed in liver, kidney, spleen, blood and tumor at 3 and 9 h post-injection. Scintigraphic images revealed that the radioactivity was mainly concentrated in tumor, liver, kidney and bladder; and in the heart, lung, and muscle was significantly lower at 3 h. The radioactivity distribution in the images is consistent with the in vivo biodistribution data. Our works demonstrated that K237/FA-PEG-PLGA nanoparticles have great potential as biodegradable drug carriers, especially for tumors expressing the folate and KDr receptor.

/pdf/immune-activity-and-biodistribution-of-polypeptide-k237-and-5bm2s3eiuv.pdf

Immune activity and biodistribution of polypeptide K237 and folic acid conjugated amphiphilic PEG-PLGA copolymer nanoparticles radiolabeled with 99mTc

This study aims to develop a new folate receptor (FR)-targeting agent for SPECT imaging with improved contrast and evaluate the modification strategies of multimerization and/or PEGylation in the development of new radio-folates. A series of novel folate derivatives have been synthesized and radiolabeled with 99mTc using tricine and TPPTS as coligands. To better investigate their pharmacokinetics, cell uptake, biodistribution, and microSPECT/CT imaging were evaluated. Four radioligands displayed high KB cell uptake after incubation for 2 and 4 h. Presaturated with excess folic acid (FA) resulted in a significant blocking effect in KB cells, indicating specificity of these radioligands toward FR. Biodistribution and microSPECT imaging studies in KB tumor-bearing mice showed that the folate conjugate 99mTc-HYNFA with poly(ethylene glycol) (PEG) and triazole linkage displayed the highest tumor uptake (16.30 ± 2.01 %ID/g at 2 h p.i. and 14.9 ± 0.62 %ID/g at 4 h p.i. in mice biodistribution) and best imaging c...

Development of a New FR-Targeting Agent 99mTc-HYNFA with Improved Imaging Contrast and Comparison of Multimerization and/or PEGylation Strategies for Radio-Folate Modification.

Radiochemistry with {Al18F}2+: Current status and optimization perspectives for efficient radiofluorination by complexation

The aim of this study was to evaluate positron emission tomography (PET) imaging with [68Ga]NODAGA-c(RGDfK) ([68Ga]RGD), in comparison with 2-deoxy-2-[18F]fluoro-D-glucose ([18F]FDG), for early monitoring of the efficacy of an antiangiogenic agent associated or not with chemotherapy, in a mouse model of glioblastoma (GB). Mice bearing U87MG human GB cells line were parted into five groups of five mice each. One group was imaged at baseline before the treatment phase; another group was treated with bevacizumab (BVZ), another group with temozolomide (TMZ), another group with both agents, and the last one was the control group. Tumors growth and biological properties were evaluated by caliper measurements and PET imaging at three time points (baseline, during treatment t1 = 4–6 days and t2 = 10–12 days). At the end of the study, tumors were counted and analyzed by immunohistochemistry (CD31 to evaluate microvessel density). The tumor volume assessed by caliper measurements was significantly greater at t1 in the control group than in the TMZ + BVZ-treated group or in the BVZ-treated group. At t2, tumor volume of all treated groups was significantly smaller than that of the control group. [18F]FDG PET failed to reflect this efficacy of treatment. In contrast, at t1, the [68Ga]RGD tumor uptake was concordant with tumor growth in controls and in treated groups. At t2, a significant increase in tumor uptake of [68Ga]RGD vs. t1 was only observed in the TMZ-treated group, reflecting a lack of angiogenesis inhibition, whereas TMZ + BVZ resulted in a dramatic tumor arrest, reduction in microvessel density and stable tumor [68Ga]RGD uptake. [68Ga]RGD is a useful PET agent for in vivo angiogenesis imaging and can be useful for monitoring antiangiogenic treatment associated or not with chemotherapy.

[ 68 Ga]RGD Versus [ 18 F]FDG PET Imaging in Monitoring Treatment Response of a Mouse Model of Human Glioblastoma Tumor with Bevacizumab and/or Temozolomide

// Yanfen Cui 1, * , Huanhuan Liu 1, * , Sheng Liang 2 , Caiyuan Zhang 1 , Weiwei Cheng 2 , Wangxi Hai 3, 4, 5 , Bing Yin 1 , Dengbin Wang 1 1 Department of Radiology, Xinhua Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai 200092, China 2 Department of Nuclear Medicine, Xinhua Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai 200092, China 3 School of Pharmacy, Shanghai Jiao Tong University, Shanghai 200240, China 4 Med-X Research Institute, Shanghai Jiao Tong University, Shanghai 200030, China 5 Med-X Ruijin Hospital Micro PET/CT Research Center, Ruijin Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai 200025, China * These authors contributed equally to this work Correspondence to: Dengbin Wang, e-mail: dbwang8@aliyun.com Keywords: antiangiogenic therapy, Endostar, 18F-FDG, 18F-AlF-NOTA-PRGD2, NPC Received: October 21, 2015      Accepted: March 14, 2016      Published: March 26, 2016 ABSTRACT Purpose: Radiolabeled arginine-glycine-aspartic acid (RGD) peptides have been developed for PET imaging of integrin avβ3 in the tumor vasculature, leading to great potential for noninvasively evaluating tumor angiogenesis and monitoring antiangiogenic treatment. The aim of this study was to investigate a novel one-step labeled integrin-targeted tracer, 18 F-AlF-NOTA-PRGD2, for PET/CT for detecting tumor angiogenesis and monitoring the early therapeutic efficacy of antiangiogenic agent Endostar in human nasopharyngeal carcinoma (NPC) xenograft model. Experimental design and results: Mice bearing NPC underwent 18 F-AlF-NOTA-PRGD2 PET/CT at baseline and after 2, 4, 7, and 14 days of consecutive treatment with Endostar or PBS, compared with 18 F-FDG PET/CT. Tumors were harvested at all imaging time points for histopathological analysis with H & E and microvessel density (MVD) and integrin avβ3 immunostaining. The maximum percent injected dose per gram of body weight (%ID/gmax) tumor uptake of 18 F-AlF-NOTA-PRGD2 PET/CT was significantly lower than that in the control group starting from day 2 ( p < 0.01), much earlier and more accurately than that of 18 F-FDG PET/CT. Moreover, a moderate linear correlation was observed between tumor MVD and the corresponding tumor uptake of 18 F-AlF-NOTA-PRGD2 PET/CT ( r = 0.853, p < 0.01). Conclusions: 18 F-AlF-NOTA-PRGD2 PET/CT can be used for in vivo angiogenesis imaging and monitoring early response to Endostar antiangiogenic treatment in NPC xenograft model, favoring its potential clinical translation.

/pdf/the-feasibility-of-18f-alf-nota-prgd2-pet-ct-for-monitoring-56l7m602mi.pdf

The feasibility of 18F-AlF-NOTA-PRGD2 PET/CT for monitoring early response of Endostar antiangiogenic therapy in human nasopharyngeal carcinoma xenograft model compared with 18F-FDG.

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The feasibility of 18F-AlF-NOTA-PRGD2 PET/CT for monitoring early response of Endostar antiangiogenic therapy in human nasopharyngeal carcinoma xenograft model compared with 18F-FDG.