bluuebunny/crossref_metadata_2025 huggingface dataset:
Gold Nanorods Targeted to Delta Opioid Receptor: Plasmon-Resonant Contrast and Photothermal Agents
Authors: Black Kvar C. , Kirkpatrick Nathaniel D. , Troutman Timothy S. , Xu Liping , Vagner Josef , Gillies Robert J. , Barton Jennifer K. , Utzinger Urs , Romanowski Marek
Published: March 2018

Molecularly targeted gold nanorods were investigated for applications in both diagnostic imaging and disease treatment with cellular resolution. The nanorods were tested in two genetically engineered cell lines derived from the human colon carcinoma HCT-116, a model for studying ligand-receptor interactions. One of these lines was modified to express delta opioid receptor (δOR) and green fluorescent protein, whereas the other was receptor free and expressed a red fluorescent protein, to serve as the control. Deltorphin, a high-affinity ligand for δOR, was stably attached to the gold nanorods through a thiol-terminated linker. In a mixed population of cells, we demonstrated selective imaging and destruction of receptor-expressing cells while sparing those cells that did not express the receptor. The molecularly targeted nanorods can be used as an in vitro ligand-binding and cytotoxic treatment assay platform and could potentially be applied in vivo for diagnostic and therapeutic purposes with endoscopic technology.
Monitoring Therapeutical Intervention with Ezetimibe Using Targeted Near-Infrared Fluorescence Imaging in Experimental Atherosclerosis
Authors: Graf Kristof , Dietrich Thore , Tachezy Michael , Scholle Frank-Detlef , Licha Kai , Stawowy Philipp , Grafe Michael , Hauff Peter , Fleck Eckart
Published: March 2018

Ezetimibe (EZE), an inhibitor of cholesterol absorption, reduces atherosclerosis in apolipoprotein E–deficient (apo–/–) mice. The matrix protein ED-B fibronectin (ED-B) is upregulated in atherosclerotic lesions. Using a novel conjugate for near-infrared fluorescence (NIRF) imaging targeting ED-B, we studied the effect of EZE on plaque lesion formation in apoE–/– mice. ApoE–/– mice received EZE (5 μg/kg/d) or chow up to the age of 4, 6, and 8 months. NIRF imaging of aortic lesions was performed 24 hours after intravenous application ex vivo and in vivo. Plaque lesion formation was analyzed by histology and immunohistochemistry. Aortic lesion formation detected by Sudan staining and NIRF imaging was significantly reduced at 6 and 8 months ( p < .001). Plaque areas determined by NIRF imaging significantly correlated with Sudan staining ( p < .001). EZE treatment resulted in a significant reduction in plaque macrophage and ED-B immunoreactivity (both p < .05) in brachiocephalic lesions. There was a significant reduction in plaque size in brachiocephalic arteries in 8-month-old mice treated with EZE compared with mice during short-term treatment ( p < .05), indicating EZE plaque regression. Targeted NIRF imaging showed a correlation to histologic lesion extension during therapeutical intervention in experimental atherosclerosis.
Multimodal Imaging of Neural Progenitor Cell Fate in Rodents
Authors: Waerzeggers Yannic , Klein Markus , Miletic Hrvoje , Himmelreich Uwe , Li Hongfeng , Monfared Parisa , Herrlinger Ulrich , Hoehn Mathias , Coenen Heinrich Hubert , Weller Michael , Winkeler Alexandra , Jacobs Andreas Hans
Published: March 2018

For clinical application of stem cell–based therapies, noninvasive detection of applied stem cells is of high importance. We report on the feasibility of detecting implanted neural progenitor cells (NPCs) noninvasively and follow their fate and functional status by sequential multimodal molecular imaging and reporter gene technology. We investigated C17.2 cells stably expressing herpes simplex virus type 1–thymidine kinase (HSV-1- tk) and green fluorescent protein ( gfp) (C17.2- tkIRES gfp = C17.2-TIG) or HSV-1- tk, gfp, and firefly luciferase ( luc) (C17.2- lucIRES tkgfp = C17.2-LITG) and determined the detection sensitivity of positron emission tomography (PET) and bioluminescence imaging (BLI) for these cells in culture and in vivo in subcutaneous and intracranial glioma models. In addition, PET and BLI were used to further investigate and follow the fate of implanted C17.2-LITG cells in an intracranial glioma model. We show that both imaging modalities are sensitive in detecting reporter gene expressing NPCs; however, PET, by the use of 9-[4-[18F]fluoro-3-hydroxymethyl)butyl]guanine ([18F]FHBG), detects NPCs only at sites of disrupted blood-brain barrier. Furthermore, both imaging modalities can be used to detect stem cell fate and migration and indicate excessive proliferation and aberrant migration. In conclusion, multimodal imaging can be used for longitudinal noninvasive monitoring of grafted NPCs in rodents.
High-Power, Computer-Controlled, Light-Emitting Diode–Based Light Sources for Fluorescence Imaging and Image-Guided Surgery
Authors: Gioux Sylvain , Kianzad Vida , Ciocan Razvan , Gupta Sunil , Oketokoun Rafiou , Frangioni John V.
Published: March 2018

Optical imaging requires appropriate light sources. For image-guided surgery, in particular fluorescence-guided surgery, a high fluence rate, a long working distance, computer control, and precise control of wavelength are required. In this article, we describe the development of light-emitting diode (LED)-based light sources that meet these criteria. These light sources are enabled by a compact LED module that includes an integrated linear driver, heat dissipation technology, and real-time temperature monitoring. Measuring only 27 mm wide by 29 mm high and weighing only 14.7 g, each module provides up to 6,500 lx of white (400–650 nm) light and up to 157 mW of filtered fluorescence excitation light while maintaining an operating temperature ≤ 50°C. We also describe software that can be used to design multimodule light housings and an embedded processor that permits computer control and temperature monitoring. With these tools, we constructed a 76-module, sterilizable, three-wavelength surgical light source capable of providing up to 40,000 lx of white light, 4.0 mW/cm2 of 670 nm near-infrared (NIR) fluorescence excitation light, and 14.0 mW/cm2 of 760 nm NIR fluorescence excitation light over a 15 cm diameter field of view. Using this light source, we demonstrated NIR fluorescence–guided surgery in a large-animal model.
Molecular Imaging of Prostate Cancer: A Concise Synopsis
Authors: Jadvar Hossein
Published: March 2018

Prostate cancer is the most common malignancy in men and continues to be a major public health problem. Imaging of prostate cancer remains particularly challenging owing to disease heterogeneity. Molecular imaging can provide unprecedented opportunities for deciphering the molecular mechanisms that are involved in the development and natural progression of prostate cancer from a localized process to the hormone-refractory metastatic disease. Such understanding will be the key for targeted imaging and therapy and for predicting and evaluating treatment response and prognosis. In this article, we review briefly the contribution of multimodality molecular imaging methods for the in vivo characterization of the pathophysiology of prostate cancer.
Dual-Modality Probes for in Vivo Molecular Imaging
Authors: Lee Seulki , Chen Xiaoyuan
Published: March 2018

Various imaging modalities have been exploited and are successfully employed to investigate the anatomic or functional dissemination of tissues in the body. However, no single imaging modality allows overall structural, functional, and molecular information as each imaging modality has its own unique strengths and weaknesses. The combination of two popular imaging modalities that investigates the strengths of different methods might offer the prospect of improved diagnostic and therapeutic monitoring abilities. To date, only a few hybrid systems have become clinically adopted, but there are encouraging signs that the new generation of multimodality systems will be undergoing evaluation in the near future. On the other hand, significant progress has been made toward the creation of dual-modality imaging probes, which can be used as novel tools for future multimodality systems. The interdisciplinary research that couples molecular imaging science to nanotechnology has generated synergistically integrated novel dual-modality imaging probes. These all-in-one probes take full advantage of two different imaging modalities and could provide unique information that impacts preclinical and, eventually, clinical diagnostics. This review discusses the advantages and challenges in developing dual-modality imaging probes and summarizes the current state-of-the-art systems with respect to their unique design strategies and applications.
Impact of Magnetic Labeling on Human and Mouse Stem Cells and Their Long-Term Magnetic Resonance Tracking in a Rat Model of Parkinson Disease
Authors: Stroh Albrecht , Boltze Johannes , Sieland Katharina , Hild Katharina , Gutzeit Cindy , Jung Tobias , Kressel Jenny , Hau Susann , Reich Doreen , Grune Tilman , Zimmer Claus
Published: March 2018

Magnetic resonance imaging (MRI) of magnetically labeled stem cells has become a valuable tool in the understanding and evaluation of experimental stem cell–based therapies of degenerative central nervous system disorders. This comprehensive study assesses the impact of magnetic labeling of both human and rodent stem cell–containing populations on multiple biologic parameters as maintenance of stemness and oxidative stress levels. Cells were efficiently magnetically labeled with very small superparamagnetic iron oxide particles. Only under the condition of tailored labeling strategies can the impact of magnetic labeling on vitality, proliferation, pluripotency, and oxidative stress levels be minimized. In a rat model of Parkinson disease, magnetically labeled mouse embryonic stem cells were tracked by high-field MRI for 6 months. Significant interindividual differences concerning the spatial distribution of cells became evident. Histologically, transplanted green fluorescent protein–positive iron oxide–labeled cells were clearly identified. No significant increase in oxidative stress levels at the implantation site and no secondary uptake of magnetic label by host phagocytotic cells were observed. Our study strongly suggests that molecular MRI approaches must be carefully tailored to the respective cell population to exert minimal physiologic impact, ensuring the feasibility of this imaging approach for clinical applications.
Metabolism of Orthotopic Mouse Brain Tumor Models
Authors: Rosol Michael , Harutyunyan Ira , Xu JingYing , Melendez Elizabeth , Smbatyan Goar , Finlay Jonathan L. , Krieger Mark D. , Gonzalez-Gomez Ignacio , Reynolds C. Patrick , Nelson Marvin D. , Erdreich-Epstein Anat , Blüml Stefan
Published: March 2018

We used magnetic resonance spectroscopy to determine whether orthotopic mouse brain tumors grown as xenografts in immunocompromised mice either from human brain tumor cells implanted immediately after surgery or from cultured human tumor lines show metabolic profiles comparable to those of the original tumors. Using a 7 T scanner, spectra were acquired from mice with a human atypical teratoid/rhabdoid tumor (AT/RT) either implanted directly from the surgical specimen or first grown in culture, directly implanted choroid plexus carcinoma (CPC), and two medulloblastoma cell lines. The results were compared with spectra from these same tumors or tumor types in patients and with controls. Metabolic variability of tumors from a single cell line was also evaluated using the medulloblastoma lines. The main metabolic features of human tumors were qualitatively replicated in xenografts. AT/RTs in mice exhibited choline, creatine, and myo-inositol levels comparable to those observed in the patient. As in patients, choline was prominent in experimental CPC. Tumors from a single cell line were comparable. Significant correlations were found with key metabolites in humans and mice; however, differences including lower lipids in the implanted AT/RTs than in patient spectra and taurine observed in all animal spectra were also noted. The causes of these dissimilarities warrant further investigation.
Comparative Analysis of Nanoparticle-Antibody Conjugations: Carbodiimide Versus Click Chemistry
Authors: Thorek Daniel L.J. , Elias ew R. , Tsourkas Andrew
Published: March 2018

The ability to modify the physical, chemical, and biologic properties of nanoparticles has led to their use as multifunctional platforms for drug delivery and diagnostic imaging applications. Typically, these applications involve functionalizing the nanoparticles with targeting agents. Antibodies remain an attractive choice as targeting agents because of their large epitope space and high affinity; however, implementation of antibody-nanoparticle conjugates is plagued by low coupling efficiencies and the high cost of reagents. Click chemistry may provide a solution to this problem, with reported coupling efficiencies nearing 100%. Although click chemistries have been used to functionalize nanoparticles with small molecules, they have not previously been used to functionalize nanoparticles with antibodies. Concerns associated with extending this procedure to antibodies are that reaction catalysts or the ligands required for cross-linking may result in loss of functionality. We evaluated the efficiency of conjugations between antibodies and superparamagnetic iron oxide nanoparticles using click chemistry as well as the functionality of the product. The results were compared with conjugates formed through carbodiimide cross-linking. The click reaction allowed for a higher extent and efficiency of labeling compared with carbodiimide, thus requiring less antibody. Further, conjugates prepared via the click reaction exhibited improved binding to target receptors.
Repetitive Noninvasive Monitoring of HSV1-tk-Expressing T Cells Intravenously Infused into Nonhuman Primates Using Positron Emission Tomography and Computed Tomography with 18F-FEAU
Authors: Dotti Gianpietro , Tian Mei , Savoldo Barbara , Najjar Amer , Cooper Laurence J.N. , Jackson James , Smith Amanda , Mawlawi Osama , Uthamanthil Rajesh , Borne Agatha , Brammer David , Paolillo Vincenzo , Alauddin Mian , Gonzalez Carlos , Steiner David , Decker William K. , Marini Frank , Kornblau Steven , Bollard Catherine M. , Shpall Elizabeth J. , Gelovani Juri G.
Published: March 2018

Adoptive transfer of antigen-specific cytotoxic T lymphocytes (CTLs) has been successfully used to treat patients with different types of cancer. However, the long-term spatial-temporal dynamics of the distribution of systemically infused CTLs remains largely unknown. Noninvasive imaging of adoptively transferred CTLs using molecular-genetic reporter imaging with positron emission tomography and computed tomography (PET-CT) represents an innovative approach to understanding the long-term migratory patterns and therapeutic potential of adoptively transferred T cells. Here we report the application of repetitive PET-CT imaging with [18F]fluoro-5-ethyl-1-beta-D-arabinofuranosyluracil (18F-FEAU) in two nonhuman primates demonstrating that autologous polyclonal macaque T lymphocytes activated and transduced with a retroviral vector encoding for the sr39 mutant herpes simplex virus 1 thymidine kinase ( sr39HSV1-tk) reporter gene can be detected after intravenous infusion in discrete lymphoid organs and in sites of inflammation. This study represents a proof of principle and supports the application of 18F-FEAU PET-CT imaging for monitoring the distribution of intravenously administered sr39HSV1-tk gene-transduced CTLs in humans.
Patient-Tailored, Imaging-Guided, Long-Term Temozolomide Chemotherapy in Patients with Glioblastoma
Authors: Galldiks Norbert , Kracht Lutz W. , Burghaus Lothar , Ullrich Roland T. , Backes Heiko , Brunn Anna , Heiss Wolf-Dieter , Jacobs Andreas H.
Published: March 2018

We present two patients with glioblastoma with an unusually stable clinical course and long-term survival who were treated after surgery and radiotherapy with adjuvant temozolomide (TMZ) chemotherapy for 17 and 20 cycles, respectively. Afterward, adjuvant TMZ chemotherapy was discontinued in one patient and the dosage of TMZ was reduced in the other. In addition to clinical status and magnetic resonance imaging, the biologic activity of the tumors was monitored by repeated methyl-11C-l-methionine (MET) and 3′-deoxy-3′-18F-fluorothymidine (FLT) positron emission tomography (PET) studies in these patients. In these patients, repeated MET-and FLT-PET imaging documented complete response to the initial treatment regimen, including resection, radiation, and TMZ, and during the course of the disease, recurrent, uncontrollable tumor activity. Continuation or dose escalation of TMZ in both patients was shown to be ineffective to overcome the metabolic activity of the tumor. Our data suggest that repeated MET- and FLT-PET imaging provide information on the biologic activity of a tumor that is highly useful to monitor and detect changes in activity.
Unconventional Nuclides for Radiopharmaceuticals
Authors: Holland Jason P. , Williamson Matthew J. , Lewis Jason S.
Published: March 2018

Rapid and widespread growth in the use of nuclear medicine for both diagnosis and therapy of disease has been the driving force behind burgeoning research interests in the design of novel radiopharmaceuticals. Until recently, the majority of clinical and basic science research has focused on the development of 11C-, 13N-, 15O-, and 18F-radiopharmaceuticals for use with positron emission tomography (PET) and 99mTc-labeled agents for use with single-photon emission computed tomography (SPECT). With the increased availability of small, low-energy cyclotrons and improvements in both cyclotron targetry and purification chemistries, the use of “nonstandard” radionuclides is becoming more prevalent. This brief review describes the physical characteristics of 60 radionuclides, including β+, β−−, γ-ray, and α-particle emitters, which have the potential for use in the design and synthesis of the next generation of diagnostic and/or radiotherapeutic drugs. As the decay processes of many of the radionuclides described herein involve emission of high-energy γ-rays, relevant shielding and radiation safety issues are also considered. In particular, the properties and safety considerations associated with the increasingly prevalent PET nuclides 64Cu, 68Ga, 86Y, 89Zr, and 124I are discussed.
Novel Intraoperative Near-Infrared Fluorescence Camera System for Optical Image-Guided Cancer Surgery
Authors: Mieog J. Sven D. , Vahrmeijer Alexander L. , Hutteman Merlijn , van der Vorst Joost R. , van Hooff Maurits Drijfhout , Dijkstra Jouke , Kuppen Peter J.K. , Keijzer Rob , Kaijzel Eric L. , Que Ivo , van de Velde Cornelis J.H. , Löwik Clemens W.G.M.
Published: March 2018

Current methods of intraoperative tumor margin detection using palpation and visual inspection frequently result in incomplete resections, which is an important problem in surgical oncology. Therefore, real-time visualization of cancer cells is needed to increase the number of patients with a complete tumor resection. For this purpose, near-infrared fluorescence (NIRF) imaging is a promising technique. Here we describe a novel, handheld, intraoperative NIRF camera system equipped with a 690 nm laser; we validated its utility in detecting and guiding resection of cancer tissues in two syngeneic rat models. The camera system was calibrated using an activated cathepsin-sensing probe (ProSense, VisEn Medical, Woburn, MA). Fluorescence intensity was strongly correlated with increased activated-probe concentration ( R 2 = .997). During the intraoperative experiments, a camera exposure time of 10 ms was used, which provided the optimal tumor to background ratio. Primary mammary tumors ( n = 20 tumors) were successfully resected under direct fluorescence guidance. The tumor to background ratio was 2.34 using ProSense680 at 10 ms camera exposure time. The background fluorescence of abdominal organs, in particular liver and kidney, was high, thereby limiting the ability to detect peritoneal metastases with cathepsin-sensing probes in these regions. In conclusion, we demonstrated the technical performance of this new camera system and its intraoperative utility in guiding resection of tumors.
Magnetic Resonance Imaging of Monocytes Labeled with Ultrasmall Superparamagnetic Particles of Iron Oxide Using Magnetoelectroporation in an Animal Model of Multiple Sclerosis
Authors: Engberink Raoul D. Oude , van der Pol Susanne M.A. , Walczak Pjotr , van der Toorn Annette , Viergever Max A. , Dijkstra Christine D. , Bulte Jeff W.M. , de Vries Helga E. , Blezer Erwin L.A.
Published: March 2018

Infiltrated monocytes play a crucial role in the demyelination process during multiple sclerosis (MS), an inflammatory disease of the central nervous system (CNS). Still, methods to monitor their infiltration pattern over time are lacking. In this study, magnetoelectroporation (MEP) was used to label rat monocytes with the superparamagnetic iron oxide particles Sinerem, Endorem, and Supravist. Supravist-labeled monocytes were injected in rats that we induced with experimental autoimmune encephalomyelitis, a model for MS. Imaging at 4.7 and 9.4 T revealed multiple foci of decreased signal intensity predominantly located in the cerebellum. Immunohistochemical evaluation confirmed the presence of intracellular iron in infiltrated cells, indicating the suitability of MEP to specifically follow labeled monocytes in vivo in this disease model. This technique may be further optimized and potentially used in MS patients to assess monocyte migration into the brain and to monitor the efficacy of therapeutic agents aimed at blocking cellular migration into the CNS.
Experimental Evaluation of Depth-of-Interaction Correction in a Small-Animal Positron Emission Tomography Scanner
Authors: Green Michael V. , Ostrow Harold G. , Seidel Jurgen , Pomper Martin G.
Published: March 2018

Human and small-animal positron emission tomography (PET) scanners with cylindrical geometry and conventional detectors exhibit a progressive reduction in radial spatial resolution with increasing radial distance from the geometric axis of the scanner. This “depth-of-interaction” (DOI) effect is sufficiently deleterious that many laboratories have devised novel schemes to reduce the magnitude of this effect and thereby yield PET images of greater quantitative accuracy. Here we examine experimentally the effects of a particular DOI correction method (dual-scintillator phoswich detectors with pulse shape discrimination) implemented in a small-animal PET scanner by comparing the same phantom and same mouse images with and without DOI correction. The results suggest that even this relatively coarse, two-level estimate of radial gamma ray interaction position significantly reduces the DOI parallax error. This study also confirms two less appreciated advantages of DOI correction: a reduction in radial distortion and radial source displacement as a source is moved toward the edge of the field of view and a resolution improvement detectable in the central field of view likely owing to improved spatial sampling.
Early Therapy Evaluation of Combined Cetuximab and Irinotecan in Orthotopic Pancreatic Tumor Xenografts by Dynamic Contrast-Enhanced Magnetic Resonance Imaging
Authors: Kim Hyunki , Folks Karri D. , Guo Lingling , Sellers Jeffery C. , Fineberg Naomi S. , Stockard Cecil R. , Grizzle William E. , Buchsbaum Donald J. , Morgan Desiree E. , George James F. , Zinn Kurt R.
Published: March 2018

Early pancreatic cancer response following cetuximab and/or irinotecan therapies was measured by serial dynamic contrast-enhanced magnetic resonance imaging (DCE-MRI) before and during therapy. Groups 1 to 4 ( n = 6/group) of SCID mice bearing orthotopic pancreatic adenocarcinoma xenografts expressing luciferase were treated with phosphate-buffered saline, cetuximab, irinotecan, or cetuximab combined with irinotecan, respectively, twice weekly for 3 weeks. DCE-MRI was performed on days 0, 1, 2, and 3 after therapy initiation, whereas anatomic magnetic resonance imaging was performed on days 0, 1, 2, 3, 6, and 13. Bioluminescence imaging was performed on days 0 and 21. At day 21, all tumors were collected for further histologic analyses (Ki-67 and CD31 staining), whereas tumor dimensions were measured by calipers. The Ktrans values in the 0.5 mm–thick peripheral tumor region were calculated, and the changes in Ktrans during the 3 days posttherapy were compared to tumor volume changes, bioluminescent signal changes, and histologic findings. The Ktrans changes in the peripheral tumor region after 3 days of therapy were linearly correlated with 21-day decreases in tumor volume ( p < .001), bioluminescent signal ( p = .050), microvessel densities ( p = .002), and proliferating cell densities ( p = .001). This study supports the clinical use of DCE-MRI for pancreatic cancer patients for early assessment of an anti–epidermal growth factor receptor therapy combined with chemotherapy.
Dual-Modality Monitoring of Tumor Response to Cyclophosphamide Therapy in Mice with Bioluminescence Imaging and Small-Animal Positron Emission Tomography
Authors: Ma Xibo , Liu Zhaofei , Yang Xin , Gao Qiujuan , Zhu Shouping , Qin Chenghu , Liu Kai , Zhang Bo , Han Dong , Wang Fan , Tian Jie
Published: March 2018

The purpose of this study was to noninvasively monitor the therapeutic efficacy of cyclophosphamide (CTX) in a mouse model by dual-modality molecular imaging: positron emission tomography (PET) and bioluminescence imaging (BLI). Firefly luciferase (fLuc) transfected HCC-LM3-fLuc human hepatocellular carcinoma cells were injected subcutaneously into BALB/c nude mice to establish the experimental tumor model. Two groups of HCC-LM3-fLuc tumor-bearing mice ( n = 7 per group) were treated with saline or CTX (100 mg/kg on days 0, 2, 5, and 7). BLI and 18F-fluorodeoxyglucose (18F-FDG) PET scans were done to evaluate the treatment efficacy. CTX induced a 25.25 ± 13.13% and 35.91 ± 25.85% tumor growth inhibition rate on days 9 and 12 posttreatment, respectively, as determined by BLI. A good linear correlation was found between the tumor sizes measured by caliper and the BLI signals determined by optical imaging ( R 2 = .9216). 18F-FDG imaging revealed a significant uptake reduction in the tumors of the CTX-treated group compared to that in the saline control group (5.30 ± 1.97 vs 3.00 ± 2.11% ID/g) on day 16 after CTX treatment. Dual-modality molecular imaging using BLI and small-animal PET can play important roles in the process of chemotherapy and will provide noninvasive and reliable monitoring of the therapeutic response.
ATP-Binding Cassette Transporters Modulate Both Coelenterazine- and D-Luciferin-Based Bioluminescence Imaging
Authors: Huang Ruimin , Vider Jelena , Serganova Inna , Blasberg Ronald G.
Published: March 2018

Bioluminescence imaging (BLI) of luciferase reporters provides a cost-effective and sensitive means to image biological processes. However, transport of luciferase substrates across the cell membrane does affect BLI readout intensity from intact living cells. To investigate the effect of ATP-binding cassette (ABC) transporters on BLI readout, we generated click beetle (cLuc), firefly (fLuc), Renilla (rLuc), and Gaussia (gLuc) luciferase HEK-293 reporter cells that overexpressed different ABC transporters (ABCB1, ABCC1, and ABCG2). In vitro studies showed a significant BLI intensity decrease in intact cells compared to cell lysates, when ABCG2 was overexpressed in HEK-293/cLuc, fLuc, and rLuc cells. Selective ABC transporter inhibitors were also applied. Inhibition of ABCG2 activity increased the BLI intensity more than two-fold in HEK-293/cLuc, fLuc, and rLuc cells; inhibition of ABCB1 elevated the BLI intensity two-fold only in HEK-293/rLuc cells. BLI of xenografts derived from HEK-293/ABC transporter/luciferase reporter cells confirmed the results of inhibitor treatment in vivo. These findings demonstrate that coelenterazine-based rLuc-BLI intensity can be modulated by ABCB1 and ABCG2. ABCG2 modulates d-luciferin-based BLI in a luciferase type–independent manner. Little ABC transporter effect on gLuc-BLI intensity is observed because a large fraction of gLuc is secreted. The expression level of ABC transporters is one key factor affecting BLI intensity, and this may be particularly important in luciferase-based applications in stem cell research.
Glypican-3 Targeting of Liver Cancer Cells Using Multifunctional Nanoparticles
Authors: Park James O. , Stephen Zachary , Sun Conroy , Veiseh Omid , Kievit Forrest M. , Fang Chen , Leung Matthew , Mok Hyejung , Zhang Miqin
Published: March 2018

Imaging is essential in accurately detecting, staging, and treating primary liver cancer (hepatocellular carcinoma [HCC]), one of the most prevalent and lethal malignancies. We developed a novel multifunctional nanoparticle (NP) specifically targeting glypican-3 (GPC3), a proteoglycan implicated in promotion of cell growth that is overexpressed in most HCCs. Quantitative real-time polymerase chain reaction was performed to confirm the differential GPC3 expression in two human HCC cells, Hep G2 (high) and HLF (negligible). These cells were treated with biotin-conjugated GPC3 monoclonal antibody (αGPC3) and subsequently targeted using superparamagnetic iron oxide NPs conjugated to streptavidin and Alexa Fluor 647. Flow cytometry demonstrated that only GPC3-expressing Hep G2 cells were specifically targeted using this αGPC3-NP conjugate (fourfold mean fluorescence over nontargeted NP), and magnetic resonance imaging (MRI) experiments showed similar findings (threefold R2 relaxivity). Confocal fluorescence microscopy localized the αGPC3 NPs only to the cell surface of GPC3-expressing Hep G2 cells. Further characterization of this construct demonstrated a negatively charged, monodisperse, 50 nm NP, ideally suited for tumor targeting. This GPC3-specific NP system, with dual-modality imaging capability, may enhance pretreatment MRI, enable refined intraoperative HCC visualization by near-infrared fluorescence, and be potentially used as a carrier for delivery of tumor-targeted therapies, improving patient outcomes.
Emerging Nanomaterial Governance Systems: The State of Play
Authors: Bergeson Lynn L.
Published: March 2018

Domestic laws, their implementing regulations and policies, and government and private-party governance programs are now being carefully reviewed and revised to enhance their utility to manage the potential risks posed by nanoscale materials. Whether existing laws and their implementing programs are adequate to address such risks will continue to inspire debate and legislative and regulatory initiatives for years to come. This article reviews existing legal and governance oversight systems and analyzes their strengths and deficiencies in addressing the potential risks posed by nanoscale materials and in fostering nanotechnology's promise. Particular attention is devoted to emerging regulatory approaches the US Environmental Protection Agency is taking under the Toxic Substances Control Act and the Federal Insecticide, Fungicide, and Rodenticide Act, the two domestic chemical product laws primarily responsible for ensuring the safety of chemical substances and mixtures.
Techniques for Molecular Imaging Probe Design
Authors: Reynolds Fred , Kelly Kimberly A.
Published: March 2018

Molecular imaging allows clinicians to visualize disease-specific molecules, thereby providing relevant information in the diagnosis and treatment of patients. With advances in genomics and proteomics and underlying mechanisms of disease pathology, the number of targets identified has significantly outpaced the number of developed molecular imaging probes. There has been a concerted effort to bridge this gap with multidisciplinary efforts in chemistry, proteomics, physics, material science, and biology—all essential to progress in molecular imaging probe development. In this review, we discuss target selection, screening techniques, and probe optimization with the aim of developing clinically relevant molecularly targeted imaging agents.
Model System for Live Imaging of Neuronal Responses to Injury and Repair
Authors: Gravel Mathieu , Weng Yuan-Cheng , Kriz Jasna
Published: March 2018

Although it has been well established that induction of growth-associated protein-43 (GAP-43) during development coincides with axonal outgrowth and early synapse formation, the existence of neuronal plasticity and neurite outgrowth in the adult central nervous system after injuries is more controversial. To visualize the processes of neuronal injury and repair in living animals, we generated reporter mice for bioluminescence and fluorescence imaging bearing the luc (luciferase) and gfp (green fluorescent protein) reporter genes under the control of the murine GAP-43 promoter. Reporter functionality was first observed during the development of transgenic embryos. Using in vivo bioluminescence and fluorescence imaging, we visualized induction of the GAP-43 signals from live embryos starting at E10.5, as well as neuronal responses to brain and peripheral nerve injuries (the signals peaked at 14 days postinjury). Moreover, three-dimensional analysis of the GAP-43 bioluminescent signal confirmed that it originated from brain structures affected by ischemic injury. The analysis of fluorescence signal at cellular level revealed colocalization between endogenous protein and the GAP-43-driven gfp transgene. Taken together, our results suggest that the GAP-43-luc/gfp reporter mouse represents a valid model system for real-time analysis of neurite outgrowth and the capacity of the adult nervous system to regenerate after injuries.
Codon-Optimized Luciola Italica Luciferase Variants for Mammalian Gene Expression in Culture and in Vivo
Authors: Maguire Casey A. , van der Mijn Johannes C. , Degeling Marja H. , Morse Danielle , Tannous Bakhos A.
Published: March 2018

Luciferases have proven to be useful tools in advancing our understanding of biologic processes. Having a multitude of bioluminescent reporters with different properties is highly desirable. We characterized codon-optimized thermostable green- and red-emitting luciferase variants from the Italian firefly Luciola italica for mammalian gene expression in culture and in vivo. Using lentivirus vectors to deliver and stably express these luciferases in mammalian cells, we showed that both variants displayed similar levels of activity and protein half-lives as well as similar light emission kinetics and higher stability compared to the North American firefly luciferase. Further, we characterized the red-shifted variant for in vivo bioluminescence imaging. Intramuscular injection of tumor cells stably expressing this variant into nude mice yielded a robust luciferase activity. Light emission peaked at 10 minutes post-D-luciferin injection and retained > 60% of signal at 1 hour. Similarly, luciferase activity from intracranially injected glioma cells expressing the red-shifted variant was readily detected and used as a marker to monitor tumor growth over time. Overall, our characterization of these codon-optimized luciferases lays the groundwork for their further use as bioluminescent reporters in mammalian cells.
Monoclonal Antibodies Conjugated with Superparamagnetic Iron Oxide Particles Allow Magnetic Resonance Imaging Detection of Lymphocytes in the Mouse Brain
Authors: Luchetti Alessandro , Milani Davide , Ruffini Francesca , Galli Rossella , Falini Andrea , Quattrini Angelo , Scotti Giuseppe , Comi Giancarlo , Martino Gianvito , Furlan Roberto , Politi Letterio S.
Published: March 2018

We investigated the potential of antibody-vectorialized superparamagnetic iron oxide (SPIO) particles as cellular specific magnetic resonance contrast agents to image lymphocyte populations within the central nervous system (CNS), with the final goal of obtaining a reliable tool for noninvasively detecting and tracking specific cellular populations in vivo. We used superparamagnetic particles bound to a monoclonal antibody. The particle is the contrast agent, by means of its T2* relaxation properties; the antibody is the targeting vector, responsible for homing the particle to target a surface antigen. To investigate the efficiency of particle vectorialization by these antibodies, we compared two types of antibody-vectorialized CD3-specific particles in vivo. We successfully employed vectorialized SPIO particles to image B220+ cells in a murine model of B-cell lymphoma. Likewise, we were able to identify CD3+ infiltrates in a murine model of multiple sclerosis. The specificity of the technique was confirmed by immunohistochemistry and electron microscopy of corresponding sections. Our findings suggest that indirect binding of the antibody to a streptavidinated particle allows for enhanced particle vectorialization compared to covalent binding of the antibody to the particle.
Single-Photon Emission Computed Tomographic Imaging of the Early Time Course of Therapy-Induced Cell Death Using Technetium 99m Tricarbonyl His-Annexin A5 in a Colorectal Cancer Xenograft Model
Authors: Vangestel Christel , Van de Wiele Christophe , Mees Gilles , Mertens Koen , Staelens Steven , Reutelingsperger Chris , Pauwels Patrick , Van Damme Nancy , Peeters Marc
Published: March 2018

As apoptosis occurs over an interval of time after administration of apoptosis-inducing therapy in tumors, the changes in technetium 99m (99mTc)-tricarbonyl (CO)3 His-annexin A5 (His-ann A5) accumulation over time were examined. Colo205-bearing mice were divided into six treatment groups: (1) control, (2) 5-fluorouracil (5-FU; 250 mg/kg), (3) irinotecan (100 mg/kg), (4) oxaliplatin (30 mg/kg), (5) bevacizumab (5 mg/kg), and (6) panitumumab (6 mg/kg). 99mTc-(CO)3 His-ann A5 was injected 4, 8, 12, 24, and 48 hours posttreatment, and micro–single-photon emission computed tomography was performed. Immunostaining of caspase-3 (apoptosis), survivin (antiapoptosis), and LC3-II (autophagy marker) was also performed. Different dynamics of 99mTc-(CO)3 His-ann A5 uptake were observed in this colorectal cancer xenograft model, in response to a single dose of three different chemotherapeutics (5-FU, irinotecan, and oxaliplatin). Bevacizumab-treated mice showed no increased uptake of the radiotracer, and a peak of 99mTc-(CO)3 His-ann A5 uptake in panitumumab-treated mice was observed 24 hours posttreatment, as confirmed by caspase-3 immunostaining. For irinotecan-, oxaliplatin-, and bevacizumab-treated tumors, a significant correlation was established between the radiotracer uptake and caspase-3 immunostaining ( r = .8, p < .05; r = .9, p < .001; r = .9, p < .001, respectively). For 5-FU- and panitumumabtreated mice, the correlation coefficients were r = .7 ( p = .18) and r = .7 ( p = .19), respectively. Optimal timing of annexin A5 imaging after the start of different treatments in the Colo205 model was determined.
In Vivo Method to Monitor Changes in HER2 Expression Using Near-Infrared Fluorescence Imaging
Authors: Hassan Moinuddin , Chernomordik Victor , Zielinski Rafal , Ardeshirpour Yasaman , Capala Jacek , Gandjbakhche Amir
Published: March 2018

Human epidermal growth factor receptor type 2 (HER2) is a well-known biomarker that is overexpressed in many breast carcinomas. HER2 expression level is an important factor to optimize the therapeutic strategy and monitor the treatment. We used albumin binding domain–fused HER2-specific Affibody molecules, labeled with Alexa Fluor750 dye, to characterize HER2 expression in vivo. Near-infrared optical imaging studies were carried out using mice with subcutaneous HER2-positive tumors. Animals were divided into groups of five: no treatment and 12 hours and 1 week after treatment of the tumors with the Hsp90 inhibitor 17-dimethylaminoethylamino-17-demethoxygeldanamycin (17-DMAG). The compartmental ligands–receptor model, describing binding kinetics, was used to evaluate HER2 expression from the time sequence of the fluorescence images after the intravenous probe injection. The normalized rate of accumulation of the specific fluorescent biomarkers, estimated from this time sequence, linearly correlates with the conventional ex vivo enzyme-linked immunosorbent assay (ELISA) readings for the same tumor. Such correspondence makes properly arranged fluorescence imaging an excellent candidate for estimating HER2 overexpression in tumors, complementing ELISA and other ex vivo assays. Application of this method to the fluorescence data from HER2-positive xenografts reveals that the 17-DMAG treatment results in downregulation of HER2. Application of the AngioSense 750 probe confirmed the antiangiogenic effect of 17-DMAG found with Affibody–Alexa Fluor 750 conjugate.
[18F]Fluoroacetate Positron Emission Tomography for Hepatocellular Carcinoma and Metastases: An Alternative Tracer for [11C]Acetate?
Authors: Ho Chi-lai , Cheung Man-ki , Chen Sirong , Cheung Tan To , Leung Yim Lung , Cheng Kam Chau , Yeung Wing Ding
Published: March 2018

[11C]Acetate (ACT) positron emission tomography/computed tomography (PET/CT) is useful in the detection of hepatocellular carcinoma (HCC). This study aimed to evaluate whether [18F]fluoroacetate (FAC) could be an alternative analogue of [11C]ACT for the diagnosis of HCC. [18F]FAC was synthesized using the precursor t-butyl 2-(methanesulfonyloxy)ethanoate. Five volunteer patients with known HCC were recruited after consent. Whole-body [18F]FAC PET/CT was performed at 20 minutes and 1 hour postinjection and compared to [11C]ACT PET/CT at 20 minutes postinjection to assess biodistribution and tumor uptake characteristics. Qualitative and semiquantitative analyses were performed with statistical correlations on the physiologic organs of accumulation and HCC lesions for both tracers. [18F]FAC was obtained with 99% radiochemical purity, and the reaction yield was 16.0% with 1-hour synthesis time. The biodistribution of [18F]FAC on PET/CT was significantly different from that of [11C]ACT ( p < .05) by the lack of preferential uptake in any specific organ, particularly the pancreas, resembling the pattern of blood-pool retention although partly metabolized via the bowel. There was no significant defluorination, and none of the [11C]ACT-avid HCC lesions showed increased [18F]FAC activity. These were different from the results reported on other species. [18F]FAC may not be a potential alternative tracer for [11C]ACT in PET/CT evaluation of HCC in human subjects.
Feasibility of Vascular Endothelial Growth Factor Imaging in Human Atherosclerotic Plaque Using 89Zr-Bevacizumab Positron Emission Tomography
Authors: Golestani Reza , Zeebregts Clark J. , van Scheltinga Anton G.T. Terwisscha , Hooge Marjolijn N. Lub-de , van Dam Gooitzen M. , Glaudemans Andor W.J.M. , Dierckx Rudi A.J.O. , Tio René A. , Suurmeijer Albert J.H. , Boersma Hendrikus H. , Nagengast Wouter B. , Slart Riemer H.J.A.
Published: March 2018

Intraplaque angiogenesis is associated with the occurrence of atherosclerotic plaque rupture. Cardiovascular molecular imaging can be used for the detection of rupture-prone plaques. Imaging with radiolabeled bevacizumab, a monoclonal anti-vascular endothelial growth factor (VEGF)-A, can depict VEGF levels corresponding to the angiogenic status in tumors. We determined the feasibility of 89Zr-bevacizumab imaging for the detection of VEGF in carotid endarterectomy (CEA) specimens. Five CEA specimens were coincubated with 89Zr-bevacizumab and aspecific 111In-labeled IgG to determine the specificity of bevacizumab accumulation. In 11 CEA specimens, 89Zr-bevacizumab micro-positron emission tomography (PET) was performed following 2 hours of incubation. Specimens were cut in 4 mm wide segments and were stained for VEGF and CD68. In each segment, the mean percent incubation dose per gram of tissue (%Inc/g) and tissue to background ratio were determined. A 10-fold higher accumulation of 89Zr-bevacizumab compared to 111In-IgG uptake was demonstrated by gamma counting. The mean %Inc/ghot spot was 2.2 ± 0.9 with a hot spot to background ratio of 3.6 ± 0.8. There was a significant correlation between the segmental tissue to background uptake ratio and the VEGF score (ρ = .74, p < .001). It is feasible to detect VEGF tissue concentration within CEA specimens using 89Zr-bevacizumab PET. 89Zr-bevacizumab accumulation in plaques is specific and correlates with immunohistochemistry scores.
Electron Paramagnetic Resonance Spectrometry and Imaging in Melanomas: Comparison between Pigmented and Nonpigmented Human Malignant Melanomas
Authors: Godechal Quentin , Ghanem Ghanem E. , Cook Martin G. , Gallez Bernard
Published: March 2018

It has been known for a long time that the melanin pigments present in normal skin, hair, and most of malignant melanomas can be detected by electron paramagnetic resonance (EPR) spectrometry. In this study, we used EPR imaging as a tool to map the concentration of melanin inside ex vivo human pigmented and nonpigmented melanomas and correlated this cartography with anatomopathology. We obtained accurate mappings of the melanin inside pigmented human melanoma samples. The signal intensity observed on the EPR images correlated with the concentration of melanin within the tumors, visible on the histologic sections. In contrast, no EPR signal coming from melanin was observed from nonpigmented melanomas, therefore demonstrating the absence of EPR-detectable pigments inside these particular cases of skin cancer and the importance of pigmentation for further EPR imaging studies on melanoma.
Optimization of [11C]Raclopride Positron Emission Tomographic Rat Studies: Comparison of Methods for Image Quantification
Authors: Torrent Èlia , Farré Magí , Abasolo Ibane , Millan Olga , LLop Jordi , Gispert Juan Domingo , Ruiz Alba , Pareto Deborah
Published: March 2018

The goal of this study was to compare different quantification approaches and reconstruction methods to estimate the binding potential in [11C]raclopride studies in rats. The final aim was to determine if the results obtained with short-acquisition scanning were comparable to the results obtained with long-acquistion (conventional) scanning. We analyzed two rat data sets: a baseline versus a pretreatment study (with cold raclopride) and a young versus an old animal group comparison. The study results support the contention that optimization of [11C]raclopride positron emission tomographic studies in rats by shortening the acquisition time is feasible. In addition, filtered backprojection is recommended as a reconstruction algorithm, although iterative methods may be more sensitive to detect within-group differences.
Impact of Anesthetics on 3′-[18F]Fluoro-3′-Deoxythymidine ([18F]FLT) Uptake in Animal Models of Cancer and Inflammation
Authors: Fuchs Kerstin , Kukuk Damaris , Mahling Moritz , Quintanilla-Martinez Leticia , Reischl Gerald , Reutershan Jörg , Lang Florian , Röcken Martin , Pichler Bernd J. , Kneilling Manfred
Published: March 2018

The aim of this study was to evaluate the impact of different anesthetics on 3′-[18F]fluoro-3′-deoxythymidine ([18F]FLT) uptake in carcinomas and arthritic ankles. To determine the amount of [18F]FLT uptake in subcutaneous CT26 colon carcinomas or arthritic ankles, spontaneously room air/medical air–breathing mice were anesthetized with isoflurane, a combination of medetomidine/midazolam, or ketamine/xylazine. Mice were kept conscious or anesthetized during [18F]FLT uptake before the 10-minute static positron emission tomographic (PET) investigations. [18F]FLT uptake in CT26 colon carcinomas and arthritic ankles was calculated by drawing regions of interest. We detected a significantly reduced (4.4 ± 0.9 %ID/cm3) [18F]FLT uptake in the carcinomas of ketamine/xylazine-anesthetized mice compared to the [18F]FLT-uptake in carcinomas of medetomidine/midazolam- (7.0 ± 1.5 %ID/cm3) or isoflurane-anesthetized mice (6.4 ± 1.5 %ID/cm3), whereas no significant differences were observed in arthritic ankles regardless of whether mice were anesthetized or conscious during tracer uptake. The time-activity curves of carcinomas and arthritic ankles yielded diverse [18F]FLT accumulation related to the used anesthetics. [18F]FLT uptake dynamics are different in arthritic ankles and carcinoma, and the magnitude and pharmacokinetics of [18F]FLT uptake are sensitive to anesthetics. Thus, for preclinical in vivo [18F]FLT PET studies in experimental tumor or inflammation models, we recommend the use of isoflurane anesthesia as it yields a stable tracer uptake and is easy to handle.