Brenda Robledo¹, Xiaoyong Zhang¹, and Xiaoping P. Hu^1
1Biomedical Engineering, Emory University/Georgia Institute of Technology, Atlanta, Georgia, United States

In magnetotactic bacteria, the gene mms6 expresses a protein thought to initiate magnetite crystal formation. We previously found that transfecting glioma cells with mms6 increased the cells’ ability to uptake iron and increased their spin-spin relaxation rate (R2) in vitro. We hypothesized that tumors established with glioma cells transfected with mms6 would uptake endogenous iron and produce MR contrast. Our results show that mms6-positive tumors exhibit a larger R2 in vivo, likely due to the increased intracellular iron accumulation observed by Prussian staining the tumor. Our results suggest that mms6 may function as an MR reporter gene in cancer studies.

Amnon Bar-Shir^1,2, Yajie Liang^1,2, Assaf A. Gilad^1,2, and Jeff W.M. Bulte^1,2
1Department of Radiology, Johns Hopkins University, Baltimore, MD, United States, ²Institute for Cell Engineering, Johns Hopkins University, Baltimore, MD, United States

Positively charged amino acids (mostly lysine and arginine) in peptide and proteins enable their use as CEST-based contrast agents or reporter genes. We show here that superpositively-charged mutants of the green fluorescent protein (GFP) reporter gene can generate superior CEST contrast. The additional, water-exposed, lysine and arginine amino acids of these mutants were found to increase the CEST contrast obtained from the baseline guanidine (arginine) and amide (lysine and arginine) exchangeable protons. These mutant GFPs retained their fluorescence thus making it a bimodal reporter gene.

Amnon Bar-Shir¹, Guanshu Liu², Kannie W.Y. Chan², Michael T. McMahon², Peter C.M. van Zijl², Jeff W.M. Bulte^1,3, and Assaf A. Gilad^1,3
1Radiology, Johns Hopkins University, Baltimore, MD, United States, ²Kennedy Krieger Research Institute, Baltimore, MD, United States, ³Institute for Cell Engineering, Johns Hopkins University School of Medicine, Baltimore, MD, United States

We have developed a novel CEST-MRI reporter gene based on human protamine-1, and demonstrated its expression and detection in mammalian cells, as well as in a three-dimensional cell culture model of immune-isolated cells. Due to its biocompatibility, this humanized reporter gene is expected to have higher cellular tolerance with minimal immune response.

Marina Radoul¹, Batya Cohen², Moriel Vandsburger², Dorit Granot², Eyal Shimoni³, Alon Harmelin⁴, Raz Zarivach⁵, and Michal Neeman^2
1Radiology, UCSF, San Francisco, CA, United States, ²Biological Regulation, Weizmann Institute of Science, Rehovot, Israel, ³Chemical Research Support, Weizmann Institute of Science, Rehovot, Israel, ⁴Veterinary Resources, Weizmann Institute of Science, Rehovot, Israel, ⁵Life Sciences, Ben-Gurion University of the Negev, Beer-Sheva, Israel

Ferritin is one of the most extensively studied MRI reporter genes. However, compared to iron in magnetite, iron in ferritin demonstrates lower relaxivity and thus lowers sensitivity for detection by MRI. Here we report on a new recombinant fusion protein HA-Ferritin-M6A considerably enhanced r2 relaxivity and cell iron loading which represents a significant advance over existing Ferritin reporter gene strategies.

Enza Di Gregorio¹, Giuseppe Ferrauto¹, Eliana Gianolio¹, Daniela Delli Castelli¹, and Silvio Aime^1
1Molecular Biotechnology & Health Sciences, Molecular Imaging Center, Torino, Italy

Different strategies to label cells with paramagnetic MRI contrast agents have been exploited in the last years like pinocytosis, electroporation, receptor/transporter mediated endocytosis, external labeling. Herein we show that hypotonic swelling of cells is a new efficient route to label cells with paramagnetic Gd-complexes. In fact, the cytoplasmatic uptake shifts to much higher loadings the “quenching” effect on the relaxivity observed when the paramagnetic Gd-complexes are compartmentalized into endosomal vesicles.

Yasir Loai¹, Nurus Sakib¹, Rafal Janik², Warren D. Foltz³, and Hai-Ling Margaret Cheng^1,4
1The Hospital for Sick Children, Toronto, Ontario, Canada, ²Sunnybrook Health Sciences Centre, Toronto, Ontario, Canada, ³University Health Network, Toronto, Ontario, Canada, ⁴Medical Biophysics, University of Toronto, Toronto, Ontario, Canada

Positive T1 contrast MRI offers improved specificity and spatial delineation over conventional negative-contrast imaging, and gadolinium oxide (Gd₂O₃) nanoparticles have shown promise as a sensitive T1 agent for labeling. However, it is not known if signal enhancement in labeled cells is maintained at high field strengths, where relaxivity is known to decline. This study explores the potential of Gd₂O₃ for positive-contrast MRI at 7 Tesla. It is demonstrated in human aortic endothelial cells that large amounts of Gd₂O₃ were ingested spontaneously and that significant and stable positive T1 contrast on cells was achieved for at least 7 days.

Oliviero Gobbo^1,2, Friedrich Wetterling³, Kieran Crosbie-Staunton², Peter Vaes⁴, Stephanie Teughels⁴, Farouk Markos⁵, Marek Radomski¹, Adriele Prina-Mello², and Yuri Volkov^2
1School of Pharmacy and Pharmaceutical Sciences, Trinity College Dublin, Dublin, Ireland, ²School of Medicine, Trinity College Dublin, Dublin, Ireland, ³School of Engineering, Trinity College Dublin, Dublin, Ireland, ⁴PEPRIC nv, Leuven, Belgium, ⁵Physiology, University College Cork, Cork, Ireland

The biodistribution of superparamagnetic iron oxide nanoparticles (SPIO) was evaluated in a mouse model using MRI measurements and a new analytical technique based on particle electron paramagnetic resonance (pEPR). Additionally, the pEPR results were also compared to inductively coupled plasma mass spectrometry (ICP-MS) iron analysis. Our results indicate that both techniques were equally sensitive. The iron measurements by pEPR in the organs were consistent with signal intensity changes recorded by MRI. Overall the data showed that this new technique is suitable for pharmacokinetic and biodistribution studies of SPIO.

Bo Zheng¹, Tandis Vazin^1,2, Wisely Yang¹, Patrick W. Goodwill¹, Emine U. Saritas¹, Laura R. Croft¹, David V. Schaffer^1,2, and Steven M. Conolly^3,4
1Bioengineering, UC Berkeley, Berkeley, CA, United States, ²Chemical and Biomolecular Engineering, UC Berkeley, Berkeley, CA, United States, ³Bioengineering, University of California, Berkeley, Berkeley, CA, United States, ⁴Electrical Engineering and Computer Sciences, UC Berkeley, Berkeley, CA, United States

Magnetic Particle Imaging (MPI), a new technique that images distributions of superparamagnetic iron oxide nanoparticles by exploiting their nonlinear magnetization, can achieve high positive-contrast and quantitative clinical cell tracking, angiography, and inflammation imaging. Here, we present the first experimental demonstration of stem cell tracking with MPI. We show experimentally that MPI signal has excellent positive contrast, is highly linear with cell number, and is not depth-attenuated or diffused in tissue, in contrast to optical techniques. The detection sensitivity for MPI stem cell imaging is currently 10K cells, with potential for improvement by more than 2 orders of magnitude.

Chih-Lung Chen¹, Cheng-Hung Chou², Chen-Hsuan Lin¹, Wen-Yuan Hsieh¹, Shian-Jy Wang¹, and Chen Chang^2
1Industrial Technology Research Institute, Hsinchu, Taiwan, ²Institute of Biomedical Sciences, Academia Sinica, Taipei, Taiwan

The activation of T-cells correlates with the pathogenesis of rheumatoid arthritis (RA). Understanding the genesis, migration, and distribution of the T-cells provides important perspectives regarding RA. We developed an optimal carboxylated group of iron-oxide particles and adapted it to conjugate with CD3 antibody. We then investigated the labeling efficiency and binding specificity of the nano-sized iron oxide-based contrast agent IOPC and IOPC conjugated CD3 by cellular MRI via intravenous infusion. Specifically, we have detected a migration and accumulation of the T-cells in the arthritis joint in a rat RA model with in vivo MRI by IOPC-CD3.

Tatjana Atanasijevic¹, Jasmin Herz¹, Dorian McGavern¹, and Alan P. Koretsky^1
1NINDS, NIH, Bethesda, MD, United States

Viral infection of the central nervous system (CNS) is a common cause of inflammatory disease. Anti-viral T cells recruited from the periphery play a critical role in fighting CNS viral infections. The ability to track single T cells in the brain with MRI would help pre-clinical studies and open novel diagnostic possibilities. Here it is demonstrated that T cells can be labeled with MPIOs in short incubation times and sorted for cells that have internalized particles. These cells can be re-introduced into LCMV-infected mice and detected by MRI opening the possibility of tracking single T cells migrating in the brain.

Naomi Santa Maria¹, Thomas Ng², Sharon Lin², Sarah McCaig³, Desiree Crow³, Jianyi Wang³, Andrew Raubitschek³, and Russell E. Jacobs^2
1Biology, Caltech, Pasadena, CA, United States, ²Caltech, Pasadena, CA, United States, ³City of Hope, Duarte, CA, United States

MRI can provide a noninvasive tool to characterize adoptive NK cell therapy. We aimed to implement MRI-based NK cell tracking methods that could be clinically translatable by using an FDA-approved USPIO cell label on NK cells isolated from human peripheral blood. MRI as a noninvasive in vivo cellular imaging technique could further elucidate optimization of adoptive NK cell transfer as a cancer therapy.

Giuseppe Ferrauto¹, Pierangela Giustetto¹, Daniela Delli Castelli¹, Marta Ruzza¹, Francesca Garello¹, Silvio Aime¹, and Enzo Terreno^1
1Molecular Biotechnology & Health Sciences, Molecular Imaging Center, Torino, Italy

The development of innovative strategies for labeling cells with Gd-based MRI agents is an important topic. It has been demonstrated that the ability of a labeling agent to generate a contrast when internalized into a cell is significantly higher if it is localized in the cytosol. Ultrasound stimulation can permeabilize cell membranes, allowing the passage of molecules from the external solution to cytosol. The purpose of this work was to design a proper experimental set-up for optimizing the cell labeling procedure via sonoporation. Furthermore the study was aimed at evaluating the effect of the presence of liposomes on labeling efficiency.

Fang-Cheng Yeh¹, Li Liu², T Kevin Hitchens², and Chien Ho^2
1Biomedical Engineering, Carnegie Mellon University, Pittsburgh, PA, United States, ²Pittsburgh NMR Center for Biomedical Research, Pittsburgh, PA, United States

We obtained the R1, R2, and R2* maps of a cell phantom created by mixing ultra-small superparamagnetic iron oxide (USPIO) labeled cells with raw cell matrix to simulate the labeling condition. Our analysis shows that R1, R2, and R2* values exhibit a good linear correlation with the number of cells (correlation coefficients > 0.9). Using the iron concentration of 1.25 pg Fe/cell, R2* value gives the best quantification index for cell density, about 107~109 cells per mL, the R2 values for cell density are in the range of 109 cells per mL, and the R1 values for cell density are greater than 1010 cells per mL.

Dorit Granot¹ and Erik M. Shapiro^2
1Department of Biological Regulation, Weizmann Institute of Science, Rehovot, Israel, ²Department of Radiology, Michigan State University, East Lansing, Michigan, United States

Endogenous labeling of stem/ progenitor cells via intracerebroventricular injection of MPIOs has become standard methodology for MRI imaging of adult neurogenesis. While this method is well characterized in the naïve rodent brain, it has not been fully investigated in disease models. Here we describe challenges in this methodology that can confound data analysis when this technique is applied to a rat model of stroke.

Erik M. Shapiro¹, Ronen Globinsky², Xenios Papademetris², and Margaret F. Bennewitz^3
1Department of Radiology, Michigan State University, East Lansing, Michigan, United States, ²Department of Radiology, Yale University School of Medicine, New Haven, Connecticut, United States, ³Department of Biomedical Engineering, Yale University, New Haven, Connecticut, United States

In this work, MPIO labeled single MSCs were robustly detected in vitro and in vivo with 3D T2* MRI and quantified using automated image processing techniques. The effect of TE and resolution on spot size and intensity was evaluated within in vitro agarose samples, containing dispersed MPIO labeled single MSCs. MPIO labeled MSCs were injected intracardially to create an in vivo magnetically labeled single cell model in the rat brain, which was again optimized using TE and also TR imaging parameters. The presence of magnetically labeled single cells in the brain was confirmed with histology. For the first time, image processing techniques were used to generate automated counts of MPIO labeled MSCs in the rat brain of live animals from MRI scans.

Samuel Fielden¹, Alexander Klibanov^1,2, Frederick H. Epstein^1,3, Yaqin Xu¹, Brent French^1,2, and Craig Meyer^1,3
1Biomedical Engineering, University of Virginia, Charlottesville, VA, United States, ²Medicine, University of Virginia, Charlottesville, VA, United States, ³Radiology, University of Virginia, Charlottesville, VA, United States

Fluorine-19 (19F) is an attractive second-nucleus for contrast-enhanced MRI. However, for 19F cellular and molecular imaging, in order to achieve useful image resolution in reasonable scan times, methods must be developed to efficiently generate and utilize signal arising from small volumes of contrast agent. Here, we attempt to improve 19F imaging of cardiac inflammation through a 3-pronged approach: First, through pulse sequences optimized to maximize SNR; second, by incorporating side information from proton images in a constrained iterative reconstruction; finally, by exploiting the underlying sparsity of 19F images using model-based image reconstructions.

Verena Hoerr¹, Harry Parkes², Kathrin Halama¹, Sonja Mertsch¹, Volker Senner¹, Astrid Jeibmann¹, and Cornelius Faber^3
1University Hospital Muenster, Muenster, Germany, ²Royal Marsden Hospital, Sutton, United Kingdom, ³University Hospital Münster, Muenster, Germany

We investigated in vivo the effect of iron oxide nanoparticles (IONPs) on C6 glioma cells with regards to growth behavior and metabolic pathogenesis by MRI and NMR metabolomics using statistical pattern recognition techniques. While tumor growth was similar for labeled and unlabeled tumors, 1H NMR spectra from urine of mice transplanted with iron labeled C6 glioma cells differed significantly from those of untreated cells and showed significant increase in trans-aconitate, N,N-dimethylglycine and 2-phenylproprionate. Our results indicate that IONPs may have significant impact on cell behavior in vivo which may result in metabolic changes superposing the pathological ones.

Qing Ye¹, Yijen L. Wu¹, Lesley M. Foley¹, Parker H. Mills¹, T Kevin Hitchens¹, Fang-Cheng Yeh^1,2, Haosen Zhang¹, Danielle F. Eytan¹, Li Liu¹, and Chien Ho^1
1NMR Center for Biomedical Research and Department of Biological Sciences, Carnegie Mellon University, Pittsburgh, PA, United States, ²Department of Biomedical Engineering, Carnegie Mellon University, Pittsburgh, PA, United States

Chronic cardiac allograft rejection (CCAR) remains a major obstacle for long-term heart graft survival. Early identification the disease by noninvasive method is highly desirable. By using cellular MRI, we investigated the characteristics of CCAR progression over time in a rat model. Our preliminary results revealed that CCAR appears heterogeneous in its early stages and the accumulation of iron-labeled cells can be an indicator of the lesion formation prior to irreversible vascular changes occur. Cellular MRI is able to evaluate graft status noninvasively over time, which may be a reliable alternative for assessment of CCAR and potentially translatable to clinical work.

Yasuo Takehara¹, Naoki Kato², Satoshi Yoshise², Jean-Sebastien Raynaud³, Philippe Robert³, Claire Corot³, Kazuya Hokamura⁴, and Harumi Sakahara^5
1Radiology, Hamamatsu University Hospital, Hamamatsu, Shizuoka, Japan, ²Guerbet Japan, Chiyoda-ku, Tokyo, Japan, ³Guerbet Research, Roissy CDG, Cedex, France,⁴Pharmacology, Hamamatsu University School of Medicine, Hamamatsu, Shizuoka, Japan, ⁵Radiology, Hamamatsu University School of Medicine, Hamamatsu, Shizuoka, Japan

Under general anesthesia, five VX2 tumor bearing rabbits were examined with contrast enhanced MRI on 3.0T clinical scanner with phased array knee coil. Newly developed USPIO P904 was intravenously administered at a dose of 100 micro mol Fe/kg. Pre and 24 hrs post-contrast MRI was imaged with 3DT2*GRE. Metastatic and non-metastatic popliteal lymph nodes were excised and the specimens were stained with high sensitivity ion stain, macrophage stain and cytokeratin stain. Close histopathological-MRI correlations disclosed that P904 successfully increased the metastatic foci in the lymph node. Newly developed USPIO P904 may be a promising second generation USPIO after ferumoxtran-10.

Daisuke Kokuryo¹, Yasutaka Anraku², Akihiro Kishimura², Sayaka Tanaka³, Mitsunobu R. Kano⁴, Nobuhiro Nishiyama³, Tsuneo Saga¹, Ichio Aoki¹, and Kazunori Kataoka^2,3
1Molecular Imaging Center, National Institute of Radiological Sciences, Chiba, Chiba, Japan, ²Graduate School of Engineering, The University of Tokyo, Tokyo, Tokyo, Japan,³Graduate School of Medicine, The University of Tokyo, Tokyo, Tokyo, Japan, ⁴Graduate School of Medicine, Dentistry and Pharmaceutical Sciences, Okayama University, Okayama, Okayama, Japan

A newly developed SPIO-loaded and fluorescence dye (Cy5)-labeled polyion complex nanocarrier, termed SPIO-Cy5-PICsome, composed of two biocompatible oppositely charged block copolymers was applied to evaluate its ability to detect small tumors with MRI. In vitro r₂ of the SPIO-Cy5-PICsomes was 2.54 times higher than that of free ferucarbotran. In in vivo experiments using subcutaneously xenografted mice, MR signal from the tumor changed during the 3 hours after SPIO-Cy5-PICsome administration. A small tumor was also detected at 24 hours after administration. SPIO-Cy5-PICsomes are a powerful nanocarrier with the potential to detect small and early-stage tumor for early diagnosis.

YunMing Wang¹, ShouCheng Wu¹, and YuJen Chen^1
1Department of Biological Science and Technology, National Chiao Tung University, HsinChu, Taiwan

We developed an MR/optical imaging contrast agents for the diagnosis and treatment of pancreatic cancer. A highly sensitive and specific T2 weighted MR-optical imaging agent has been synthesized. The results of the experiments show significant negative contrast enhancement in mucin4 positive cell lines. As a result, we demonstrated that the T2 weighted MR-optical imaging agent can specifically target mucin4 and can be potentially used for the detection of pancreatic cancer.

Guan Wang^1,2, Yingli Fu¹, Steven M. Shea³, Judy Cook¹, and Dara L. Kraitchman^1,4
1Radiology and Radiological Science, Johns Hopkins University, Baltimore, MD, United States, ²Electrical and Computer Engineering, Johns Hopkins University, Baltimore, Maryland, United States, ³Center for Applied Medical Imaging, Siemens Corporation, Corporate Research and Technology, Baltimore, MD, United States, ⁴Molecular and Comparative Pathobiology, Johns Hopkins University, Baltimore, MD, United States

Microencapsulated stem cell (SC) offers a novel means to transplant mismatched SCs to avoid immunorejection for the treatement of peripheral arterial disease (PAD) that is too extensive for the conventional therapy. We produced dual X-ray/MR-visible microcapsules (XMRCaps) by impregnated the perfluorooctyl bromine (PFOB) to enable cell tracking with non-invasive imaging modalities. Here we first explore quantitative serial cell tracking using c-arm CT and ¹⁹F-MRI of XMRCaps in a rabbit PAD model using conventional clinical imaging systems. Results indicate that in vivo XMRCaps volume tracking could be achieved by both CT and MRI, while only MRI demonstrates the XMRCaps degradation.

Taro Toyota^1,2, Naoto Ohguri², Kouichi Maruyama³, Masanori Fujinami², Tsuneo Saga³, and Ichio Aoki^3
1The University of Tokyo, Meguro, Tokyo, Japan, ²Chiba University, Inage, Chiba, Japan, ³National Institute of Radiological Sciences, Inage, Chiba, Japan

We describe biodegradable probes made of giant vesicles (GVs; closed lipid membranes with diameters >1 m) that encapsulate SPIO for use as an MRI contrast agent. These SPIO-containing GVs (SPIO-GVs) exhibited excellent contrast enhancement in the single cell of medaka fish (Oryzias latipes) embryos immediately after their microinjection, and this enhancement disappeared when the GV membranes were destroyed.

Rheal A. Towner¹, Nataliya Smith¹, Philippe Garteiser¹, Debra Saunders¹, Florea Lupu², Robert Silasi-Mansat², Dario C. Ramirez³, Sandra E. Gomez-Mejiba³, Ronald P. Mason⁴, Marilyn I. Ehrenshaft⁴, Fernando Bozza⁵, Marcus Frenandes de Oliveira⁶, and Hugo C. Castro Faria-Neto^7
1Advanced Magnetic Resonance Center, Oklahoma Medical Research Foundation, Oklahoma City, OK, United States, ²Cardiovascular Biology, Oklahoma Medical Research Foundation, Oklahoma City, OK, United States, ³Laboratory of Experimental and Therapeutic Medicine, National University of San Luis, San Luis, San Luis, Argentina,⁴Laboratory of Pharmacology & Chemistry, National Institute of Environmental Health Sciences, Research Triangle Park, NC, United States, ⁵Instituto de Pesquisa Clinica Evandro Chagas, Fundação Oswaldo Cruz, Rio de Janeiro, RJ, Brazil, ⁶Instituto de Bioquímica Médica, Universidade Federal do Rio de Janeiro, Rio de Janeiro, RJ, Brazil,⁷Instituto de Pesquisa Clinica Evandro Chagas, Fundação Oswaldo Cruz, Rio de Janeiro, Rio de Janeiro, Brazil

Oxidative stress from free radicals plays a major role in sepsis. A combination of immuno-spin-trapping (IST) and targeted molecular magnetic resonance imaging (mMRI) was used to detect in vivo levels of membrane-bound radicals (MBR) in brain tissues from mice with cecal ligation puncture (CLP)-induced sepsis. The spin trapping compound DMPO (5,5-dimethyl pyrroline N-oxide) was used to trap radicals. An anti-DMPO probe (anti-DMPO antibody covalently bound to an albumin-Gd-DTPA-biotin construct was used to detect MBR in vivo with mMRI. This method can be applied towards any radical-associated pathological condition for the in vivo assessment of membrane-bound protein and/or lipid radical levels.

Rheal A. Towner¹, Nataliya Smith¹, Debra Saunders¹, Patricia Coutinho De Souza¹, Leah Henry¹, Florea Lupu², Robert Silasi-Mansat², Marilyn I. Ehrenshaft³, Ronald P. Mason³, Sandra E. Gomez-Mejiba⁴, and Dario C. Ramirez^4
1Advanced Magnetic Resonance Center, Oklahoma Medical Research Foundation, Oklahoma City, OK, United States, ²Cariovascular Biology, Oklahoma Medical Research Foundation, Oklahoma City, OK, United States, ³Laboratory of Pharmacology & Chemistry, National Institute of Environmental Health Sciences, Research Triangle Park, NC, United States, ⁴Laboratory of Experimental Medicine & Therapeutics, National University of San Luis, San Luis, San Luis, Argentina

Free radicals associated with oxidative stress play a major role in cancer. By combining immuno-spin-trapping (IST) and targeted molecular magnetic resonance imaging (mMRI), we detected in vivo levels of membrane-bound radicals (MBR) within tumors of GL261 glioma-bearing mice. The spin trapping agent DMPO (5,5-dimethyl pyrroline N-oxide) traps MBR which can be detected in vivo with a targeted molecular MRI probe that detects DMPO-trapped-MBR. This is the first report regarding the detection of in vivo levels of MBR from a glioma model. This novel non-invasive method can be applied to investigate free radical mechanisms in the pathogenesis of various cancers.

Meser M. Ali¹, Nadimpalli RS Verma¹, Janic Branislava¹, James R. Ewing², Robert A. Knight², and Ali S. Arbab^1
1Radiology, Henry Ford Hospital, Detroit, Michigan, United States, ²Neurology, Henry Ford Hospital, Detroit, Michigan, United States

Water soluble membrane peptide (pHLIP) is conjugated with anionic dendrimer-based paramagnetic nanoparticle. pHLIP-tagged nanoparticles bind to and are internalized by breast cancer cells in vitro. Systemic delivery of dendrimer-based nanoparticles lead to accumulation of the nanoparticles in a flank mouse model of breast cancer that are detected by optical and MR imaging.

Simonetta Geninatti¹, Juan Carlos Cutrin¹, Diana Burgelea¹, Dario Livio Longo¹, Walter Dastru¹, and Silvio Aime^1
1Molecular Biotechnology and healt sciences, University of Torino, Torino, TO, Italy

Curcumin/Gd loaded Apoferritin is herein proposed as a new theranostic agent able to deliver simultaneously therapeutic and imaging probes to the liver. The incapsulation of curcumin inside the apoferritin cavity increases significantly its stability and bioavailability by maintaining its antioxidant and anti-inflammatory properties. Curcumin/Gd loaded Apoferritin was able to protect hepatocytes by the thiocetamide toxic action generating acute hepatitis injury.

Ki-Hye Jung¹, Hee-Kyung Kim², Min-Kyoung Kang², Ji-Ae Park³, Eun-Young Jeon⁴, Seung-Tae Woo⁵, Joo-Hyun Kim⁵, Tae-Jeong Kim¹, and Yongmin Chang^2,6
1Applied Chemistry, Kyungpook National University, Daegu, Korea, ²Medical & Biological Engineering, Kyungpook National University, Daegu, Korea, ³Molecular Imaging Research Center, Korea Institute of Radiological & Medical Science, Seoul, Korea, ⁴The Advanced Medical Technology Cluster for Diagnosis & Prediction, Kyounpook National University, Daegu, Korea, ⁵Bayer Healthcare, Medical care, Seoul, Korea, ⁶Diagnostic Radiology and Molecular Medicine, Kyungpook National University, Daegu, Korea

We report the synthesis of DO3A derivatives of 2,2- diaminobiphenyl and their Gd complexes of the type [Gd(1)(H₂O)]·xH₂O (2a,b)for use as new MRI blood-pool contrast agents that provide strong and prolonged vascular enhancement. Pharmacokinetic inertness of 2 compares well with that of structurally related Dotarem, a DOTA-based MRI CA currently in use. They show interaction with HSA to give association constants (K_a) in the order of two (¡­10²), revealing the existence of the blood-pool effect. The in-vivo MR images of mice obtained with 2 are coherent, showing strong signal enhancement in both heart, abdominal aorta, and small vessels.

Sona Saksena¹, Adnan Hirad^1,2, Stephen B. Pickup¹, Harish Poptani¹, Ari D. Goldberg¹, Anatoliy V. Popov¹, and Edward James Delikatny^1
1Radiology, University of Pennsylvania, Philadelphia, PA, United States, ²School of Medicine and Dentistry, University of Rochester, Rochester, New York, United States

Bacterial infections, both localized and disseminated (bacteremia), are responsible for significant morbidity and mortality in the community and hospital settings. A robust method to noninvasively identify and localize pathogenic bacterial sources with high sensitivity and specificity would greatly aid in the timely diagnosis and treatment of bacteremia. In an animal model of localized bacterial infection, E. coli exposed to ZnDPA-DOTA-thiourea reduced T1 by a factor of three indicating binding of ZnDPA-DOTA-thiourea to bacteria. We demonstrate that detection of bacteria in an animal model is feasible via changes in T1 relaxation.

Hee-Kyung Kim¹, Ki-Hye Jung², Min-Kyoung Kang¹, Ji-Ae Park³, Eun-Young Jeon⁴, Seung-Tae Woo⁵, Joo-Hyun Kim⁵, Tae-Jeong Kim², and Yongmin Chang^1,6
1Medical & Biological Engineering, Kyungpook National University, Daegu, Korea, ²Applied Chemistry, Kyungpook National University, Daegu, Korea, ³Molecular Imaging Research Center, Korea Institute of Radiological & Medical Science, Seoul, Korea, ⁴The Advanced Medical Technology Cluster for Diagnosis & Prediction, Kyungpook National University, Daegu, Korea, ⁵Bayer Healthcare, Medical Care, Seoul, Korea, ⁶Diagnostic Radiology and Molecular Medicine, Kyungpook National University, Daegu, Daegu, Korea

DO3A-benzothiazole conjugates have been prepared as a new family of multifunctional MRI/optical imaging probes with concomitant antitumor activity as well as tumor-specificity. Its R₁ relaxivity is 3.84 mM^-1sec^-1, almost the same values as that of structurally related Dotarem^®. The pattern of in vivo MRI enhacement compares well with those of liver-specific MRI CAs. More characteristically, it is to be noted that excretion is made via bile duct, confirming hepatobiliary uptake. T₁-weighted MR images of MCF-7 cells incubated with Gd-DO3A-BT, revealing the tumor-specificity of the present series. In addition, antitumor activity of the present system represented as GI₅₀ and TGI values.

Hai-Ling Margaret Cheng^1,2, Weiran Cheng^3,4, Inga E. Haedicke^3,4, Joris Tchouala Nofiele^1,2, and Xiao-an Zhang^3,4
1Medical Biophysics, University of Toronto, Toronto, Ontario, Canada, ²The Hospital for Sick Children, Toronto, Ontario, Canada, ³Physical and Environmental Sciences, University of Toronto Scarborough, Toronto, Ontario, Canada, ⁴Chemistry, University of Toronto, Toronto, Ontario, Canada

Gadolinium-based contrast agents are less efficient at high fields and are potentially toxic. Recently, the Zhang group developed a new class of T1 contrast agents based on the manganese porphyrin (MnP) structure with improved efficacy and safety. This study investigates MRI properties of two specific versions: a small polar MnP and a larger dimer. In-vitro measurements at 3 Tesla demonstrate high T1 relaxivities and a relatively weak T2 effect. Signal enhancement in rats is significantly greater compared to Gd-DTPA, and biodistribution is specific to each MnP. Potential applications are broad and include cardiac, liver, angiography, and perfusion and permeability imaging.

Min-Kyoung Kang¹, Hee-Kyung Kim¹, Ki-Hye Jung², Ji-Ae Park³, Seung-Tae Woo⁴, Joo-Hyun Kim⁴, Eun-Young Jeon⁵, Tae-Jeong Kim², and Yongmin Chang^1,6
1Medical & Biological Engineering, Kyungpook National University, Daegu, Korea, ²Applied Chemistry, Kyungpook National University, Daegu, Korea, ³Molecular Imaging Research Center, Korea Institute of Radiological & Medical Science, Seoul, Korea, ⁴Bayer Healthcare, Medical care, Seoul, Korea, ⁵The Advanced Medical Technology Cluster for Diagnosis & Prediction, Kyungpook National University, Daegu, Korea, ⁶Diagnostic Radiology and Molecular Medicine, Kyungpook National University, Daegu, Korea

Gadolinium nanoparticles (GdNPs) based perfectly soluble potential theragnostic agents formulated as Gd@SiO₂-NHCO-DO3A-BT. The preparation initially requires the formation of Gd@SiO₂ through self-condensation of TEOS on the surface of GdNPs. Gd@SiO₂-NH₂ thus formed was dispersed in diethylen glycol to react with APTES. In order to increase solubility as well as used by potential bimodal contrast agents, Gd@SiO₂-NH₂ was further conjugated with DO3A-benzothiazole to give the desired product Gd@SiO₂-NHCO-DO3A-BT. Gd@SiO₂-NHCO-DO3A reveals high MR relaxivity (R₁ = 8.29 mM^-1s^-1) and may be put into a new family of potential multifunctional MRI/optical CAs.

Xiaoli Liu¹, A.B. Madhankumar¹, Patti A. Miller², Becky Webb¹, Kari A. Duck¹, James R. Connor¹, and Qing X. Yang^1,2
1Department of Neurosurgery, The Pennsylvania State University College of Medicine, Hershey, PA, United States, ²Department of Radiology, The Pennsylvania State University College of Medicine, Hershey, PA, United States

Previous work demonstrated that inteleukin-13 receptors alpha 2 (IL-13R2) are highly expressed in glioma cells, but not in the normal cells. Thus, the IL-13R2 receptor was used as a target for delivering MRI contrast agent specifically to gliomas. In this work, we demonstrated that our targeted liposomes captured infiltrating tumor that were totally absent in Magnevist-enhanced MRI.

Jesús Pacheco-Torres^1,2, Pilar Lopez-Larrubia¹, Elena Nieto³, Ramón Alajarín³, Julio Álvarez-Builla³, Paloma Ballesteros², and Sebastián Cerdán^1
1Instituto de Investigaciones Biomédicas - CSIC, Madrid, Madrid, Spain, ²Universidad Nacional de Educación a Distancia (UNED), Madrid, Madrid, Spain, ³Universidad de Alcalá, Alcalá de Henares, Madrid, Spain

Measurement of tumor oxygenation has gained importance in the last decades due to the known relationship between tumor hypoxia and tumor aggressiveness, poor outcome and resistance to therapies. Several techniques have been developed for this end (oxygen electrodes, EPR, PET…) but none of them has gained widespread acceptance. 2-Nitroimidazole derivatives (EF5, Pimonidzole, ¹⁸F-MISO...) have been extensively used as molecular markers of hypoxia in combination with different techniques as immunohistochemistry, PET or ¹⁹F-MRI. Here we evaluate, for the first time to our knowledge, the use of these hypoxia markers in combination with ¹H-MRSI to generate oxygenation maps in vivo.

Jang Woo Park¹, Hui-jin Song¹, Hee-Kyung Kim¹, Jeehye Seo¹, Seong-Uk Jin¹, Jong Su Baeck¹, Moon Han¹, Yongmin Chang^2,3, and Young-Hwan Lee*^4
1Medical & Biological Engineering, Kyungpook National University, Daegu, Daegu, Korea, ²Diagnostic Radiology, Kyungpook National University, Daegu, Daegu, Korea, ³Molecular Medicine, School of Medicine, Kyungpook National University, Daegu, Daegu, Korea, ⁴Radiology, Daegu Catholic University Medical Center, Daegu, Daegu, Korea

Magnetic resonance imaging (MRI) can help to diagnose disease progression in rheumatoid arthritis (RA) by measuring potential inflammatory activity from vascular permeability. To calculate permeability value, dynamic contrast enhanced (DCE) MRI and relating pharmacokinetic models which was defined by Tofts and Kermode was used. Vascular permeability reflects angiogenesis and vascular structural changes the blood vessel wall by Rheumatoid arthritis, so this study make vascular permeability map and compare permeability value for each RA progression and the efficacy of therapeutic intervention. This study demonstrates the successful application of vascular permeability for inflammatory disease such as RA, and permeability value form DEC-MRI can be quantitative index of RA diagnose.

Shreya Mukherjee¹, Galen S. Loving¹, and Peter Caravan^2
1Department of Radiology, A. A. Martinos Center for Biomedical Imaging, Massachusetts General Hospital, Charlestown, Massachusetts, United States, ²Department of Radiology, Massachusetts General Hospital, Charlestown, Massachusetts, United States

Redox reactions are ubiquitous in biochemical activities. However, the lack of suitable redox responsive probes has hindered the non-invasive observation of intracellular redox activities through molecular imaging. We hypothesized that a redox-activated MR probe based on Mn2+/Mn3+ couple would be stable with respect to metal dissociation in both oxidation states, sensitive to biological reductants, and sufficiently reactive to act as an in vivo sensor. Here we report the design and characterization of a potential redox probe. The feasibility of this probe to act as redox responsive MR agents was tested under physiologically relevant reducing conditions. We anticipate that the probe activation would be limited primarily to regions where the normal mechanisms that regulate extracellular redox have been severely impaired.

Jesús Pacheco-Torres¹, Paloma Ballesteros², Pilar Lopez-Larrubia¹, and Sebastián Cerdán^1
1Instituto de Investigaciones Biomédicas - CSIC, Madrid, Madrid, Spain, ²Universidad Nacional de Educación a Distancia (UNED), Madrid, Madrid, Spain

2-Nitroimidazole derivatives have been traditionally used as molecular markers of hypoxia due to their preferential reduction and subsequent trapping in vivo under hypoxic conditions. However, the reduction mechanism and its rate determining steps remained largely unexplored. We show that it is the intracellular redox state (NADP/NADPH, GSSG/GSH), rather than the oxygen tension by itself, what determines the reduction rate of these compounds, the reaction rate being limited mainly by the GSH concentration. This is a general mechanism occurring in all 2-Nitroimidazole derivatives investigated. Also, we report the appearance and the kinetics of new signals belonging to reaction intermediates.

Eveliina Lammentausta¹, Gamzegul M. Behrouz², Elli-Noora Salo³, Ville-Veikko Telkki², Susanna Ahola², Jessica M. Rosenholm⁴, Roberto Blanco Sequeiros^1,5, and Miika T. Nieminen^3,5
1Department of diagnostic Radiology, Oulu University Hospital, OYS, Oulu, Finland, ²Department of Physics, University of Oulu, Oulu, Oulu, Finland, ³Department of diagnostic Radiology, Oulu University Hospital, OYS, Finland, Finland, ⁴Center for Functional Materials, Laboratory of Physical Chemistry, Department of Natural Sciences, Åbo Akademi University, Turku, Turku, Finland, ⁵Department of Radiology, University of Oulu, Oulu, Oulu, Finland

Novel amorphous manganese oxide (MnOx) nanostructures were examined in various concentrations from 0.01 mM t0 1 mM at four different field strengths (3T, 4.7T, 7.1T and 9.4T) to determine its T1 relaxivity. MnOx displayed substantially higher relaxivities than typical clinically used gadolinium based contrast agents and thus is a very promising candidate for stem cell labeling and dynamic imaging studies.

Bashar Issa^1,2, Ihab M. Obaidat¹, Shahnaz M. Qadri², and Yousef Haik^2,3
1Physics, UAE University, Al-Ain, AD, United Arab Emirates, ²UNCG, Greensboro, NC, United States, ³Mechanical Eng., UAE University, Al-Ain, AD, United Arab Emirates

Magnetic nanoparticles have been previously used as both MRI contrast and hyperthermia agents. The overall aim is to develop a MRI-based thermal mapping technique for the heated tissue. The first step is the modeling of relaxation times at different temperatures. Echo Limited Regime is used to fit the T2 data using a modified particle size that takes into account the clustering of particles. It is believed that thermally enhanced surface layer spins plays pivotal role in the thermally reversible agglomeration of particles up to a temperature around Curie temperature 43^oC. Thermally induced agglomeration can be used as temperature sensor.

Ya-Han Yang¹, Fang-Hsin Lin¹, Yi-Tzu Lu¹, Ruey-An Doong¹, and Hsu-Hsia Peng^1
1Department of Biomedical Engineering and Environmental Sciences, National Tsing Hua University, Hsinchu, Taiwan

Au-Fe₃O₄ heterostructures have been used as bifunctional probes for optical imaging and MRI. The aim of this study is to investigate the morphological effect on MRI relaxivity for pure Fe₃O₄ nanoparticles (NPs), 5 nm Au dumbbell-like NPs (mAu DBNPs), 10 nm Au dumbbell-like NPs (LAu DBNPs), and 10 nm Au flower-like NPs (LAu FLNPs). The mAu DBNPs showed stronger r2 relaxivity than that of LAu DBNPs and LAu FLNPs exhibited higher relaxivity than that of LAu DBNPs, demonstrating the morphological effect on MR relaxivity. Therefore, to manufacture proper configurations of heterostructures are able to enhance T2 contrast in MRI applications.

Erik M. Shapiro¹ and Kevin S. Tang^2
1Department of Radiology, Michigan State University, East Lansing, Michigan, United States, ²Department of Biomedical Engineering, Yale University, New Haven, Connecticut, United States

The objective of this study was to identify a cryoprotection scheme to enhance redispersion of PLGA encapsulated iron oxide NPs in water and to study the effect this would have on magnetic cell labeling. We discovered that optimal percentage of dextrose for retaining initial particle characteristics was 1% with increasing percentages having little effect on average particle size and distribution and decreasing percentages having increasing degrees of aggregation. We found that for magnetic cell labeling, increasing dextrose cryoprotection decreased labeling efficiency, however all cryoprotectant percentages labeled cells robustly enough to enable single cell detection on MRI.

Gisela E. Hagberg¹, Aneta Keliris², Ilgar Mamedov³, Matteo Placidi³, Hellmut Merkle⁴, Nikos K. Logothetis³, and Klaus Scheffler^1,2
1Biomedical Magnetic Resonance, University Hospital Tuebingen, Tuebingen, Germany, ²High-field Magnetic Resonance, Max Planck Institute for Biological Cybernetics, Tuebingen, Germany, ³Physiology of Cognitive Processes, Max Planck Institute for Biological Cybernetics, Tuebingen, Germany, ⁴LFMI-NINDS, National Institutes of Health, Bethesda, MD, United States

¹⁹F-labelled compounds have unique benefits for biological applications but are hampered by low sensitivity. Lanthanide-complexes that shorten the ¹⁹F T₁ and T₂ relaxation times can boost the SNR in spoiled gradient echo sequences (FLASH). We investigated the MRI signal systematically for a wide range of T₁ and T₂ times for FLASH and balanced steady state free precession (tFISP). For long T₂ times the tFISP signal is always greater, and for short relaxation times the signal gain depends on the duration of encoding and spoiling. None of the available compounds had ‘ideal’ relaxation times that gives the highest possible signal. Our results can be used to design better ¹⁹F contrast agents tailored to a specific MRI sequence.

David P. Cormode¹, Willem J M Mulder², and Erik M. Shapiro^3
1Radiology, University of Pennsylvania, Philadelphia, PA, United States, ²Translational and Molecular Imaging Institute, Mount Sinai School of Medicine, New York, NY, United States, ³Radiology, Michigan State University, East Lansing, MI, United States

We herein report the development and use of a new type of particle as a contrast agent for MRI-related imaging: a magnetic megaparticle. We will report the synthesis and characterization of the megaparticle, as well as the results of long-term biocompatibility experiments and cell-labeling. The particle could be used for tracking very large numbers of cells using a hand held magnetic device, which we also integrated into an iPhone based imaging system. The particle facilitates optical imaging, as well. The megaparticle will be broadly applicable for the study of a variety of diseases.

Erik M. Shapiro¹ and Michael K. Nkansah^2
1Department of Radiology, Michigan State University, East Lansing, Michigan, United States, ²Department of Biomedical Engineering, Yale University, New Haven, Connecticut, United States

Magnetic particles are a key technology behind MRI-based cell tracking. We describe the first characterization of in vivo biodegradation rate of a specifically designed magnetic nanoparticle dedicated for magnetic cell labeling. PLGA-encapsulated magnetic nanoparticles, ~ 100 nm @ 84% iron weight were injected intravenously into mice. Inert MPIOs and Feridex, were also injected into additional mice. Serial MRI of the liver over 12 weeks revealed that Feridex was rapidly degraded within two weeks while inert MPIOs exhibited no biodegradation. 2:1 NPs exhibited an intermediate biodegradation rate, with 80% clearance of the iron at the end of 12 weeks.

Igor Jacobs¹, Siem Wouters¹, Henk Keizer², Henk Janssen², Eliana Gianolio³, Silvio Aime³, Gustav J. Strijkers¹, and Klaas Nicolay^1
1Biomedical NMR, Department of Biomedical Engineering, Eindhoven University of Technology, Eindhoven, Netherlands, ²SyMO-Chem BV, Eindhoven, Netherlands,³Dipartimento di Chimica & Centro di Imaging Molecolare, Università degli Studi di Torino, Torino, Italy

DCE-MRI is widely used for evaluation of tumor treatment. Macromolecular contrast agents may be preferred for determination of specific pharmacokinetic parameters and treatment-induced vascular changes. In this study (albumin-binding) dendritic contrast agents of various molecular weights were extensively characterized. Albumin-binding (confirmed in vitro) led to increased circulation half-lives, while a size-dependent range of circulation half-lives was observed for the non-albumin-binding dendrimers. Tumor/muscle uptake ratios of the dendrimers were higher than of Gd-DOTA. These findings imply that these agents likely possess a range of tumor wash-in and wash-out rates, making them suitable for investigation of the size-dependency of pharmacokinetic parameters.

Min-Kyoung Kang¹, Hee-Kyung Kim¹, Ki-Hye Jung², Ji-Ae Park³, Seung-Tae Woo⁴, Joo-Hyun Kim⁴, Eun-Young Jeon⁵, Tae-Jeong Kim², and Yongmin Chang^1,6
1Medical & Biological Engineering, Kyungpook National University, Daegu, Korea, ²Applied Chemistry, Kyungpook National University, Daegu, Korea, ³Molecular Imaging Research Center, Korea Institute of Radiological & Medical Science, Seoul, Korea, ⁴Bayer Healthcare, Medical care, Seoul, Korea, ⁵The Advanced Medical Technology Cluster for Diagnosis & Prediction, Kyungpook National University, Daegu, Korea, ⁶Diagnostic Radiology and Molecular Medicine, Kyungpook National University, Daegu, Korea

Gold/gadolinium core-shell nanoparticles of the formula Au@SiO₂@Gd@PEG were synthesized for use as a CT/MR bimodal contrast agent. The preparation initially requires the formation of Au@SiO₂ through self-condensation of TEOS on the surface of AuNPs. Au@SiO₂ thus formed was dispersed in aqueous alcohol to react with Gd(NO₃)₃ in the presence of urea, leading to the formation of Au@SiO₂@Gd core-shell nanoparticles. In order to increase solubility as well as biocompatibility further coated with PEG. These systems reveal both high CT attenuation and MR relaxivities (R₁ = 13.01 mM^-1sec^-1) so may be put into entry a new class of CT/MR bimodal imaging probes.

Michael Peller¹, Martin Hossann², Zulfiya Syunyaeva², Rolf D. Issels², Maximilian F. Reiser¹, and Lars H. Lindner^2
1Institute for Clinical Radiology, University Hospital Munich, Ludwig-Maximilians University, München, Germany, ²Department of Internal Medicine III, University Hospital Munich, Ludwig-Maximilians University, München, Germany

Thermosensitive liposomes (TSL) with encapsulated contrast agents (CA) have been proposed for MRI-assisted thermotherapy in tumors. For such purpose an effective temperature induced r1-relaxivity change and stability in the presence of serum components is needed. Here, temperature induced r1 change of 6 approved Gd-based CAs comprising diverse chemical structures and charges encapsulated in phosphatidyldiglycerol (DPPG2)-TSL were characterized. The shelf life of TSL was also investigated. CAs with nonionic chemical structure were more suitable than those with ionic structure. Of these Gd-DTPA-BMA showed effective r1-change and the highest shelf life

Marina Radoul¹, Fortune Kohen², Hagit Dafni³, Moriel Vandsburger², Sharon G. G. Wolf⁴, and Michal Neeman^2
1Radiology, UCSF, San Francisco, CA, United States, ²Biological Regulation, Weizmann Institute of Science, Rehovot, Israel, ³Veterinary Resources, Weizmann Institute of Science, Rehovot, Israel, ⁴Chemical Research Support, Weizmann Institute of Science, Rehovot, Israel

One of the most common ECM components is hyaluronan (HA). Hyaluronidase (HYAL) degrades high molecular weight HA into low molecular weight fragments thus altering the ECM to become permissive to angiogenesis. Our goal is to detect HYAL non-invasively by MRI in order to predict the tilt of angiogenic balance within the tumor microenvironment. Here we demonstrate how r1 and r2 relaxivities altered in response to degradation of a novel contrast agent HA-GdDTPA nanoparticles by hyaluronidase secreted by ES-2 ovarian carcinoma cells.

In Ok Ko¹, Ji-Ae Park¹, Jung Young Kim¹, Wonho Lee¹, Sang Moo Lim², and Kyeong Min Kim^1
1Molecular Imaging Research Center, Korea Institute of Radiological & Medical Science, Seoul, Korea, ²Department of Nuclear Medicine, Korea Institute of Radiological & Medical Science, Seoul, Korea

We designed two integrin 3-specific MRI contrast agents, which is an inserted aminocyclopentane (ACP) or amicocyclohexane (ACH)-carboxylic acid into c(RGDK) to improve the binding affinity, and evaluated their tumor targeting efficacy in U87MG tumor bearing mice. Substitution of ACP or ACH in the lead structure c(RGD-ACP-K)-DOTA and c(RGD-ACH-K)-DOTA exhibited much higher binding affinity for 3 integrin than c(RGDyK). The in vivo MR images of mice obtained with c(RGD-ACP-K)-DOTA-Gd and c(RGD-ACH-K)-DOTA-Gd showed a significant enhancement in the tumor.

Miloslav Polasek¹ and Peter Caravan^2
1Radiology, A. A. Martinos Center for Biomedical Imaging, Massachusetts General Hospital/Harvard Medical School, Charlestown, Massachusetts, United States, ²Radiology, Massachusetts General Hospital, Charlestown, Massachusetts, United States

We explored a novel design of DOTA-like compounds where removal of an acetate arm on N1 is counterbalanced by a donor arm on N7. Surprisingly, presence of a non-coordinating moiety on N1 lowered kinetic stability of the Gd chelates. Choice of the donor arm on N7 influenced both kinetic stability and water exchange rate, the latter could be tuned over 2 orders of magnitude.

Eszter Boros¹, Miloslav Polasek¹, Zhaoda Zhang¹, and Peter Caravan^2
1Department of Radiology, Massachusetts General Hospital, Harvard Medical School, The Athinoula A. Martinos Center for Biomedical Imaging, Charlestown, MA, United States,²Department of Radiology, Massachusetts General Hospital, Harvard Medical School, Massachusetts General Hospital, Charlestown, MA, United States

We investigated applications of the alanine analogue of Gd(DOTA), Gd(DOTAla). Fmoc protected DOTAla suitable for solid phase peptide synthesis was synthesized and integrated into polypeptide structures containing 1-3 Gd(DOTAla) complexes (GdL1, GdL2, GdL3).GdL3 is superior to commercial contrast agents gadoteridol and gadofosveset /HSA (human serum albumin) at high fields. The modularity of design, the ease of solid phase synthesis, high kinetic inertness (t_1/2 = 61±4h) for Gd3, and optimal water exchange rate renders the Gd(DOTAla) scaffold a suitable platform for the development of high field T1 agents based on Gd.

Samuel Maritim¹, Daniel Coman^2,3, Yuegao Huang², Majura Hoque², and Fahmeed Hyder^2,4
1Diagnostic radiology, Yale University, New Haven, CT, United States, ²Diagnostic Radiology, Yale University, New Haven, CT, United States, ³Quantitative Neuroscience with Magnetic Resonance (QNMR), Yale University, New Haven, CT, United States, ⁴Biomedical Engineering, Yale University, New Haven, CT, United States

Conventional T1 and T2 contrast agents offer great tissue contrast. To go beyond shades of gray in typical molecular/cellular MRI, we developed a new ultra-high speed 3D chemical shift imaging (CSI) method called Biosensor Imaging of Redundant Deviation in Shifts (BIRDS), which requires that we detect protons emanating from the agent (e.g., TmDOTP5-), itself instead of the agent’s effect on water proton relaxation times. Here we show how resilient BIRDS can be for pH and temperature mapping, specifically when TmDOTP5- is in presence of high concentrations of typical T1 and T2 agents and even when TmDOTP5- inside in liposomes.

Gary Zabow^1,2, Stephen Dodd¹, and Alan P. Koretsky^1
1NINDS, National Institutes of Health, Bethesda, Maryland, United States, ²Electromagnetics Division, National Institute of Standards & Technology, Boulder, Colorado, United States

A new class of microengineered multispectral contrast agent is introduced based on ellipsoidal microshell structures. In principle, the new ellipsoidal geometries allow for higher spectral resolution than previously demonstrated microfabricated multispectral agents, improving detection sensitivity and agent multiplexing potential. This talk discusses the theory behind these new agents, considers ways to fabricate the required microstructure geometries, and presents initial NMR data from the first sets of such agents.

Nikita Oskolkov¹, Kannie W.Y. Chan², Amnon Bar-Shir², Peter C.M. van Zijl^1,3, Jeff W.M. Bulte^2,4, Assaf A. Gilad^2,4, and Michael T. McMahon^1,3
1Russell H. Morgan Department of Radiology and Radiological Science, The Johns Hopkins University School of Medicine, Baltimore, MD, United States, ²Russell H. Morgan Department of Radiology and Radiological Science, Johns Hopkins University, Baltimore, MD, United States, ³F.M. Kirby Research Center for Functional Brain Imaging, Kennedy Krieger Institute, Baltimore, MD, United States, ⁴Cellular Imaging Section and Vascular Biology Program, Institute for Cell Engineering, Baltimore, MD, United States

We have synthesized human protamine-1 (hPRM1), a compound biologically relevant for packing cellular DNA, which is rich in arginine and generates high CEST contrast associated with the exchangeable protons in the guanidyl group. We have also determined how the contrast varies upon binding of hPRM1 to nucleotides, the natural role of this protein, which is relevant to how it might perform in vivo as contrast material. This synthetic approach has resulted in a high yield and retention of the peptide’s ability to bind DNA, potentially enabling use of hPRM-1 as an alternative to recombinant or naturally occurring protamine.

Nikita Oskolkov¹, Xiaolei Song¹, Kannie W.Y. Chan², Michael Giano³, Jeff W.M. Bulte^2,4, Peter C.M. van Zijl^1,4, Joel Schneider³, and Michael T. McMahon^1,4
1Russell H. Morgan Department of Radiology and Radiological Science, The Johns Hopkins University School of Medicine, Baltimore, MD, United States, ²Russell H. Morgan Department of Radiology and Radiological Science, Johns Hopkins University, Baltimore, MD, United States, ³National Cancer Institute, National Cancer Institute, Frederick, MD, United States, ⁴F.M. Kirby Research Center for Functional Brain Imaging, Kennedy Krieger Institute, Baltimore, MD, United States

Chemical Exchange Saturation Transfer (CEST) is a novel MRI contrast mechanism for detection of water exchangeable protons. We have designed peptides which form hydrogels suitable for use as adjuvants in cell therapy. These peptides are designed to form strong hydrogen bonding networks in order to slow down imino proton chemical exchange. These peptide-based hydrogels possess a wide range of unique properties that make them potentially applicable for different biological studies.

Yann Jamin¹, Thomas R. Eykyn^1,2, Evon Poon³, Caroline J. Springer³, and Simon P. Robinson^1
1Division of Radiotherapy and Imaging, The Institute of Cancer Research, Sutton, Surrey, United Kingdom, ²Division of Imaging Sciences and Biomedical Engineering, Kings College London, London, United Kingdom, ³Division of Cancer Therapeutics, The Institute of Cancer Research, Sutton, Surrey, United Kingdom

The exchange rates of amine protons with bulk water are much faster than those of amide protons. We show here that this property can be exploited using chemical exchange saturation transfer magnetic resonance (CEST-MR) to monitor the activity of the bacterial protein carboxypeptidase G2 (CPG2), an enzyme utilized in cancer gene therapy. We demonstrate that CPG2 activity leads to the “activation” of a concentration-dependent CEST signal at a resonance offset of +3 ppm from the water frequency (GluCEST), induced by the CPG2-mediated release of glutamate (amine) from CPG2 substrates (amides).

Dina V. Hingorani¹, Edward T. Randtke², and Marty Pagel^3
1Chemistry and Biochemistry, University of Arizona, Tucson, Arizona, United States, ²Chemistry and Biochemistry, University of Arizona, Tucson, AZ, United States,³Biomedical Engineering, University of Arizona, Tucson, AZ, United States

We have characterized the CEST effect of a TGase-responsive PARACEST MRI contrast agent that is conjugated to a protein and hydrophilic peptides that include arginine. The appearance of CEST at -11 ppm differs from the appearance of CEST at +4, +11, and +22 ppm after conjugation of the agent a hydrophobic ZQR peptide, which demonstrates outstanding specificity of CEST for different molecular conformations, which may be exploited to design responsive CEST agents. CEST at -11 ppm before TGase-catalyzed conjugation indicated the formation of a non-covalent supramolecular adduct, which may be further exploited to design responsive CEST agents.

Jonatan A. Snir¹, Mojmír Suchý^2,3, Alex X. Li⁴, Robert H.E Hudson⁵, Stephen H. Pasternak^6,7, and Robert Bartha^8
1Department of Medical Biophysics, Robarts Research Institute, London, Ontario, Canada, ²Department of Chemistry, Western University, London, Ontario, Canada, ³Imaging Research Laboratories, Robarts Research Institute, London, On, Canada, ⁴Imaging Research Laboratories, Robarts Research Institute, London, Ontario, Canada, ⁵Department of Chemistry, Western University, London, On, Canada, ⁶Department of Clinical Neurological Sciences, Robarts Research Institute, London, Ontario, Canada, ⁷Department of Physiology and Pharmacology, Schulich School of Medicine, Western University, London, Ontario, Canada, ⁸Imaging Research Laboratories, Robarts Research Institute, London, Onta, Canada

Programmed cell death (apoptosis) is an important feature for studies of cancer therapy as well as ischemia and neurological pathologies. Recently, we have synthesized a novel MRI and fluorescent contrast agent containing a cleavage site specific to Caspase 3. Prostate cancer cells were either irradiated with ultraviolet radiation or maintained without insult. 24 hour incubation with our contrast agent permitted differentiation of irradiated versus control cells with both confocal microscopy and PARACEST MRI. This work provides a proof-of-principle of PARACEST imaging for the detection of apoptotic cell population following ionizing radiation.

Edward T. Randtke¹, Liu Qi Chen¹, Rene Corrales¹, and Marty Pagel^2
1Chemistry and Biochemistry, University of Arizona, Tucson, AZ, United States, ²Biomedical Engineering, University of Arizona, Tucson, AZ, United States

Most CEST MRI methods fail to accurately determine fast exchange rates (> 20% of the chemical shift difference). We have investigated the accuracies of the Bloch fitting, QUEST, QUESP, omega-plot, and concentration-dependent methods using theoretical simulations and experimental measurements. We have also developed new analysis methods and compared these methods with existing analysis methods. Our results show that the Bloch fitting method is most accurate for determining slow and fast exchange rates, the omega-plot method is acceptable for determining slow exchange rates, and the Hanes-Woolf linear QUESP method is acceptable for determining fast exchange rates.

Todd C. Soesbe^1,2, S. James Ratnaker¹, Zoltan Kovacs¹, and A. Dean Sherry^1,3
1Advanced Imaging Research Center, UT Southwestern Medical Center, Dallas, Texas, United States, ²Department of Radiology, UT Southwestern Medical Center, Dallas, Texas, United States, ³Department of Chemistry, The University of Texas at Dallas, Richardson, Texas, United States

Magnetic resonance imaging (MRI) offers superior anatomic resolution and soft tissue contrast compared to x-ray computed tomography, making it an excellent tool for cancer prevention studies. It was recently shown that lanthanide-based Ln3+DOTA chelates (Ln3+ ≠ La3+, Gd3+, Lu3+) create enhanced negative contrast (i.e., darkening) in MRI through the chemical exchange of water molecules. The level of this “T2-exchange” contrast, which adds to the inherent paramagnetic T2 contrast of the Ln3+ ion, reaches a maximum at a specific water molecule exchange rate. It was also recently demonstrated that T2-exchange contrast could be increased by several orders of magnitude through simple linear polymerization of the Ln3+DOTA chelate. We hypothesize that by using these methods a highly sensitive molecule-sized T2 contrast agent can be created. The transverse relaxivity (r2) would be an order of magnitude greater than any currently existing contrast agent (e.g., super paramagnetic iron oxide nanoparticles), while retaining the advantages of using small molecules rather than nanoparticles for improved biological targeting, uptake, and clearing.

Iman Daryaei¹ and Marty Pagel^2
1Chemistry and Biochemistry, University of Arizona, Tucson, AZ, United States, ²Biomedical Engineering, University of Arizona, Tucson, AZ, United States

We have developed a MRI contrast agent that changes T2 relaxivity after treatment with nitric oxide. This change in T2 relaxation is attributed to a change in the chemical exchange rate of a proton on the agent, which changes T2 exchange relaxation. The T1 relaxivity does not change after treatment with nitric oxide, so that a ratio of T2- and T1-weighted images can detect nitric oxide in a concentration-independent manner. These results demonstrate that a new class of responsive MRI contrast agents can be developed by changing the chemical exchange rate of an agent and obtaining T2-weighted and T1-weighted images.

Nirbhay N. Yadav^1,2, Jiadi Xu^1,2, Amnon Bar-Shir^3,4, Qin Qin^1,2, and Peter C.M. van Zijl^1,2
1Russell H. Morgan Department of Radiology and Radiological Science, Johns Hopkins University School of Medicine, Baltimore, MD, United States, ²FM Kirby Research Center, Kennedy Krieger Institute, Baltimore, MD, United States, ³Russell H. Morgan Department of Radiology and Radiological Science, Johns Hopkins University, Baltimore, MD, United States, ⁴The Institute for Cell Engineering, Johns Hopkins University School of Medicine, Baltimore, MD, United States

We show that natural D-glucose can be used as an exogenous T2 relaxation agent, particularly at field strengths available for human MRI. Transverse relaxation and diffusion measurements were carried out on D-glucose phantoms at different concentrations, pH, and magnetic field strengths (3 T and 7 T). The results show strong dependence of water transverse relaxivity on glucose concentration, sample pH, and field strength. We show the increased relaxivity is due to the 5 exchangeable hydroxyl protons in glucose and that the greatest relaxivity is observed in the physiological pH range.

Jason Bini^1,2, Philip Robson¹, Claudia Calcagno¹, Antoine Millon^1,3, Mark Lobatto^1,4, and Zahi A. Fayad^1,5
1Translational and Molecular Imaging Institute, Mount Sinai School of Medicine, New York, New York, United States, ²Department of Biomedical Engineering, City College of New York, New York, New York, United States, ³Department of Vascular Surgery, University Hospital of Lyon, Lyon, France, ⁴Department of Vascular Medicine, Academic Medical Center, Amsterdam, Netherlands, ⁵Department of Radiology, Mount Sinai School of Medicine, New York, New York, United States

In this study, we propose a radial k-space MR acquisition sequence designed to redistribute coherent breathing artifacts that result from Cartesian k-space trajectories into incoherent pseudo-noise spread across the image domain. It is proposed that the use of a radial sequence with automatic segmentation, replacing subjective user interaction in image processing, will facilitate more robust segmentation of MR images to generate attenuation maps. The objective of the current study was to then qualitatively and quantitatively evaluate the respective MR-based attenuation maps generated, in addition to their resultant quantitative PET images, to evaluate alternative preclinical MR/PET protocols.

Renata Madru¹, Thuy Tran², Adnan Bibic³, Sarah Fredriksson⁴, Freddy Ståhlberg⁵, Linda Knutsson⁵, and Sven-Erik Strand^5
1Medical Radiation Physics, Lunds University, Lund, Sweden, ²Lund University BioImaging Centrum, Lund University, Lund, Skane, Sweden, ³Lund University BioImaging Centrum, Lund University, Lund, Sweden, ⁴Genovis AB, Lund, Sweden, ⁵Medical Radiation Physics, Lund University, Lund, Sweden

The purpose of this study was to develop a new PET/MRI probe to improve the current sentinel lymph node technique used for diagnostic and staging of breast cancer and malignant melanoma. Here we demonstrate the feasibility of labeling the synthetized SPIONs with the generator produced Ga-68 and accumulation of the 68Ga-SPIONs in lymph nodes after subcutanious injection in rats, verified by PET and MRI. The results are encouraging for future clinical applications adding important pre-operative information which may lead to new therapeutic strategies.