Laboratory of Molecular Imaging

Singapore, Singapore

Laboratory of Molecular Imaging

Singapore, Singapore
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Leuze C.,Japan National Institute of Radiological Sciences | Leuze C.,Max Planck Institute for Human Cognitive and Brain Sciences | Leuze C.,Chiba University | Kimura Y.,Japan National Institute of Radiological Sciences | And 6 more authors.
NeuroImage | Year: 2012

The ability of manganese ions (Mn 2+) to enter cells through calcium ion (Ca 2+) channels has been used for depolarization dependent brain functional imaging with manganese-enhanced MRI (MEMRI). The purpose of this study was to quantify changes to Mn 2+ uptake in rat brain using a dynamic manganese-enhanced MRI (dMEMRI) scanning protocol with the Patlak and Logan graphical analysis methods. The graphical analysis was based on a three-compartment model describing the tissue and plasma concentration of Mn. Mn 2+ uptake was characterized by the total distribution volume of manganese (Mn) inside tissue (V T) and the unidirectional influx constant of Mn 2+ from plasma to tissue (K i). The measurements were performed on the anterior (APit) and posterior (PPit) parts of the pituitary gland, a region with an incomplete blood brain barrier. Modulation of Ca 2+ channel activity was performed by administration of the stimulant glutamate and the inhibitor verapamil. It was found that the APit and PPit showed different Mn 2+ uptake characteristics. While the influx of Mn 2+ into the PPit was reversible, Mn 2+ was found to be irreversibly trapped in the APit during the course of the experiment. In the PPit, an increase of Mn 2+ uptake led to an increase in V T (from 2.8±0.3ml/cm 3 to 4.6±1.2ml/cm 3) while a decrease of Mn 2+ uptake corresponded to a decrease in V T (from 2.8±0.3ml/cm 3 to 1.4±0.3ml/cm 3). In the APit, an increase of Mn 2+ uptake led to an increase in K i (from 0.034±0.009min -1 to 0.049±0.012min -1) while a decrease of Mn 2+ uptake corresponded to a decrease in K i (from 0.034±0.009min -1 to 0.019±0.003min -1). This work demonstrates that graphical analysis applied to dMEMRI data can quantitatively measure changes to Mn 2+ uptake following modulation of neural activity. © 2011 Elsevier Inc.

Li K.,Institute of Materials Research and Engineering of Singapore | Ding D.,National University of Singapore | Prashant C.,Laboratory of Molecular Imaging | Qin W.,Hong Kong University of Science and Technology | And 6 more authors.
Advanced Healthcare Materials | Year: 2013

Understanding the localization and engraftment of tumor cells at postintravasation stage of metastasis is of high importance in cancer diagnosis and treatment. Advanced fluorescent probes and facile methodologies for cell tracing play a key role in metastasis studies. In this work, we design and synthesize a dual-modality imaging dots with both optical and magnetic contrast through integration of a magnetic resonance imaging reagent, gadolinium(III), into a novel long-term cell tracing probe with aggregation-induced emission (AIE) in far-red/near-infrared region. The obtained fluorescent-magnetic AIE dots have both high fluorescence quantum yield (25%) and T1 relaxivity (7.91 mM-1 s-1) in aqueous suspension. After further conjugation with a cell membrane penetrating peptide, the dual-modality dots can be efficiently internalized into living cells. The gadolinium(III) allows accurate quantification of biodistribution of cancer cells via intraveneous injection, while the high fluorescence provides engraftment information of cells at single cellular level. The dual-modality AIE dots show obvious synergistic advantages over either single imaging modality and hold great promises in advanced biomedical studies. A dual-modality imaging probe is developed through integration of gadolinium(III) into fluorescent dots with aggregation-induced emission (AIE). The obtained fluorescent-magnetic AIE dots allow accurate quantification of biodistribution and engraftment in organ tissues with single cell resolution, which provide vital information of cancer cell behavior at postintravasation stage of metastasis. © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Nagarajan V.,Laboratory of Molecular Imaging | Nagarajan V.,Singapore Institute for Clinical science | Gopalan V.,Laboratory of Molecular Imaging | Kaneko M.,Laboratory of Molecular Imaging | And 7 more authors.
American Journal of Physiology - Heart and Circulatory Physiology | Year: 2013

Obesity is a major risk factor in the development of cardiovascular disease, type 2 diabetes, and its pathophysiological precondition insulin resistance. Very little is known about the metabolic changes that occur in the myocardium and consequent changes in cardiac function that are associated with high-fat accumulation. Therefore, cardiac function and metabolism were evaluated in control rats and those fed a high-fat diet, using magnetic resonance imaging, magnetic resonance spectroscopy, mRNA analysis, histology, and plasma biochemistry. Analysis of blood plasma from rats fed the high-fat diet showed that they were insulin resistant (P < 0.001). Our high-fat diet model had higher heart weight (P = 0.005) and also increasing trend in septal wall thickness (P = 0.07) compared with control diet rats. Our results from biochemistry, magnetic resonance imaging, and mRNA analysis confirmed that rats on the high-fat diet had moderate diabetes along with mild cardiac hypertrophy. The magnetic resonance spectroscopy results showed the extramyocellular lipid signal only in the spectra from high-fat diet rats, which was absent in the control diet rats. The intramyocellular lipids in high-fat diet rats was higher (8.7%) compared with rats on the control diet (6.1%). This was confirmed by electron microscope and light microscopy studies. Our results indicate that lipid accumulation in the myocardium might be an early indication of the cardiovascular pathophysiology associated with type 2 diabetes. © 2013 the American Physiological Society.

PubMed | Systems Pharmacology, University of Minnesota, Laboratory of Molecular Imaging and Thomas Jefferson University
Type: Journal Article | Journal: The Journal of biological chemistry | Year: 2016

A network model for the determination of tumor metabolic fluxes from (13)C NMR kinetic isotopomer data has been developed and validated with perfused human DB-1 melanoma cells carrying the BRAF V600E mutation, which promotes oxidative metabolism. The model generated in the bonded cumomer formalism describes key pathways of tumor intermediary metabolism and yields dynamic curves for positional isotopic enrichment and spin-spin multiplets. Cells attached to microcarrier beads were perfused with 26 mm [1,6-(13)C2]glucose under normoxic conditions at 37 C and monitored by (13)C NMR spectroscopy. Excellent agreement between model-predicted and experimentally measured values of the rates of oxygen and glucose consumption, lactate production, and glutamate pool size validated the model. ATP production by glycolytic and oxidative metabolism were compared under hyperglycemic normoxic conditions; 51% of the energy came from oxidative phosphorylation and 49% came from glycolysis. Even though the rate of glutamine uptake was 50% of the tricarboxylic acid cycle flux, the rate of ATP production from glutamine was essentially zero (no glutaminolysis). De novo fatty acid production was 6% of the tricarboxylic acid cycle flux. The oxidative pentose phosphate pathway flux was 3.6% of glycolysis, and three non-oxidative pentose phosphate pathway exchange fluxes were calculated. Mass spectrometry was then used to compare fluxes through various pathways under hyperglycemic (26 mm) and euglycemic (5 mm) conditions. Under euglycemic conditions glutamine uptake doubled, but ATP production from glutamine did not significantly change. A new parameter measuring the Warburg effect (the ratio of lactate production flux to pyruvate influx through the mitochondrial pyruvate carrier) was calculated to be 21, close to upper limit of oxidative metabolism.

Hendrikse J.,University Utrecht | Petersen E.T.,National Neuroscience Institute | Petersen E.T.,Arhus University Hospital | Chng S.M.,National Neuroscience Institute | And 3 more authors.
Radiology | Year: 2010

Purpose: To investigate the effect of variations in anatomic features of the circle of Willis on the perfusion territory to deep structures, including the nucleus caudatus, the nucleus lentiformis, and the thalamus. Materials and Methods: The ethics committee of the study institution approved the study protocol. A total of 159 patients with first-time clinical symptoms of cerebral ischemia were recruited. Contributions to the perfusion territory were visualized with territorial arterial spin-labeling magnetic resonance (MR) imaging. The anatomic features of the circle of Willis were evaluated with time-of-flight MR angiography. Perfusion territory contributions were compared among circle of Willis variants by using the Cochran-Mantel-Haenszel test. Results: The perfusion territory contributions to the deep-brain structures could be evaluated in 119 of 159 patients (75%). With a fetal-type circle of Willis (41 of 238 hemispheres; 17%), there was a contribution from the ipsilateral internal carotid artery to the thalamus in all 41 hemispheres (100%), compared with 96 of the 197 hemispheres (49%) without a fetal-type circle of Willis. In the 19 patients with a hypoplastic A1 segment, there was more often a contribution of the contralateral internal carotid artery to the perfusion of the nucleus caudatus (10 of 19; 53%) and the nucleus lentiformis (5 of 19; 26%). Conclusion: The perfusion territory contributions to deep-brain structures vary widely. These differences can be partly explained by variations in the anatomic features of the circle of Willis. © RSNA, 2010.

News Article | August 25, 2016

Multidrug resistance (MDR) is the mechanism by which many cancers develop resistance to chemotherapy drugs, resulting in minimal cell death and the expansion of drug-resistant tumors. To address the problem of resistance, researchers have developed nanoparticles that simultaneously deliver chemotherapy drugs to tumors and inhibit the MDR proteins that pump the therapeutic drugs out of the cell. The process is known as chemosensitization, as blocking this resistance renders the tumor highly sensitive to the cancer-killing chemotherapy. MDR is a major factor in the failure of many chemotherapy drugs. The problem affects the treatment of a wide range of blood cancers and solid tumors, including breast, ovarian, lung, and colon cancers. Researchers at the National Institute of Biomedical Imaging and Bioengineering (NIBIB), a part of the National Institutes of Health (NIH), are engineering multi-component nanoparticles that significantly enhance the killing of cancer cells. The results of their experiments are reported in recent articles in Scientific Reports and Applied Materials & Interfaces. The work is led by senior author Xiaoyuan (Shawn) Chen, Ph.D., Senior Investigator, Laboratory of Molecular Imaging and Nanomedicine, NIBIB. His collaborators include scientists and engineers in China at Southeast University, Shenzhen University, Guangxi Medical University, and Shanghai Jiao Tong University, in addition to chemical engineers at the University of Leeds, United Kingdom. Says Chen about his substantial network of collaborators, “success in this medically important endeavor has required a team with a wide range of expertise to engineer nanoparticles that survive the journey to the tumor site, enter the tumor, and successfully perform the multiple functions for chemosensitization.” Targeting Multidrug-resistant Breast Cancer The two publications report on the engineering of two separate nanoparticles that test different strategies for achieving chemosensitization of cancer cells. The first targets MDR breast cancer. The engineered round nanoparticle is made of several layers. The center of the particle is loaded with the anti-cancer drug doxorubicin. The drug is surrounded by a water-repelling (hydrophobic) capsule to protect it from the watery environment when the particle is injected into the circulatory system of an experimental animal or individual with cancer. The particle has several outer layers with different properties. One of the outermost components, a molecule called PEG, is hydrophilic (mixes with water) and helps the particle move through the bloodstream until it encounters the breast tumor cells. Another component on the surface of the particle, biotin, functions to bind specifically to the cancer cells and helps the drug-carrying nanoparticle to enter the cell. Once inside the breast cancer cell, a fourth component called curcumin, which is intertwined with the doxorubicin center, is released along with the doxorubicin. The curcumin is the component that blocks the cell machinery that would pump the doxorubicin out of the cell. Without the ability to pump out the medicine, the cell is exposed to very high concentration of doxorubicin, which kills the breast cancer cells. Experiments in mice demonstrated that the multi-component nanoparticles were effective at targeting breast tumor cells—accumulating at much higher concentrations in the cancer cells than in the other mouse tissues. Histology showed that the treated mice had a great reduction in cancer cell density in the tumor tissue compared with mice given saline or doxorubicin alone (not integrated into a nanoparticle). Complete analysis of the treated mice confirmed that the nanoparticle efficiently accumulated at the tumor site and achieved optimal tumor killing in the mouse breast cancer model. Changing Nanoparticle Components Tests Alternate Anti-cancer Strategies In the work published in Applied Materials & Interfaces, Chen and his colleagues describe the engineering of another nanoparticle that uses a different approach to the problem of MDR. This second nanoparticle is similar to the first in that it contains the centrally encapsulated doxorubicin surrounded by an outer hydrophilic surface layer that allows efficient transport through the bloodstream. However, this particle uses the gas nitric oxide (NO), which is known to block the system that pumps doxorubicin out of the cell. In addition, the NO is released from a compound called BNN6, which is activated by ultraviolet (UV) light. Thus, this nanoparticle is designed to be administered in the bloodstream and then activated with UV light when it reaches its cancer target. In experiments in cell culture, when hit with UV light the nanoparticles burst -- releasing the cell-killing doxorubicin and causing BNN6 to release the NO gas. The combination successfully inhibited the MDR machinery, resulting in chemosensitization and efficient cancer-cell killing. Based on the successful testing of this nanoparticle in cultured cells, the group expects it to perform well when tested in experiments in mice. Smart Nanomedicines vs Multidrug Resistance Chemotherapy is the most common treatment for cancer. Unfortunately, these drugs often cause minimal damage to tumors, because of MDR, and this can result in the expansion of populations of MDR tumors. Also, most chemotherapy drugs have very narrow therapeutic windows, frequently showing toxicity to healthy tissues and organs even at doses lower than required for a therapeutic effect. Therefore, there is an urgent need to devise ways to achieve high doses in tumor cells while eliminating harm to healthy tissue. Chen concludes, “The mechanism of MDR is interesting scientifically, but also incredibly important medically. That is why we are using our bioengineering skills to develop strategies to optimize the effect of these drugs on the cancer while reducing the toxicity to the surrounding tissues, which is both a major impediment to successful treatment as well as extremely taxing for cancer patients.” The work was funded by support from the Intramural Research Program, NIBIB. Funding from China was provided by The National Key Program for Developing Basic Research, the National Science Foundation, the Shenzhen Basic Research Program, the China Scholarship Council, and the Instrumental Analysis Center of Shanghai Jiao Ton University. Additional funds were provided by the European Union.

News Article | December 12, 2016

Biocompatible nanocapsules, loaded with an amino acid and equipped with an enzyme now combine two anti-tumor strategies into a synergistic treatment concept. Researchers hope this increases effectiveness and decreases side effects. In the journal Angewandte Chemie, the scientists explain the concept: tumor cells are deprived of their nutrient glucose as this is converted to toxic nitrogen monoxide (NO) and hydrogen peroxide (H2O2). NO is a toxic gas that causes smog. However, in low concentrations in the body it is an important messenger molecule that regulates such things as circulation and libido. It is also an important physiological defense weapon against fungi and bacteria. In higher concentrations, NO is capable of killing tumor cells and increasing the effectiveness of photodynamic and radiological treatments. For clinical use, NO needs to be released in the target area from a biocompatible precursor. The natural amino acid L-arginine (L-Arg) may be useful in such a system, because the native enzyme inducible NO synthase (iNOS) makes NO from L-Arg. NO is also formed when L-Arg is oxidized by H2O2. This is interesting because the microenvironment around tumors is rich in H2O2. This approach to NO gas therapy is being pursued by researchers at Shenzhen University (China), the National Institutes of Health (Bethesda, USA), and the University of Maryland (College Park, USA). Their special twist is to combine this gas therapy with a method for starving cancer cells in a synergistic treatment. Instead of starving a tumor by blocking the blood vessels that feed it, the researchers intend to remove the glucose that the tumor needs for nutrition by consuming it in a metabolic reaction: the enzyme glucose oxidase (GOx) converts the glucose into gluconic acid and H2O2. The increased H2O2 concentration is a useful side effect, because H2O2 is both cytotoxic and accelerates the release of NO from L-Arg. Another useful side effect is that H2O2 and NO react to form highly toxic peroxynitrites that damage the tumor cells. The research team led by Peng Huang, Tianfu Wang, and Xiaoyuan Chen has now reached an important milestone in the development of this concept. They have developed biocompatible, biodegradable, porous nanocapsules made of organosilicates that transport GOx and L-Arg into tumor cells simultaneously. GOx is bound to the surface; L-Arg is stored inside the capsule. While the GOx is active immediately after injection of the nanocapsules into the tumor, L-Arg is released little by little, first through the capsule pores, then as the capsule disintegrates. Their large cavity also allows the capsules to serve as an ultrasound contrast material for better localization of the tumor. Experiments with both cell cultures and mice have demonstrated the significant synergistic effect of this combination therapy, which successfully inhibits cell growth, initiates cell death, and shrinks the tumors in mice. Dr. Xiaoyuan (Shawn) Chen is a senior investigator and chief of the Laboratory of Molecular Imaging and Nanomedicine (LOMIN), National Institute of Biomedical Imaging and Bioengineering (NIBIB), National Institutes of Health (NIH). He received the ACS Bioconjugate Chemistry Lecturer Award (2016), NIH Director's Award (2014) and NIBIB Mentor Award (2012).

Gandesiri M.,Friedrich - Alexander - University, Erlangen - Nuremberg | Chakilam S.,Friedrich - Alexander - University, Erlangen - Nuremberg | Ivanovska J.,Friedrich - Alexander - University, Erlangen - Nuremberg | Benderska N.,Friedrich - Alexander - University, Erlangen - Nuremberg | And 10 more authors.
Apoptosis | Year: 2012

The histone deacetylase inhibitor (HDACi) LBH589 has been verified as an effective anticancer agent. The identification and characterization of new targets for LBH589 action would further enhance our understanding of the molecular mechanisms involved in HDACi therapy. The role of the tumor suppressor death-associated protein kinase (DAPK) in LBH589-induced cytotoxicity has not been investigated to date. Stable DAPK knockdown (shRNA) and DAPK overexpressing (DAPK+++) cell lines were generated from HCT116 wildtype colon cancer cells. LBH589 inhibited cell proliferation, reduced the long-term survival, and up-regulated and activated DAPK in colorectal cancer cells.Moreover, LBH589 significantly suppressed the growth of colon tumor xenografts and in accordance with the in vitro studies, increased DAPK levels were detected immunohistochemically. LBH589 induced a DAPK-dependent autophagy as assessed by punctuate accumulation of LC3-II, the formation of acidic vesicular organelles, and degradation of p62 protein. LBH589-induced autophagy seems to be predominantly caused by DAPK protein interactions than by its kinase activity. Caspase inhibitor zVAD increased autophagosome formation, decreased the cleavage of caspase 3 and PARP but didn't rescue the cells from LBH589-induced cell death in crystal violet staining suggesting both caspase-dependent as well as caspase-independent apoptosis pathways. Pre-treatment with the autophagy inhibitor Bafilomycin A1 caused caspase 3-mediated apoptosis in a DAPK-dependent manner. Altogether our data suggest that DAPK induces autophagy in response to HDACi-treatment. In autophagy deficient cells, DAPK plays an essential role in committing cells to HDACi induced apoptosis. © Springer Science+Business Media, LLC 2012.

Magnitsky S.,Laboratory of Molecular Imaging | Roesch A.,Wistar Institute | Roesch A.,Saarland University | Herlyn M.,Wistar Institute | Glickson J.D.,Laboratory of Molecular Imaging
Magnetic Resonance in Medicine | Year: 2011

Slowly cycling cells are believed to play a critical role in tumor progression and metastatic dissemination. The goal of this study was to develop a method for in vivo detection of slowly cycling cells. To distinguish these cells from more rapidly proliferating cells that constitute the vast majority of cells in tumors, we used the well-known effect of label dilution due to division of cells with normal cycle and retention of contrast agent in slowly dividing cells. To detect slowly cycling cells, melanoma cells were labeled with iron oxide particles. After labeling, we observed dilution of contrast agent in parallel with cell proliferation in the vast majority of normally cycling cells. A small and distinct subpopulation of iron-retaining cells was detected by flow cytometry after 20 days of in vitro proliferation. These iron-retaining cells exhibited high expression of a biological marker of slowly cycling cells, JARID1B. After implantation of labeled cells as xenografts into immunocompromised mice, iron-retaining cells were detected in vivo and ex vivo by magnetic resonance imaging that was confirmed by Prussian Blue staining. Magnetic resonance imaging detects not only iron retaining melanoma cells but also iron positive macrophages. Proposed method opens up opportunities to image subpopulation of melanoma cells, which is critical for continuous tumor growth. Copyright © 2011 Wiley Periodicals, Inc.

Padmanabhan S.,Nanyang Technological University | Shinoj V.K.,Nanyang Technological University | Murukeshan V.M.,Nanyang Technological University | Padmanabhan P.,Laboratory of Molecular Imaging
Journal of Biomedical Optics | Year: 2010

A simple optical method using hollow-core photonic crystal fiber for protein detection has been described. In this study, estrogen receptor (ER) from a MCF-7 breast carcinoma cell lysates immobilized inside a hollow-core photonic crystal fiber was detected using anti-ER primary antibody with either Alexa ™ Fluor 488 (green fluorescent dye) or 555 (red Fluorescent dye) labeled Goat anti-rabbit IgG as the secondary antibody. The fluorescence fingerprints of the ERα protein were observed under fluorescence microscope, and its optical characteristics were analyzed. The ERα protein detection by this proposed method is based on immuno binding from sample volume as low as 50 nL. This method is expected to offer great potential as a biosensor for medical diagnostics and therapeutics applications. © 2010 Society of Photo-Optical Instrumentation Engineers.

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