The Experts below are selected from a list of 360 Experts worldwide ranked by ideXlab platform
Ming Zhao - One of the best experts on this subject based on the ideXlab platform.
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99m Tc-labeled C2A domain of synaptotagmin I as a target-specific molecular probe for noninvasive imaging of acute myocardial infarction
2015Co-Authors: Ming Zhao, Xiaoguang Zhu, Jundong Zhou, Kutlan S. Ozker, Wei Fang, Robert C. Molthen, Robert S. HellmanAbstract:The exposure of phosphatidylserine (PtdS) is a common molec-ular marker for both apoptosis and necrosis and enables the si-multaneous detection of these distinct modes of cell death. Our aim was to develop a radiotracer based on the PtdS-binding ac-tivity of the C2A domain of synaptotagmin I and assess 99mTc-C2A-GST (GST is glutathione S-transferase) using a reperfused acute myocardial infarction (AMI) rat model.Methods: The bind-ing of C2A-GST toward apoptosis and necrosis was validated in vitro. After labeling with 99mTc via 2-Iminothiolane thiolation, radiochemical purity and radiostability were tested. Pharma-cokinetics and biodistribution were studied in healthy rats. The uptake of 99mTc-C2A-GST within the area at risk was quantified by direct g-counting, whereas nonspecific accumulation was es-timated using inactivated 99mTc-C2A-GST. In vivo planar imaging of AMI in rats was performed on a g-camera using a parallel-hol
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in vivo dynamic imaging of myocardial cell death using 99mtc labeled c2a domain of synaptotagmin i in a rat model of ischemia and reperfusion
Nuclear Medicine and Biology, 2007Co-Authors: Ming Zhao, Lars R Furenlid, Yichun Chen, Harrison H BarrettAbstract:Abstract Objectives This study was designed to investigate the capability of a small-animal SPECT imager, FastSPECT II, for dynamic rat heart imaging and to characterize the in vivo kinetic properties of 99mTc-C2A-glutathione-s-transferase (GST), a molecular probe targeting apoptosis and necrosis, in detecting cell death in ischemic–reperfused rat hearts. Methods C2A-GST was radiolabeled with 99mTc via 2-Iminothiolane thiolation. Myocardial ischemia–reperfusion was induced by 30-min ligation of the left coronary artery followed by 120-min reperfusion in seven rats. FastSPECT II cardiac images of 99mTc-C2A-GST in list-mode acquisition were recorded for 2 h using FastSPECT II. Results Tomographic images showed a focal radioactive accumulation (hot spot) in the lateral and anterior walls of the left ventricle. The hot spot was initially visualized 10 min after injection and persisted on the 2-h images. Quantitative analysis demonstrated that the hot-spot radioactivity increased significantly within 30 min postinjection and experienced no washout up to the end of the 2-h study. The ratio of the hot spot/viable myocardium was 4.52±0.24, and infarct-to-lung ratio was 8.22±0.63 at 2 h postinjection. The uptake of 99mTc-C2A-GST in the infarcted myocardium was confirmed by triphenyl tetrazolium chloride staining and autoradiography analysis. Conclusions FastSPECT II allows quantitative dynamic imaging and functional determination of radiotracer kinetics in rat hearts. An in vivo kinetic profile of 99mTc-C2A-GST in the ischemic–reperfused rat heart model was characterized successfully. The pattern of accelerated 99mTc-C2A-GST uptake in the ischemic area at risk after reperfusion may be useful in detecting and quantifying ongoing myocardial cell loss induced by ischemia–reperfusion.
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99mtc labeled c2a domain of synaptotagmin i as a target specific molecular probe for noninvasive imaging of acute myocardial infarction
The Journal of Nuclear Medicine, 2006Co-Authors: Ming Zhao, Jundong Zhou, Kutlan S. Ozker, Wei Fang, Robert C. Molthen, Shundong Ji, Robert S. HellmanAbstract:UNLABELLED: The exposure of phosphatidylserine (PtdS) is a common molecular marker for both apoptosis and necrosis and enables the simultaneous detection of these distinct modes of cell death. Our aim was to develop a radiotracer based on the PtdS-binding activity of the C2A domain of synaptotagmin I and assess 99mTc-C2A-GST (GST is glutathione S-transferase) using a reperfused acute myocardial infarction (AMI) rat model. METHODS: The binding of C2A-GST toward apoptosis and necrosis was validated in vitro. After labeling with 99mTc via 2-Iminothiolane thiolation, radiochemical purity and radiostability were tested. Pharmacokinetics and biodistribution were studied in healthy rats. The uptake of 99mTc-C2A-GST within the area at risk was quantified by direct gamma-counting, whereas nonspecific accumulation was estimated using inactivated 99mTc-C2A-GST. In vivo planar imaging of AMI in rats was performed on a gamma-camera using a parallel-hole collimator. Radioactivity uptake was investigated by region-of-interest analysis, and postmortem tetrazolium staining versus autoradiography. RESULTS: Fluorescently labeled and radiolabeled C2A-GST bound both apoptotic and necrotic cells. 99mTc-C2A-GST had a radiochemical purity of >98% and remained stable. After intravenous injection, the uptake in the liver and kidneys was significant. For 99mTc-C2A-GST, radioactivity uptake in the area at risk reached between 2.40 and 2.63 %ID/g (%ID/g is percentage injected dose per gram) within 30 min and remained plateaued for at least 3 h. In comparison, with the inactivated tracer the radioactivity reached 1.06 +/- 0.49 %ID/g at 30 min, followed by washout to 0.52 +/- 0.23 %ID/g. In 7 of 7 rats, the infarct was clearly identifiable as focal uptake in planar images. At 3 h after injection, the infarct-to-lung ratios were 2.48 +/- 0.27, 1.29 +/- 0.09, and 1.46 +/- 0.04 for acute-infarct rats with (99m)Tc-C2A-GST, sham-operated rats with (99m)Tc-C2A-GST, and acute-infarct rats with 99mTc-C2A-GST-NHS (NHS is N-hydroxy succinimide), respectively. The distribution of radioactivity was confirmed by autoradiography and histology. CONCLUSION: The C2A domain of synaptotagmin I labeled with fluorochromes or a radioisotope binds to both apoptotic and necrotic cells. Ex vivo and in vivo data indicate that, because of elevated vascular permeability, both specific binding and passive leakage contribute to the accumulation of the radiotracer in the area at risk. However, the latter component alone is insufficient to achieve detectable target-to-background ratios with in vivo planar imaging.
Robert S. Hellman - One of the best experts on this subject based on the ideXlab platform.
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99m Tc-labeled C2A domain of synaptotagmin I as a target-specific molecular probe for noninvasive imaging of acute myocardial infarction
2015Co-Authors: Ming Zhao, Xiaoguang Zhu, Jundong Zhou, Kutlan S. Ozker, Wei Fang, Robert C. Molthen, Robert S. HellmanAbstract:The exposure of phosphatidylserine (PtdS) is a common molec-ular marker for both apoptosis and necrosis and enables the si-multaneous detection of these distinct modes of cell death. Our aim was to develop a radiotracer based on the PtdS-binding ac-tivity of the C2A domain of synaptotagmin I and assess 99mTc-C2A-GST (GST is glutathione S-transferase) using a reperfused acute myocardial infarction (AMI) rat model.Methods: The bind-ing of C2A-GST toward apoptosis and necrosis was validated in vitro. After labeling with 99mTc via 2-Iminothiolane thiolation, radiochemical purity and radiostability were tested. Pharma-cokinetics and biodistribution were studied in healthy rats. The uptake of 99mTc-C2A-GST within the area at risk was quantified by direct g-counting, whereas nonspecific accumulation was es-timated using inactivated 99mTc-C2A-GST. In vivo planar imaging of AMI in rats was performed on a g-camera using a parallel-hol
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99mtc labeled c2a domain of synaptotagmin i as a target specific molecular probe for noninvasive imaging of acute myocardial infarction
The Journal of Nuclear Medicine, 2006Co-Authors: Ming Zhao, Jundong Zhou, Kutlan S. Ozker, Wei Fang, Robert C. Molthen, Shundong Ji, Robert S. HellmanAbstract:UNLABELLED: The exposure of phosphatidylserine (PtdS) is a common molecular marker for both apoptosis and necrosis and enables the simultaneous detection of these distinct modes of cell death. Our aim was to develop a radiotracer based on the PtdS-binding activity of the C2A domain of synaptotagmin I and assess 99mTc-C2A-GST (GST is glutathione S-transferase) using a reperfused acute myocardial infarction (AMI) rat model. METHODS: The binding of C2A-GST toward apoptosis and necrosis was validated in vitro. After labeling with 99mTc via 2-Iminothiolane thiolation, radiochemical purity and radiostability were tested. Pharmacokinetics and biodistribution were studied in healthy rats. The uptake of 99mTc-C2A-GST within the area at risk was quantified by direct gamma-counting, whereas nonspecific accumulation was estimated using inactivated 99mTc-C2A-GST. In vivo planar imaging of AMI in rats was performed on a gamma-camera using a parallel-hole collimator. Radioactivity uptake was investigated by region-of-interest analysis, and postmortem tetrazolium staining versus autoradiography. RESULTS: Fluorescently labeled and radiolabeled C2A-GST bound both apoptotic and necrotic cells. 99mTc-C2A-GST had a radiochemical purity of >98% and remained stable. After intravenous injection, the uptake in the liver and kidneys was significant. For 99mTc-C2A-GST, radioactivity uptake in the area at risk reached between 2.40 and 2.63 %ID/g (%ID/g is percentage injected dose per gram) within 30 min and remained plateaued for at least 3 h. In comparison, with the inactivated tracer the radioactivity reached 1.06 +/- 0.49 %ID/g at 30 min, followed by washout to 0.52 +/- 0.23 %ID/g. In 7 of 7 rats, the infarct was clearly identifiable as focal uptake in planar images. At 3 h after injection, the infarct-to-lung ratios were 2.48 +/- 0.27, 1.29 +/- 0.09, and 1.46 +/- 0.04 for acute-infarct rats with (99m)Tc-C2A-GST, sham-operated rats with (99m)Tc-C2A-GST, and acute-infarct rats with 99mTc-C2A-GST-NHS (NHS is N-hydroxy succinimide), respectively. The distribution of radioactivity was confirmed by autoradiography and histology. CONCLUSION: The C2A domain of synaptotagmin I labeled with fluorochromes or a radioisotope binds to both apoptotic and necrotic cells. Ex vivo and in vivo data indicate that, because of elevated vascular permeability, both specific binding and passive leakage contribute to the accumulation of the radiotracer in the area at risk. However, the latter component alone is insufficient to achieve detectable target-to-background ratios with in vivo planar imaging.
Ute Schepers - One of the best experts on this subject based on the ideXlab platform.
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2 Iminothiolane as a useful coupling reagent for polyamine solid phase synthesis
Synlett, 2008Co-Authors: Frank Hahn, Klaus Mullen, Ute SchepersAbstract:Here, the versatility of 2-Iminothiolane to act as coupling reagent for solid-phase synthesis of polyamine conjugates is shown. This method, which supersedes the use of elaborate protection group strategies, allows the mild coupling of biomacromolecules and other functional moieties. Spermine conjugates with diverse maleimido building blocks were synthesized by a quick and selective reaction.
James R Christie - One of the best experts on this subject based on the ideXlab platform.
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targeted polymeric micelles for sirna treatment of experimental cancer by intravenous injection
ACS Nano, 2012Co-Authors: James R Christie, Yu Matsumoto, Kanjiro Miyata, Takahiro Nomoto, Shigeto Fukushima, Kensuke Osada, Julien Halnaut, Frederico Pittella, Hyun Jin Kim, Nobuhiro NishiyamaAbstract:Small interfering ribonucleic acid (siRNA) cancer therapies administered by intravenous injection require a delivery system for transport from the bloodstream into the cytoplasm of diseased cells to perform the function of gene silencing. Here we describe nanosized polymeric micelles that deliver siRNA to solid tumors and elicit a therapeutic effect. Stable multifunctional micelle structures on the order of 45 nm in size formed by spontaneous self-assembly of block copolymers with siRNA. Block copolymers used for micelle formation were designed and synthesized to contain three main features: a siRNA binding segment containing thiols, a hydrophilic nonbinding segment, and a cell-surface binding peptide. Specifically, poly(ethylene glycol)-block-poly(L-lysine) (PEG-b-PLL) comprising lysine amines modified with 2-Iminothiolane (2IT) and the cyclo-Arg-Gly-Asp (cRGD) peptide on the PEG terminus was used. Modification of PEG-b-PLL with 2IT led to improved control of micelle formation and also increased stability in the blood compartment, while installation of the cRGD peptide improved biological activity. Incorporation of siRNA into stable micelle structures containing the cRGD peptide resulted in increased gene silencing ability, improved cell uptake, and broader subcellular distribution in vitro and also improved accumulation in both the tumor mass and tumor-associated blood vessels following intravenous injection into mice. Furthermore, stable and targeted micelles inhibited the growth of subcutaneous HeLa tumor models and demonstrated gene silencing in the tumor mass following treatment with antiangiogenic siRNAs. This new micellar nanomedicine could potentially expand the utility of siRNA-based therapies for cancer treatments that require intravenous injection.
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targeted polymeric micelles for sirna treatment of experimental cancer by intravenous injection
ACS Nano, 2012Co-Authors: James R Christie, Yu Matsumoto, Kanjiro Miyata, Takahiro Nomoto, Shigeto Fukushima, Kensuke Osada, Julien Halnaut, Frederico Pittella, Nobuhiro Nishiyama, Kazunori KataokaAbstract:Small interfering ribonucleic acid (siRNA) cancer therapies administered by intravenous injection require a delivery system for transport from the bloodstream into the cytoplasm of diseased cells to perform the function of gene silencing. Here we describe nanosized polymeric micelles that deliver siRNA to solid tumors and elicit a therapeutic effect. Stable multifunctional micelle structures on the order of 45 nm in size formed by spontaneous self-assembly of block copolymers with siRNA. Block copolymers used for micelle formation were designed and synthesized to contain three main features: a siRNA binding segment containing thiols, a hydrophilic nonbinding segment, and a cell-surface binding peptide. Specifically, poly(ethylene glycol)-block-poly(l-lysine) (PEG-b-PLL) comprising lysine amines modified with 2-Iminothiolane (2IT) and the cyclo-Arg-Gly-Asp (cRGD) peptide on the PEG terminus was used. Modification of PEG-b-PLL with 2IT led to improved control of micelle formation and also increased stabilit...
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effect of polymer structure on micelles formed between sirna and cationic block copolymer comprising thiols and amidines
Biomacromolecules, 2011Co-Authors: James R Christie, Yu Matsumoto, Kanjiro Miyata, Takahiro Nomoto, Kensuke Osada, Daniel Menasco, Tsz Chung Lai, Matthew Pennisi, Shigeto FukushimaAbstract:Small interfering RNA (siRNA) has great therapeutic potential for the suppression of proteins associated with disease, but delivery methods are needed for improved efficacy. Here, we investigated the properties of micellar siRNA delivery vehicles prepared with poly(ethylene glycol)-block-poly(l-lysine) (PEG-b-PLL) comprising lysine amines modified to contain amidine and thiol functionality. Lysine modification was achieved using 2-Iminothiolane (2-IT) [yielding PEG-b-PLL(N2IM-IM)] or dimethyl 3,3′-dithiobispropionimidate (DTBP) [yielding PEG-b-PLL(MPA)], with modifications aimed to impart disulfide cross-linking ability without compromising cationic charge. These two lysine modification reagents resulted in vastly different chemistry contained in the reacted block copolymer, which affected micelle formation behavior and stability along with in vitro and in vivo performance. Amidines formed with 2-IT were unstable and rearranged into a noncharged ring structure lacking free thiol functionality, whereas ami...
Kanjiro Miyata - One of the best experts on this subject based on the ideXlab platform.
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targeted polymeric micelles for sirna treatment of experimental cancer by intravenous injection
ACS Nano, 2012Co-Authors: James R Christie, Yu Matsumoto, Kanjiro Miyata, Takahiro Nomoto, Shigeto Fukushima, Kensuke Osada, Julien Halnaut, Frederico Pittella, Hyun Jin Kim, Nobuhiro NishiyamaAbstract:Small interfering ribonucleic acid (siRNA) cancer therapies administered by intravenous injection require a delivery system for transport from the bloodstream into the cytoplasm of diseased cells to perform the function of gene silencing. Here we describe nanosized polymeric micelles that deliver siRNA to solid tumors and elicit a therapeutic effect. Stable multifunctional micelle structures on the order of 45 nm in size formed by spontaneous self-assembly of block copolymers with siRNA. Block copolymers used for micelle formation were designed and synthesized to contain three main features: a siRNA binding segment containing thiols, a hydrophilic nonbinding segment, and a cell-surface binding peptide. Specifically, poly(ethylene glycol)-block-poly(L-lysine) (PEG-b-PLL) comprising lysine amines modified with 2-Iminothiolane (2IT) and the cyclo-Arg-Gly-Asp (cRGD) peptide on the PEG terminus was used. Modification of PEG-b-PLL with 2IT led to improved control of micelle formation and also increased stability in the blood compartment, while installation of the cRGD peptide improved biological activity. Incorporation of siRNA into stable micelle structures containing the cRGD peptide resulted in increased gene silencing ability, improved cell uptake, and broader subcellular distribution in vitro and also improved accumulation in both the tumor mass and tumor-associated blood vessels following intravenous injection into mice. Furthermore, stable and targeted micelles inhibited the growth of subcutaneous HeLa tumor models and demonstrated gene silencing in the tumor mass following treatment with antiangiogenic siRNAs. This new micellar nanomedicine could potentially expand the utility of siRNA-based therapies for cancer treatments that require intravenous injection.
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targeted polymeric micelles for sirna treatment of experimental cancer by intravenous injection
ACS Nano, 2012Co-Authors: James R Christie, Yu Matsumoto, Kanjiro Miyata, Takahiro Nomoto, Shigeto Fukushima, Kensuke Osada, Julien Halnaut, Frederico Pittella, Nobuhiro Nishiyama, Kazunori KataokaAbstract:Small interfering ribonucleic acid (siRNA) cancer therapies administered by intravenous injection require a delivery system for transport from the bloodstream into the cytoplasm of diseased cells to perform the function of gene silencing. Here we describe nanosized polymeric micelles that deliver siRNA to solid tumors and elicit a therapeutic effect. Stable multifunctional micelle structures on the order of 45 nm in size formed by spontaneous self-assembly of block copolymers with siRNA. Block copolymers used for micelle formation were designed and synthesized to contain three main features: a siRNA binding segment containing thiols, a hydrophilic nonbinding segment, and a cell-surface binding peptide. Specifically, poly(ethylene glycol)-block-poly(l-lysine) (PEG-b-PLL) comprising lysine amines modified with 2-Iminothiolane (2IT) and the cyclo-Arg-Gly-Asp (cRGD) peptide on the PEG terminus was used. Modification of PEG-b-PLL with 2IT led to improved control of micelle formation and also increased stabilit...
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effect of polymer structure on micelles formed between sirna and cationic block copolymer comprising thiols and amidines
Biomacromolecules, 2011Co-Authors: James R Christie, Yu Matsumoto, Kanjiro Miyata, Takahiro Nomoto, Kensuke Osada, Daniel Menasco, Tsz Chung Lai, Matthew Pennisi, Shigeto FukushimaAbstract:Small interfering RNA (siRNA) has great therapeutic potential for the suppression of proteins associated with disease, but delivery methods are needed for improved efficacy. Here, we investigated the properties of micellar siRNA delivery vehicles prepared with poly(ethylene glycol)-block-poly(l-lysine) (PEG-b-PLL) comprising lysine amines modified to contain amidine and thiol functionality. Lysine modification was achieved using 2-Iminothiolane (2-IT) [yielding PEG-b-PLL(N2IM-IM)] or dimethyl 3,3′-dithiobispropionimidate (DTBP) [yielding PEG-b-PLL(MPA)], with modifications aimed to impart disulfide cross-linking ability without compromising cationic charge. These two lysine modification reagents resulted in vastly different chemistry contained in the reacted block copolymer, which affected micelle formation behavior and stability along with in vitro and in vivo performance. Amidines formed with 2-IT were unstable and rearranged into a noncharged ring structure lacking free thiol functionality, whereas ami...
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block catiomer polyplexes with regulated densities of charge and disulfide cross linking directed to enhance gene expression
Journal of the American Chemical Society, 2004Co-Authors: Kanjiro Miyata, Nobuhiro Nishiyama, Atsushi Harada, Yoshinori Kakizawa, Yuichi Yamasaki, Hiroyuki Koyama, Kazunori KataokaAbstract:A block catiomer polyplex, showing a high stability in the extracellular medium and an efficient release of plasmid DNA (pDNA) in the intracellular compartment, was developed by controlling both the cationic charge and disulfide cross-linking densities of the backbone polycations. Poly(ethylene glycol)-poly(L-lysine) block copolymer (PEG-PLL) was thiolated using either of two thiolation reagents, N-succinimidyl 3-(2-pyridyldithio)propionate (SPDP) or 2-Iminothiolane (Traut's reagent), to investigate the effects of both the charge and disulfide cross-linking densities on the properties of the polyplexes. The introduction of thiol groups by SPDP proceeded through the formation of amide linkages to concomitantly decrease the cationic charge density of PLL segment, whereas Traut's reagent promoted the thiolation with the introduction of cationic imino groups to keep the charge density constant. These thiolated PEG-PLLs were complexed with pDNA to form the disulfide cross-linked block catiomer polyplexes, which had the size of approximately 100 nm. Both thiolation methods were similarly effective in introducing disulfide cross-links to prevent the polyplex from the dissociation through a counter polyanion exchange in the extracellular oxidative condition. On the other hand, the efficient release of pDNA responding to the reductive condition mimicking the intracellular environment was only achieved for the polyplex thiolated with SPDP, a system compensating for the decrease in the charge density with the disulfide cross-linking. This distinctive sensitivity toward oxidative and reductive environments was nicely correlated with the remarkable difference in the transfection efficiency between these two types of thiolated polyplexes (SPDP and Traut's reagent types): the former revealed approximately 50 times higher transfection efficiency toward 293T cells than the latter. Obviously, the balance between the densities of the cationic charge and disulfide cross-linking in the thiolated polyplex played a crucial role in the delivery and controlled release of entrapped pDNA into the microenvironment of intracellular compartment to achieve the high transfection efficiency.
