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Novel Smart MR Contrast Agents for In Vivo Molecular Imaging of pH, Calcium, and Enzyme Activity

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http://pubman.mpdl.mpg.de/cone/persons/resource/persons84083

Mishra,  AK
Department Physiology of Cognitive Processes, Max Planck Institute for Biological Cybernetics, Max Planck Society;

http://pubman.mpdl.mpg.de/cone/persons/resource/persons84137

Pfeuffer,  J
Department Physiology of Cognitive Processes, Max Planck Institute for Biological Cybernetics, Max Planck Society;

http://pubman.mpdl.mpg.de/cone/persons/resource/persons84063

Logothetis,  NK
Department Physiology of Cognitive Processes, Max Planck Institute for Biological Cybernetics, Max Planck Society;

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Citation

Mishra, A., Pfeuffer, J., & Logothetis, N. (2004). Novel Smart MR Contrast Agents for In Vivo Molecular Imaging of pH, Calcium, and Enzyme Activity. Poster presented at 3rd Annual Meeting of the Society of Molecular Imaging, St. Louis, MO, USA.


Cite as: http://hdl.handle.net/11858/00-001M-0000-0013-D7F9-B
Abstract
Two novel gadolinium-based magnetic resonance (MR) contrast agents for molecular imaging were designed and synthesized. They have the potential to trace physiological changes of extracellular pH, calcium concentration, and enzymatic activity. DO3A-EP; 1,4,7 tris(carboxymethyl)-10-(2-phosphono-ethyl)-1,4,7,10-tetraazacyclododecane (L1) and DO3A-EA-P5P; 1,4,7 tris(carboxymethyl)-10-2-[(3-hydroxy-2-methyl-5-phosphonooxymethyl-pyridin-4-ylmethylene)-amino]-ethyl- 1,4,7,10-tetraazacyclododecane (L2) were synthesized from 1,4,7,10-tetraazacyclododecane (Cyclen) by reaction with tert-butyl bromoacetate, giving an excellent yield of 80. L1 was prepared by reaction with diethyl 2-bromoethyl phosphonate. L2 was prepared by the reaction of 1,4,7-tris (carbobutoxymethyl)-10-(4-aminoethyl)-1,4,7,10-tetraazacyclododecane and pyridoxal 5’ phosphate monohydrate. The corresponding carboxylate derivative was obtained by cleaving the tert-butyl group by trifluoroacetic acid and anisole at 0ºC. All the derivatives and final chelates were characterized on the basis of 1H, 13C, and 31P NMR and ESI-MSn mass spectrometry. For initial MR results, the gadolinium complex of DO3A-EP was prepared in aqueous conditions at pH 6.3. In vitro MR relaxivity studies were performed at 300 MHz to probe relaxivity changes with different pH. For Gd-DO3A-EP at 21ºC, r1 increased by 70 from 2.3 to 3.9 s-1mM-1 (pH 7.5 to pH 5.5) and r2 increased by 57 from 2.8 to 4.4 s-1mM-1 (pH 7.5 to pH 5.5).