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Lanthanide(III) complexes of rhodamine-DO3A conjugates as agents for dual-modal imaging

Rivas, Charlotte; Stasiuk, Graeme J.; Gallo, Juan; Minuzzi, Florencia; Rutter, Guy A.; Long, Nicholas J.

Authors

Charlotte Rivas

Graeme J. Stasiuk

Juan Gallo

Florencia Minuzzi

Guy A. Rutter

Nicholas J. Long



Abstract

Two novel dual-modal MRI/optical probes based on a rhodamine-DO3A conjugate have been prepared. The bis aqua-Gd(III) complex Gd.L1 and mono aqua-Gd(III) complex Gd.L2 behave as dual-modal imaging probes (r1 = 8.5 and 3.8 mM-1s-1 for Gd.L1 and Gd.L2 respectively; λex = 560 nm and λem = 580 nm for both complexes). The rhodamine fragment is pH sensitive and upon lowering of pH an increase in fluorescence intensity is observed as the spirolactam ring opens to give the highly fluorescent form of the molecule. The ligands are bimodal when coordinated to Tb(III) ions, inducing fluorescence from both the lanthanide center and the rhodamine fluorophore, on two independent time-frames. Confocal imaging experiments were carried out to establish the localization of Gd.L2 in HEK cells. Co-localisation with MitoTracker® Green confirmed that Gd.L2 compartmentalizes in the mitochondria. Gd.L2 was also evaluated as an MRI probe for imaging tumors in BALB/c nude mice bearing M21 xenografts. A 36.5% decrease in T1 within the tumor was observed 30 minutes post injection showing that Gd.L2 is preferentially up taken in the tumor. Gd.L2 is the first small molecule MR/fluorescent dual-modal imaging agent to display an off-on pH switch upon its preferential uptake within the more acidic micro-environment of tumor cells.

Journal Article Type Article
Publication Date Dec 16, 2013
Journal Inorganic chemistry
Print ISSN 0020-1669
Electronic ISSN 1520-510X
Publisher American Chemical Society
Peer Reviewed Peer Reviewed
Volume 52
Issue 24
Pages 14284-14293
APA6 Citation Rivas, C., Stasiuk, G. J., Gallo, J., Minuzzi, F., Rutter, G. A., & Long, N. J. (2013). Lanthanide(III) complexes of rhodamine-DO3A conjugates as agents for dual-modal imaging. Inorganic chemistry, 52(24), (14284-14293). doi:10.1021/ic402233g. ISSN 0020-1669
DOI https://doi.org/10.1021/ic402233g
Keywords Dual mode imaging, Magnetic resonance imaging, Fluorescence, Rhodamine, Lanthanides
Publisher URL http://pubs.acs.org/doi/abs/10.1021/ic402233g
Copyright Statement © 2013 American Chemical Society - This ACS article is provided to You under the terms of this ACS AuthorChoice/Editors’ Choice via Creative Commons CC-BY agreement between You and the American Chemical Society (“ACS”), a federally-chartered nonprofit located at 1155 16th Street NW, Washington DC 20036. Your access and use of this ACS article means that you have accepted and agreed to the Terms and Conditions of this Agreement. ACS and You are collectively referred to in this Agreement as “the Parties”).
Additional Information This is a copy of an article published in Inorganic chemistry, 2013, v.52 issue 24.

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Copyright Statement
© 2013 American Chemical Society - This ACS article is provided to You under the terms of this ACS AuthorChoice/Editors’ Choice via Creative Commons CC-BY agreement between You and the American Chemical Society (“ACS”), a federally-chartered nonprofit located at 1155 16th Street NW, Washington DC 20036. Your access and use of this ACS article means that you have accepted and agreed to the Terms and Conditions of this Agreement. ACS and You are collectively referred to in this Agreement as “the Parties”).



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