title: MMP-2/9-Specific Activatable Lifetime Imaging Agent.
abstract: Optical (molecular) imaging can benefit from a combination of the high signal-to-background ratio of activatable fluorescence imaging with the high specificity of luminescence lifetime imaging. To allow for this combination, both imaging techniques were integrated in a single imaging agent, a so-called activatable lifetime imaging agent. Important in the design of this imaging agent is the use of two luminophores that are tethered by a specific peptide with a hairpin-motive that ensured close proximity of the two while also having a specific amino acid sequence available for enzymatic cleavage by tumor-related MMP-2/9. Ir(ppy)3 and Cy5 were used because in close proximity the emission intensities of both luminophores were quenched and the influence of Cy5 shortens the Ir(ppy)3 luminescence lifetime from 98 ns to 30 ns. Upon cleavage in vitro, both effects are undone, yielding an increase in Ir(ppy)3 and Cy5 luminescence and a restoration of Ir(ppy)3 luminescence lifetime to 94 ns. As a reference for the luminescence activation, a similar imaging agent with the more common Cy3-Cy5 fluorophore pair was used. Our findings underline that the combination of enzymatic signal activation with lifetime imaging is possible and that it provides a promising method in the design of future disease specific imaging agents.
authors.affiliation: Interventional Molecular Imaging Laboratory, Department of Radiology, Leiden University Medical Center, Leiden 2300RC, The Netherlands. m.t.m.rood@lumc.nl.
authors.forename: Marcus T M
authors.initials: MT
authors.lastname: Rood
authors.affiliation: Division of Cell Biology I, Netherlands Cancer Institute, Amsterdam 1066CX, The Netherlands. m.raspe@nki.nl.
authors.forename: Marcel
authors.initials: M
authors.lastname: Raspe
authors.affiliation: Interventional Molecular Imaging Laboratory, Department of Radiology, Leiden University Medical Center, Leiden 2300RC, The Netherlands. janbart.tenhove@wur.nl.|Laboratory of BioNanoTechnology, Wageningen University, Wageningen 6700EK, The Netherlands. janbart.tenhove@wur.nl.
authors.forename: Jan Bart
authors.initials: JB
authors.lastname: ten Hove
authors.affiliation: Division of Cell Biology I, Netherlands Cancer Institute, Amsterdam 1066CX, The Netherlands. k.jalink@nki.nl.
authors.forename: Kees
authors.initials: K
authors.lastname: Jalink
authors.affiliation: Interventional Molecular Imaging Laboratory, Department of Radiology, Leiden University Medical Center, Leiden 2300RC, The Netherlands. aldrik.velders@wur.nl.|Laboratory of BioNanoTechnology, Wageningen University, Wageningen 6700EK, The Netherlands. aldrik.velders@wur.nl.
authors.forename: Aldrik H
authors.initials: AH
authors.lastname: Velders
authors.affiliation: Interventional Molecular Imaging Laboratory, Department of Radiology, Leiden University Medical Center, Leiden 2300RC, The Netherlands. f.w.b.van_leeuwen@lumc.nl.|Laboratory of BioNanoTechnology, Wageningen University, Wageningen 6700EK, The Netherlands. f.w.b.van_leeuwen@lumc.nl.
authors.forename: Fijs W B
authors.initials: FW
authors.lastname: van Leeuwen
mesh_terms: D002232:Carbocyanines / Q000737:chemistry; D045744:Cell Line, Tumor; D003584:Cytological Techniques / Q000379:methods; D031541:Fluorescence Resonance Energy Transfer / Q000379:methods*; D005456:Fluorescent Dyes / Q000737:chemistry* / Q000378:metabolism; D006801:Humans; D007495:Iridium / Q000737:chemistry; D020778:Matrix Metalloproteinase 2 / Q000032:analysis* / Q000378:metabolism; D020780:Matrix Metalloproteinase 9 / Q000032:analysis* / Q000378:metabolism; D057054:Molecular Imaging / Q000379:methods*
chemical_list: D002232:Carbocyanines; D005456:Fluorescent Dyes; C085321:cyanine dye 5; D007495:Iridium; D020778:Matrix Metalloproteinase 2; D020780:Matrix Metalloproteinase 9
keywords: FRET; MMP; enzymatic activation; fluorescence; iridium; lifetime imaging; luminescence