Rood Marcus T M, Raspe Marcel, ten Hove Jan Bart, Jalink Kees, Velders Aldrik H, van Leeuwen Fijs W B
Interventional Molecular Imaging Laboratory, Department of Radiology, Leiden University Medical Center, Leiden 2300RC, The Netherlands.
Division of Cell Biology I, Netherlands Cancer Institute, Amsterdam 1066CX, The Netherlands.
Sensors (Basel). 2015 May 12;15(5):11076-91. doi: 10.3390/s150511076.
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.
光学（分子）成像可受益于可激活荧光成像的高信噪比与发光寿命成像的高特异性的结合。为实现这种结合，两种成像技术被整合到一种单一的成像剂中，即所谓的可激活寿命成像剂。在这种成像剂的设计中，重要的是使用两种发光团，它们通过具有发夹结构的特定肽连接在一起，这确保了两者紧密接近，同时还具有可被肿瘤相关的基质金属蛋白酶-2/9酶切的特定氨基酸序列。使用了Ir(ppy)3和Cy5，因为在紧密接近时，两种发光团的发射强度都会淬灭，并且Cy5的影响会使Ir(ppy)3的发光寿命从98纳秒缩短至30纳秒。在体外切割后，这两种效应都会消除，导致Ir(ppy)3和Cy5的发光增加，并且Ir(ppy)3的发光寿命恢复到94纳秒。作为发光激活的参考对照，使用了具有更常见的Cy3-Cy5荧光团对的类似成像剂。我们的研究结果强调，酶促信号激活与寿命成像的结合是可行的，并且它为未来疾病特异性成像剂的设计提供了一种有前景的方法。
