Near-infrared fluorescence probes for enzymes based on binding affinity modulation of squarylium dye scaffold

Daihi Oushiki, Hirotatsu Kojima, Yuki Takahashi, Toru Komatsu, Takuya Terai, Kenjiro Hanaoka, Makiya Nishikawa, Yoshinobu Takakura, Tetsuo Nagano

Research output: Contribution to journalArticlepeer-review

51 Citations (Scopus)


We present a novel design strategy for near-infrared (NIR) fluorescence probes utilizing dye-protein interaction as a trigger for fluorescence enhancement. The design principle involves modification of a polymethine dye with cleavable functional groups that reduce the dye's protein-binding affinity. When these functional groups are removed by specific interaction with the target enzymes, the dye's protein affinity is restored, protein binding occurs, and the dye's fluorescence is strongly enhanced. To validate this strategy, we first designed and synthesized an alkaline phosphatase (ALP) sensor by introducing phosphate into the squarylium dye scaffold; this sensor was able to detect ALP-labeled secondary antibodies in Western blotting analysis. Second, we synthesized a probe for β-galactosidase (widely used as a reporter of gene expression) by means of β-galactosyl substitution of the squarylium scaffold; this sensor was able to visualize β-galactosidase activity both in vitro and in vivo. Our strategy should be applicable to obtain NIR fluorescence probes for a wide range of target enzymes.

Original languageEnglish
Pages (from-to)4404-4410
Number of pages7
JournalAnalytical Chemistry
Issue number10
Publication statusPublished - 2012 May 15
Externally publishedYes

ASJC Scopus subject areas

  • Analytical Chemistry


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