Journal of Fluorescence

, Volume 26, Issue 6, pp 2079–2086 | Cite as

A Novel Water-soluble Ratiometric Fluorescent Probe Based on FRET for Sensing Lysosomal pH

  • Guang-Jie Song
  • Su-Yun Bai
  • Jing Luo
  • Xiao-Qun Cao
  • Bao-Xiang Zhao


A new ratiometric fluorescent probe based on Förster resonance energy transfer (FRET) for sensing lysosomal pH has been developed. The probe (RMPM) was composed of imidazo[1,5-α]pyridine quaternary ammonium salt fluorophore as the FRET donor and the rhodamine moiety as the FRET acceptor. It’s the first time to report that imidazo[1,5-α]pyridine quaternary ammonium salt acts as the FRET donor. The ratio of fluorescence intensity of the probe at two wavelengths (I424/I581) changed significantly and responded linearly toward minor pH changes in the range of 5.4–6.6. It should be noted that it’s rare to report that a ratiometric pH probe could detect so weak acidic pH with pKa = 6.31. In addition, probe RMPM exhibited excellent water-solubility, fast-response, all-right selectivity and brilliant reversibility. Moreover, RMPM has been successfully applied to sensing lysosomal pH in HeLa cells and has low cytotoxicity.


Ratiometric fluorescent probe Water-solubility Imidazo[1,5-α]pyridine quaternary ammonium salt Lysosomal pH Image 



This study is supported by the Natural Science Foundation of Shandong Province (ZR2014BM004) and (ZR2013BM020).

Supplementary material

10895_2016_1902_MOESM1_ESM.docx (1.6 mb)
ESM 1 (DOCX 1603 kb)


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Copyright information

© Springer Science+Business Media New York 2016

Authors and Affiliations

  1. 1.School of Chemical EngineeringTaishan Medical UniversityTai’anChina
  2. 2.Institute of Organic Chemistry, School of Chemistry and Chemical EngineeringShandong UniversityJinanChina
  3. 3.Institute of Developmental Biology, School of Life ScienceShandong UniversityJinanChina
  4. 4.School of Life ScienceTaishan Medical UniversityTai’anChina

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