Tracking bacterial infection of macrophages using a novel red-emission pH sensor

Yuguang Jin, Yanqing Tian, Weiwen Zhang, Sei Hum Jang, Alex K Y Jen, Deirdre Meldrum

Research output: Contribution to journalArticlepeer-review

25 Scopus citations


The relationship between bacteria and host phagocytic cells is key to the induction of immunity. To visualize and monitor bacterial infection, we developed a novel bacterial membrane permeable pH sensor for the noninvasive monitoring of bacterial entry into murine macrophages. The pH sensor was constructed using 2-dicyanomethylene-3-cyano-4,5,5-trimethyl-2,5-dihydrofuran (TCF) as an electron-withdrawing group and aniline as an electron-donating group. A piperazine moiety was used as the pH-sensitive group. Because of the strong electron-donating and -withdrawing units conjugated in the sensing moiety M, the fluorophore emitted in the red spectral window, away from the autofluorescence regions of the bacteria. Following the engulfment of sensor-labeled bacteria by macrophages and their subsequent merger with host lysosomes, the resulting low-pH environment enhances the fluorescence intensity of the pH sensors inside the bacteria. Time-lapse analysis of the fluorescent intensity suggested significant heterogeneity of bacterial uptake among macrophages. In addition, qRT-PCR analysis of the bacterial 16 S rRNA gene expression within single macrophage cells suggested that the 16 S rRNA of the bacteria was still intact 120 min after they had been engulfed by macrophages. A toxicity assay showed that the pH sensor has no cytotoxicity towards either E. coli or murine macrophages. The sensor shows good repeatability, a long lifetime, and a fast response to pH changes, and can be used for a variety of bacteria.

Original languageEnglish (US)
Pages (from-to)1375-1384
Number of pages10
JournalAnalytical and bioanalytical chemistry
Issue number3
StatePublished - Oct 2010


  • Bacterial infection
  • Mouse macrophage
  • Red emitter
  • pH sensor

ASJC Scopus subject areas

  • Analytical Chemistry
  • Biochemistry


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