Acidic pH-Activatable Visible to Near-Infrared Switchable Ratiometric Fluorescent Probe for Live-Cell Lysosome Targeted Imaging

Ayan Mukherjee, Pranab Chandra Saha, Rabi Sankar Das, Tapas Bera, Samit Guha

Research output: Contribution to journalArticlepeer-review

29 Scopus citations

Abstract

Here, we have designed and synthesized acidic pH-activatable visible to NIR switchable ratiometric pH-sensitive fluorescent dye. The design consists of a cell-permeable organic probe containing a lysosome targeting morpholine functionality and an acidic pH-activatable oxazolidine moiety. The visible closed oxazolidine form (λabs 418 nm) can be switched to the highly conjugated NIR Cy-7 form (λabs 780 nm) through ring opening of the oxazolidine moiety at acidic pH. This switching of the ratiometric fluorescent probe is highly reversible and can be controlled by pH. NMR, UV/vis, and fluorescence spectroscopies allowed monitoring of pH switching behavior of the probe. This bioresponsive in situ acidic organelle activatable fluorophore showed reversible pH-switchable ratiometric optical properties, high photostability, huge bathochromic emission shift of 320 nm from basic to acidic pH, off-to-on narrow NIR absorption and emission bands with enhanced molar extinction coefficient at lysosomal pH, good quantum yield, low cytotoxicity, and targeted imaging ability of live cell lysosomes with ideal pKa. The report demonstrated ratiometric imaging with improved specificity of the acidic lysosome while minimizing signals at the NIR region from nontargeted neutral or basic organelles in human carcinoma HeLa and A549 as well as rat healthy H9c2(2-1) live cells, which is monitored by confocal laser scanning microscopy.

Original languageEnglish
Pages (from-to)2141-2146
Number of pages6
JournalACS Sensors
Volume6
Issue number6
DOIs
StatePublished - 25 Jun 2021
Externally publishedYes

Bibliographical note

Publisher Copyright:
© 2021 American Chemical Society.

Keywords

  • cyanine dye
  • live-cell imaging
  • lysosome targeting
  • pH switching
  • ratiometric probe

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