A ratiometric lysosomal pH chemosensor based on fluorescence resonance energy transfer

• A new FRET based chemosensor NR1 was designed and synthesized.
• NR1 provided selective and ratiometirc fluorescence response for H+ over biological species.
• NR1 can localize in lysosomes and monitor live cell pH changes in vitro.

In this work, we presented a naphthalimide–rhodamine based fluorescence resonance energy transfer system (FRET) NR1 as a ratiometric and intracellular pH probe, in which 1,2,3-triazole was identified as an ideal bridge and biocompatibility. It could selectively monitor pH variations in methanol/HEPES solution at room temperature. When the pH changed from 6.20 to 2.00, both the fluorescence intensities at 580 nm and the intensity ratios, R (I580 nm/I538 nm) increased, which allowed the detection of pH changes by both normal fluorescence and ratiometric fluorescence methods. The observation is consistent with the increased FRET from the 1,8-naphthalimide (donor) to the ring-opened, colored form of rhodamine (acceptor). Moreover, as NR1 is lysosomal with low cytotoxicity, it will be helpful for investigating the pivotal role of H+ in a biological context, especially in lysosomes through direct intracellular imaging.

A new FRET based chemosensor NR1 could provide selective and ratiometirc fluorescence detection for H+ over biological metal ions and amino acids in vivo, and localize in lysosomes and monitor live cell pH changes.Figure optionsDownload as PowerPoint slide