An ESIPT based naphthalimide chemosensor for visualizing endogenous ONOO^- in living cells

Area of Science:

• Chemical Sensing
• Biomedical Imaging
• Fluorescence Spectroscopy

Background:

• Peroxynitrite (ONOO-) is a reactive nitrogen species implicated in various physiological and pathological processes.
• Selective and sensitive detection of ONOO- in biological systems is crucial for understanding its role.
• Existing methods for ONOO- detection often lack specificity or require complex experimental setups.

Purpose of the Study:

• To design and synthesize a novel naphthalimide-based chemosensor (N-CBT) for selective detection of peroxynitrite (ONOO-) in living cells.
• To investigate the sensing mechanism based on Excited-State Intramolecular Proton Transfer (ESIPT).
• To evaluate the performance of N-CBT for quantitative and qualitative visualization of ONOO- in biological environments.

Main Methods:

• Synthesis of the naphthalimide chemosensor N-CBT incorporating 2-benzothiazoleacetonitrile.
• Spectroscopic characterization (UV-Vis absorption and fluorescence emission) in aqueous solutions.
• Computational studies to elucidate the ESIPT mechanism and tautomeric transformations.
• Cell-based assays to demonstrate the selective imaging of endo/exogenous peroxynitrite in living cells.

Main Results:

• N-CBT exhibits a unique eight-membered ring hydrogen bonding configuration facilitating ESIPT.
• The chemosensor displays efficient green fluorescence regeneration upon reaction with ONOO-, with a 34-fold enhancement at 518 nm.
• A good linear response was observed for ONOO- detection in the range of 1–14 μM, with a low detection limit of 37 nM.
• Successful application of N-CBT for selective visualization of cellular peroxynitrite in living cells.

Conclusions:

• N-CBT is a highly effective chemosensor for selective and sensitive detection of peroxynitrite.
• The ESIPT mechanism enables efficient fluorescence turn-on response for ONOO- visualization.
• N-CBT demonstrates significant potential for real-time monitoring of peroxynitrite in biological research and diagnostics.