Bis-Pseudoindoxyls: A Compact Fluorophore with Red-Shifted Absorption and Fluorescence for Bioimaging Applications

Area of Science:

• Organic chemistry
• Photophysics
• Cell biology

Background:

• Development of novel fluorophores is crucial for advanced imaging techniques.
• Bis-pseudoindoxyls represent a new class of single benzene-based fluorophores.
• Red-emitting dyes are highly desirable for minimizing cellular autofluorescence and enabling deeper tissue penetration.

Purpose of the Study:

• To synthesize and characterize a new class of bis-pseudoindoxyl fluorophores.
• To investigate the photophysical properties of these novel compounds.
• To evaluate their applicability in long-term live-cell imaging of lipid droplets.

Main Methods:

• Visible-light-induced radical cyclization to construct the core scaffold (14CO25NH).
• N-alkylation to tune spectral properties and introduce functional groups.
• Spectroscopic analysis (absorption and emission maxima, quantum yield determination).
• Live-cell imaging experiments using the optimized dye (14CO25Nallyl) to visualize lipid droplets.

Main Results:

• Successful synthesis of the bis-pseudoindoxyl core scaffold.
• N-alkylation led to significant bathochromic shifts in absorption and emission.
• The optimized dye 14CO25Nallyl showed absorption at 621 nm and emission at 687 nm.
• A moderate quantum yield was observed in chloroform, suitable for imaging applications.
• Demonstrated long-term live-cell imaging of lipid droplets in the red spectral region.

Conclusions:

• Bis-pseudoindoxyls are a promising new class of single benzene-based fluorophores.
• The developed red-emitting dyes are effective for long-term live-cell imaging of lipid droplets.
• These fluorophores offer potential for various biological imaging applications requiring red spectral detection.