Styrylpyridinium Derivatives for Fluorescent Cell Imaging

Area of Science:

• Organic Chemistry
• Materials Science
• Biomedical Imaging

Background:

• Styrylpyridinium (SP) compounds are explored for their spectroscopic and cell labeling properties.
• Designing SP compounds with varied electron-donating groups, linkers, and electron-withdrawing parts is crucial for tuning their optical characteristics.

Purpose of the Study:

• To synthesize and characterize novel styrylpyridinium (SP) compounds.
• To investigate their spectroscopic properties, including fluorescence and Stokes' shifts.
• To evaluate their potential as near-infrared fluorescent probes for biomedical applications.

Main Methods:

• Synthesis of various SP compounds, including geminal bis-SP derivatives.
• Spectroscopic analysis to determine fluorescence, Stokes' shifts, and photoluminescence quantum yield (PLQY).
• Cytotoxicity assays on cancerous (HT-1080, MH-22A) and normal (NIH3T3) cell lines.
• Cell staining experiments and liposome formation studies.

Main Results:

• Compounds with divinyl linkers and julolidine donors showed intense near-infrared fluorescence (~760 nm).
• SP compound 6e demonstrated high cytotoxicity to cancer cells (IC50 ~0.4-1.0 µg/mL) with moderate basal toxicity (LD50 = 477 mg/kg).
• Large Stokes' shifts were observed (up to 352 nm), with highest PLQY for compounds 6a,b (15.1%, 12.2%).
• Compound 6e localized in the cytoplasm, not nuclei, and formed 118 nm liposomes, indicating self-assembly.

Conclusions:

• Novel SP compounds possess strong near-infrared fluorescence and large Stokes' shifts.
• Compound 6e shows potential as a cytoplasm-specific fluorescent probe with self-assembly capabilities.
• These findings support the development of new biocompatible dyes for advanced biomedical imaging.