A fluoran-based viscosity probe with high-performance for lysosome-targeted fluorescence imaging

Area of Science:

• Chemical Biology
• Biophysical Chemistry
• Fluorescence Spectroscopy

Background:

• Viscosity is a critical biophysical parameter influencing cellular functions.
• Developing selective and sensitive probes for viscosity detection is essential for biological research.
• Existing probes may lack specificity or exhibit pH-dependent responses.

Purpose of the Study:

• To synthesize and characterize a new fluorescent probe, Lyso-Fl, for viscosity sensing.
• To evaluate the probe's response to viscosity changes and its selectivity.
• To assess the probe's applicability in cellular imaging for monitoring viscosity variations.

Main Methods:

• Facile preparation of Lyso-Fl via esterification of spironolactone fluoran dye Rdi with ethanol.
• Characterization of fluorescence response to varying viscosity levels (1.01 cP to 1256 cP).
• Assessment of pH independence and selectivity among biological species.
• Cytotoxicity evaluation and application in cell imaging of dexamethasone-stimulated viscosity changes.

Main Results:

• Lyso-Fl exhibits significant fluorescence enhancement with increasing viscosity.
• Both emission intensity and fluorescence lifetime show linear correlation with viscosity.
• The probe demonstrates selective viscosity response and pH independence (pH 1-10).
• Lyso-Fl shows low cytotoxicity and effective lysosome-targeting for cell imaging.

Conclusions:

• Lyso-Fl is a novel, viscosity-selective fluorescent probe with excellent performance.
• The probe's linear response and pH independence make it reliable for viscosity measurements.
• Lyso-Fl is suitable for monitoring cellular viscosity changes, particularly in lysosomes, with low cytotoxicity.