Exploring 4-Amino-1,8-Naphthalimides: Lifetime-Based Sensing of Chemical Micro-Environments.

Area of Science:

• Photochemistry
• Biophysical chemistry
• Chemical biology

Background:

• Fluorescence lifetime imaging microscopy (FLIM) is crucial for studying biological systems.
• Limited availability of suitable fluorescent probes hinders FLIM applications.
• Naphthalimide derivatives are known for their photophysical properties.

Purpose of the Study:

• To synthesize and characterize novel 4-amino-1,8-naphthalimide derivatives as environment-sensitive fluorescent probes.
• To evaluate their photophysical properties, including solvatochromism and fluorescence lifetime sensitivity to polarity and viscosity.
• To assess their potential for detecting microenvironmental changes in biological samples, such as disease states.

Main Methods:

• Synthesis of a library of fifteen 4-amino-1,8-naphthalimides with diverse amine substituents.
• Photophysical characterization including absorption, emission spectra, solvatochromism, and fluorescence lifetime measurements.
• Application of selected probes (compounds 13 and 17) to rat serum samples to assess their sensitivity to biological microenvironments.

Main Results:

• The synthesized naphthalimides exhibited strong solvatochromism and varied fluorescence lifetimes.
• Compound 13 showed high brightness and significant fluorescence lifetime sensitivity to polarity.
• Compound 13 differentiated between healthy and acute pancreatitis rat serum samples based on polarity changes, while compound 17 showed no viscosity sensitivity.

Conclusions:

• 4-amino-1,8-naphthalimides are promising environment-sensitive fluorescent probes, particularly for polarity sensing.
• Compound 13 demonstrates potential for fluorescence lifetime-based diagnostics of disease-related microenvironmental changes in biological fluids.
• This study expands the understanding of naphthalimide photophysics and their utility in bioimaging.