Fluorescent proton sensors based on energy transfer

Area of Science:

• Organic Chemistry
• Photochemistry
• Biomedical Sensing

Background:

• Energy transfer cassettes are valuable for sensing applications.
• Existing pH sensors can be difficult to visualize intracellularly.
• Previous work demonstrated an energy transfer cassette for intracellular pH imaging.

Purpose of the Study:

• To investigate structure-property relationships in energy transfer cassettes.
• To explore pH-dependent fluorescence in xanthene- and BODIPY-based systems.
• To correlate photophysical properties with frontier orbital energies.

Main Methods:

• Synthesis of novel energy transfer cassettes (1-4) with varying donor units (xanthene or BODIPY).
• Photophysical characterization, including pH-dependent fluorescence measurements.
• Electrochemical analysis to determine frontier orbital energy levels.

Main Results:

• Xanthene-containing cassettes exhibited pH-dependent fluorescence (red at acidic pH, green at basic pH).
• BODIPY-containing cassettes showed efficient energy transfer largely independent of pH.
• Orbital energy level differences correlated with observed pH-fluorescence profiles.

Conclusions:

• Energy transfer cassettes with distinct donor/acceptor units offer tunable fluorescence for pH sensing.
• Orbital energy levels are critical in modulating energy transfer and photophysical properties.
• These cassettes represent a promising platform for developing new biomedical sensors.