Photoswitchable Fluorescent Hydrazone for Super-Resolution Cell Membrane Imaging.

Area of Science:

• Molecular probes
• Super-resolution microscopy
• Photochemistry

Background:

• Super-resolution microscopy requires molecular probes with controllable "ON" and "OFF" states.
• Previous hydrazone photochrome (1) had limitations: low brightness and UV-dependent switching.

Purpose of the Study:

• Optimize hydrazone photochromes for enhanced brightness and visible light photoswitching.
• Develop novel probes for super-resolution imaging of cellular structures.

Main Methods:

• Structural modification of hydrazone photochrome (1) by incorporating rigid electron-donating groups (azetidine, difluoroazetidine, julolidine).
• Design of electron push-pull hydrazones (5-7) with varying electron-withdrawing groups (cyano, nitro, dicyanovinyl).
• Development of a fluorogenic probe (8) activated by visible light.

Main Results:

• Rigidifying electron-donating groups enhanced brightness, particularly in julolidine derivative (4).
• Push-pull hydrazones (5-7) showed red-shifted photoswitching wavelengths and improved brightness.
• Fluorogenic probe (8) enabled super-resolution imaging with high localization precision (17-25 nm).

Conclusions:

• Optimized hydrazone structures significantly improve brightness and photoswitching properties.
• Developed probes are suitable for advanced super-resolution microscopy applications.
• Visible light-activated probe (8) demonstrates potential for live and fixed-cell imaging.