Optical Membrane Control with Red Light Enabled by Red-Shifted Photolipids

Area of Science:

• Biophysics
• Materials Science
• Synthetic Biology

Background:

• Photoswitchable phospholipids (photolipids) with azobenzene groups offer light-controlled manipulation of lipid bilayers.
• Conventional azobenzene photolipids are limited to UV-A/blue light, hindering biophysical and photopharmaceutical applications.
• A need exists for photolipids responsive to longer, tissue-penetrating wavelengths.

Purpose of the Study:

• To synthesize and characterize novel photoswitchable phospholipids responsive to red light.
• To investigate the effects of red light-induced isomerization on liposome properties.
• To demonstrate the utility of these red-light-responsive photolipids in controlling membrane dynamics and vesicle morphology.

Main Methods:

• Synthesis of tetra-ortho-chloro azobenzene-substituted phosphatidylcholine (t-azo-PC).
• Preparation of nano- and micrometer-sized liposomes from t-azo-PC.
• Photoisomerization studies using irradiation with red light (≥630 nm).
• Characterization of membrane properties using small-angle X-ray scattering and dynamic light scattering.
• Observation of liposome shape transitions and vesicle division under controlled light conditions.

Main Results:

• t-azo-PC liposomes undergo photoisomerization upon irradiation with red light (≥630 nm).
• Photoswitching significantly alters membrane fluidity and mechanical properties.
• Minimal changes in bilayer thickness and area expansion were observed.
• Controlled light exposure induced shape transitions (budding, pearling) and vesicle division.
• Photostationary state and photoswitching efficiency were tunable with specific wavelengths.

Conclusions:

• Tetra-ortho-chloro azobenzene-substituted phosphatidylcholine (t-azo-PC) represents a novel class of photolipids responsive to red light.
• These red-light-responsive photolipids enable precise, light-triggered control over liposome morphology and membrane dynamics.
• t-azo-PC offers significant potential as a nanophotonic tool for synthetic biology and advanced biomedical applications.