Hypocrellin-B acetate as a fluorogenic substrate for enzyme-assisted cell photosensitization

Area of Science:

• Biochemistry
• Cell Biology
• Photochemistry

Background:

• Photosensitizing molecules (PSs) are crucial in photodynamic therapy.
• Chemical modification of PSs can alter their photophysical properties and cellular accumulation.
• Enzyme-cleavable substituents can enable targeted PS activation within cells.

Purpose of the Study:

• To investigate the photophysical properties and cellular interactions of native Hypocrellin-B (HypB) and its acetylated derivative (HypB-Ac).
• To compare the intracellular accumulation, spectral properties, and phototoxicity of HypB and HypB-Ac in HeLa cells.
• To assess the impact of HypB-Ac treatment on cellular organelles after irradiation.

Main Methods:

• Synthesis and characterization of HypB and HypB-Ac.
• Spectroscopic analysis of absorption and fluorescence properties.
• Cellular incubation studies with HeLa cells to monitor intracellular accumulation via fluorescence.
• Dark toxicity and phototoxicity assays upon irradiation at 480 nm.
• Microscopic examination of cellular organelle integrity post-treatment.

Main Results:

• HypB-Ac exhibited altered absorption and fluorescence spectra compared to HypB.
• Intracellular accumulation of HypB-Ac was significantly higher than HypB in HeLa cells within 15 minutes.
• HypB-Ac demonstrated markedly higher phototoxicity than HypB upon 480 nm irradiation.
• Treatment with HypB-Ac led to significant disorganization of cytoplasmic organelles, including the endoplasmic reticulum, Golgi apparatus, and microtubules.

Conclusions:

• Acetylation of HypB enhances its cellular internalization and accumulation via membrane trafficking.
• HypB-Ac serves as an effective fluorogenic substrate, allowing monitoring of enzyme hydrolysis.
• The enhanced phototoxicity and organelle disruption by HypB-Ac suggest improved efficacy for photodynamic applications.