Influence of Rose Bengal Dimerization on Photosensitization

Area of Science:

• Photochemistry
• Biomedical Engineering
• Ophthalmology

Background:

• Protein crosslinking using rose Bengal (RB) photosensitization has significant medical applications.
• Understanding the RB photosensitization mechanism is crucial for enhancing treatment efficacy.
• Investigating the photochemical properties of RB monomers and dimers is essential for optimizing its use.

Purpose of the Study:

• To determine the photochemical efficiencies of monomeric RB (RB_M^2-) and dimeric RB (RB_D^2-).
• To identify the optimal pH for anaerobic RB photosensitization in corneal tissue.
• To elucidate the role of RB dimers in the photosensitization process.

Main Methods:

• Absorption spectroscopy and dynamic light scattering (DLS) to quantify RB monomer and dimer fractions.
• RB self-photosensitized bleaching assays to evaluate photoactivity.
• Ex vivo rabbit cornea experiments to assess pH-dependent anaerobic photosensitization.

Main Results:

• Dimeric RB (RB_D^2-) was identified as non-photosensitizing, with monomeric RB (RB_M^2-) being the active species.
• Absorption spectra and DLS confirmed the presence of RB dimers at concentrations above 0.10 mM.
• Optimal anaerobic photosensitization in corneal tissue occurred at pH 8.5, particularly with arginine (Arg).

Conclusions:

• Dimeric RB does not contribute to photosensitization; monomeric RB is the effective photosensitizer.
• The optimal pH for anaerobic RB-photosensitized protein crosslinking in corneal tissue is 8.5.
• These findings provide a basis for optimizing RB-mediated treatments in medical applications.