Influence of Rose Bengal Dimerization on Photosensitization

Protein crosslinking photosensitized by rose Bengal (RB2-) has multiple medical applications and understanding the photosensitization mechanism can improve treatment effectiveness. To this end, we investigated the photochemical efficiencies of monomeric RB2- (RBM2-) and dimeric RB2- (RBD2-) and the optimal pH for anaerobic RB2- photosensitization in cornea. Absorption spectra and dynamic light scattering (DLS) measurements were used to estimate the fractions of RBM2- and RBD2-. RB2- self-photosensitized bleaching was used to evaluate the photoactivity of RBM2- and RBD2-. The pH dependence of anaerobic RB2- photosensitization was evaluated in ex vivo rabbit corneas. The 549 nm/515 nm absorption ratio indicated that concentrations > 0.10 mm RB contained RBD2-. Results from DLS gave estimated mean diameters for RBM2- and RBD2- of 0.70 +/- 0.02 nm and 1.75 +/- 0.13 nm, respectively, and indicated that 1 mm RB2- contained equal fractions of RBM2- and RBD2-. Quantum yields for RB2- bleaching were not influenced by RBD2- in RB2- solutions although accounting for RB2- concentration effects on the reaction kinetics demonstrated that RBD2- is not a photosensitizer. Optimal anaerobic photosensitization occurred at pH 8.5 for solutions containing 200 mm Arg. These results suggest potential approaches to optimizing RBM2--photosensitized protein crosslinking in tissues.

Automated summary

The study investigated the photochemical efficiencies of monomeric and dimeric rose Bengal photosensitized protein crosslinking and the optimal pH conditions for anaerobic photosensitization. Results showed that the optimal anaerobic photosensitization occurred at pH 8.5 in solutions containing Arg. The study also found that the concentrations of RBM2- and RBD2- were equal in 1 mm RB2- solutions.