Influence of Rose Bengal Dimerization on Photosensitization.

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