abstract
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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¿ (RB
M 2¿) and dimeric RB2¿ (RBD 2¿) 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 RBM 2¿ and RBD 2¿. RB2¿ self-photosensitized bleaching was used to evaluate the photoactivity of RBM 2¿ and RBD 2¿. 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 RBD 2¿. Results from DLS gave estimated mean diameters for RBM 2¿ and RBD 2¿ of 0.70 ± 0.02 nm and 1.75 ± 0.13 nm, respectively, and indicated that 1 mm RB2¿ contained equal fractions of RBM 2¿ and RBD 2¿. Quantum yields for RB2¿ bleaching were not influenced by RBD 2¿ in RB2¿ solutions although accounting for RB2¿ concentration effects on the reaction kinetics demonstrated that RBD 2¿ 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 RBM 2¿-photosensitized protein crosslinking in tissues. © 2021 American Society for Photobiology.