Evaluation of the Photostability and Photodynamic Efficacy of Rose Bengal Loaded in Multivesicular Liposomes

Purpose: Rose Bengal (RB) is a potential photodynamic sensitizer in anticancer therapy. The purpose of this study was to prepare multivesicular liposomes (MVL) loaded with RB to enhance its photostability and intracellulaer photodynamic efficacy.
Methods: Four MVL-RB formulations were prepared by reverse phase evaporation technique using a double emulsion method. The photostability of RB in phosphate buffer and in MVL was studied by monitoring the change in its absorption spectra at different time points following photoirradiation at 550 nm. Photodynamic cytotoxicity, intracellular uptake and localization of the most photostable MVL-RB were studied on baby hamster kidney fibroblasts to evaluate its photodynamic efficacy, compared with free RB.
Results: MVL-RB demonstrated significantly slower photodegradation rates with 10-fold extended halflife compared with free RB in buffer (p < 0.05). The degradation followed pseudo first order kinetics. Photodynamic cytotoxicity studies revealed that MVL-RB increased cell mortality by 1.6 -2.5-fold, compared to free RB, and this could be attributed to its enhanced intracellular uptake and different localization pattern in the cell, in addition to increased photostability.
Conclusion: Loading RB in MVL is a promising approach to improve the photodynamic efficacy of RB, by enhancing its photostability and delivery into cells.

Keywords
Rose Bengal, Photodynamic therapy, Multivesicular liposomes, Photostability, Phototoxicity