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

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

Zinc octa-n-alkyl phthalocyanines in photodynamic therapy: photophysical properties, accumulation and apoptosis in cell cultures, studies in erythrocytes and topical application to Balb/c mice skin

Two octa-substituted phthalocyanines, namely 1,4,8,11,15,18,22,25-octakis(decyl) phthalocyaninato zinc(II) (ZnODPc) and 1,4,8,11,15,18,22,25-octakis(pentyl) phthalocyaninato zinc(II) (ZnOPPc), were investigated for their use in photodynamic therapy ( PDT) after topical application. Both substances exhibited favourable properties as photosensitisers in vitro: absorption maxima around 700 nm with absorption coefficients of about 190000 (M-1 cm(-1)), a singlet oxygen quantum yield of 0.47 +/- 0.02 (ZnODPc), and good accumulation in keratinocytes and. broblasts. Cell death after phthalocyanine-photosensitisation appeared to occur mainly via apoptosis. The in vivo experiments demonstrated a good accumulation of the phthalocyanines after topical application in a tetrahydrofuran - azone formulation onto the dorsal skin of Balb/c mice: [(4.6 - 4.7) +/- 1.0]% of deposited dye could be recovered after 3 h from deposition. ZnODPc showed significantly better skin-photosensitising properties than ZnOPPc and is therefore a potential candidate for the treatment of psoriasis