Absorption and emission spectral shifts of rose bengal associated with DMPC liposomes

Rose bengal is a water-soluble xanthene dye that is currently used in ophthalmology for the diagnosis of dry eyes. Although the dye is also a potential photosensitizer for photodynamic therapy of tumors, owing to insufficient lipophilicity and tumor accumulation, the clinical application of rose bengal in photodynamic therapy has been hampered. Liposomal encapsulation was seen as a promising approach to overcome these disadvantages, to which end, the spectral properties of the dye in the presence of materials for liposome preparation were studied. The presence of phospholipid influenced the spectral properties of the dye, probably due to the establishment of an equilibrium between monomeric and dimeric forms of the dye, since the photophysical properties of rose bengal depend strongly on its environment. The liposomal encapsulation of the dye generates stronger emission than the free form of the colorant; increased lipid:dye ratio further enhances this emission.