Photodynamic therapy of Porphyromonas gingivalis via liposome-encapsulated sensitizers.

Photodynamic therapy exploits the light-activation of a photosensitizer to cause cytotoxicity. Liposomes can be used to deliver hydrophobic photosensitizers to bacteria. Positively charged dioleoyltrimethylammoniumpropane:palmitoyloleoylphosphatidylcholine (1:1) liposomes bound quantitatively to the periodontal pathogen, Porphyromonas gingivalis. Following illumination, free and liposomal zinc phthalocyanine reduced the colony-forming unit (CFU) to 65 percent and 23 percent of controls, respectively. Thus, localization of the photosensitizer at the surface of bacteria via liposome binding enhanced the photodynamic cytotoxicity of zinc phthalocyanine.