[Photodynamic diagnosis and preoperative chemotherapy for biliary tract cancer]

Cancer cells synthesize substantial amounts of protoporphyrin IX( PPIX) from aminolevulinic acid( ALA). PPIX emits red fluorescence when illuminated under blue light. Photodynamic diagnosis (PDD), based on this phenomenon, is currently used; however, various microorganisms also show the same fluorescence with ALA when illuminated under blue light, resulting in false-positive PDD results.

To avoid misdiagnosis, we incorporated novel systems into the PDD system. ALA, blue light (wavelength, 380-450 nm), different kinds of cell lines, and bacteria were used in this in vitro study. We used a 70% deacetylated chitosan solution (DAC-70 Sol), developed in-house, as an antibacterial agent and prepared ALA/DAC-70 Sol, used as a novel photoimaging agent. The antibacterial function of ALA/DAC-70 Sol was examined in vitro, and the photodiagnostic effects on using the novel systems were clinically evaluated using bile from patients with biliary tract cancer.

DAC-70 Sol demonstrated an effective bactericidal function in vitro. Red fluorescence could clearly be identified, enabling the detection of cancer cells in the bile using ALA/DAC-70 Sol.

Our novel systems have a great potential for use in clinical photodynamic cytodiagnosis( PDCD), which plays an important role in preoperative cancer chemotherapy.