Methylene blue mediated photodynamic therapy in experimental colorectal tumors in mice.
Methylene blue (MB+) is a well-known dye in medicine and has been discussed as an easily applicable drug for the topical treatment during photodynamic therapy (PDT). The therapeutic response of MB+ was investigated in vivo by local injection of MB+ in a xenotransplanted subcutanous tumor (adeno-carcinoma, G-3) in female nude mice. MB+ in a concentration of 1% was applied both undiluted and diluted to 0.1 and 0.01% with isotonic sodium chloride. Treatment with 1% MB+ and subsequent irradiation at 662 nm with 100 J/cm2 led to complete tumor destruction in 79% of the treated animals. A decrease of the fluence rate from 100 to 50 mW/cm2 increased the phototoxic response as well as fractionated light application. Small sensitizer concentrations reduced the PDT effect significantly. It seems that the light induced reaction of MB+ could be correlated with the rapid production of reactive oxygen species. Below a threshold dose of MB+ oxidative damage of the tissue is prevented. However, above this dose, as a point of no return, MB+ acts as an extremely potent oxidant.
Orth
K
K
Department of General Surgery, University of Ulm, Chirurgische Klinik I, Germany.
Beck
G
G
Genze
F
F
Rück
A
A
D000230:Adenocarcinoma / Q000188:drug therapy*; D000818:Animals; D015179:Colorectal Neoplasms / Q000188:drug therapy*; D004195:Disease Models, Animal; D005260:Female; D006801:Humans; D008751:Methylene Blue / Q000627:therapeutic use*; D051379:Mice; D008819:Mice, Nude; D010778:Photochemotherapy / Q000379:methods*; D017319:Photosensitizing Agents / Q000627:therapeutic use*
D017319:Photosensitizing Agents; D008751:Methylene Blue