Increased cytotoxicity and phototoxicity in the methylene blue series via chromophore methylation.

The cytotoxic and photodynamic activities of the commercially-available biological stains methylene blue (MB), 1,9-dimethyl MB (Taylor's Blue) and a newly synthesised compound, 1-methyl MB, were measured against the murine mammary tumour cell line, EMT-6. Both 1-methyl MB and 1,9-dimethyl MB exhibited increased dark toxicity with concomitant higher phototoxicity compared to MB at a light dose of 7.2 J cm-2. While increasing the light dose as a function of the fluence rate increased the photocytotoxicity of MB, this had little effect on the methylated derivatives. In vitro chemical testing proved that successive methylation rendered the phenothiazinium chromophore both more resistant to reduction to its inactive leuco form, and also led to increased levels of singlet-oxygen production, thus providing a possible explanation for the increased toxicities of the methylated derivatives. Comparisons are made with the benzo[a]phenothiazinium photosensitizer, EtNBS.

[1]  R. Rees,et al.  THE PHOTOKILLING OF BLADDER CARCINOMA CELLS in vitro BY PHENOTHIAZINE DYES , 1990, Photochemistry and photobiology.

[2]  D. Valenzeno,et al.  PHYSICOCHEMICAL DETERMINANTS OF THE SENSITIZING EFFECTIVENESS FOR PHOTOOXIDATION OF NERVE MEMBRANES BY FLUORESCEIN DERIVATIVES , 1979, Photochemistry and photobiology.

[3]  N. C. Fawcett,et al.  Ground and excited state properties of some new highly water soluble N-substituted thiazine dyes for photogalvanic applications , 1983 .

[4]  A. Leo,et al.  Substituent constants for correlation analysis in chemistry and biology , 1979 .

[5]  Louis Cincotta,et al.  Novel Phenothiazinium Photosensitizers For Photodynamic Therapy , 1989, Other Conferences.

[6]  Á. Villanueva,et al.  Photodynamic damage to HeLa cell microtubules induced by thiazine dyes , 1996, Cancer Chemotherapy and Pharmacology.

[7]  Á. Villanueva,et al.  Uptake and photoeffectiveness of two thiazines in HeLa cells. , 1993, Anti-cancer drug design.

[8]  A. Rück,et al.  Intraluminal treatment of inoperable oesophageal tumours by intralesional photodynamic therapy with methylene blue , 1995, The Lancet.

[9]  H. Sloviter,et al.  In vivo staining and retardation of growth of sarcomata in mice , 1946, The Anatomical record.

[10]  Q. Peng,et al.  Biodistribution of a methylene blue derivative in tumor and normal tissues of rats. , 1993, Journal of photochemistry and photobiology. B, Biology.

[11]  A. Cincotta,et al.  Phototoxicity, redox behavior, and pharmacokinetics of benzophenoxazine analogues in EMT-6 murine sarcoma cells. , 1993, Cancer research.

[12]  J. Kelly,et al.  Photochemical interactions of methylene blue and analogues with DNA and other biological substrates. , 1993, Journal of photochemistry and photobiology. B, Biology.

[13]  M. Wainwright.  Non-porphyrin photosensitizers in biomedicine , 1997 .

[14]  A. Cincotta,et al.  NOVEL RED ABSORBING BENZO[a]PHENOXAZINIUM and BENZO[a]PHENOTHIAZINIUM PHOTOSENSITIZERS: in vitro EVALUATION , 1987, Photochemistry and photobiology.

[15]  S. Chang,et al.  The effect of methylene blue-sensitized photodynamic treatment on bladder cancer cells: a further study on flow cytometric basis. , 1993, The Journal of urology.

[16]  R. Devonshire,et al.  Methylene blue and the photodynamic therapy of superficial bladder cancer. , 1989, Journal of photochemistry and photobiology. B, Biology.

[17]  L. Strekowski,,et al.  A synthetic route to 3-(dialkylamino)phenothiazin-5-ium salts and 3,7-disubstituted derivatives containing two different amino groups , 1993 .

[18]  James B. Mitchell,et al.  Evaluation of a tetrazolium-based semiautomated colorimetric assay: assessment of chemosensitivity testing. , 1987, Cancer research.

[19]  T. Miyawaki,et al.  PHOTOACTIVE METHYLENE BLUE DYE DERIVATIVES SUITABLE FOR COUPLING TO PROTEIN , 1993 .

[20]  D. Huhn,et al.  The effect of methylene blue phototreatment on plasma proteins and in vitro coagulation capability of single‐donor fresh‐frozen plasma , 1994, Transfusion.

[21]  J. Clavilier,et al.  Organic monolayer formation at a sulphur modified gold electrode: The methylene blue/leucomethylene blue redox couple , 1987 .

[22]  S. Chang,et al.  Photoinactivation of bladder tumor cells by methylene blue: study of a variety of tumor and normal cells. , 1990, The Journal of urology.

[23]  S. Chang,et al.  Ultrastructural changes of bladder cancer cells following methylene blue-sensitized photodynamic treatment. , 1991, European urology.

[24]  A. Cincotta,et al.  Novel photodynamic effects of a benzophenothiazine on two different murine sarcomas. , 1994, Cancer research.

[25]  J. Riley.  Retardation of growth of a transplantable carcinoma in mice fed basic metachromatic dyes. , 1948, Cancer research.

[26]  R. Grainger,et al.  Is there a role for in vivo methylene blue staining in the prediction of bladder tumour recurrence? , 1995, British Journal of Urology.