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Photodynamic therapy in cancer treatment

Discovery of new effective cancer treatments is an important priority of the European Research Area. Photodynamic therapy (PDT) is a promising approach to treat cancer using the action of molecular oxygen.
Photodynamic therapy in cancer treatment
Photosensitizers are molecules that induce a chemical change in another molecule upon absorption of light. This class of compounds is employed in PDT, a well-recognised process for the treatment of cancer and other diseases. The PDT mechanism involves penetration of the drug into the cancer cell followed by binding to a biomolecule, absorption of light energy, oxidation of the biomolecule by the reactive oxygen leading to cell death.

Methylene blue (MB) is a phenothiazine-based dye that has shown promising results in PDT treatment. The noncovalent binding of MB to DNA was experimentally analysed in the past. The EU-funded PHOTOBLUE (Towards rational design of cancer therapeutic drugs: a first principles study of the photosensitization mechanism of methylene blue (Photoblue)) project focused on the in depth analysis of MB interactions with DNA to facilitate the rational design of PDT drugs.

Small and planar molecules like MB can bind to DNA in four different ways. Through simulation analysis, researchers identified intercalation as the most favourable binding mode.

A proper electronic distribution of the photosensitizer is necessary for efficient excitation energy transfer to oxygen (intersystem crossing) and initiation of DNA damage. At the next stage of the project, the reorganisation of MB electrons after absorption of light was studied. Simulation analysis predicted that intersystem crossing of the MB intercalated into DNA would have more favourable results than when the drug is in aqueous solution. In addition, the analysis highlighted the possibilities of structural modifications of MB to increase the efficiency of intersystem crossing.

In conclusion, PHOTOBLUE activities helped understand PDT mechanisms at the molecular level. This knowledge is going to assist in the design of new and efficient photosensitizers for cancer treatment.

Related information


Photodynamic therapy, cancer, photosensitizer, methylene blue, PHOTOBLUE, simulation analysis
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