Researchers from the Karlsruhe Institute of Technology, Germany and University of Kiev, Ukraine have developed a new photodynamic substance that may be useful for attacking tumors. Photodynamic therapy typically involves using light to create free radicals out of oxygen. A special substance is delivered to the area of treatment and light is used to activate the reaction. The problem is that tumors are typically low oxygen environments, so this way of killing cancer cells is not sufficiently effective. The team has reported in journalAngewandte Chemie the development of a new molecule, called GS-DProSw, that is activated using light but doesn’t require nearby oxygen to cause cancer death.

The molecule is deactivated by shining ultraviolet light on it. It is then delivered to the site of treatment, remaining off during this step. Once positioned, laser light can be used to turn the molecule back on and to make it toxic to nearby cells. Wherever there is no light, the molecules stay inactive and don’t damage tissue that should remain unharmed.

The technology was tested on laboratory animals showing that the therapy works quite well and only where the researchers wanted it to.

Some details from Karlsruhe Institute of Technology:

To initiate an oxygen-independent reaction in a PDT, the molecule applied has to be of cytotoxic nature. This means that it has to directly attack the tumor tissue irrespective of other reaction partners. A suitable molecule with cytotoxic properties against tumors is the biomolecule gramicidin S (GS), a natural antibiotic. To prevent it from damaging healthy tissue, the research team inserted a photo-switchable diaryl ethene segment into the ring structure. As a result, the GS-DProSw molecule can be switched between two states with the help of light: The agent can be administered in the inactive state and is activated at the desired location by specific irradiation with light. There, it attacks the surrounding tumor tissue and contrary to conventional PDT, it does not require any oxygen for this purpose.

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