A photosensitising dye for use in a targeted and non-invasive form of cancer therapy has been developed by scientists in Turkey.

Engin Akkaya and colleagues at the Middle East Technical University and at Hacettepe University have synthesised and assessed the suitability of a new class of water-soluble dyes for use in photodynamic therapy (PDT). 

PDT, still a relatively young technique, uses a light-sensitive drug (or photosensitiser) and visible light energy to produce reactive oxygen species which attack surrounding cancer cells. The light used for PDT can come from a laser or other sources such as light-emitting diodes (LEDs) and is preferably red in colour since this penetrates cell tissues better than blue light. 

The photosensitiser, which is introduced into the cells before light is shone onto the tumour, must have certain properties to make it suitable and successful. For example, it must absorb light within a certain wavelength range for the method not to be actively harmful. This is known as the therapeutic window. It must absorb strongly so that it can efficiently produce the reactive oxygen species needed to attack the surrounding cancer cells and it has to be ineffective until exposed to light. In addition, a prime requirement for use in human cells is that it is water-soluble. 

There are current PDT sensitisers which do not satisfy all of these requirements. However, all of these requirements appear to be met by the dye developed by Akkaya's group, and this new dye has 'spectacular photoinduced cytotoxicity at very low concentrations and even under low fluence rate LED irradiation,' said Akkaya. 

The lower dose and light illumination levels required as a result of the improved efficiency of the photosensitiser can only benefit the further development of non-invasive and less toxic forms of targeted cancer therapy. 

Sue Askey