• ​Skin cancers due to overexposure to the sun are rising sharply. The WHO has counted two to three million cases per year. These cancers are sometimes treated by local ablation therapy. Photodynamic therapy was invented to avoid this type of treatment. A cream is applied to the skin containing an active ingredient that attacks and destroys the tumoral cells under the effect of light.

• But this technique is not efficacious against deep lesions. CEA-Leti and Inserm have overcome this limitation by developing a patch with micro needles measuring between 400 and 750 microns in length. These needles reach the interface between the epidermis and the dermis.
  

The patch and the needles, which take effect in just 1 hour, are made of a material that combines water, a pharmaceutical-grade polymer and the active ingredient, explains Mathilde Champeau, the doctoral student in charge of the project. The patch is placed on the skin and exposed to light from LEDs emitting at 635 nm. It dissolves in less than 1 hour. The active ingredient is metabolized by the tumoral cells, then attacks and destroys them under the effect of the light. 

• While the concept of the patch may seem simple, it has taken several years to define its characteristics: the choice of polymer and active ingredient, the development of a "clean" collective manufacturing process, the spacing and shape of the needles, which must not be deformed when applied to the skin, despite their tiny size.

• The small size of the needles means that the treatment is painless, which prevents patients from feeling apprehensive. But they will have to wait for another 3 to 5 years for the clinical trials of the new patch to be completed.
  

*the Inserm OncoThAI unit, which is part of Lille university hospital and Lille university