5. Conclusion

As we have seen, the gradual understanding of the photophysical mechanisms behind the photodynamic effect has, since the 1970s, led to systematic molecular engineering work that has resulted in significant optimization of the spectroscopic properties of photosensitizers. At the same time, advances in light source engineering - not detailed in this article, but just as important to the success of a treatment - have helped to make PDT a credible and very often advantageous alternative to other therapeutic approaches to cancer treatment. However, the clinical use of PDT is still limited, due to the difficulty of treating deep-seated tumours, and to certain undesirable effects (photosensitization) linked to the distribution of the photosensitizer outside the tumour tissue, which require certain precautions. A major challenge for the future will be to develop photosensitizers capable of resolving...