ABSTRACT

In section 4.3.2(vi) reasons were advanced to explain the major emphasis placed on PDT sensitisers related to the porphyrins. However, these reasons are not overwhelm­ ing, and certainly do not prevent consideration of photosensitisers based on other chromophores, as this chapter will show. Indeed, histochemistry is based on the differential staining of tissues, including tumour tissues, with a variety of organic dyes. It has to be said, however, that in many cases the proposed PDT sensitisers, for example the xanthenes, have simply been selected from what was available on the shelf, and have not been subjected to thoughtful structural variation and bioassay to sort out the best therapeutic candidate.