ABSTRACT
HpD and its relatives, including commercial variants, were considered in the last chapter. These compounds comprise the first generation of photosensitisers. Second generation photosensitisers are those subsequently developed and are generally single substances, not necessarily porphyrins, with improved activity and selectivity. Third generation photosensitisers have an additional targetting mechanism, for example by covalent attachment to monoclonal antibodies. These are still at an early stage of development.
