Fig. 6. Examples of multifunctional photodynamic dyes.

In addition to its standalone photodynamic therapy function, cyanine dyes can exhibit other therapeutic and diagnostic capabilities. Chimeric compounds 14a, 14b, and 16 are cleaved to form active hemicyanine photosensitizers 15a, 15b, and 17, as well as cytostatic drugs. The conjugation of the phenanthrimidazole Ru²⁺ complex with heptamethine dyes (18a, 18b, and 19) demonstrates enhanced efficacy under hypoxic conditions (thank to cytotoxicity and activation of type I mechanism) compared to the original cyanine dye. The fusion of porphyrin with the heptamethine structural motif (20) results in the development of a potent theragnostic photosensitizer. Furthermore, the theranostic heptamethine and hemicyanine dyes (21 and 23) can also serve as fluorescence probes for cysteine and aminopeptidase, respectively.