Phenothiazinium derivatives for pathogen inactivation in blood products

Phenothiazine-based photosensitisers have been employed in photoantimicrobial research for nearly 80 years, both as lead and novel compounds. However, the main structural variations have mainly involved the auxochromic side chains and little has been reported concerning either peripheral substitution or structures with chromophores other than those of the phenothiazinium or annelated benzo[ a]phenothiazinium type. In terms of application, the phenothiazinium series has featured commonly in cytology and cytopathology, as well as in haematological staining. The current work covers the evolution of improved photosensitisers based on the phenothiazine ring system, with particular reference to the field of pathogen inactivation, and the structural alteration of lead compounds such as methylene blue and Nile blue to yield improved photosensitisers for this important aspect of blood product safety.