Methylene blue derivatives - suitable photoantimicrobials for blood product disinfection?

Photodynamic antimicrobial agents based on the well-established phenothiazi nium biological stain methylene blue offer a simple method for the inactiva tion or destruction of pathogens contained in donated blood and blood produ cts. The technique is currently concentrated on viruses and the disinfectiv e procedure can be carried out in blood bags using basic low-power light so urces. Pathogens of the bacterial, yeast and protozoal classes are also sus ceptible to phenothiaziniums. The photoantimicrobial mode of action is usua lly via oxidative damage to cellular components, either due to redox reacti ons between the agent and a biomolecular target or by the action of reactiv e oxygen species generated in situ by photodynamic action. The targeting of various microbial species is discussed in relation to the physicochemical make-up of the photosensitizers, and future directions are suggested. (C) 2 000 Elsevier Science B.V. and International Society of Chemotherapy. All ri ghts reserved.