Chalcogenoxanthylium photosensitizers for the photodynamic purging of blood-borne viral and bacterial pathogens.

Thio- and selenoxanthylium dyes were prepared by the addition of 2-lithiothiophene, 4-N,N-dimethylaminophenylmagnesium bromide, and 1-naphthylmagnesium bromide to the appropriate 2,7-bis-N,N-dimethylaminochalcogenoxanthen-9-one, followed by dehydration and ion exchange to the chloride salts. The corresponding chalcogenoxanthylium dyes were evaluated as photosensitizers for the inactivation of intracellular and extracellular virus in red blood cell suspensions and for the inactivation of selected strains of gram (+) and gram (-) bacteria in red blood cell suspensions. Selected combinations of photosensitizer and light gave >6 log10 inactivation of intracellular and extracellular virus, and >4 log10 inactivation of extracellular bacteria with varying levels of hemolyis, following a 42-day storage of red blood cell suspensions. Photocleavage experiments with plasmid DNA and the chalcogenoxanthylium dyes suggested the genomic material contained in the virus and in the bacteria as one possible target for the photodynamic action of some of these dyes.