Phototoxicity against tumor cells and Sindbis virus by an octahedral rhodium bisbipyridyl complex and evidence for the genome as a target in viral photoinactivation

An octahedral rhodium complex (cis-dichloro(dipyrido3,2a-2',3'c]phenazine)(1,10-phenanthroline)rhodium(III) chloride; DPPZPHEN) has been prepared that can penetrate tumor cell membranes and the Sindbis viral capsid. The compound is phototoxic to these entities when irradiated with UVA light. Model studies with calf thymus and supercoiled plasmid DNA indicate that the complex can both bind with, and nick, nucleic acid. Analysis of Sindbis virus, following irradiation with the metal complex, confirmed that the viral genome was rendered noninfectious by this treatment.