Readily available fluorescein isothiocyanate-conjugated antibodies can be easily converted into targeted phototoxic agents for antibacterial, antiviral, and anticancer therapy.

Fluorescein-labeled antibodies have little, if any, photodynamic effect because energy acquired by light absorption is rapidly dissipated in fluorescence. However, they can be easily and efficiently converted to selective photodynamic sensitizers by iodination under mild conditions. We have outlined general experimental procedures that can be used to turn a fluorescein-labeled anti-Escherichia coli antibody into a photodynamic sensitizer that selectively kills E. coli while sparing closely related Salmonella typhimurium. These results demonstrate that iodination did not destroy the specificity or activity of the antibody. This technique should be applicable to the large number of fluoresceinated antibodies that are commercially available. Thus, this strategy provides a simple way to rapidly prepare a large number of targeted phototoxic agents that can be used for the selective destruction with light of nearly any type of tissue or organism.