Biological Evaluation of Chalcogenorhodamine Dyes

Chalcogenorhodamine dyes that had been tested for their effect on P-glycoprotein (P-gp) activity were further tested for their use as photosensitizers for photodynamic therapy. These analogues were shown to be substrates of P-gp, and exhibited the amide/thioamide "switch", in which thioamides were able to accumulate more in Colo-26 cells than amides. The selenium (Se) analogues were shown to localize in the mitochondria of Colo-26 cells. Phototoxicity assays showed that the thioamide derivatives were more effective photosensitizers than the amide derivatives, while all of the derivatives showed no dark toxicity. The dyes were also shown to be useful as photosensitizers for combination treatment with Doxorubicin.