The photoreactive [Ru(TAP)2(phen)]2+(TAP = 1,4,5,8-tetraazaphenanthrene; phen = 1,10-phenanthroline) complex tethered to the cell-penetrating peptide (CPP) TAT was studied in vitro and in cellulo. The tethering of the complex does not affect its behavior under blue-light irradiation in the presence of guanine-containing oligodeoxyribonucleotides (ODNG). Thus, the luminescence is quenched in the presence of ODNG, and gel electrophoresis experiments showed the appearance of products corresponding to the irreversible attachment of the conjugate to ODNGupon illumination. The cellular uptake of the conjugate was examined by flow cytometry, inductively coupled plasma mass spectrometry (ICP-MS), and confocal imaging microscopy. These experiments showed that the [Ru(TAP)2(phen-TAT)] conjugate is readily taken up by HeLa cells and, despite these favorable factors, the cellular survival was 100 %, as measured by a 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay. A possible origin of the inactivity of [Ru(TAP)2(phen-TAT)] under irradiation is proposed on the basis of the fluorescence-activated cell sorting (FACS), ICP-MS, and confocal microscopy results. ; SCOPUS: ar.j ; info:eu-repo/semantics/published