Ruthenium polypyridyl peptide conjugates: membrane permeable probes for cellular imaging

Two novel polyarginine labelled ruthenium polypyridyl dyes are reported, one conjugated to five, (Ru-Ahx-R5), and one to eight arginine residues, (Ru-Ahx-R8). Both complexes exhibit long-lived, intense, and oxygen sensitive luminescence. (Ru-R8) is passively, efficiently and very rapidly transported across the cell membrane into the cytoplasm without requirement for premeablisation of the cell membrane. Such ruthenium polypyridyl peptide conjugates open up the possibility for targeted cell delivery for environmentally sensitive intensity and lifetime imaging