Synthesis, Characterization, and Biological Evaluation of New Ru(II) Polypyridyl Photosensitizers for Photodynamic Therapy

Two
Ru­(II) polypyridyl complexes, Ru­(DIP)2(bdt) (1) and [Ru­(dqpCO2Me)­(ptpy)]2+ (2) (DIP = 4,7-diphenyl-1,10-phenanthroline, bdt = 1,2-benzenedithiolate,
dqpCO2Me = 4-methylcarboxy-2,6-di­(quinolin-8-yl)­pyridine),
ptpy = 4′-phenyl-2,2′:6′,2″-terpyridine)
have been investigated as photosensitizers (PSs) for photodynamic
therapy (PDT). In our experimental settings, the phototoxicity and
phototoxic index (PI) of 2 (IC50(light): 25.3
μM, 420 nm, 6.95 J/cm2; PI >4) and particularly
of 1 (IC50(light): 0.62 μM, 420 nm,
6.95 J/cm2; PI: 80) are considerably superior compared
to the two clinically
approved PSs porfimer sodium and 5-aminolevulinic acid. Cellular uptake
and distribution of these complexes was investigated by confocal microscopy
(1) and by inductively coupled plasma mass spectrometry
(1 and 2). Their phototoxicity was also
determined against the Gram-(+) Staphylococcus aureus and Gram-(−) Escherichia coli for potential antimicrobial PDT (aPDT) applications. Both complexes
showed significant aPDT activity (420 nm, 8 J/cm2) against
Gram-(+) (S. aureus; >6 log10 CFU reduction) and, for 2, also against Gram-(−) E. coli (>4 log10 CFU reduction).