Liposomes encapsulated iridium(III) polypyridyl complexes enhance anticancer activity in vitro and in vivo.

Three iridium(III) complexes [Ir(ppy) 2 (CPIP)](PF 6) (Ir-1 , ppy = 2-phenylpyridine, CPIP = 2-(4-chlorophenyl)-1 H -imidazo[4,5-f][1,10]phenanthroline), [Ir(ppy) 2 (DCPIP)](PF 6) (Ir-2 , DCPIP = 2-(3,4-dichlorophenyl)-1 H -imidazo[4,5- f ][1,10]phenanthroline) and [Ir(ppy) 2 (TCPIP)](PF 6) (Ir-3 , TCPIP = 2,3,5-trichlorophenyl)-1H-imidazo[4,5-f][1,10]phenanthroline) were synthesized and characterized. The complexes Ir-1 , Ir-2 and Ir-3 were encapsulated in liposomes to form Ir-1-Lipo , Ir-2-Lipo and Ir-3-Lipo. Morphology, size distribution, and zeta potential of liposomes were examined by transmission electron microscopy (TEM) and Zetasizer. The cytotoxic activity in vitro of Ir-1 , Ir-2 and Ir-3 against cancer A549, HTC-116, HepG2, BEL-7402, Eca-109, B16, HeLa SGC-7901 and normal NIH3T3 cells was evaluated by 3-(4,5-dimethylthiazole-2-yl)-2,5-biphenyl tetrazolium bromide (MTT) method. Ir-2 and Ir-3 show no cytotoxic activity against the selected cancer cells, and Ir-1 displays moderate cytotoxic effect on the cell growth in A549 cells. However, Ir-1 , Ir-2 and Ir-3 were encapsulated in liposomes, the cytotoxic activity was greatly enhanced. In particular, Ir-1-Lipo and Ir-2-Lipo can effectively inhibit the cell growth in A549 cells with a low IC 50 value of 3.1 ± 0.3 and 1.2 ± 0.4 μM. The apoptosis was assayed by flow cytometry. Ir-1 , Ir-2 and Ir-3 reveal weak apoptotic effect, whereas Ir-1-Lipo , Ir-2-Lipo and Ir-3-Lipo induce an apoptotic percentage of 55.6%, 69.3% and 16.7% in A549 cells, respectively. Specially, in the assay of antitumor activity in vivo, the inhibiting percentage of tumor growth induced by Ir-2 is 27.65%, while inhibiting percentage of tumor growth caused by Ir-2-Lipo is 57.45%. Obviously, the liposomes can enhance anticancer activity in vitro and in vivo compared with the complexes. The results show that the iridium(III) complexes encapsulated liposomes induce apoptosis in A549 cells through ROS-mediated lysosome-mitochondria dysfunction pathway and target the microtubules. Iridium(III) complexes [Ir(ppy) 2 (CPIP)](PF 6) (Ir - 1 , ppy = 2-phenylpyridine, CPIP = 2-(4-chlorophenyl)-1 H -imidazo[4,5-f][1,10]phenanthroline), [Ir(ppy) 2 (DCPIP)](PF 6) (Ir - 2 , DCPIP = 2-(3,4-dichlorophenyl)-1 H -imidazo[4,5- f ][1,10]phenanthroline) and [Ir(ppy) 2 (TCPIP)](PF 6) (Ir - 3 , TCPIP = 2,3,5-trichlorophenyl)-1H-imidazo[4,5-f][1,10]phenanthroline) were synthesized and characterized. Ir-1 , Ir-2 and Ir-3 were encapsulated in liposomes Ir-1-Lipo , Ir-2-Lipo and Ir-3-Lipo. The anticancer activity of them was investigated in vitro and in vivo. Unlabelled Image • Complexes Ir-1, Ir-2, Ir-3 and their liposomes were synthesized and characterized. • The cytotoxicity in vitro was studied by 3-(4,5-dimethylthiazole-2-yl)-2,5-biphenyl tetrazolium bromide (MTT) method. • Colonies, apoptosis, reactive oxygen species (ROS), mitochondrial membrane potential were investigated. • The effect of liposomes Ir-1-Lipo, Ir-2-Lipo and Ir-3-Lipo on microtubules was explored. • The antitumor in vivo of Ir-2-Lipo was studied. [ABSTRACT FROM AUTHOR]