Targeting And In Vitro And In Vivo Anticancer Studies Of Fluorescent Iridium (III) Complexes Modified With Triphenylamine/phenylcarbazol

Platinum-based chemotherapy drugs have been fully applied to the clinical application,however,serious renal toxicity and drug resistance greatly limit their application.Therefore,the design and development of metal anticancer drugs with different mechanism of action from cisplatin and less toxicity have become a research hotspot.Half-sandwich Ir(Ⅲ)complex is one of the most promising anticancer drugs,which showing good targeting,fluorescence,physical stability and excellent antiproliferation activity against tumor cells through structural regulation,and can be used as a potential substitute for platinum-based drugs.Therefore,a series of lysosometargeted half-sandwich Ir(Ⅲ)salicylaldehyde Schiff base complexes([(η5Cpx)Ir(O^N)Cl])and mitochondria-targeted half-sandwich Ir(Ⅲ)pyridine complexes([(η5-Cpx)Ir(L)Cl2])were designed and developed.The antitumor activity,photophysical properties,cell targeting,uptake mechanism and anticancer mechanism of these complexes were investigated.The details are as follows:First,four triphenylamine/N-phenylcarbazole-appended half-sandwich Ir(Ⅲ)salicylaldehyde Schiff base complexes([(η5-Cpx)Ir(O^N)Cl])were designed and prepared.These complexes can be stably existed in plasma(103 mM NaCl),while showing good hydrolytic properties in cytoplasmic environment(4 mM NaCl),which facilitating the transport of these complexes in plasma and showing anticancer activity in cells after uptake.Irl and Ir3 showed almost the similar anti-proliferation activity in vitro to cisplatin under the same conditions(IC50 values are 24.4±5.2,uM and 18.2±1.3μM,respectively).The introduction of triphenylamine/N-phenylcarbazole effectively improved the anti-proliferative activity and endowed these complexes with appropriate fluorescence properties.Laser confocal microscopy certificated that the entry of the complexes into A549 cells following an energy-dependent mechanism,accumulating in lysosomes(Pearson colocalization coefficient is 0.77),then leading to lysosomal damage and cell death.Flow cytometry confirmed that complexes could not effectively block A549 cell cycle,however,which could reduce the membrane potential of mitochondria,catalyzing the oxidation of coenzyme nicotinamide adenine dinucleotide(NADH),promoting the excessive accumulation of reactive oxygen species,inducing apoptosis,and displaying an anticancer mechanism of oxidation.At the same time,these complexes could effectively inhibit the migration of A549 cells,showing dual functions of anti-proliferation and anti-migration.Secondly,ten triphenylamine modified half-sandwich Ir(Ⅲ)pyridine complexes([(η5-Cpx)Ir(L)Cl2])were designed and synthesized.Complexes had good intracellular hydrolysis performance and remained stable in the plasma environment.Complexes showed potential antiproliferative activity.Ir6 had the best anti-proliferative activity on A549 cells(IC50:26.7±0.9μM).The introduction of triphenylamine unit with large steric hindrance led to the reduction of intermolecular π-π interaction in solution(Free state),then inhibiting the molecular vibration and rotation,endowing these complexes excellent fluorescence characteristics.The absolute fluorescence quantum yield in solution was 15.57%(Ir6)with a large stokes shift(145 nm),which reduced selfabsorption and was conducive to intracellular imaging.Laser confocal detection showed that Ir6 could effectively accumulate in mitochondria with a Pearson colocalization coefficient of 0.95,and inducing apoptosis.Western blot further confirmed that Ir6 could regulate the expression of Bcl-2,PARP,Bax and Cyt-c proteins through the classical mitochondrial pathway,and promoting the apoptosis of A549 cells.Flow cytometry proved that Ir6 could significantly block the A549 cells cycle in G2/M phase,leading to a significant decrease in mitochondrial membrane potential and an excessive accumulation of intracellular reactive oxygen species,and ultimately inducing apoptosis.Nude mouse model experiments further confirmed that Ir6 had better anti-proliferation,anti-migration ability and safety than cisplatin.Above all,triphenylamine/phenylcarbazole-modified half-sandwich Ir(Ⅲ)complexes have shown potential application prospects in the field of metallic anticancer drugs,which can be used as a potential substitute for platinum drugs and further study.