Cyclometalated iridium(III) complexes, because of their photophysical properties, have the potential for use as luminescent probes for cellular imaging. We previously reported on a pH-activatable iridium complex that contains three N,N-diethylamino groups, namely, fac-Ir(deatpy)3 5, which was synthesized via a regioselective aromatic substitution reaction at the 5'-position with tolylpyridine groups of fac-Ir(tpy)3 2. It was found that 5 shows a considerable enhancement in emission intensity in the pH range from neutral to slightly acidic (pH 6.5-7.4) in aqueous solution and selectively stains lysosome in HeLa-S3 cells, due to the protonation of the diethylamino groups. In addition, 5 functions as a pH-dependent singlet oxygen ((1)O2) generator and induces necrosis-like cell death. However, observing the green emission of 5 is often hampered by autofluorescence emanating from nearby tissues. To overcome this problem, we designed and synthesized a series of new pH-activatable Ir(III) complexes that contain diethylamino, guanidyl, and iminoimidazolidinyl groups on the mpiq ligand of Ir(mpiq)3 7 and the tfpiq ligand of Ir(tfpiq)3 8, which exhibit a red emission, namely, Ir(deampiq)3 13, Ir(gmpiq)3 14, Ir(imzmpiq)3 15, and Ir(imztfpiq)3 16. The emission intensity of these Ir complexes is enhanced substantially by protonation of their basic groups, and they induce the necrosis-like cell death of HeLa-S3 cells by photoirradiation at 465 nm. A strong orange-red emission of Ir(mpiq-NO2)3 9 and Ir(tfpiq-NO2)3 10 is also reported.
We report on the efficient synthesis of tris-heteroleptic iridium (Ir) complexes based on the degradation of tris-cyclometalated Ir complexes (IrL, L: cyclometalating ligand) in the presence of Brønsted and Lewis acids such as HCl (in 1,4-dioxane), AlCl, TMSCl, and ZnX (X = Br or Cl), which affords the corresponding halogen-bridged Ir dimers (μ-complexes). Tris-cyclometalated Ir complexes containing electron-withdrawing groups such as fluorine, nitro, or CF moieties on the ligands were less reactive. This different reactivity was applied to the selective degradation of heteroleptic Ir complexes such as fac-Ir(tpy)(Fppy) (fac-12) (tpy: 2-(4'-tolyl)pyridine and Fppy: 2-(4',6'-difluorophenyl)pyridine), mer-Ir(tpy)(Fppy) (mer-12), and mer-Ir(mpiq)(Fppy) (mer-15) (mpiq: 1-(4'-methylphenyl)isoquinoline). For example, the reaction of mer-12 with ZnBr gave the heteroleptic μ-complex [{Ir(tpy)(Fppy)(μ-Br)}] 27b as a major product, resulting from the selective elimination of the tpy ligand of mer-12, and treatment of 27b with acetylacetone (acacH) afforded the corresponding tris-heteroleptic Ir complex Ir(tpy)(Fppy)(acac)18. In addition, another tris-heteroleptic Ir complex 35a having 8-benzenesulfonylamidoquinoline (8BSQ) ligand was synthesized. Mechanistic studies of this degradation reaction and the photochemical properties, especially a dual emission, of these newly synthesized tris-heteroleptic Ir complexes are also reported.
Islet transplantation employing DCD can ameliorate severe hypoglycemic episodes, significantly improve HbA1c levels, sustain significant levels of C-peptide, and achieve insulin independence after multiple transplantations. Thus, DCD can be an important resource for islet transplantation if used under strict releasing criteria and in multiple transplantations, particularly in countries where heart-beating donors are not readily available.
Background: Spontaneous regression of a malignant tumor is a rare phenomenon. So far, 13 cases of spontaneous regression of hepatocellular carcinoma (HCC) have been described in the English literature. We report a case of HCC, with spontaneous complete necrosis demonstrated by histological examination. Methods: A 73-year-old male was admitted to our hospital complaining of general fatigue. CT and US revealed a huge mass measuring 9.5 cm at the left lobe. Angiographies showed hypovascular tumor stains. The levels of alpha-fetoprotein (AFP) and PIVKA-2 on admission were high, at 55 ng/ml and 62,300 mAU/ml, respectively. We diagnosed hypovascular HCC and performed a left lobectomy on October 16, 2000. Results: In the histological examination, no viable cells were found. The levels of AFP and PIVKA-2 had already decreased to 14 ng/ml and 1,420 mAU/ml, before laparotomy. Conclusion: Changes in tumor markers and histological findings reveal that this phenomenon occurred without specific treatment.
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