Cobalt(III) Chaperone Complexes of Curcumin: Photoreduction, Cellular Accumulation and Light-Selective Toxicity towards Tumour Cells

A sequential enzyme-activated and light-triggered pro-prodrug nanosystem for cancer detection and therapy

A sequential enzyme-activated and light-triggered pro-prodrug has been developed for cancer biomarker detection and on-demand therapy.

Curcumin "Drug" Stabilized in Oxidovanadium(IV)-BODIPY Conjugates for Mitochondria-Targeted Photocytotoxicity

Ternary oxidovanadium(IV) complexes of curcumin (Hcur), dipicolylamine (dpa) base, and its derivatives having pendant noniodinated and di-iodinated boron-dipyrromethene (BODIPY) moiety (L₁ and L₂, respectively), namely, [VO(dpa)(cur)]ClO₄ (1), [VO(L₁)(cur)]ClO₄ (2), and [VO(L₂)(cur)]ClO₄ (3) and their chloride salts (1a-3a) were prepared, characterized, and studied for anticancer activity. The chloride salts were used for biological studies due to their aqueous solubility. Complex 1 was structurally characterized by single-crystal X-ray crystallography. The complex has a VO²⁺ moiety bound to dpa ligand showing N,N,N-coordination in a facial mode, and curcumin is bound in its mono-anionic enolic form. The V-O(cur) distances are 1.950(18) and 1.977(16) Å, while the V-N bond lengths are 2.090(2), 2.130(2), and 2.290(2) Å. The bond trans to V═O is long due to trans effect. The complexes are stable in a solution phase over a long period of time of 48 h without showing any apparent degradation of the curcumin ligand. The diiodo-BODIPY ligand (L₂) or Hcur alone showed limited solution stability in dark. The emissive BODIPY (L₁) containing complex 2a showed preferential mitochondrial localization in MCF-7 cells in cellular imaging experiments. The cytotoxicity of the complexes was studied by MTT assay. The BODIPY complex 3a showed excellent photodynamic therapy effect in visible light (400-700 nm) giving IC₅₀ values of 2-6 μM in HeLa and MCF-7 cancer cells, while being less toxic in dark (∼100 μM). The cell death was apoptotic in nature involving reactive oxygen species (ROS). Mechanistic data from pUC19 DNA photocleavage studies revealed photogenerated ROS as primarily ¹O₂ from the BODIPY moiety and ·OH radicals from the curcumin ligand.

Monofunctional BODIPY-Appended Imidazoplatin for Cellular Imaging and Mitochondria-Targeted Photocytotoxicity

Monofunctional platinum(II) complexes of formulation cis-[Pt(NH₃)₂(L)Cl](NO₃), where L is an imidazole base conjugated to 4,4-difluoro-4-bora-3a,4a-diaza-s-indacene (BODIPY) with emissive (L¹ in 1) and nonemissive (L² in 2) moieties were prepared and characterized, and their singlet oxygen-mediated photoinduced cytotoxicity was studied. The 1-methylimidazole (1-MeIm) complex 3 was prepared as a control and for structural characterization by X-ray crystallography. Complexes 1 and 2 showed strong visible absorption bands at 500 nm (ε = 2.7 × 10⁴ M^-1 cm^-1) and 540 nm (1.4 × 10⁴ M^-1 cm^-1). Complex 1 is emissive with a band at 510 nm (Φ_F = 0.09) in 1% dimethyl sulfoxide/Dulbecco's Modified Eagle's Medium (pH 7.2). Singlet oxygen generation upon photoirradiation with visible light (400-700 nm) was evidenced from 1,3-diphenylisobenzofuran titration experiments showing significant photosensitizing ability of the BODIPY complexes. Both 1 and 2 were remarkably photocytotoxic in visible light (400-700 nm, 10 J cm^-2) in skin keratinocyte HaCaT and breast cancer MCF-7 cells giving IC₅₀ values in nanomolar concentration. The complexes were, however, essentially nontoxic to the cells in the dark (IC₅₀ > 80 μM). Complex 2 having a diiodo-BODIPY unit is nonemissive but an efficient photosensitizer with high singlet oxygen generation ability in visible light (400-700 nm). Confocal microscopy using the emissive complex 1 showed significant mitochondrial localization of the complex. Cell death via apoptotic pathway was observed from the Annexin-V-FITC/PI assay. The formation of Pt-DNA adducts was evidenced from the binding experiments of the complexes 1 and 2 with 9-ethylguanine as a model nucleobase from ¹H NMR and mass spectral studies.

Bis(thiosemicarbazone) Complexes of Cobalt(III). Synthesis, Characterization, and Anticancer Potential

Nine bis(thiosemicarbazone) (BTSC) cobalt(III) complexes of the general formula [Co(BTSC)(L)2]NO3 were synthesized, where BTSC = diacetyl bis(thiosemicarbazone) (ATS), pyruvaldehyde bis(thiosemicarbazone) (PTS), or glyoxal bis(thiosemicarbazone) (GTS) and L = ammonia, imidazole (Im), or benzylamine (BnA). These compounds were characterized by multinuclear NMR spectroscopy, mass spectrometry, cyclic voltammetry, and X-ray crystallography. Their stability in phosphate-buffered saline was investigated and found to be highly dependent on the nature of the axial ligand, L. These studies revealed that complex stability is primarily dictated by the axial ligand following the sequence NH3 > Im > BnA. The cellular uptake and cytotoxicity in cancer cells were also determined. Both the cellular uptake and cytotoxicity were significantly affected by the nature of the equatorial BTSC. Complexes of ATS were taken up much more effectively than those of PTS and GTS. The cytotoxicity of the complexes was correlated to that of the free ligand. Cell uptake and cytotoxicity were also determined under hypoxic conditions. Only minor differences in the hypoxia activity and uptake were observed. Treatment of the cancer cells with the copper-depleting agent tetrathiomolybdate decreased the cytotoxic potency of the complexes, indicating that they may operate via a copper-dependent mechanism. These results provide a structure-activity relationship for this class of compounds, which may be applied for the rational design of new cobalt(III) anticancer agents.

New cyclometalated Ir(iii) complexes with NCN pincer and meso-phenylcyanamide BODIPY ligands as efficient photodynamic therapy agents

A new class of cyclometalated iridium(iii) with NCN pincer andmeso-phenylcyanamide BODIPY ligands has been synthesized and studied for photodynamic therapy.

The discovery of half-sandwich iridium complexes containing lidocaine and (pyren-1-yl)ethynyl derivatives of phenylcyanamide ligands for photodynamic therapy

The new design of two cyclopentadienyl iridium(iii) complexes with (pyren-1-yl)ethynyl derivatives of phenylcyanamide and lidocaine ligands, have been studied for photodynamic therapy.

Structural, photolysis and biological studies of novel mixed metal Cu(I)-Sb(III) mixed ligand complexes

Direct reaction of copper(I) halides with triphenylstibine (tpSb) and 2-mercapto-thiazolidine (tzdtH) in 1:1:1 molar ratio, results in the formation of the [CuX(μ2-S)-tzdtH)(tpSb)]2 (X=Cl (1), Br (2) and I (3)) complexes. The complexes have been characterized by melting point, FT-IR, UV-vis, (1)H NMR spectroscopic data and X-ray crystallography. Complexes 1-3 are di-nuclear and they are the first examples of mixed metals (CuSb), mixed ligand (thioamide, stibine and halogen) containing complexes. Two μ2-S (1-3) atoms bridge the two copper(I) ions with tetrahedral geometry. The coordination sphere around copper atoms is completed by one Sb from tpSb and one halogen (chlorine, bromine or iodine) atom. Intermolecular via N-H⋯X (Cl (1) and Br (2)) interactions stabilized the assembly. The short coppercopper bond distances of 3.103 (1), 3.061 (2) and 3.110, 3.108 (3) Ǻ found in 1-3 indicates d(10)-d(10) interaction between metal centers. The complexes exhibit high photo-sensitivity to UVB light. The complexes 1-3 and the already known [Cu(μ2-I)(tpSb)2]2 (4) were tested for their in vitro cytotoxic activity against human cancer cell lines: MCF-7 (breast, estrogen receptor (ER) positive), MDA-MB-231 (breast, estrogen receptor (ER) negative) and MRC-5 (normal human fetal lung fibroblast cells) with sulforhodamine B (SRB) colorimetric assay. Since estrogen receptors (ERs) are located in MCF-7, in contrast to MDA-MB-231 cells, the estrogenic effect of 1-4 on MCF-7 cells was studied by the mean of methylene blue assay. Compound 4 exhibits the highest estrogenic effect. None of 1-4 exceeds the activity of cisplatin against MCF-7 cells, but they are more active than cisplatin towards MDA-MB-231 cells. UVB light increases the effectiveness of complexes on MCF-7 cells which in the case of 4 is up to 28% higher than the corresponding initial complex (without irradiation).

The Potent Inhibitory Effect of a Naproxen-Appended Cobalt(III)-Cyclam Complex on Cancer Stem Cells

We report the potency against cancer stem cells (CSCs) of a new cobalt(III)-cyclam complex (1) that bears the nonsteroidal anti-inflammatory drug, naproxen. The complex displays selective potency for breast CSC-enriched HMLER-shEcad cells over breast CSC-depleted HMLER cells. Additionally, it inhibited the formation of three-dimensional tumour-like mammospheres, and reduced their viability to a greater extent than clinically used breast cancer drugs (vinorelbine, cisplatin and paclitaxel). The anti-mammosphere potency of 1 was enhanced under hypoxia-mimicking conditions. Detailed mechanistic studies revealed that DNA damage and cyclooxygenase-2 (COX-2) inhibition contribute to the cytotoxic mechanism of 1. To the best of our knowledge, 1 is the first cobalt-containing compound to show selective potency for CSCs over bulk cancer cells.

Synthesis of highly functionalized 2,2'-bipyridines by cyclocondensation of β-ketoenamides - scope and limitations

The scope of a flexible route to unsymmetrically functionalized bipyridines is described. Starting from 1,3-diketones 1a–e, the corresponding β-ketoenamines 2a–e were converted into different β-ketoenamides 3a–g by N-acylation with 2-pyridinecarboxylic acid derivatives. These β-ketoenamides were treated with a mixture of TMSOTf and Hünig’s base to promote the cyclocondensation to 4-hydroxypyridine derivatives. Their immediate O-nonaflation employing nonafluorobutanesulfonyl fluoride provided the expected 4-nonafloxy-substituted bipyridine derivatives 5a–g in moderate to good overall yields. The bipyridyl nonaflates are excellent precursors for palladium-catalyzed reactions as demonstrated by representative Suzuki and Sonogashira couplings. Thus, a library of specifically substituted bipyridine derivatives was generated, showing the versatility of the simple 1,3-diketone-based approach to this important class of ligands.

Mitochondrial selectivity and remarkable photocytotoxicity of a ferrocenyl neodymium(iii) complex of terpyridine and curcumin in cancer cells

A mixed-ligand neodymium(iii) complex of ferrocene appended terpyridine and curcumin targets the mitochondria and shows remarkable visible-light induced cytotoxicity in HeLa and MCF-7 cancer cells while being much less toxic in dark and to MCF-10A normal cells.

Photoactive platinum(ii) β-diketonates as dual action anticancer agents

Cyclometallated platinum(ii) β-diketonates show significant photocytotoxicity in skin-keratinocyte HaCaT cells [IC₅₀: ∼10 μM (visible light, 400–700 nm), ≥60 μM (dark)].