Dicopper(II) Complexes of p-Cresol-2,6-Bis(dpa) Amide-Tether Ligands: Large Enhancement of Oxidative DNA Cleavage, Cytotoxicity, and Mechanistic Insight by Intracellular Visualization

Dicopper Complexes of p-Cresol-2,6-bis(amide-tether-dpa4-X) (X = MeO and Cl): Selective ROS Generation and Cytotoxicity Enhancement Controlled by Electronic and Hydrophobic Effects of the MeO and Cl Groups

Two new p-cresol-2,6-bis(amide-tether-dpa4-X) ligands (HL4-X, X = MeO and Cl) and their dicopper complexes [Cu2(μ-1,1-OAc)(μ-1,3-OAc)(L4-MeO)]Y (Y = PF6 1a, OAc 1b) and [Cu2(μ-1,3-OAc)2(L4-Cl)]Y (Y = ClO4 2a, OAc 2b) were synthesized. The electronic and hydrophobic effects of the MeO and Cl groups were examined compared with nonsubstituted complex [Cu2(μ-1,1-OAc)(μ-1,3-OAc)(L)]+ (3). The electronic effects were found in crystal structures, spectroscopic characterization, and redox potentials of these complexes. 1b and 2b were reduced to Cu(I)Cu(I) with sodium ascorbate and reductively activated O2 to produce H2O2 and HO•. The H2O2 release and HO• generation are promoted by the electronic effects. The hydrophobic effects increased the lipophilicity of 1b and 2b. Cellular ROS generation of 1b, 2b, and 3 was visualized by DCFH-DA. To examine the intracellular behavior, boron dipyrromethene (Bodipy)-modified complexes 4B and 5B corresponding to 1b and 2b were synthesized. These support that 1b and 2b are localized at the ER and Golgi apparatus. The cytotoxicity of 1b and 2b against various cell lines was examined by MTT assay. 1b and 2b were 7- and 41-fold more cytotoxic than 3. 1b generated ROS selectively in cancer cell but 2b nonselectively in cancer and normal cells, causing cancer- and normal-cell-selective cytotoxicity, respectively.

Polyoxometalates as Potential Artificial Enzymes toward Biological Applications

Artificial enzymes, as alternatives to natural enzymes, have attracted enormous attention in the fields of catalysis, biosensing, diagnostics, and therapeutics because of their high stability and low cost. Polyoxometalates (POMs), a class of inorganic metal oxides, have recently shown great potential in mimicking enzyme activity due to their well-defined structure, tunable composition, high catalytic efficiency, and easy storage properties. This review focuses on the recent advances in POM-based artificial enzymes. Different types of POMs and their derivatives-based mimetic enzyme functions are covered, as well as the corresponding catalytic mechanisms (where available). An overview of the broad applications of representative POM-based artificial enzymes from biosensing to theragnostic is provided. Insight into the current challenges and the future directions for POMs-based artificial enzymes is discussed.

Roles of DNA Target in Cancer Cell-Selective Cytotoxicity by Dicopper Complexes with DNA Target/Ligand Conjugates

The DNA target/ligand conjugates (HLX, X = Pn and Mn, n = 1-3) were synthesized where various lengths of -CONH(CH2CH2O)nCH2CH2NHCO- linkers with a 9-phenanthrenyl (P) or methyl (M) terminal as DNA targets replace the methyl group of 2,6-di(amide-tether cyclen)-p-cresol ligand (HL). DNA binding, DNA cleavage, cellular uptake, and cytotoxicity of [Cu2(μ-OH)(LX)](ClO4)2 (1X) are examined and compared with those of [Cu2(μ-OH)(L)](ClO4)2 (1) to clarify roles of DNA targets. Upon reaction of 1X with H2O2, μ-1,1-O2H complexes are formed for DNA cleavage. 1P1, 1P2, and 1P3 are 22-, 11-, 3-fold more active for conversion of Form II to III in the cleavage of supercoiled plasmid DNA with H2O2 than 1, where the short P-linker may fix a dicopper moiety within a small number of base pairs to facilitate DNA double-strand breaks (dsb). This enhances the proapoptotic activity of 1P1, 1P2, and 1P3, which are 30-, 12-, and 9.9-fold cytotoxic against HeLa cells than 1. DNA dsb and cytotoxicity are 44% correlated in 1P1-3 but 5% in 1M1-3, suggesting specific DNA binding of P-linkers and nonspecific binding of M-linkers in biological cells. 1P1-3 exert cancer cell-selective cytotoxicity against lung and pancreas cancer and normal cells where the short P-linker enhances the selectivity, but 1M1-3 do not. Intracellular visualization, apoptosis assay, and caspase activity assay clarify mitochondrial apoptosis caused by 1P1-3. The highest cancer cell selectivity of 1P1 may be enabled by the short P-linker promoting dsb of mitochondrial DNA with H2O2 increased by mitochondrial dysfunction in cancer cells.

Nuclease-like metalloscissors: Biomimetic candidates for cancer and bacterial and viral infections therapy

Despite the extensive and rapid discovery of modern drugs for treatment of cancer, microbial infections, and viral illnesses; these diseases are still among major global health concerns. To take inspiration from natural nucleases and also the therapeutic potential of metallopeptide antibiotics such as the bleomycin family, artificial metallonucleases with the ability of promoting DNA/RNA cleavage and eventually affecting cellular biological processes can be introduced as a new class of therapeutic candidates. Metal complexes can be considered as one of the main categories of artificial metalloscissors, which can prompt nucleic acid strand scission. Accordingly, biologists, inorganic chemists, and medicinal inorganic chemists worldwide have been designing, synthesizing and evaluating the biological properties of metal complexes as artificial metalloscissors. In this review, we try to highlight the recent studies conducted on the nuclease-like metalloscissors and their potential therapeutic applications. Under the light of the concurrent Covid-19 pandemic, the human need for new therapeutics was highlighted much more than ever before. The nuclease-like metalloscissors with the potential of RNA cleavage of invading viral pathogens hence deserve prime attention.

Terpyridine copper(II) complexes as potential anticancer agents by inhibiting cell proliferation, blocking the cell cycle and inducing apoptosis in BEL-7402 cells

Four mononuclear terpyridine complexes [Cu(H-L^a)Cl₂]·CH₃OH (1), [Cu(H-L^a)Cl]ClO₄ (2), [Cu(H-L^b)Cl₂]·CH₃OH (3), and [Cu(H-L^b)(CH₃OH)(DMSO)](ClO₄)₂ (4) were prepared and fully characterized. Complexes 1-4 exhibited higher cytotoxic activity against several tested cancer cell lines especially BEL-7402 cells compared to cisplatin, and they showed low toxicity towards normal human liver cells. ICP-MS detection indicated that the copper complexes were accumulated in mitochondria. Mechanistic studies demonstrated that the copper complexes induced G0/G1 arrest and altered the expression of the related proteins of the cell cycle. All copper complexes reduced the mitochondrial membrane potential while increasing the intracellular ROS levels and the release of Ca²⁺. They also up-regulated Bax and down-regulated Bcl-2 expression levels, caused cytochrome c release and the activation of the caspase cascade, and induced mitochondrion-mediated apoptosis. Animal studies demonstrated that complex 1 suppressed tumor growth in a mouse xenograft model bearing BEL-7402 tumor cells.

Enhancement of Cancer-Cell-Selective Cytotoxicity by a Dicopper Complex with Phenanthrene Amide-Tether Ligand Conjugate via Mitochondrial Apoptosis

Dicopper complexes [Cu2(μ-OH)(Ln)](ClO4)2 [n = 1 (1) and 2 (2)] with a novel phenanthrene amide-tether ligand conjugate (HL1) and the original p-cresol-2,6-bis(amidecyclen) (HL2) were synthesized. A phenanthrene unit of 1...