Copper(II) and cadmium(II) complexes derived from Strandberg-type polyoxometalate clusters: Synthesis, crystal structures, spectroscopy and biological activities

Insights into organic-inorganic hybrid molecular materials: organoimido functionalized polyoxomolybdates

Polyoxometalates (POMs) are polyatomic anions that comprise transition metal group 5 (V, Nb, Ta) or group 6 (Mo, W) oxyanions connected together by shared oxygen atoms. POMs are fascinating because of their exclusive and remarkable characteristics. One of the most interesting features of POMs is their capability to function as an electron relay by performing stepwise multi-electron redox reactions while maintaining their structural integrity. Functionalization of POMs with amino organic compounds results in organoimido derivatives of polyoxometalates, which have aroused interest due to augmentation of their properties. Comprehensive study has shown that the synthesis methodologies to obtain desired organoimido derivatives of POMs by employing various imido-releasing reagents have progressed drastically in recent decades, particularly the innovative DCC-dehydrating technique. These organoimido functionalized POMs have been used as major building blocks to develop unique nanostructured organic-inorganic hybrid molecular materials. Many conventional organic synthesis processes such as Pd-catalyzed carbon-carbon coupling and esterification reactions have been performed with organoimido functionalized POMs where the presence of POM triggered the reaction process. Thus, investigation of the reactivity of organoimido derivatives of POMs foreshadows the intriguing future of POMs chemistry.

A blend hydrogel based on polyoxometalate for long-term and repeatedly localized antibacterial application study

Herein, a polyoxometalate (POM)-based blend hydrogel system was in situ constructed by incorporating cetyltrimethylammoniumbromide (CTAB)-encapsulated POM cationic micelles to bare hydrogel matrixes followed by copolymerization of multivalent crosslinking groups. It was demonstrated that the fabricated blend hydrogel possessed tunable physicochemical properties, good swelling behavior (maximum swelling rate of 229% in buffer solution of pH 8.0), excellent local action and sustained release of POM component (release ratio achieved nearly 100% at the time of 120 min). Antibacterial activity study revealed that the introduction of POM greatly improved the bioavailability of itself, namely, leading to a more effective enhancement of therapeutic effects (survival ratio of both strains less than 5%). Besides, bactericidal rates (ca. 51%) were achieved even after six runs repeated, thereby verifying the biological application potential of this material. Finally, the practical application potentials were investigated and future prospects in relevant research areas were forecasted.

Crystal structure of tetrakis(1H-benzo[d]imidazol-3-ium) bis(μ5-phenylphosphonato)-pentakis(μ2-oxido)-decaoxo-penta-molybdenum dihydrate, C40H42Mo5N8O23P2

C40H42Mo5N8O23P2, triclinic, P1̄ (no. 2), a = 10.9867(2) Å, b = 15.4753(3) Å, c = 15.5666(3) Å, α = 85.583(2)°, β = 81.294(2)°, γ = 84.844(2)°, V = 2600.18(9) Å3, Z = 2, R gt(F) = 0.0208, wR ref(F 2) = 0.0485, T = 293(2) K.

Polyoxometalates in Biomedicine: Update and Overview

BACKGROUND

Polyoxometalates (POMs) are negatively charged metal-oxo clusters of early transition metal ions in high oxidation states (e.g., WVI, MoVI, VV). POMs are of interest in the fields of catalysis, electronics, magnetic materials and nanotechnology. Moreover, POMs were shown to exhibit biological activities in vitro and in vivo, such as antitumor, antimicrobial, and antidiabetic.

METHODS

The literature search for this peer-reviewed article was performed using PubMed and Scopus databases with the help of appropriate keywords.

RESULTS

This review gives a comprehensive overview of recent studies regarding biological activities of polyoxometalates, and their biomedical applications as promising anti-viral, anti-bacterial, anti-tumor, and anti-diabetic agents. Additionally, their putative mechanisms of action and molecular targets are particularly considered.

CONCLUSION

Although a wide range of biological activities of Polyoxometalates (POMs) has been reported, they are to the best of our knowledge not close to a clinical trial or a final application in the treatment of diabetes or infectious and malignant diseases. Accordingly, further studies should be directed towards determining the mechanism of POM biological actions, which would enable fine-tuning at the molecular level, and consequently efficient action towards biological targets and as low toxicity as possible. Furthermore, biomedical studies should be performed on solutionstable POMs employing physiological conditions and concentrations.

Effective inhibitory activity against MCF-7, A549 and HepG2 cancer cells by a phosphomolybdate based hybrid solid

A novel P₂Mo₅ cluster based hybrid solid [{4,4′-H₂bpy}{4,4′-Hbpy}₂{H₂P₂Mo₅O₂₃}]·5H₂O with effective anti-proliferation activity against MCF-7, HepG2 and A549 cancer cells comparable with a routinely used chemotherapeutic agent, methotrexate (MTX).

Synthesis, characterization and bioactivities of a new covalent copper(II) compound derived from {P2Mo5O23}6- and thiosemicarbazones

In this article, a new compound H₂[{Cu(HL)(H₂O)}₂(P₂Mo₅O₂₃)]·5H₂O (1) (HL = 2-acetylpyrazine thiosemicarbazone) has been synthesized and structurally characterized by single-crystal X-ray diffraction of and other detection techniques. Interestingly, the structure of 1 is different from many reported copper-based complexes, in which the [P₂Mo₅O₂₃]^6-, two Cu²⁺ ions and two HL were directly connected by covalent bands. Biological studies demonstrated that 1 indicated moderate antibacterial activity against Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus), and a better cytotoxicity against human hepatic cancer line (SMMC-7721) than Mitoxantrone (Mito), the current clinical anticancer drug. Besides, the antibacterial mechanisms of 1 have been studied by the membrane integrity disruption, the destructive reactive oxygen species generation (ROS), the glutathione (GSH) depletion and the depressed enzymatic activity of respiratory chain dehydrogenases (RCD). These results revealed that the combination of HL, Cu²⁺, [P₂Mo₅O₂₃]^6- shows a higher antibacterial and cytotoxic activity.

Crystal structure of bis[diaqua(1,10-phenanthroline-κ 2 N, N′)-copper(II)]diphenylphosphopentamolybdate dihydrate, C36H38Cu2Mo5N4O27P2

C36H38Cu2Mo5N4O27P2, monoclinic, C2/c (no. 15), a = 15.6362(11) Å, b = 13.2418(9) Å, c = 23.6641(14) Å, β = 98.858(6)°, V = 4841.2(6) Å3, Z = 4, R gt(F) = 0.0219, wR ref(F 2) = 0.0522, T = 293(2) K.

Polyoxometalates as Potential Next-Generation Metallodrugs in the Combat Against Cancer

Polyoxometalates (POMs) are an emerging class of inorganic metal oxides, which over the last decades demonstrated promising biological activities by the virtue of their great diversity in structures and properties. They possess high potential for the inhibition of various tumor types; however, their unspecific interactions with biomolecules and toxicity impede their clinical usage. The current focus of the field of biologically active POMs lies on organically functionalized and POM-based nanocomposite structures as these hybrids show enhanced anticancer activity and significantly reduced toxicity towards normal cells in comparison to unmodified POMs. Although the antitumor activity of POMs is well documented, their mechanisms of action are still not well understood. In this Review, an overview is given of the cytotoxic effects of POMs with a special focus on POM-based hybrid and nanocomposite structures. Furthermore, we aim to provide proposed mode of actions and to identify molecular targets. POMs are expected to develop into the next generation of anticancer drugs that selectively target cancer cells while sparing healthy cells.

A polyoxometalate-modified magnetic nanocomposite: a promising antibacterial material for water treatment

A polyoxometalate-modified magnetic nanocomposite integrates the double antibacterial effects of both Fe₃O₄ and polyoxometalate, rendering it a promising candidate as an antimicrobial material.

A novel binuclear hydrazone-based Cd(II) complex is a strong pro-apoptotic inducer with significant activity against 2D and 3D pancreatic cancer stem cells

A novel binuclear Cd complex (1) with hydrazone-based ligand was prepared and characterized by spectroscopy and single crystal X-ray diffraction techniques. Complex 1 reveals a strong pro-apoptotic activity in both human, mammary adenocarcinoma cells (MCF-7) and pancreatic AsPC-1 cancer stem cells (CSCs). While apoptosis undergoes mostly caspase-independent, 1 stimulates the activation of intrinsic pathway with noteworthy down regulation of caspase-8 activity in respect to non-treated controls. Distribution of cells over mitotic division indicates that 1 caused DNA damage in both cell lines, which is confirmed in DNA interaction studies. Compared to 1, cisplatin (CDDP) does not achieve cell death in 2D cultured AsPC-1 cells, while induces different pattern of cell cycle changes and caspase activation in 2D cultured MCF-7 cells, implying that these two compounds do not share similar mechanism of action. Additionally, 1 acts as a powerful inducer of mitochondrial superoxide production with dissipated trans-membrane potential in the majority of the treated cells already after 6 h of incubation. On 3D tumors, 1 displays a superior activity against CSC model, and at 100 μM induces disintegration of spheroids within 2 days of incubation. Fluorescence spectroscopy, along with molecular docking show that compound 1 binds to the minor groove of DNA. Compound 1 binds to the human serum albumin (HSA) showing that the HSA can effectively transport and store 1 in the human body. Thus, our current study strongly supports further investigations on antitumor activity of 1 as a drug candidate for the treatment of highly resistant pancreatic cancer.

Hydrothermal Synthesis, Structural Characterization, and Interaction Mechanism with DNA of Copper(II) Complex Containing 2,2'-Bipyridine

A Cu(II) complex [Cu(bipy)(H₂O)₂(SO₄)] _n (bipy = 2,2'-bipyridine) was synthesized by hydrothermal method and characterized structurally by elemental analyses, single crystal X-ray diffraction, infrared spectra, and thermogravimetry and differential scanning calorimetry. The Cu(II) was hexacoordinated by two N atoms from bipy, two O atoms from different sulfate radical anions, and two O atoms from two water molecules, forming a slightly distorted octahedral geometry, and bridged by sulfato groups into polymeric chains. Under the condition of physiological pH, the interaction mechanism between the complex and hsDNA was explored with acridine orange as a fluorescence probe by spectroscopic methods. The binding modes between the complex and hsDNA were the electrostatic and embedded modes.