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.

Metallacarboranes are a class of inorganic boron clusters that have recently been recognized as biologically active compounds. Herein, we report on the host–guest complexation of several cobalt bis­(1,2-dicarbollide) anions (COSANs) with cyclodextrins (CDs) in aqueous solution. The binding affinities reach micromolar values, which are among the highest known values for native CDs, and exceed those for neutral hydrophobic organic guest molecules. The entrapment of the COSANs inside the cavity of CDs was confirmed using NMR and UV–visible spectroscopy, mass spectrometry, cyclic voltammetry, and isothermal titration calorimetry. Complexation by CDs greatly influences the photophysical and electrochemical properties of COSANs. In combination with indicator displacement assays, a label-free fluorescence-based method was developed to allow real-time monitoring of the translocation of COSANs through lipid bilayer membranes.

Electrocatalytic reduction of water, also known as the hydrogen evolution reaction (HER), may be one of the solutions for a sustainable energy supply in the future, but the current use of precious platinum electrocatalysts is a major drawback, owing to the high cost. So, it is urgent to discover cost‐effective and earth‐abundant materials to replace precious‐metal electrocatalysts in order to make this technology economically viable. Herein, we report the preparation and application of three new nanocomposites based on polyoxometalates (POMs) and reduced oxidized‐graphene flakes (rGF_ox) as HER electrocatalysts (ECs). In highly acidic medium (pH=0.3), the POM@rGF_ox ECs showed similar overpotentials (0.033–0.044 V vs. RHE) for a current density of 10 mA cm−2, and these are very close to the state‐of‐the‐art HER EC, 20 wt% Pt/C (0.024 V). The POM‐based nanocomposites also exhibited excellent exchange current densities (0.65–1.02 mA cm−2) and very low Tafel slopes (0.033–0.041 V dec−1). P5W30@rGF_ox exhibited the best HER metrics and also showed long‐term electrochemical stability, as the overpotential only changed 0.009 V for j=10 mA cm−2 after 1000 linear sweep voltammetry cycles. Besides highlighting POM‐oxidized‐graphene flakes composites as a new class of nanomaterial with several important electrochemical applications, this work also points out that the POM shape, size, charge, and composition (W/P ratio) may play an important role in fine‐tuning the HER activity, and opens new avenues for designing a new set of highly efficient, cost‐effective, and durable non‐precious‐metal HER ECs in acidic medium.

No abstract

We have synthesized and structurally characterized three tetra-(ptolyl)antimony(III)-containing heteropolytungstates, [{(p-tolyl)Sb III } 4 (A-α-XW 9 O 34 ) 2 ] n− [X = P V (1-P), As V (1-As), or Ge IV (1-Ge)], in aqueous solution using conventional, one-pot procedures. The polyanions 1-P, 1-As, and 1-Ge were fully characterized in the solid state and in solution and were shown to be soluble and stable in aqueous medium at pH 7. Biological studies demonstrated that all three polyanions possess significant antibacterial and antitumor activities. The minimum inhibitory concentrations of 1-P, 1-As, and 1-Ge were determined against four kinds of bacteria, including the two pathogenic bacteria strains, Vibrio parahaemolyticus and Vibrio vulnificus. The three novel polyanions also showed high cytotoxic potency in the human cell lines A549 (non-small cell lung cancer), CH1/ PA-1 (ovarian teratocarcinoma), and SW480 (colon carcinoma).