Polyoxometalates as antitumor agents: Bioactivity of a new polyoxometalate with copper on a human osteosarcoma model

Copper metabolism in osteoarthritis and its relation to oxidative stress and ferroptosis in chondrocytes

Ferroptosis, an iron-ion-dependent process of lipid peroxidation, damages the plasma membrane, leading to non-programmed cell death. Osteoarthritis (OA), a prevalent chronic degenerative joint disease among middle-aged and older adults, is characterized by chondrocyte damage or loss. Emerging evidence indicates that chondrocyte ferroptosis plays a role in OA development. However, most research has concentrated on ferroptosis regulation involving typical iron ions, potentially neglecting the significance of elevated copper ions in both serum and joint fluid of patients with OA. This review aims to fill this gap by systematically examining the interplay between copper metabolism, oxidative stress, ferroptosis, and copper-associated cell death in OA. It will provide a comprehensive overview of copper ions' role in regulating ferroptosis and their dual role in OA. This approach seeks to offer new insights for further research, prevention, and treatment of OA.

Polyoxometalate inhibition of SOX2-mediated tamoxifen resistance in breast cancer

BACKGROUND

Increased cancer stem cell (CSC) content and SOX2 overexpression are common features in the development of resistance to therapy in hormone-dependent breast cancer, which remains an important clinical challenge. SOX2 has potential as biomarker of resistance to treatment and as therapeutic target, but targeting transcription factors is also challenging. Here, we examine the potential inhibitory effect of different polyoxometalate (POM) derivatives on SOX2 transcription factor in tamoxifen-resistant breast cancer cells.

METHODS

Various POM derivatives were synthesised and characterised by infrared spectra, powder X-ray diffraction pattern and nuclear magnetic resonance spectroscopy. Estrogen receptor (ER) positive breast cancer cells, and their counterparts, which have developed resistance to the hormone therapy tamoxifen, were treated with POMs and their consequences assessed by gel retardation and chromatin immunoprecipitation to determine SOX2 binding to DNA. Effects on proliferation, migration, invasion and tumorigenicity were monitored and quantified using microscopy, clone formation, transwell, wound healing assays, flow cytometry and in vivo chick chorioallantoic membrane (CAM) models. Generation of lentiviral stable gene silencing and gene knock-out using CRISPR-Cas9 genome editing were applied to validate the inhibitory effects of the selected POM. Cancer stem cell subpopulations were quantified by mammosphere formation assays, ALDEFLUOR activity and CD44/CD24 stainings. Flow cytometry and western blotting were used to measure reactive oxygen species (ROS) and apoptosis.

RESULTS

POMs blocked in vitro binding activity of endogenous SOX2. [P2W18O62]6- (PW) Wells-Dawson-type anion was the most effective at inhibiting proliferation in various cell line models of tamoxifen resistance. 10 µM PW also reduced cancer cell migration and invasion, as well as SNAI2 expression levels. Treatment of tamoxifen-resistant cells with PW impaired tumour formation by reducing CSC content, in a SOX2-dependent manner, which led to stem cell depletion in vivo. Mechanistically, PW induced formation of reactive oxygen species (ROS) and inhibited Bcl-2, leading to the death of tamoxifen-resistant cells. PW-treated tamoxifen-resistant cells showed restored sensitivity to tamoxifen.

CONCLUSIONS

Together, these observations highlight the potential use of PW as a SOX2 inhibitor and the therapeutic relevance of targeting SOX2 to treat tamoxifen-resistant breast cancer.

Lindqvist-type Polyoxometalates Act as Anti-breast Cancer Drugs via Mitophagy-induced Apoptosis

OBJECTIVE

Lindqvist-type polyoxometalates (POMs) exhibit potential antitumor activities. This study aimed to examine the effects of Lindqvist-type POMs against breast cancer and the underlying mechanism.

METHODS

Using different cancer cell lines, the present study evaluated the antitumor activities of POM analogues that were modified at the body skeleton based on molybdenum-vanadium-centered negative oxygen ion polycondensations with different side strains. Cell colony formation assay, autophagy detection, mitochondrial observation, qRT-PCR, Western blotting, and animal model were used to evaluate the antitumor activities of POMs against breast cancer cells and the related mechanism.

RESULTS

MO-4, a Lindqvist-type POM linking a proline at its side strain, was selected for subsequent experiments due to its low half maximal inhibitory concentration in the inhibition of proliferation of breast cancer cells. It was found that MO-4 induced the apoptosis of multiple types of breast cancer cells. Mechanistically, MO-4 activated intracellular mitophagy by elevating mitochondrial reactive oxygen species (ROS) levels and resulting in apoptosis. In vivo, breast tumor growth and distant metastasis were significantly reduced following MO-4 treatment.

CONCLUSION

Collectively, the results of the present study demonstrated that the novel Lindqvist-type POM MO-4 may exhibit potential in the treatment of breast cancer.

Roles and mechanisms of copper homeostasis and cuproptosis in osteoarticular diseases

Copper is an essential trace element in the human body that is extensively distributed throughout various tissues. The appropriate level of copper is crucial to maintaining the life activities of the human body, and the excess and deficiency of copper can lead to various diseases. The copper levels in the human body are regulated by copper homeostasis, which maintains appropriate levels of copper in tissues and cells by controlling its absorption, transport, and storage. Cuproptosis is a distinct form of cell death induced by the excessive accumulation of intracellular copper. Copper homeostasis and cuproptosis has recently elicited increased attention in the realm of human health. Cuproptosis has emerged as a promising avenue for cancer therapy. Studies concerning osteoarticular diseases have elucidated the intricate interplay among copper homeostasis, cuproptosis, and the onset of osteoarticular diseases. Copper dysregulation and cuproptosis cause abnormal bone and cartilage metabolism, affecting related cells. This phenomenon assumes a critical role in the pathophysiological processes underpinning various osteoarticular diseases, with implications for inflammatory and immune responses. While early Cu-modulating agents have shown promise in clinical settings, additional research and advancements are warranted to enhance their efficacy. In this review, we summarize the effects and potential mechanisms of copper homeostasis and cuproptosis on bone and cartilage, as well as their regulatory roles in the pathological mechanism of osteoarticular diseases (e.g., osteosarcoma (OS), osteoarthritis (OA), and rheumatoid arthritis (RA)). We also discuss the clinical-application prospects of copper-targeting strategy, which may provide new ideas for the diagnosis and treatment of osteoarticular diseases.

Microwave-assisted hydrothermal fabrication of hierarchical-stacked mesoporous decavanadate-intercalated ZnAl nanolayered double hydroxide to exterminate different developmental stages of Trichinella spiralis and Schistosoma mansoniin-vitro

Hierarchically stacked mesoporous zinc-aluminium nanolayered-double-hydroxide intercalated with decavanadate (ZnAl-LDH-V₁₀O₂₈) is constructed using anion-exchange process via microwave-hydrothermal treatment. Physicochemical properties of ZnAl-LDH-V₁₀O₂₈ are characterized in detail. Decavanadate anions are intimately interacted with ZnAl-LDH nanosheets, generating highly ordered architecture of well-dimensioned stacking blocks of brucite-like nanolayers (∼8 nm). Such hierarchy improves surface-porosity and electrical-impedivity of ZnAl-LDH-V₁₀O₂₈ with declining its zeta-potential (ζ_av = 8.8 mV). In-vitro treatment of various developmental-stages of Trichinella spiralis and Schistosoma mansoni by ZnAl-LDH-V₁₀O₂₈ is recognized using parasitological and morphological (SEM/TEM) analyses. ZnAl-LDH-V₁₀O₂₈ exterminates muscle-larvae and adult-worms of Trichinella spiralis, and juvenile and adult Schistosoma mansoni, yielding near 100% mortality with rates achieving 5%/h within about 17 h of incubation. This parasiticidal behavior results from the symphony of biological activity gathering decavanadate and LDH-nanosheets. Indeed, ZnAl-LDH-V₁₀O₂₈ nanohybrid sample, as a promissory biocide for killing food-borne/waterborne parasites, becomes a futuristic research hotspot for studying its in-vivo bioactivity and impact-effectiveness on parasite molecular biology.

Polyoxometalates Impact as Anticancer Agents

Polyoxometalates (POMs) are oxoanions of transition metal ions, such as V, Mo, W, Nb, and Pd, forming a variety of structures with a wide range of applications. Herein, we analyzed recent studies on the effects of polyoxometalates as anticancer agents, particularly their effects on the cell cycle. To this end, a literature search was carried out between March and June 2022, using the keywords "polyoxometalates" and "cell cycle". The effects of POMs on selected cell lines can be diverse, such as their effects in the cell cycle, protein expression, mitochondrial effects, reactive oxygen species (ROS) production, cell death and cell viability. The present study focused on cell viability and cell cycle arrest. Cell viability was analyzed by dividing the POMs into sections according to the constituent compound, namely polyoxovanadates (POVs), polyoxomolybdates (POMos), polyoxopaladates (POPds) and polyoxotungstates (POTs). When comparing and sorting the IC₅₀ values in ascending order, we obtained first POVs, then POTs, POPds and, finally, POMos. When comparing clinically approved drugs and POMs, better results of POMs in relation to drugs were observed in many cases, since the dose required to have an inhibitory concentration of 50% is 2 to 200 times less, depending on the POMs, highlighting that these compounds could become in the future an alternative to existing drugs in cancer therapy.

The Cuproptosis-Related Long Noncoding RNA Signature Predicts Prognosis and Tumour Immune Analysis in Osteosarcoma

Background

Cuprotopsis is a type of programmed cell death discovered in recent years. Long noncoding RNAs (lncRNAs) play an important regulatory role in programmed cell death. The effect of cuproptosis-related lncRNAs on osteosarcoma is unknown. Our work, based on cuproptosis-related lncRNAs, proposes a gene signature to assess the prognosis of patients with osteosarcoma.

Methods

Osteosarcoma gene expression data from The Cancer Genome Atlas (TCGA), clinical features of osteosarcoma and RNA sequencing data of normal adipose tissue were obtained from the UCSC Xena database. A cuproptosis-related lncRNA risk model was established to calculate the risk score. At the same time, cluster analysis, clinicopathological analysis, functional enrichment analysis, and prediction of compounds with potential therapeutic value were evaluated. We analyzed whether there was a correlation between the risk score and tumour immunity. RT-qPCR was used to verify the expression level of lncRNA.

Results

Nine lncRNAs (AC124798.1, AC006033.2, AL450344.2, AL512625.2, LINC01060, LINC00837, AC004943.2, AC064836.3, and AC100821.2) were identified to create a risk model and indicate the prognosis of patients with osteosarcoma. The high-risk group had a worse prognosis than the low-risk group. Analysis of clinicopathological features, principal component analysis, receiver operating characteristic curve, c-index curve, and comparative analysis of models proved that the model is reliable. Functional enrichment analysis suggests that the risk score may correlate with cell energy metabolism and tumour-related biological function. Three potentially therapeutic compounds have been predicted. These analyses may be beneficial to the treatment of osteosarcoma in the future. RT-qPCR verified the expression level of three lncRNA (LINC01060, NKILA, and SNHG8).

Conclusions

Cuproptosis-related lncRNAs have a strong relationship with osteosarcoma patients. Nine lncRNA models can effectively forecast the prognosis of osteosarcoma and may play a significant role in the individualized treatment of osteosarcoma patients in the future.

Polyoxometalate Nanoparticles as a Potential Glioblastoma Therapeutic via Lipid-Mediated Cell Death

Polyoxometalate nanoparticles (POMs) are a class of compounds made up of multiple transition metals linked together using oxygen atoms. POMs commonly include group 6 transition metals, with two of the most common forms using molybdenum and tungsten. POMs are suggested to exhibit antimicrobial effects. In this study, we developed two POM preparations to study anti-cancer activity. We found that Mo-POM (NH₄)Mo₇O₂₄) and W-POM (H₃PW₁₂O₄₀) have anti-cancer effects on glioblastoma cells. Both POMs induced morphological changes marked by membrane swelling and the presence of multinucleated cells that may indicate apoptosis induction along with impaired cell division. We also observed significant increases in lipid oxidation events, suggesting that POMs are redox-active and can catalyze detrimental oxidation events in glioblastoma cells. Here, we present preliminary indications that molybdenum polyoxometalate nanoparticles may act like ferrous iron to catalyze the oxidation of phospholipids. These preliminary results suggest that Mo-POMs (NH₄)Mo₇O₂₄) and W-POMs (H₃PW₁₂O₄₀) may warrant further investigation into their utility as adjunct cancer therapies.

Promising application of polyoxometalates in the treatment of cancer, infectious diseases and Alzheimer's disease

As shown in studies conducted in recent decades, polyoxometalates (POMs), as inorganic metal oxides, have promising biological activities, including antitumor, anti-infectious and anti-Alzheimer’s activities, due to their special structures and properties. However, some side effects impede their clinical applications to a certain extent. Compared with unmodified POMs, POM-based inorganic–organic hybrids and POM-based nanocomposite structures show significantly enhanced bioactivity and reduced side effects. In this review, we introduce the biological activities of POMs and their derivatives and highlight the side effects of POMs on normal cells and organisms and their possible mechanisms of action. We then propose a development direction for overcoming their side effects. POMs are expected to constitute a new generation of inorganic metal drugs for the treatment of cancer, infectious diseases, and Alzheimer's disease.

Graphical abstract

Glutathione-Depleting Nanomedicines for Synergistic Cancer Therapy

Cancer cells frequently exhibit resistance to various molecular and nanoscale drugs, which inevitably affects the drugs' therapeutic outcomes. Overexpression of glutathione (GSH) has been observed in many cancer cells, and solid evidence has corroborated the resulting tumor resistance to a variety of anticancer therapies, suggesting that this biochemical characteristic of cancer cells can be developed as a potential target for cancer treatments. The single treatment of GSH-depleting agents can potentiate the responses of the cancer cells to different cell death stimuli; therefore, as an adjunctive strategy, GSH depletion is usually combined with mainstream cancer therapies for enhancing the therapeutic outcomes. Propelled by the rapid development of nanotechnology, GSH-depleting agents can be readily constructed into anticancer nanomedicines, which have shown a steep rise over the past decade. Here, we review the common GSH-depleting nanomedicines which have been widely applied in synergistic cancer treatments in recent years. Some current challenges and future perspectives for GSH depletion-based cancer therapies are also presented. With the understanding of the structure-property relationship and action mechanisms of these biomaterials, we hope that the GSH-depleting nanotechnology will be further developed to realize more effective disease treatments and even achieve successful clinical translations.

Inhibition of Mitochondrial ATP Synthesis and Regulation of Oxidative Stress Based on {SbW8 O30 } Determined by Single-Cell Proteomics Analysis

The 10-nuclear heteroatom cluster modified {SbW₈ O₃₀ } was successfully synthesized and exhibited inhibitory activity (IC₅₀ =0.29 μM). Based on proteomics analysis, Na₄ Ni₂ Sb₂ W₂ -SbW₈ inhibited ATP production by affecting the expression of 16 related proteins, hindering metabolic functions in vivo and cell proliferation due to reactive oxygen species (ROS) stress. In particular, the low expression of FAD/FMN-binding redox enzymes (relative expression ratio of the experimental group to the control=0.43843) could be attributed to the redox mechanism of Na₄ Ni₂ Sb₂ W₂ -SbW₈ , which was consistent with the effect of polyoxometalates (POMs) and FMN-binding proteins on ATP formation. An electrochemical study showed that Na₄ Ni₂ Sb₂ W₂ -SbW₈ combined with FMN to form Na₄ Ni₂ Sb₂ W₂ -SbW₈ -2FMN complex through a one-electron process of the W atoms. Na₄ Ni₂ Sb₂ W₂ -SbW₈ acted as catalase and glutathione peroxidase to protect the cell from ROS stress, and the inhibition rates were 63.3 % at 1.77 μM of NADPH and 86.06 % at 10.62 μM of 2-hydroxyterephthalic acid. Overall, our results showed that POMs can be specific oxidative/antioxidant regulatory agents.

Antitumor effect of a pyrazolone-based-complex [Cu(PMPP-SAL)(EtOH)] against murine melanoma B16 cell in vitro and in vivo

Pyrazolone-based derivative metal complexes were reported to have cytotoxicity in some tumor cells. In this study, the antitumor effect of [Cu(PMPP-SAL)(EtOH)] (PMPP-SAL = N-(1-phenyl-3-methyl-4-propenylidene-5-pyrazolone)- salicylidene hydrazide anion) in murine melanoma B16 cells in vitro and in vivo was investigated. The results showed that [Cu(PMPP-SAL)(EtOH)] inhibited the survival of B16 cells in vitro, and the IC50 value was superior to cisplatin (DDP) (p < 0.001). B16 cell apoptosis was significantly higher in comparison to the control group (DMSO) (p < 0.01), and cell cycle arrest occurred at the G0/G1 phase. When challenged C57 BL/6J mice were treated with [Cu(PMPPSAL)(EtOH)], a smaller volume of B16 solid tumors were reported than the control group (p < 0.01), with lower positive expression indices of CD 34, vascular endothelial growth factor (VEGF) and basic fibroblast growth factor (bFGF) (p < 0.01). Moreover, the tumor growth was suppressed in mice due to the induction of apoptosis, as detected by the TUNEL assay (p < 0.001). In summary, [Cu(PMPP-SAL)(EtOH)] effectively inhibited the growth of B16 cells in vitro and in vivo due to the induction of apoptosis and the inhibition of intra-tumoral angiogenesis, demonstrating its therapeutic potential in melanoma treatment.

The Aquaporin-3-Inhibiting Potential of Polyoxotungstates

Polyoxometalates (POMs) are of increasing interest due to their proven anticancer activities. Aquaporins (AQPs) were found to be overexpressed in tumors bringing particular attention to their inhibitors as anticancer drugs. Herein, we report for the first time the ability of polyoxotungstates (POTs), such as of Wells-Dawson P2W18, P2W12, and P2W15, and Preyssler P5W30 structures, to affect aquaporin-3 (AQP3) activity and impair melanoma cell migration. The tested POTs were revealed to inhibit AQP3 function with different effects, with P2W18, P2W12, and P5W30 being the most potent (50% inhibitory concentration (IC50) = 0.8, 2.8, and 3.2 µM), and P2W15 being the weakest (IC50 > 100 µM). The selectivity of P2W18 toward AQP3 was confirmed in yeast cells transformed with human aquaglyceroporins. The effect of P2W12 and P2W18 on melanoma cells that highly express AQP3 revealed an impairment of cell migration between 55% and 65% after 24 h, indicating that the anticancer properties of these compounds may in part be due to the blockage of AQP3-mediated permeability. Altogether, our data revealed that P2W18 strongly affects AQP3 activity and cancer cell growth, unveiling its potential as an anticancer drug against tumors where AQP3 is highly expressed.

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.

Exploring Wells-Dawson Clusters Associated With the Small Ribosomal Subunit

The polyoxometalate P₂W₁₈O626-, the Wells-Dawson cluster, stabilized the ribosome sufficiently for the crystallographers to solve the phase problem and improve the structural resolution. In the following we characterize the interaction of the Wells-Dawson cluster with the ribosome small subunit. There are 14 different P₂W₁₈O626- clusters interacting with the ribosome, and the types of interactions range from one simple residue interaction to complex association of multiple sites including backbone interactions with a Wells-Dawson cluster. Although well-documented that bridging oxygen atoms are the main basic sites on other polyoxometalate interaction with most proteins reported, the W=O groups are the main sites of the Wells-Dawson cluster interacting with the ribosome. Furthermore, the peptide chain backbone on the ribosome host constitutes the main sites that associate with the Wells-Dawson cluster. In this work we investigate the potential of one representative pair of closely-located Wells-Dawson clusters being a genuine Double Wells-Dawson cluster. We found that the Double Wells-Dawson structure on the ribosome is geometrically sound and in line with other Double Wells-Dawson clusters previously observed in the solid state and solution. This information suggests that the Double Wells-Dawson structure on the ribosome is real and contribute to characterization of this particular structure of the ribosome.

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.

Decavanadate Inhibits Mycobacterial Growth More Potently Than Other Oxovanadates

51V NMR spectroscopy is used to document, using speciation analysis, that one oxometalate is a more potent growth inhibitor of two Mycobacterial strains than other oxovanadates, thus demonstrating selectivity in its interaction with cells. Historically, oxometalates have had many applications in biological and medical studies, including study of the phase-problem in X-ray crystallography of the ribosome. The effect of different vanadate salts on the growth of Mycobacterium smegmatis (M. smeg) and Mycobacterium tuberculosis (M. tb) was investigated, and speciation was found to be critical for the observed growth inhibition. Specifically, the large orange-colored sodium decavanadate (V10O 28 6 - ) anion was found to be a stronger inhibitor of growth of two mycobacterial species than the colorless oxovanadate prepared from sodium metavanadate. The vanadium(V) speciation in the growth media and conversion among species under growth conditions was monitored using 51V NMR spectroscopy and speciation calculations. The findings presented in this work is particularly important in considering the many applications of polyoxometalates in biological and medical studies, such as the investigation of the phase-problem in X-ray crystallography for the ribosome. The findings presented in this work investigate the interactions of oxometalates with other biological systems.

Crystal structure, Hirshfeld surface analysis, spectroscopic and biological studies on sulfamethazine and sulfaquinoxaline ternary complexes with 2,2′-biquinoline

Three ternary complexes with sulfaquinoxaline or sulfamethazine have been synthesized and their structural, spectroscopic and biological properties have been studied.

In vitro and in vivo antifungal activities and mechanism of heteropolytungstates against Candida species

The antifungal activities of heteropolytungstates, α-1,2,3-K₆H[SiW₉V₃O₄₀] (SiW-3), K₁₃[Ce(SiW₁₁O₃₉)₂]·17H₂O (SiW-5), K₁₃[Eu(SiW₁₁O₃₉)₂]·25H₂O (SiW-10), K₆PV₃W₉O₄₀ (PW-6), α-K₄PVW₁₁O₄₀ (PW-8), were screened in 29 Candida albicans, 8 Candida glabrata, 3 Candida krusei, 2 Candida parapsilosis, 1 Candida tropicalis, and 1 Cryptococcus neoformans strains using the CLSI M27-A3 method. SiW-5 had the highest efficacy with a minimum inhibitory concentration (MIC) values of <0.2–10.2 μM in vitro. The antifungal mechanism, acute toxicity and in vivo antifungal activity of SiW-5 were then evaluated in C. albicans. The results showed that SiW-5 damaged the fungal cell membrane, reduce the ergosterol content and its main mode of action was through inhibition of ergosterol biosynthesis. Real-time PCR showed that ERG1, ERG7, ERG11 and ERG28 were all significantly upregulated by SiW-5. An acute toxicity study showed the 50% lethal dose (LD₅₀) of SiW-5 for ICR mice was 1651.5 mg/kg. And in vivo antifungal studies demonstrated that SiW-5 reduced both the morbidity and fungal burden of mice infected with C. albicans. This study demonstrates that SiW-5 is a potential antifungal candidate against the Candida species.

Silver Cation Coordination Study to AsW9 Ligand – A Trilacunar Arsenotungstate Compound

Objective: The main objective of this research is to find the coordination ratio between AsW9and Ag+, as a preliminary study for synthesizing a new silver-arsenotungstate complex. Material and method: The ligand:cation molar ratio in complexes was determined by conductometric and potentiometric titrations of AsW9with silver salts: CH3COOAg, AgNO3. Results: The ratio was obtained from the inflexion points of the curves when molar ratio was plotted versus conductivity, or from the equivalence point when silver added volume was plotted versus pH value. Each graphic shows one point of inflexion corresponding to 1:1.54 ratio of AsW9:Ag+. In the same manner, the equivalent volumes determined by graphical method gave the ratio 1:1.53. The spectral results confirmed that a AsW9:Ag+complex was formed since the ligand absorption maxima values have been changed from 190 nm to 197 nm in the case of using AgNO3and 196 nm for CH3COOAg corresponding to the W=Odbond, and from 246.5 nm to 274 nm (AgNO3) and 270 nm (CH3COO-Ag+) for the W-Ob,c-W bond. Conclusions: Silver cation exhibit a preference for AsW9in a ratio of 3 to 2. This ratio can be associated to a sandwich type arrangement, with two trilacunary Keggin building blocks incorporating 3 metal cations in a tetrahedral geometry.

A survey of the different roles of polyoxometalates in their interaction with amino acids, peptides and proteins

This perspective provides a comprehensive description of the different roles of POMs in their interaction with relevant biological molecules.

In vitro cell cytotoxicity profile and morphological response to polyoxometalate-stabilised gold nanoparticles

Polyoxometalate-stabilised gold nanoparticles internalise in vast quantities into kidney epithelial and skin melanoma cell lines causing antiproliferative action on tumoural cells.

Synthesis of chitosan-coated polyoxometalate nanoparticles against cancer and its metastasis

HeLa cells, before and after treatment with nanoparticles.