Combined Experimental and Computational Study of V-Substituted Lindqvist Polyoxotungstate: Screening by Docking for Potential Antidiabetic Activity.

In the current work, a novel vanadotungstate compound, (C6H9N2)4[V2W4O19]·2H2O (1), is isolated by a simple stepwise synthesis method and characterized by a combined experimental and computational study. Molecular docking is conducted for the first time for this kind of substituted Lindqvist polyoxometalates to elucidate for potential antidiabetic activity. Hence, the modeling results revealed a significant docking score of the reported compound to bind to the active sites of α-glucosidase with the lowest binding energy of -5.7 kcal/mol, where the standard drug acarbose (ACB) had -4.6 kcal/mol binding energy. The stability of binding was enhanced by strong H-bonding, van der Waals, and electrostatic interactions occurring in the three-dimensional (3D) supramolecular network of polyanionic vanadotungstate subunits templated with organic moieties as shown by X-ray diffraction and Hirshfeld analyses. Furthermore, density functional theory (DFT) calculations supported with photophysical measurements are also discussed to predict the most chemical and biological reactivity. In this view, the complete description of electronic and biological features of (1) is enhanced by determination of the highest occupied molecular orbital (HOMO)/least unoccupied molecular orbital (LUMO) energy, electronic density, ionization potential, electron affinity, etc. These chemical descriptors, intermolecular interactions, docking score, and binding free energy estimation are essential in understanding the reactivity of this bioactive compound offering potential inhibition of the α-glucosidase enzyme.

A Universal and Reversible Wet Adhesive via Straightforward Aqueous Self-Assembly of Polyethylenimine and Polyoxometalate.

The excellent adhesion of mussels under wet conditions has inspired the development of numerous catechol-based wet adhesives. Nevertheless, the performance of catechol-based wet adhesive suffers from the sensitivity toward temperature, pH, or oxidation stimuli. Therefore, it is of great significance to develop non-catechol-based wet adhesives to fully recapitulate nature's dynamic function. Herein, a novel type of non-catechol-based wet adhesive is reported, which is readily formed by self-assembly of commercially available branched polyethylenimine and phosphotungstic acid in aqueous solution through the combination of electrostatic interaction and hydrogen bonding. This wet adhesive shows reversible, tunable, and strong adhesion on diverse substrates and further exhibits high efficacy in promoting biological wound healing. During the healing of the wound, the as-prepared wet adhesive also possesses inherent antimicrobial properties, thus avoiding inflammations and infections due to microorganism accumulation.

A supramolecular complex based on a Gd-containing polyoxometalate and food-borne peptide for MRI/CT imaging and NIR-triggered photothermal therapy.

A multifunctional supramolecular complex is reported for the integrated multiple magnetic resonance imaging/computed X-ray tomography (MRI/CT) imaging and photothermal therapy, wherein a gadolinium-substituted paramagnetic polyoxometalate cluster and food-borne antioxidant peptides identified from the trepang protein hydrolysates are introduced. The as-prepared complex maintained an uniform particle size and much better biocompatibility, and is an ideal candidate for the in vivo applications. The complex allows for T1-weighted MR imaging and a high Hounsfield unit value for enhanced CT imaging. Interestingly, we demonstrate that the complex possesses outstanding photothermal cancer-killing effects due to its high photothermal conversion efficiency under the exposure of an NIR laser and enhanced antibacterial activity to avoid bacterial infection from the thermal therapeutic process. These results indicate that the supramolecular complex platform exhibit potential for accurate medical diagnosis at an early stage and effective eradication of the tumor cells.

Solution Dynamics of Hybrid Anderson-Evans Polyoxometalates.

Understanding the stability and speciation of metal-oxo clusters in solution is essential for many of their applications in different areas. In particular, hybrid organic-inorganic polyoxometalates (HPOMs) have been attracting increasing attention as they combine the complementary properties of organic ligands and metal-oxygen nanoclusters. Nevertheless, the speciation and solution behavior of HPOMs have been scarcely investigated. Hence, in this work, a series of HPOMs based on the archetypical Anderson-Evans structure, δ-[MnMo6O18{(OCH2)3C-R}2]3-, with different functional groups (R = -NH2, -CH3, -NHCOCH2Cl, -N═CH(2-C5H4N) {pyridine; -Pyr}, and -NHCOC9H15N2OS {biotin; -Biot}) and countercations (tetrabutylammonium {TBA}, Li, Na, and K) were synthesized, and their solution behavior was studied in detail. In aqueous solutions, decomposition of HPOMs into the free organic ligand, [MoO4]2-, and free Mn3+ was observed over time and was shown to be highly dependent on the pH, temperature, and nature of the ligand functional group but largely independent of ionic strength or the nature of the countercation. Furthermore, hydrolysis of the amide and imine bonds often present in postfunctionalized HPOMs was also observed. Hence, HPOMs were shown to exhibit highly dynamic behavior in solution, which needs to be carefully considered when designing HPOMs, particularly for biological applications.

In Vitro Antifungal Activity and Mechanism of Ag3PW12O40 Composites against Candida Species.

Fungal infections pose a serious threat to human health. Polyoxometalates (POMs) are metal-oxygen clusters with potential application in the control of microbial infections. Herein, the Ag3PW12O40 composites have been synthesized and verified by Fourier transform infrared (FT-IR) spectrum, transmission electron microscopy (TEM), scanning electron microscope (SEM), elemental analysis, and X-ray diffraction (XRD). The antifungal activities of Ag3PW12O40 were screened in 19 Candida species strains through the determination of minimum inhibitory concentration (MIC) by the microdilution checkerboard technique. The minimum inhibitory concentration (MIC50) values of Ag3PW12O40 are 2~32 µg/mL to the Candida species. The MIC80 value of Ag3PW12O40 to resistant clinical isolates C. albicans HL963 is 8 µg/mL, which is lower than the positive control, fluconazole (FLC). The mechanism against C. albicans HL963 results show that Ag3PW12O40 can decrease the ergosterol content. The expressions of ERG1, ERG7, and ERG11, which impact on the synthesis of ergosterol, are all prominently upregulated by Ag3PW12O40. It indicates that Ag3PW12O40 is a candidate in the development of new antifungal agents.

Near-Infrared-Controlled Nanoplatform Exploiting Photothermal Promotion of Peroxidase-like and OXD-like Activities for Potent Antibacterial and Anti-biofilm Therapies.

Nanozymes that mimic peroxidase (POD) activity can convert H2O2 into bactericidal free radicals, which is referred to as chemodynamic therapy (CDT). High glutathione (GSH) levels in the infectious tissue severely limit the performance of CDT. Herein, we report a near-infrared-controlled antibacterial nanoplatform that is based on encapsulating tungsten sulfide quantum dots (WS2QDs) and the antibiotic vancomycin in a thermal-sensitive liposome. The system exploits the photothermal sensitivity of the WS2QDs to achieve selective liposome rupture for the targeted drug delivery. We determined that WS2QDs show a strong POD-like activity under physiological conditions and the oxidase-like activity, which can oxidate GSH to further improve the CDT efficacy. Moreover, we found that increased temperature promotes multiple enzyme-mimicking activities of WS2QDs. This platform exerts antibacterial effects against Gram-positive Mu50 (a vancomycin-intermediate Staphylococcus aureus reference strain) and Gram-negative Escherichia coli and disrupts biofilms for improved penetration of therapeutic agents inside biofilms. In vivo studies with mice bearing Mu50-caused skin abscess revealed that this platform confers potent antibacterial activity without obvious toxicity. Accordingly, our work illustrates that the photothermal and nanozyme properties of WS2QDs can be deployed alongside a conventional therapeutic to achieve synergistic chemodynamic/photothermal/pharmaco therapy for powerful antibacterial effects.

An acidity-responsive polyoxometalate with inflammatory retention for NIR-II photothermal-enhanced chemodynamic antibacterial therapy.

Subcutaneous abscesses caused by drug-resistant pathogens pose a serious challenge to human health. To overcome this problem, herein an acidity-responsive aggregated W/Mo-based polyoxometalate (POM) was developed for photothermal-enhanced chemodynamic antibacterial therapy in the second near-infrared (NIR) region. The POM can self-assemble into larger-sized aggregates with stronger absorption in the NIR region, making it remain in the acidic infected tissue. Furthermore, the hydrogen peroxide at the site of infection can be converted to a hydroxyl radical for chemodynamic therapy (CDT) and simultaneously the glutathione in organisms is consumed by the POM to further enhance the CDT effect. More importantly, under laser irradiation, the hyperthermia produced by the POM not only can kill drug-resistant Staphylococcus aureus, but also enhance the performance of CDT. Benefitting from the inflammatory retention and acidity-responsive photothermal-enhanced CDT properties, the POM exhibits an obvious therapeutic effect against drug-resistant bacterial infection without significant side effects under 1060 nm laser irradiation.

Combinatorial discovery of Mo-based polyoxometalate clusters for tumor photothermal therapy and normal cell protection.

Nanomaterials with multiple functions such as precision diagnosis, therapeutic efficacy and biosafety are attractive for tumor treatment but remain a technical challenge. In this study, molybdenum (Mo)-based polyoxometalate clusters (Mo-POM) with considerable photothermal conversion efficiency (∼56.6%) and high stability (>30 days) were prepared through a modification of the Folin-Ciocalteu method. These synthetic particles accumulated at the target site, and induced thermal ablation of the tumor following near infrared (NIR) absorption. Furthermore, the Mo-POM effectively scavenged reactive oxygen species (ROS) through charge transfer between Mo(vi) and Mo(v) states, thereby avoiding off-target effects on normal cells and improving the therapeutic efficiency both in vitro and in vivo. Therefore, for the first time, we prepared Mo-POM having two key functions, i.e., photothermal therapy (PTT) for cancer cells and protection of normal cells. These exceptional features may open up the exploration of Mo-POM as new tools for PTT against tumors in clinical applications.

Selective Hydrolysis of Transferrin Promoted by Zr-Substituted Polyoxometalates.

The hydrolysis of the iron-binding blood plasma glycoprotein transferrin (Tf) has been examined at pH = 7.4 in the presence of a series of Zr-substituted polyoxometalates (Zr-POMs) including Keggin (Et2NH2)10[Zr(PW11O39)2]∙7H2O (Zr-K 1:2), (Et2NH2)8[{α-PW11O39Zr-(µ-OH) (H2O)}2]∙7H2O (Zr-K 2:2), Wells-Dawson K15H[Zr(α2-P2W17O61)2]·25H2O (Zr-WD 1:2), Na14[Zr4(α-P2W16O59)2(µ3-O)2(µ-OH)2(H2O)4]·57H2O (Zr-WD 4:2) and Lindqvist (Me4N)2[ZrW5O18(H2O)3] (Zr-L 1:1), (nBu4N)6[(ZrW5O18(µ-OH))2]∙2H2O (Zr-L 2:2)) type POMs. Incubation of transferrin with Zr-POMs resulted in formation of 13 polypeptide fragments that were observed on sodium dodecyl sulfate poly(acrylamide) gel electrophoresis (SDS-PAGE), but the hydrolysis efficiency varied depending on the nature of Zr-POMs. Molecular interactions between Zr-POMs and transferrin were investigated by using a range of complementary techniques such as tryptophan fluorescence, circular dichroism (CD), 31P-NMR spectroscopy, in order to gain better understanding of different efficiency of investigated Zr-POMs. A tryptophan fluorescence quenching study revealed that the most reactive Zr-WD species show the strongest interaction toward transferrin. The CD results demonstrated that interaction of Zr-POMs and transferrin in buffer solution result in significant secondary structure changes. The speciation of Zr-POMs has been followed by 31P-NMR spectroscopy in the presence and absence of transferrin, providing insight into stability of the catalysts under reaction condition.

An artificial class modelling approach to identify the most largely diffused cultivars of sweet cherry (Prunus avium L.) in Italy.

The nutritional and commercial value of the sweet cherry provides it a great economic importance in Italy. The aim of this study was to characterize 35 sweet cherry cultivars and one of sour cherry, by analyzing values of different pomological and nutraceutical traits, identifying cultivars with antioxidant activity and total anthocyanins content closest to those present in literature for Ferrovia (largely diffused in Italy). To this goal, a multivariate metric index through the Soft Independent Modeling of Class Analogy analyzing an artificial dataset and testing a real one, two hierarchical clustering and a principal component analysis, were performed. The multivariate analyses result simultaneously investigated all the variables highlighting cvs. Sylvia, Graffione nero Col di Mosso, Ferrovia, Mora della Punta, Bianchetta Nuchis and Sandra to be more similar to literature data of Ferrovia. This matrix index was a useful tool, to select the most commercial promising varieties.

Biosorption of tungstate onto garlic peel loaded with Fe(III), Ce(III), and Ti(IV).

In present study, garlic peel (GP) was modified by loading with Fe(III), Ti(IV), and Ce(III) through a cation exchange process, i.e., nGP-COOH + Mn+ = (nGP-COO)-Mn+ + nH+ (M = Fe, Ce, Ti), which could adsorb tungstate effectively under the weakly acidic conditions. The optimal initial pH for maximum adsorption of W(VI) was determined at 1~3 for Ti-GP, 1~4 for Fe-GP, and 3 for Ce-GP, respectively; and at pH 2.5, the corresponding maximum adsorption capacity for Fe-GP, Ti-GP, and Ce-GP was evaluated as 91.5 mg/g, 83 mg/g, and 84 mg/g tungsten respectively. Coexisting anions like chloride, sulfate, and carbonate showed little effect on tungsten adsorption, while fluoride and phosphate inhibited the adsorption drastically. The column adsorption showed that the breakthrough point for Ce-GP, Ti-GP, and Fe-GP was 180 min, 200 min, and 270 min respectively. And 0.1 mol/L NaOH effectively eluted the adsorbed tungsten, and concentration of the eluted solution had almost 6, 19.9, and 22 factors of the initial tungstate concentration correspondingly.

Fe-Doped Polyoxometalate as Acid-Aggregated Nanoplatform for NIR-II Photothermal-Enhanced Chemodynamic Therapy.

The combination of reactive oxygen species-involved chemodynamic therapy (CDT) and photothermal therapy (PTT) holds great promise in enhancing anticancer effects. Herein, a multifunctional Fe-doped polyoxometalate (Fe-POM) cluster is fabricated via a simple method. The Fe-POM can not only be utilized as PTT agents to generate a hyperthermia effect for cancer cell killing under near-infrared (NIR) II laser (1060 nm) irradiation, but also can be used as CDT agents to convert endogenous less-reactive H2 O2 into harmful ·OH and simultaneously deplete glutathione for an amplified CDT effect. Notably, the hyperthermia induced by PTT can further enhance the CDT effect, achieving a synergistic PTT/CDT effect. Owing to the self-assembling properties at lowered pH values, the Fe-POM exhibits high tumor accumulation as revealed by photoacoustic imaging. More importantly, Fe-POM enables effective destruction of tumors without inducing noticeable damage to normal tissues under 1060 nm laser irradiation. The work presents a new type of multifunctional agent with high PTT/CDT efficacy, providing promising methods for PTT-enhanced CDT in a NIR-II biowindow.

WS2 nanosheets functionalized by biomimetic lipids with enhanced dispersibility for photothermal and chemo combination therapy.

Multi-component combination therapy of cancer is currently a hot spot in the field of cancer treatment research. In this study, a WS2 nanosheet was selected as the substrate material and modified with a cell-like membrane biomimetic liposome (WS2-lipid). The lipid-modified WS2 nanomaterials were successfully prepared with good stability and biocompatibility. Its good photothermal characteristics and high drug loading amount were utilized to achieve a comprehensive chemo and photothermal therapeutic effect. The results showed that the lipid coating strongly enhanced the stability of the WS2 nanosheets before and after DOX loading and the WS2-lipid had a good photothermal performance and drug loading amount. According to the cellular results, WS2-lipid was able to be taken up by MCF-7 cells. Both photothermo-therapy and chemotherapy had a concentration dependent cytotoxicity on MCF-7 cells, and the combined application of both methods had an improved cytotoxicity. In addition, in vivo photothermal experiments indicated that lipid modification could promote intratumoral accumulation of the material. Thus, WS2-lipid can be used as a good nano-platform for phototherapy and chemotherapy combination therapy and has good application prospects in cancer therapy.

Preparation of P-g-C3N4-WS2 nanocomposite and its application in photoelectrochemical detection of 5-formylcytosine.

DNA formylation (5-formylcytosine, 5fC) is a major epigenetic modification involved in alterations in the DNA double helix structure and protein identification. Due to the low amount in all mammalian tissues and cells, it is necessary to develop a rapid, sensitive and efficient method for detecting 5fC for further understanding the biological functions of 5fC. Thus, a novel PEC biosensor was constructed using P-g-C3N4-WS2 nanocomposite as photoactive material. Firstly, AuNPs/P-g-C3N4-WS2/ITO electrode was prepared as substrate electrode. Secondly, the probe DNA and complementary DNA (containing 5fC base) was modified to the electrode surface based on the formation of Au-S bonds between AuNPs and thiol group on the probe DNA and hybridization, respectively. Finally, the amino functionalized MnO2 nanoflowers were further modified to the electrode surface by covalent interaction between the aldehyde group on the 5fC and the amino group on MnO2 nanoflowers. The sensitive and specific detection of 5fC can be achieved by oxidizing ascorbic acid with MnO2 nanoflowers and quenching the photoactivity of P-g-C3N4-WS2 nanocomposite. The sensor has a detection range of 0.01-200 nM and a detection limit of 3.8 pM. Moreover, this sensor has excellent detection specificity, stability and reproducibility.

Fluorometric determination of the activity of alkaline phosphatase based on a system composed of WS2 quantum dots and MnO2 nanosheets.

A fluorometric method is described for the detection of alkaline phosphatase (ALP) activity. It is based on the use of the product of hydrolysis of the drug amifostine (a thiophosphoester) by ALP. It is known that MnO2 nanosheets quench the blue fluorescence of tungsten disulfide quantum dots (WS2 QDs) which have excitation/emission wavelengths of 320/448 nm. However, in the presence of ALP and amifostine, the product of hydrolysis [2-(3-aminopropylamino)ethanethiol] triggers the decomposition of the MnO2 nanosheets. This results in the recovery of fluorescence. Based on this finding, an assay for ALP activity was developed that works in the 0.09-1.6 U L-1 range, with a 40 mU L-1 detection limit. The relative standard deviation is 1.87% for five repeated measurements of 0.8 U L-1 ALP. The method was applied to the analysis of ALP in real samples and gave satifactory results. Graphical abstractSchematic representation of a fluorometric method for determination of the activity of alkaline phosphatase (ALP). The fluorescence of a system composed of WS2 quantum dots and MnO2 nanosheets is quenched. Hydrolysis of the cytoprotective adjuvant amifostine (a phosphothioester) by ALP leads to a thiol that causes the decomposition of the MnO2 nanosheets. As a result, the blue fluorescence of the system becomes increasingly restored.

Concentration-dependent effects of tungstate on germination, growth, lignification-related enzymes, antioxidants, and reactive oxygen species in broccoli (Brassica oleracea var. italica L.).

The phyto-impact of tungstate is not frequently studied like other heavy metals especially in the sight of continuous accumulation of tungstate in the agriculture soils and water. Thus, the present study was aimed to investigate the supplementation of various tungstate concentrations (0, 1, 5, 10, 50, and 100) to germination water (mg L-1) or clay soil (mg kg-1) on germination and metabolism of broccoli. Lower concentrations (1-10 mg L-1) accelerated germination process and reciprocally were recorded at the highest one (100 mg L-1). The promoter effect of lower concentrations on seedlings growing on tungstate contaminated soil was underpinned from enhancement of pigments, metabolites, enzymatic and non-enzymatic antioxidants, and nitrate reductase. However, the highest concentration-noxious impacts perceived from oxidative damage and membrane integrity deregulation accompanied with no gain from increment of proline, superoxide dismutase, and glutathione-S-transferase. The depletion of phytochelatins and nitric oxide jointed with the enhancement of peroxidases, polyphenol oxidase, and phenylalanine ammonia-lyase at higher concentration reinforced lignin production which restricted plant growth. The results supported the hormetic effects of tungstate (beneficial at low concentrations and noxious at high concentration) on morphological and physiological parameters of broccoli seedlings. The stimulatory effect of tungstate on metabolic activities could serve as important components of antioxidative defense mechanism against tungstate toxicity.

Targeted photothermal therapy of mice and rabbits realized by macrophage-loaded tungsten carbide.

Although great advances have been made in photothermal therapy, the efforts hitherto have mainly achieved antitumor effects in mice with a subcutaneous tumor model, which is less clinically relevant. Therefore, it is very urgent to make further progress in investigating the possibility of larger animal models with orthotopically xenografted tumors for further clinical trials. Herein, macrophage-loaded tungsten carbide has been employed for the photothermal ablation of orthotopic breast tumors in rabbits in a targetable way. Tungsten carbide as an excellent photoactive material can induce on-site hyperthermia and even reactive oxygen species for tumor destruction; meanwhile, the macrophage is a biocarrier that behaves as a "Trojan horse" for tumor targeting. Both experimental results and theoretical simulations verified the broadband photoabsorption of WC. The WC loaded in the macrophages readily maintains the photothermal and photodynamic effects of the bare WC, while its accumulation at the tumor site is nearly 10 times that of bare WC. As such, the complete removal of solid tumors in rabbits was confirmed with the aid of B-mode ultrasound and contrast-enhanced ultrasound surveillance. Apparently, this work advances photothermal therapy one step further to large animal models with orthotopic tumors.

Mo2 C-Derived Polyoxometalate for NIR-II Photoacoustic Imaging-Guided Chemodynamic/Photothermal Synergistic Therapy.

To overcome the current limitations of chemodynamic therapy (CDT), a Mo2 C-derived polyoxometalate (POM) is readily synthesized as a new CDT agent. It permits synergistic chemodynamic and photothermal therapy operating in the second near-infrared (NIR-II) biological transparent window for deep tissue penetration. POM aggregated in an acidic tumor micro-environment (TME) whereby enables specific tumor targeting. In addition to the strong ability to produce singlet oxygen (1 O2 ) presumably via Russell mechanism, its excellent photothermal conversion enhances the CDT effect, offers additional tumor ablation modality, and permits NIR-II photoacoustic imaging. Benefitting from the reversible redox property of molybdenum, the theranostics based on POM can escape from the antioxidant defense system. Moreover, combining the specific responsiveness to TME and localized laser irradiation, side-effects shall be largely avoided.

Synthesis of Bi2WO6-x nanodots with oxygen vacancies as an all-in-one nanoagent for simultaneous CT/IR imaging and photothermal/photodynamic therapy of tumors.

All-in-one nanoagents with a single-component and all-required functions have attracted increasing attention for the imaging-guided therapy of tumors, but the design and preparation of such nanoagents remain a challenge. Herein, we report the introduction of oxygen vacancies to traditional semiconductors with heavy-metal elements for tuning photoabsorption in the near infrared (NIR) region, by using Bi2WO6 (band-gap: ∼2.7 eV) as a model. Bi2WO6-x nanodots with sizes of ∼3 or ∼8 nm have been prepared by a facile coprecipitation-solvothermal method assisted by citric acid (CA, 0.1-1.5 g) as the reduction agent. CA confers the removal of O atoms from the [Bi2O2]2+ layer during the solvothermal process, resulting in the formation of plenty of oxygen vacancies in the Bi2WO6-x crystal. As a result, NIR photoabsorption of Bi2WO6-x nanodots can be remarkably enhanced with the increase of the CA amount from 0 to 1.0 g. Under irradiation of a single-wavelength (808 nm, 1.0 W cm-2) NIR laser, black Bi2WO6-x-CA1.0 nanodots can not only efficiently produce a sufficient amount of heat with a photothermal conversion efficiency of 45.1% for photothermal therapy, but also generate singlet oxygen (1O2) for photodynamic therapy. Furthermore, due to the presence of heavy-metal (Bi and W) elements, Bi2WO6-x-CA1.0 nanodots have high X-ray attenuation ability for CT imaging. After the Bi2WO6-x-CA1.0 nanodot dispersion is injected into the tumor-bearing mice, the tumor can be imaged by using CT and an IR thermal camera. After irradiation with a single-wavelength (808 nm, 1.0 W cm-2, 10 min) NIR laser, the tumor can be completely suppressed by the synergic photothermal and photodynamic effects of Bi2WO6-x-CA1.0 nanodots, without recurrence and treatment-induced toxicity. Therefore, Bi2WO6-x nanodots have great potential as a novel all-in-one nanoagent for the imaging and phototherapy of tumors.

Enhanced denitrification performance and biocatalysis mechanisms of polyoxometalates as environmentally-friendly inorganic redox mediators.

Polyoxometalates (POMs) used in chemical catalysis field were first explored their effect on the denitrification process. Experiments demonstrated that NO3--N reduction rate with 0.05 mM phosphomolybdic acid (PMo12) was approximately 3.93-fold higher than the PMo12-free system. Simultaneously, PMo12 also had positive effect on NO2--N reduction. Compared with the PMo12-free system, the solution resistance and oxidation-reduction potential were decreased, and the activation energy (Ea) was reduced by 51.84 kJ/mol. Besides, electron conductive substances in extracellular polymeric substances were stimulated by PMo12. NADH and riboflavin were enhanced to increase denitrification electron transport system activity. Higher microbial diversity and enrichment of Salmonella were observed in the PMo12-supplemented system. Based on the above analysis, the catalyzing mechanisms of PMo12 are proposed that PMo12 made it easier for electron transferring from electron donor to electron acceptor and shifted bacterial community structure. These findings may provide a promising strategy for nitrogen wastewater treatment.