A Nickel-Containing Polyoxomolybdate as an Efficient Antibacterial Agent for Water Treatment.

In view of the water pollution issues caused by pathogenic microorganisms and harmful organic contaminants, nontoxic, environmentally friendly, and efficient antimicrobial agents are urgently required. Herein, a nickel-based Keggin polyoxomolybdate [Ni(L)(HL)]2H[PMo12O40] 4H2O (1, HL = 2-acetylpyrazine thiosemicarbazone) was prepared via a facile hydrothermal method and successfully characterized. Compound 1 exhibited high stability in a wide range of pH values from 4 to 10. 1 demonstrated significant antibacterial activity, with minimum inhibitory concentration (MIC) values in the range of 0.0019-0.2400 µg/mL against four types of bacteria, including Staphylococcus aureus (S. aureus), Bacillus subtilis (B. subtilis), Escherichia coli (E. coli), and Agrobacterium tumefaciens (A. tumefaciens). Further time-kill studies indicated that 1 killed almost all (99.9%) of E. coli and S. aureus. Meanwhile, the possible antibacterial mechanism was explored, and the results indicate that the antibacterial properties of 1 originate from the synergistic effect between [Ni(L)(HL)]+ and [PMo12O40]3-. In addition, 1 presented effective adsorption of basic fuchsin (BF) dyes. The kinetic data fitted a pseudo-second-order kinetic model well, and the maximum adsorption efficiency for the BF dyes (29.81 mg/g) was determined by the data fit of the Freundlich isotherm model. The results show that BF adsorption was dominated by both chemical adsorption and multilayer adsorption. This work provides evidence that 1 has potential to effectively remove dyes and pathogenic bacteria from wastewater.

Ultrahigh-efficiency antibacterial and adsorption performance induced by copper-substituted polyoxomolybdate-decorated graphene oxide nanocomposites.

Given the rise of drug-resistant pathogens and industrial contaminants, the development of efficient and eco-friendly water treatment technologies and materials is highly desirable and urgent. Herein, a multifunctional graphene oxide/chitosan/copper-based polyoxometalate (GO/CS/Cu-POM) nanocomposite (Cu-POM, [Cu(L)4][Cu(L)3(H2O)][Cu(L)(H2O)][P2Mo5O23]·4H2O, L = pyrazole) was synthesized by the ultrasound-assisted self-assembly strategy. The GO/CS/Cu-POM nanocomposite exhibited potent bactericidal properties against gram-positive/negative bacterial strains Staphylococcus aureus (S. aureus, 99.98%), Escherichia coli (E. coli, 99.99%), and drug-resistant E. coli bacterial strains (kanamycin-resistant E. coli 99.93% and ampicillin-resistant E. coli, 97.94%). Further, the antibacterial performance was strongly dependent on synergistic effect between GO/CS and Cu-POM in GO/CS/Cu-POM. The destruction of bacterial membrane and high levels of oxidative stress induced by GO/CS/Cu-POM played a significant role in the bactericidal process. Furthermore, the GO/CS/Cu-POM nanocomposite also displayed superior performance for removal of methylene blue (MB, 96.86%), gentian violet (GV, 97.77%), basic fuchsin (BF, 96.47%), tetracycline (TC, 78.92%) and norfloxacin (NC, 76.26%). Moreover, the main process of dye removal by GO/CS/Cu-POM was controlled by chemisorption. More importantly, the GO/CS/Cu-POM nanocomposite indicated good biocompatibility to human umbilical vein endothelial cells. Current work provides an effective strategy to design multifunctional POM-based composites for water purification and environmental protection.

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.

Supermolecular film crosslinked by polyoxometalate and chitosan with superior antimicrobial effect.

This paper reported a facile strategy to fabricate ionically crosslinked supramolecular film, in which an in situ formed chitosan ionic film was produced by post-crosslinking the chitosan chains using negatively charged anion polyoxometalate. The incorporation of polyoxometalate into the chitosan ionic system accelerated the crosslinked degree, as evidenced by an increase in surface wrinkle via scanning electron microscopy. Interestingly, the resultant supramolecular film realized the combination of prominent antimicrobial effect and excellent biocompatibility, which was considered to have enormous application potential range from biomedical to environmental science.

Multifunctional Magnetic-Fluorescent Nanoparticle: Fabrication, Bioimaging, and Potential Antibacterial Applications.

Magnetic-fluorescent nanoparticles integrating imaging and therapeutic capabilities have unparalleled advantages in the biomedical applications. Apart from the dual ability of unique biomolecular fluorescent recognition and magnetic modes, the nanoparticle also endows combined effective therapies with high physiological stability, long-term imaging, rapid response time, and excellent circulation ability. Herein, we developed a carboxyl-functionalized magnetic nanoparticle that was further functionalized by polydopamine (PDA) and Schiff base ligand (3-aminopyridine-2-carboxaldehyde N(4)-methylthiosemicarbazone, HL) to form multilayered coating single nanoparticles (Fe3O4@PDA@HL). Our work showed that the aggregation-induced emission (AIE) effect could be produced by embedding In3+ into the Fe3O4@PDA@HL nanostructure, which offered a new opportunity for utilization as a fluorescent detection and therapeutic platform. Cellular fluorescent imaging experiments provided bacterial cell biodistribution, demonstrating their excellent luminescent performance, magnetic aggregation, and separation capability. We simultaneously confirmed that the synergistic antibacterial effect was closely related to both Fe3O4@PDA@HL and In3+, leading to the disruption of membrane integrity and the leakage of intracellular components, thus inducing bacterial death. This approach presented in our work could promote the development of future bioimaging and clinical therapy applications.

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

In this work, polyoxometalate-modified magnetic nanocomposite Fe3O4@PDA@POM was prepared by coating [Cu(HL)4]2[P2Mo5O23]2·8H2O (POM, L = 2-aminopyridine) on the surface of a preassembled polydopamine (PDA)-capped carboxyl-functionalized Fe3O4 magnetic microspheres. Our studies on Gram negative bacterium Escherichia coli (E. coli) indicated that owing to the collective effect between preassembled Fe3O4 and POM, the Fe3O4@PDA@POM nanocomposite loaded on nickel foam exhibited outstanding antibacterial activity and reusability, and even after 6 cycles it has a high antibacterial capability of ca. 90%. Further extension of this investigation towards Gram positive bacterium Staphylococcus albus (S. aureus) demonstrated a similar toxicity pattern, confirming the potential applications of this material for water treatment in biochemical processes. The antibacterial mechanism of the Fe3O4@PDA@POM nanocomposite was further investigated by taking E. coli as a model microorganism.