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Stone corrosion by acid rain or biofilm formation is a global problem. In their Communication (DOI: 10.1002/anie.201809893), S. G. Mitchell, C. Streb, and co‐workers show how polyoxometalate‐ionic liquids (POM‐ILs) can be used as brush‐on anticorrosion coatings on natural stones. The POM‐ILs are designed to withstand corrosive conditions and featur...
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... surface biocidal activity of the POM-ILs on stone surfaces was quantified using a modified Japanese Industrial Standard (JIS). [33] JIS Z 2801 standard analysis showed that POM-IL 1 was more effective at reducing cell viability than the POM-IL 2, reaching up to 100 % of bacterial reduction in the BB stone (Table 4). In addition, a TBX agar method was established as a convenient means of detecting and quantifying the growth of E. coli on the stone samples. ...Context 2
... subtilis showed signs of sporulation, an indicator of cell stress. Both POM-ILs substantially reduced the number of bacterial cells on the stone surfaces, and higher bactericidal efficiency was observed for POM-IL 1 (Table 4, Fig. S11). Importantly, images of E.coli on BB with POM-IL 2 appeared to show the presence of high molecular weight extracellular polymeric substances (EPSs) secreted by the E.coli biofilm (Fig. S11), which is in line with the more dense biofilm observed by confocal microscopy (Fig. S10). ...Context 3
... images of E.coli on BB with POM-IL 2 appeared to show the presence of high molecular weight extracellular polymeric substances (EPSs) secreted by the E.coli biofilm (Fig. S11), which is in line with the more dense biofilm observed by confocal microscopy (Fig. S10). Finally, a modified optical density analysis of coated stones confirmed that POM-IL 1 was the more bactericidal compound against both E. coli and B. subtilis across all three types of stone (Table 4 and Fig. S12). ...Citations
... These coatings eventually help to render surfaces with excellent antibacterial, antibiofouling and anticorrosive properties. [38][39][40] For instance, Bains et. al. developed ionic liquid (IL)-functionalized multiwalled carbon nanotubes for hydrophobic and antibacterial coatings. ...
... al. fabricated thin films of polyoxometalate-based ionic liquids using brush-coating on the surface on stones to protect them from acid corrosion and also enhance their biocidal properties. 39 Imidazolium based ionic liquid coatings have also shown excellent potential as emerging antibacterial coatings. [41][42][43] Correspondingly, higher toxicity of imidazolium based ionic liquid coatings towards bacterial cells than mammalian cells has been concluded by Gindir et. ...
The global COVID-19 pandemic and widespread concerns about antimicrobial resistance (AMR) have intensified research efforts towards the development of innovative methods and technologies to suppress the spread of infectious pathogens facilitated by high touch surfaces. Thus, surfaces and coatings capable of inhibiting bacterial growth and preventing biofilm formation are being comprehensively explored in healthcare sectors to mitigate the spread of infectious pathogens. With the emergence of resistant strains of bacteria, due to over usage of conventional antibiotics, it becomes essential to develop a new class of materials with higher antibacterial efficiency. In the present study, the various morphologies of zinc oxide (ZnO) nanostructures have been exploited as efficient antimicrobial surfaces. This work aims to enhance the bactericidal properties of ZnO nanostructured surfaces by tuning their wettability and surface chemistry. Silicon substrates decorated with ZnO structures such as flowers, needles, and fibers are characterized by scanning electron microscopy (SEM) and atomic force microscopy (AFM). These surfaces are further spin-coated with an ionic liquid 1-decyl-3-methylimidazolium tetrafluoroborate (DMIM-BF4), which causes a drastic impairment of bacterial cell viability on the surfaces. This bactericidal activity has been compared with that of a well-known low surface energy material 1H,1H,2H,2H-perfluorooctyl-trichloroethoxysilane (FOTES) by performing spot assay and colony-forming unit (CFU) analysis. The ionic liquids, commonly known as green solvents, are found to be emerging coating materials to develop advanced antimicrobial surfaces.
... Recently, polyoxometalate-ionic liquids (POM-ILs) have gained attention in the heritage field as protective antimicrobial coatings, due to their tailorable antimicrobial properties, offered by their structural and compositional versatility (Hallett and Welton, 2011;Zakrewsky et al., 2014). These compounds, which are salts with a melting point below 100 • C, are composed of an anionic metal-oxide cluster (polyoxometalate, POM for short) and an organic cation (typically a quaternary ammonium or phosphonium cation) and have been previously reported as effective antimicrobials against different microorganisms (Kubo et al., 2017;Misra et al., 2018). Their hydrophobicity, high antimicrobial and anticorrosion activity combined with generally colourless nature, means that they can be applied at low concentrations as transparent coatings to prevent biodeterioration in heritage objects and architecture (Franco-Castillo et al., 2021). ...
... POM-ILs can prevent biofilm formation and corrosion of natural limestone of varying porosity (Misra et al., 2018). Recently, we also reported how POM-ILs can act as disinfectant agents to eliminate mould colonisation over brick surfaces (Rajkowska et al., 2020). ...
... POM-ILs 1 and 2 were synthesised according to a previously reported synthetic procedure (Misra et al., 2018). Preventol RI80 is a solution of quaternary ammonium salts as Benzalkonium chloride (alkyl-dimethylbenzylamine chloride (80%) and isopropanol (2%)) -Lanxess, Köln, Germany. ...
Phototrophic microorganisms such as cyanobacteria and microalgae can proliferate readily in underground heritage sites where the introduction of artificial illumination equipment has significantly altered previously stable environmental conditions. The extended lampenflora biofilm growth on the bas-reliefs carved in the underground Pommery Champagne cellar in Reims (France) represents a recurring biocolonisation problem which requires periodic cleaning. The aim of this work was to limit the growth of lampenflora on chalk substrates using preventative biocidal treatments based on polyoxometalate ionic liquids (POM-ILs). Biocidal assays carried out in laboratory showed how two different colourless POM-IL coatings were more effective than commercial Preventol RI80 against two algal strains isolated from the Pommery bas reliefs, Pseudostichococcus monallantoides and Chromochloris zofingiensis. However, only one POM-IL variant was capable of sustained prevention of biofilm growth when applied to wet chalk, which replicates the more drastic natural environmental conditions of the cellar and can limit the performance of the biocidal coatings. Crucially, coating concentration studies demonstrate how POM-IL-coated slabs from previous experiments retain their biocidal activity and can prevent subsequent recolonisation following the re-inoculation of coated slabs with algae and cyanobacteria. Consequently, POM-ILs represent excellent candidates to eliminate lampenflora growth on the chalk bas-reliefs in the unique subterranean environment of the Pommery Champagne cellar.
... POM-based inorganic-organic hybrids exhibit enhanced antimicrobial and adsorption properties compared to pure POMs [22,23]. Among the organic ligands, 2-acetylpyrazine thiosemicarbazone (HL) showed excellent antibacterial activity in pharmacological applications, being a superior candidate for the construction of POM-based inorganic-organic hybrids [24][25][26][27]. ...
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.
... Regarding stone restoration, dodecylbenzenesulfonate-based IL demonstrated a good antimicrobial activity when tested in vitro on four microbial strains isolated from deteriorated monuments (Table 2). Thin films of polyoxometalate-based ionic liquids (POM-ILs) combined with quaternary alkylammonium cations were experimented as water repellent and antimicrobial agents (Misra et al., 2018). The compounds efficiently reduced the number of two bacteria strains inoculated on stone samples and prevented their weathering when exposed to simulated acid rain in a laboratory test (Misra et al., 2018). ...
... Thin films of polyoxometalate-based ionic liquids (POM-ILs) combined with quaternary alkylammonium cations were experimented as water repellent and antimicrobial agents (Misra et al., 2018). The compounds efficiently reduced the number of two bacteria strains inoculated on stone samples and prevented their weathering when exposed to simulated acid rain in a laboratory test (Misra et al., 2018). Despite the potential of ILs as new and sustainable materials in combating microbial colonization of stone artworks, much research should be performed to make their application reliable and suitable. ...
In the past several years, products and methods alternative to conventional biocides, used in the conservation of cultural heritage objects, have been investigated increasingly to eradicate or prevent the growth of microorganisms and lichens on stone artworks. Although some concerns about conventional biocides are legitimate, the “run” to alternative substances is growing concern as well. This review aims at contributing to the interpretation of recent findings in innovative methods and substances focusing on i) resistance of biofilms to environmental stressors, including antimicrobials; ii) metals and metal-based compounds including nanoparticles; iii) mixtures of metal nanoparticles and metal oxides with water repellents and consolidants; iv) natural compounds (essential oils of plants, secondary metabolites of lichens, microbial by-products, microorganisms, extracts from marine organisms); v) toxicity of essential oils; vi) alternative chemicals (Ionic liquids, dimethyl sulfoxide gel, hydrolase enzymes). This review also includes a discussion on the advantages, drawbacks and limitations of the examined studies to encourage a constructive discussion among professionals involved in the field of stone heritage conservation, and to develop a sustainable path for managing the biological colonization. This state-of-the-art review indicates that further research is needed to propose alternative compounds to conventional biocides.
... Polyoxometalate O 39 ]}, as anticorrosion and antibacterial coatings, were assayed for protection of natural stones (Belgian Blue, Romery, and Dom) from weathering (corrosion) and biodeterioration (Fig. 12) [144]. Stone samples were coated with a transparent thin film of hydrophobic, acid-resistant POM-ILs with antibacterial activity. ...
Efforts to widen the scope of ionic liquids applications across diverse research areas have flourished in the last two decades with developments in understanding and tailoring their physical, chemical, and biological properties. The promising applications of ionic liquids-based materials as antimicrobial systems is due to their ability and flexibility to be tailored in varying sizes, morphologies, and surface charges. Ionic liquids are also considered as greener materials. Common methods for the preparation of ionic liquid-based materials include crosslinking, loading, grafting, and combination of ionic liquids with other polymeric materials. Recent research focuses on the tuning of the biological properties to design novel ionic liquids-based antimicrobial materials. Here we review properties, synthesis and applications of ionic liquids and ionic liquids-based materials with focus on antimicrobial activities applied to water treatment, air filtration, food packaging, and anticorrosion.
... [13] This principle has for example been used to combine POM anions with bactericidal tetra-alkylammonium cations to give POM composites with high antibacterial efficiency. [14][15][16] Here, we build on these concepts and explore how ceriumfunctionalized tungstate Keggin POMs can be combined with organo-cations, to improve antiviral activity against HIV-1 infection. As a model system, we selected the caffeinium cation, because the precursor, caffeine, is a natural compound with various promising therapeutic applications and expected to be non-toxic. ...
... Previous studies suggested that POMs inhibit virion attachment to the target cell. [14] To assess whether Caf-POM act by a similar mechanism, HIV-1 pseudoparticles were first exposed to the compound for 15 min and then used to inoculate TZM-bl cells. Alternatively, cells were treated with Caf-POM for 24 hours, washed to remove unbound compound and then infected. ...
Polyoxometalates (POMs), molecular metal oxide anions, are inorganic clusters with promising antiviral activity. Herein we report increased anti‐HIV‐1 activity of a POM when electrostatically combined with organic counter‐cations. To this end, Keggin‐type cerium tungstate POMs have been combined with organic methyl‐caffeinium (Caf) cations, and their cytotoxicity, antiviral activity and mode of action have been studied. The novel compound, Caf4K[β2‐CeSiW11O39]×H2O, exhibits sub‐nanomolar antiviral activity and inhibits HIV‐1 infectivity by acting on an early step of the viral infection cycle. This work demonstrates that combination of POM anions and organic bioactive cations can be a powerful new strategy to increase antiviral activity of these inorganic compounds.
... Of course, products based on nano-silver and nano-titania are studied frequently, but a variety of other readily available multifunctional nanomaterials have been shown to serve as alternative solutions to heritage biodeterioration issues. [9][10][11] In this review, we provide a critical summary of the state of the art in traditional and nanomaterials-based antimicrobial treatments for heritage items from a multidisciplinary perspective in order to include key considerations from the heritage conservation-restoration, materials science, and microbiological standpoints. We aim to provide an overview and comprehensive analysis of the principal and most effective nanomaterial types and the most appropriate analytical biochemical techniques that can be used to accurately evaluate their antimicrobial properties, both in vitro in laboratory cell cultures under model conditions and in situ applied to samples in realistic settings. ...
... In most of the literature examples, articles cited in this review, model substrate materials-most of which possess no true cultural or economic value-are used to evaluate the efficacy of antimicrobial treatments. In many cases these might include, for example, stone from the same quarries as those used in the construction of heritage buildings, 9,10,12 ceramic tiles or glass prepared using historically accurate production methods, filter paper, glass slides or freshly made bricks, 13 or plaster, among others. These initial proof-of-concept model laboratory studies represent one of the first and most vital stages in evaluation, since any unforeseen and undesired effects that the antimicrobial treatments might cause to the heterogeneous character of an original heritage item preclude their direct use in mitigating biodeterioration. ...
... Those quantitative results were also commensurate with qualitative analysis by ESEM, fluorescence, and confocal microscopy. 9 A recent study has demonstrated the antifungal activity of these POM-ILs against a mixed culture of molds (Engyodontium album, Cladosporium cladosporioides, Alternaria alternata, and Aspergillus fumigatus) isolated from the surface of historical bricks from the Auschwitz II-Birkenau State Museum (Poland). These POM-ILs were applied as a coating on 19 th -century brick samples and then inoculated with the mixture of molds and incubated in a climate chamber for three weeks. ...
The biodeterioration of artistic and architectural heritage represents a serious and recurring problem for museums, local authorities, and private collectors alike, where irreparable damage to unique artifacts can result in immeasurable losses to our shared cultural heritage. Here, we present an overview of the current trends in antimicrobial products used to protect heritage items from microbial colonization and prevent their deterioration. From a conservation-restoration standpoint, we contrast and compare traditional antimicrobial products with the state of the art in antimicrobial nanomaterials applied in the heritage conservation field, highlighting the promising potential of various different nanomaterials, as well as points of concern and clear red flags from some of the emerging research. Through an examination of the growing body of research in the academic literature we offer recommendations and practical advice on selecting appropriate microbiological assays and characterization techniques to better evaluate the in vitro and in situ antimicrobial properties of nanomaterials.
... Recently the application of biocidal PNC coatings having surface-killing character has seized the attention of scientists in electrochemical corrosion realm to protect materials from erosion and corrosion [90]. It is estimated that approximately 4% of global GDP is lost annually due to the deterioration of metals through corrosion phenomena, approximately 50% of which is caused by the microbial induced corrosion [91]. ...
The growth and proliferation of pathogenic microbes and bacteria on various surfaces have caused an ever-increasing awareness, necessitating scientists of diverse realm to develop potential antimicrobial materials. Among various methods of prevention, the application of biocidal polymer films and coatings has played a vital role. Generally such polymers are developed by the incorporation of antimicrobial moieties within their matrices. The design and formulation of polymer nanocomposite (PNC) films and coatings with biocidal property, have gained higher interest due to the exceptional reinforcing abilities of nanomaterials compared to other biocides. From this perspective, the aim of the present chapter is to discuss the approaches used for the fabrication and processing of surface-active, selective, leaching and nonleaching antimicrobial PNCs along with their mechanism of action. The chapter also covers the importance of naturally derived precursors for the construction of eco-friendly and cost-effective antimicrobial PNCs. Further the advantages, limitations, and the future scope of such functional PNCs have been discussed.
... However, the concentration of H 2 O 2 that is traditionally used is in the range of 166 mM to 1 M (volume ratio: 0.5−3 %) [38][39][40], and this prevents wound healing and damages adjacent normal organs during bacterial sterilization. Currently, various novel types of peroxidase-like nanomaterials that have high peroxidase-mimic activity, such as carbon-based nanomaterials [41][42][43][44], noble metals [45][46][47][48][49][50][51], ironbased nanomaterials [52][53][54][55], transitional metal dichalcogenides [56,57], and polyoxometalates [58], have been known to have obvious antibacterial effects. They can disrupt the integrity of bacterial cell membranes and cell wall permeability. ...
Backgroud: Nowadays, biofilms that are generated as a result of antibiotic abuse cause serious threats to global public health. Such films are the primary factor that contributes to the failure of antimicrobial treatment. This is due to the fact that the films prevent antibiotic infiltration, escape from innate immune attacks by phagocytes and consequently generate bacterial resistance. Therefore, exploiting novel antibacterial agents or strategies is extremely urgent.
Methods: Herein, we report a rational construction of a novel biofilm microenvironment (BME)-responsive antibacterial platform that is based on tungsten (W)-polyoxometalate clusters (POMs) to achieve efficient bactericidal effects.
Results: On one hand, the acidity and reducibility of a BME could lead to the self-assembly of POMs to produce large aggregates, which favor biofilm accumulation and enhance photothermal conversion under near-infrared (NIR) light irradiation. On the other hand, reduced POM aggregates with BME-induced photothermal-enhanced efficiency also exhibit surprisingly high peroxidase-like activity in the catalysis of bacterial endogenous hydrogen peroxide (H2O2) to produce abundant reactive oxygen species (ROS). This enhances biofilm elimination and favors antibacterial effects. Most importantly, reduced POMs exhibit the optimal peroxidase-like activity in an acidic BME.
Conclusion: Therefore, in addition to providing a prospective antibacterial agent, intelligent acid/reductive dual-responsive POMs will establish a new representative paradigm for the areas of healthcare with minimal side effects.
... Some studies have shown the higher susceptibility to salt weathering of more porous limestones [17,35,50], with similar results for granites [28] and for highly porous sandstones [53]. The same trend has been obtained in terms of the effects of acid solutions on limestones [38,44]. ...
... In a study with acid solutions, a more porous but silica richer limestone showed lower mass loss than a limestone with lower porosity but richer in calcium carbonate [44]. The presence of clay minerals can promote an incipient lamination in a low porosity limestone that favors the action of freeze-thaw [18]. ...
This work presents a review of recent publications, with publication date between 2017 and 2019, with information on the relation between rock characteristics and the effects of diverse agents associated with alteration of stone materials in the built environment. It considers information obtained from ageing tests performed under laboratory conditions and by exposure to outdoor agents. Several lithological groups were considered, with sedimentary carbonate rocks being the most frequently studied lithotypes and silicate metamorphic rocks being the group with scarcer information. In terms of ageing tests, salt weathering was the most frequent one while there was a noticeable lesser amount of information from tests with biological colonization. The collected data showed the influence of diverse features, from specific minerals to whole-rock properties and the presence of heterogeneities. These information are discussed in the context of formulating a general framework for stone decay.
