Long alkyl-chain imidazolium ionic liquids: Antibiofilm activity against phototrophic biofilms

Choline and geranate ionic liquid for subgingival biofilm control

Periodontitis is a chronic inflammatory disease that causes destruction of the periodontium and eventual tooth loss. The priority in the periodontal treatment is to remove the subgingival biofilm. Chemical removal of biofilms using antimicrobial agents has been applied in clinical practice. However, their clinical effect is still limited because the agents must overcome biofilm's significant drug tolerance, which is primarily caused by the extracellular matrix, a physical barrier that attenuates drug diffusion. This study aimed to study the use of ionic liquids (ILs), a new class of biocompatible materials, for controlling subgingival biofilms because of their excellent permeability. Choline and geranate (CAGE) IL was tested for its highly potent antiseptic behavior and permeability. Antibacterial tests revealed that the significant efficacy of CAGE against periodontopathic microorganisms was derived from their ability to destroy cell membrane, as demonstrated by membrane permeability assay and transmission electron microscopy imaging. Antibiofilm tests using two pathogenic biofilm models revealed that CAGE exerted efficacy against the biofilm-embedded bacteria, conspicuously neutralized the biofilms, and eventually destroyed the biofilm structure. Furthermore, the penetration of CAGE into the biofilm was visually confirmed using confocal laser scanning microscopy. This study highlighted the potential of CAGE as a powerful antibiofilm therapeutic.

Anticancer activity features of imidazole-based ionic liquids and lysosomotropic detergents: in silico and in vitro studies

Long-chain imidazole-based ionic liquids (compounds 2, 4, 9) and lysosomotropic detergents (compounds 7, 3, 8) with potent anticancer activity were synthesized. Their inhibitory activities against neuroblastoma and leukaemia cell lines were predicted by the new in silico QSAR models. The cytotoxic activities of the synthesized imidazole derivatives were investigated on the SK-N-DZ (human neuroblastoma) and K-562 (human chronic myeloid leukaemia) cell lines. Compounds 2 and 7 showed the highest in vitro cytotoxic effect on both cancer cell lines. The docking procedure of compounds 2 and 7 into the NAD+ coenzyme binding site of deacetylase Sirtuin-1 (SIRT-1) showed the formation of protein-ligand complexes with calculated binding energies of - 8.0 and - 8.1 kcal/mol, respectively. The interaction of SIRT1 with compounds 2, 7 and 9 and the interaction of Bromodomain-containing protein 4 (BRD4) with compounds 7 and 9 were also demonstrated by thermal shift assay. Compounds 2, 4, 7 and 9 inhibited SIRT1 deacetylase activity in the SIRT-Glo assay. Compounds 7 and 9 showed a moderate inhibitory activity against Aurora kinase A. In addition, compounds 3, 4, 8 and 9 inhibited the Janus kinase 2 activity. The results obtained showed that long-chain imidazole derivatives exhibited cytotoxic activities on K562 leukaemia and SK-N-DZ neuroblastoma cell lines. Furthermore, these compounds inhibited a panel of molecular targets involved in leukaemia and neuroblastoma tumorigenesis. All these results suggest that both long-chain imidazole-based ionic liquids and lysosomotropic detergents may be an effective alternative for the treatment of neuroblastoma and chronic myeloid leukemia and merit further investigation.

Effects of ionic liquids on biomembranes: A review on recent biophysical studies

Ionic liquids (ILs) have been emerged as a versatile class of compounds that can be easily tuned to achieve desirable properties for various applications. The ability of ILs to interact with biomembranes has attracted significant interest, as they have been shown to modulate membrane properties in ways that may have implications for various biological processes. This review provides an overview of recent studies that have investigated the interaction between ILs and biomembranes. We discuss the effects of ILs on the physical and chemical properties of biomembranes, including changes in membrane fluidity, permeability, and stability. We also explore the mechanisms underlying the interaction of ILs with biomembranes, such as electrostatic interactions, hydrogen bonding, and van der Waals forces. Additionally, we discuss the future prospects of this field.

Tuning the sensitivity of cell-based biosensors for the detection of biocides

The presence of biocides in wastewater can negatively impact the efficiency of wastewater treatment processes, particular the process of nitrification. In this paper, we describe the development of cell-based biosensors (CBBs) with tunable levels of sensitivity for rapidly detecting the presence and predicting the type and concentration of biocides. The CBB assay developed is performed by first exposing a panel of bacterial strains (E. coli, B. subtilis, B. cereus) to the sample being tested and to the control sample without biocide, and then adding a fluorescent dye (LIVE/DEAD BacLight). We then compare the fluorescence signals generated by the two samples, and the differences in the signals indicate the presence of a biocide, as previously reported in the literature. We found that the sensitivity of the CBB assay can be improved by tuning the type/salinity of the buffer used to suspend the cells, and by changing the number of cells used in the assay. These changes improved the level of detection (LOD) of the biocide Cetyltrimethylammonium bromide (CTAB) from 10 ppm to 0.625 ppm and the biocide Grotan® BK from 500 ppm to 7.8 ppm. With the optimized conditions for each strain, we also establish that the combined response from the panel of bacterial strains can be used to predict the type and concentration of biocide sample tested. Additionally, we provide evidence that the response of the tunable CBB assay can be quantitatively measured using a compact, commercially available fluorometer. Overall, the significance of this work will improve point-of-use testing and enable the discrimination between biocide-containing samples of similar toxicity and detection of lower toxicity samples, thereby improving the accuracy of the CBB assay.

A comparative evaluation of antibacterial activities of imidazolium-, pyridinium-, and phosphonium-based ionic liquids containing octyl side chains

Antibacterial activity is an essential property of ionic liquids. In this work, a comprehensive study has been performed on the antibacterial activity of ionic liquids to be utilized for further research and applications. Eighteen ionic liquids viz. Octyl Imidazolium, octyl Pyridinium, quaternary phosphonium-based cations containing bromide, sodium methane sulphonates, bis(trifluoromethane sulfonyl) imide, dichloroacetate, tetrafluoroborate, hydrogen sulfate were prepared and characterized with the help of different spectroscopic techniques. All these samples of ionic liquids were tested for their antibacterial activity against the most commonly occurring bacteria in the environment, i.e., Enterobacter aerogenes (E. aerogenes), Proteus vulgaris (P. vulgaris), Klebsiella pneumoniae (K. pneumoniae), Pseudomonas aeruginosa (P. aeruginosa), Escherichia coli (E. coli), and Streptococcus pyogenes (S. pyogenes). Most of the ionic liquids show good antibacterial properties, and imidazolium-based ionic liquids were even more antibacterial as compared to positive control. It was observed that a unique combination of cation and anion is essential to achieve desired antibacterial properties. The mechanism of antibacterial activity was further investigated using density functional theory calculations. A good correlation was found between experimental and theoretical studies.

Theoretical and Experimental Studies of Phosphonium Ionic Liquids as Potential Antibacterials of MDR Acinetobacter baumannii

A previously developed model to predict antibacterial activity of ionic liquids against a resistant A. baumannii strain was used to assess activity of phosphonium ionic liquids. Their antioxidant potential was additionally evaluated with newly developed models, which were based on public data. The accuracy of the models was rigorously evaluated using cross-validation as well as test set prediction. Six alkyl triphenylphosphonium and alkyl tributylphosphonium bromides with the C₈, C₁₀, and C₁₂ alkyl chain length were synthesized and tested in vitro. Experimental studies confirmed their activity against A. baumannii as well as showed pronounced antioxidant properties. These results suggest that phosphonium ionic liquids could be promising lead structures against A. baumannii.

Anti-barnacle biofouling coatings for the protection of marine vessels: synthesis and progress

Marine biofouling has gnawed both mobile and non-mobile marine structures since time immemorial, leading to the deterioration of designed operational capabilities as well as a loss of valuable economic revenues. Mitigation of biofouling has been the primary focus of researchers and scientists from across the globe to save billions of dollars wasted due to the biological fouling of marine structures. The availability of an appropriate environment along with favorable substrata initiates biofilm formation within a few minutes. The crucial element in establishing a gelatinous biofilm is the excreted metabolites of destructive nature and exopolymeric substances (EPSs). These help in securing as well as signaling numerous foulants to establish themselves on this substrate. The larvae of various benthic invertebrates adhere to these suitable surfaces and transform from juveniles to adult barnacles depending upon the environment. Despite biofouling being characteristically witnessed for a month or lengthier timeframe, the preliminary phases of the fouling process typically transpire on a much lesser timescale. A few natural and synthetic additives had demonstrated excellent non-toxic anti barnacle establishment capability; however, further development into commercial products is still far-fetched. This review collates the specific anti-barnacle coatings, emphasizing natural additives, their sources of extraction, general life cycle analysis, and concluding future perspectives of this niche product.

Combined utilization of metabolic inhibitors to prevent synergistic multi-species biofilm formation

Biofilm is ubiquitous in industrial water systems, causing biofouling and leading to heat transfer efficiency decreases. In particular, multi-species living in biofilms could boost biomass production and enhance treatment resistance. In this study, a total of 37 bacterial strains were isolated from a cooling tower biofilm where acetic acid and propionic acid were detected as the main carbon sources. These isolates mainly belonged to Proteobacteria and Firmicutes, which occupied more than 80% of the total strains according to the 16S rRNA gene amplicon sequencing. Four species (Acinetobacter sp. CTS3, Corynebacterium sp. CTS5, Providencia sp. CTS12, and Pseudomonas sp. CTS17) were observed co-existing in the synthetic medium. Quantitative comparison of biofilm biomass from mono- and multi-species showed a synergistic effect towards biofilm formation among these four species. Three metabolic inhibitors (sulfathiazole, 3-bromopyruvic acid, and 3-nitropropionic acid) were employed to prevent biofilm formation based on their inhibitory effect on corresponding metabolic pathways. All of them displayed evident inhibition profiles to biofilm formation. Notably, combining these three inhibitors possessed a remarkable ability to block the multi-species biofilm development with lower concentrations, suggesting an enhanced effect appeared in simultaneous use. This study demonstrates that combined utilization of metabolic inhibitors is an alternative strategy to prevent multi-species biofilm formation.

37 bacterial strains were isolated and identified from a cooling tower biofilm.

Synergistic effect of biofilm formation was observed among four species.

Three metabolic inhibitors showed effective inhibition against biofilm formation.

Targeting cellular metabolism is an effective way to inhibit biofilm formation.

Assessment of alkylimidazolium chloride ionic liquid formulations for cleaning and disinfection of environmental surfaces

BACKGROUND

Surface disinfection is fundamental to good environmental hygiene and preventing infections. Development of newer formulations that can effectively kill and remove microorganisms from the surfaces is desired.

METHODS

Here, we assessed the efficacy of 1-hexadecyl-3-methylimidazolium chloride [C₁₆MIM][Cl] ionic liquid (IL) and its formulation in ethanol for killing and removing bacteria from different environmental surfaces. Efficacy of IL and its formulation was determined on known monospecies bacterial cultures and unknown multispecies bacterial cultures on environmental surfaces.

RESULT

The surface disinfection efficacy of [C₁₆MIM][Cl] was concentration dependent and achieved 41 to 100% reduction in total viable bacterial counts of Gram positive and Gram negative bacteria at varied concentrations. The treatment of wooden surface with 0.1% [C₁₆MIM][Cl] caused 98% reduction in bacterial load within 20 s contact time as against mere 45% reduction (20 s) with 70% ethanol. Antibacterial and surface disinfection activities of [C₁₆MIM][Cl] have increased markedly when prepared in 70% ethanol, suggesting synergistic activity. A formulation comprising of 0.01% [C₁₆MIM][Cl] in 70% ethanol showed effective surface disinfection and achieved 95% to 98% reduction in bacterial load on different surfaces.

CONCLUSION

Ionic liquids are potent candidates for disinfection of environmental surfaces.

Review of the toxic effects of ionic liquids

Interest in ionic liquids (ILs), called green or designer solvents, has been increasing because of their excellent properties such as thermal stability and low vapor pressure; thus, they can replace harmful organic chemicals and help several industrial fields e.g., energy-storage materials production and biomaterial pretreatment. However, the claim that ILs are green solvents should be carefully considered from an environmental perspective. ILs, given their minimal vapor pressure, may not directly cause atmospheric pollution. However, they have the potential to cause adverse effects if leaked into the environment, for instance if they are spilled due to human mistakes or technical errors. To estimate the risks of ILs, numerous ILs have had their toxicity assessed toward several micro- and macro-organisms over the past few decades. Since the toxic effects of ILs depend on the method of estimating toxicity, it is necessary to briefly summarize and comprehensively discuss the biological effects of ILs according to their structure and toxicity testing levels. This can help simplify our understanding of the toxicity of ILs. Therefore, in this review, we discuss the key findings of toxicological information of ILs, collect some toxicity data of ILs to different species, and explain the influence of IL structure on their toxic properties. In the discussion, we estimated two different sensitivity values of toxicity testing levels depending on the experiment condition, which are theoretical magnitudes of the inherent sensitivity of toxicity testing levels in various conditions and their changes in biological response according to the change in IL structure. Finally, some perspectives, future research directions, and limitations to toxicological research of ILs, presented so far, are discussed.

A novel nanoemulsion-based microalgal growth medium for enhanced biomass production

BACKGROUND

Microalgae are well-established feedstocks for applications ranging from biofuels to valuable pigments and therapeutic proteins. However, the low biomass productivity using commercially available growth mediums is a roadblock for its mass production. This work describes a strategy to boost algal biomass productivity by using an effective CO₂ supplement.

RESULTS

In the present study, a novel nanoemulsion-based media has been tested for the growth of freshwater microalgae strain Chlorella pyrenoidosa. Two different nanoemulsion-based media were developed using 1% silicone oil nanoemulsion (1% SE) and 1% paraffin oil nanoemulsion (1% PE) supplemented in Blue-green 11 media (BG11). After 12 days of cultivation, biomass yield was found highest in 1% PE followed by 1% SE and control, i.e., 3.20, 2.75, and 1.03 g L^-1, respectively. The chlorophyll-a synthesis was improved by 76% in 1% SE and 53% in 1% PE compared with control. The respective microalgal cell numbers for 1% PE, 1% SE and control measured using the cell counter were 3.00 × 10⁶, 2.40 × 10⁶, and 1.34 × 10⁶ cells mL^-1. The effective CO₂ absorption tendency of the emulsion was highlighted as the key mechanism for enhanced algal growth and biomass production. On the biochemical characterization of the produced biomass, it was found that the nanoemulsion-cultivated C. pyrenoidosa had increased lipid (1% PE = 26.80%, 1% SE = 23.60%) and carbohydrates (1% PE = 17.20%, 1% SE = 18.90%) content compared to the control (lipid = 18.05%, carbohydrates = 13.60%).

CONCLUSIONS

This study describes a novel nanoemulsion which potentially acts as an effective CO₂ supplement for microalgal growth media thereby increasing the growth of microalgal cells. Further, nanoemulsion-cultivated microalgal biomass depicts an increase in lipid and carbohydrate content. The approach provides high microalgal biomass productivity without altering morphological characteristics like cell shape and size as revealed by field emission scanning electron microscope (FESEM) images.

Biofilm control by ionic liquids

Ionic liquids (ILs) are remarkable chemical compounds with applications in many areas of modern science. They are increasingly recognized as promising compounds to fight microorganisms in both planktonic and biofilm states, contributing to reinvent the antimicrobial pipeline. Biofilm-related infections are particularly challenging given that the scientific community has not yet identified a reliable control strategy. Understanding of the action of ILs in biofilm control is is still in a very early stage. However, given the highly tunable nature and exceptional properties of ILs, they are excellent candidates for biofilm control. Here, we review the major advances in, and challenges tothe use of ILs for effective biofilm control.

Antibacterial, Antifungal and Ecotoxic Effects of Ammonium and Imidazolium Ionic Liquids Synthesized in Microwaves

Ionic liquids are increasingly used for their superior properties. Four water-immiscible ionic liquids (butyltriethylammonium bis(trifluoromethylsulfonyl)imide, octyltriethylammonium bis(trifluoromethylsulfonyl)imide, dodecyltriethylammonium bis(trifluoromethylsulfonyl)imide, butyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide) and their water miscible precursors (bromides) were synthesized in a microwave reactor and by conventional heating. The best conditions for microwave-assisted synthesis concerning the yield and the purity of the product are proposed. The heating in the microwave reactor significantly shortened the reaction time. Biocide and ecotoxic effects of synthesized ionic liquids and their precursors were investigated. All tested compounds had at least a little effect on the growth or living of microorganisms (bacteria or mold). The precursor dodecyltriethylammonium bromide was found to be the strongest biocide, but posed a risk to the aquatic environment due to its relatively high EC50 value in the test with Vibrio fischeri. We assumed that apart from the alkyl chain length, the solubility in water, duration of action, or type of anion can influence the final biocide and ecotoxic effect.

Efficacy of imidazolium and piperidinium based ionic liquids on inhibiting biofilm formation on titanium and carbon steel surfaces

In the present study, the efficacies of three different cationic and anionic ionic liquids (ILs) on biofilm formation on materials used in cooling water systems were evaluated. Two imidazolium based ILs; 1-Ethyl 3-Methylimidazolium tetrafluoroborate - (IL-E) and 1-Butyl-3-methylimidazolium chloride - (IL-I) with anionic fluoride and chloride groups and one piperidinium based IL, N-methyl-N-propylpiperidinium bis(trifluoromethylsulfonyl)imide - (IL-M) with fluoromethyl group as anion were used. The efficacy of these ILs were evaluated on planktonic and sessile cells of major biofilm formers in cooling water systems using Gram negative bacterium Pseudomonas sp. and Gram positive bacterium Bacillus sp. Further their effect on inhibiting biofilm formation on titanium and carbon steel surfaces were also evaluated. Results showed that planktonic cells of Pseudomonas sp. and Bacillus sp. were effectively inhibited by 25 ppm of IL-M and IL-E, respectively. For both bacteria, 50 ppm of IL-I was enough to inhibit and eradicate the sessile cell formation. Among the three ILs, IL-E was the best in inhibiting the adhesion of bacterial cells on Ti and CS surfaces. These results suggest that Imidazolium based ILs are effective in controlling sessile cell formation and eradicating mature biofilm as compared to piperidinium based IL. Further, Imidazolium based IL with fluoride anion (IL-E) was the best in inhibiting adhesion of these bacterial cells and thereby biofilm formation on material surfaces. This study establishes the feasibility of using ILs in cooling water system for bacterial biofilm control along with other conventional biofouling control methods.

Heavy Metal Extraction under Environmentally Relevant Conditions Using 3-Hydroxy-2-Naphthoate- Based Ionic Liquids: Extraction Capabilities vs. Acute Algal Toxicity

We investigated the applicability of three task-specific ionic liquids (ILs) as heavy metal extracting agents by contrasting extraction capabilities with algal toxicity. The compounds tested were trihexyltetradecylphosphonium-, methyltrioctylphosphonium- and methyltrioctylammonium 3-hydroxy-2-naphthoates. Experiments were performed to assess if these ILs can provide environmentally safe residual concentrations of the target metals after extraction. Both pure water and natural mineral water samples were spiked with 20 µg L−1 of Cu, Ag, Cd, Hg and Pb, respectively. Quantitative extraction (> 99%) of Hg and Ag was achieved. Cu and Hg were below the respective no-observed-effect-concentrations (NOECs) after extraction and Ag below 0.03 µg L−1. Acute toxicity assays were conducted using two freshwater green algae Raphidocelis subcapitata and Tetradesmus obliquus. Growth inhibition and maximum photochemical quantum yield of photosystem II after 72 h were assessed. ILs were less toxic than similar compounds, but still must be classified as acute toxicants for algae. An inhibiting effect on both growth and chlorophyll fluorescence was observed. The leaching of the ILs into the samples remains a limitation regarding their environmental-friendly applicability. Nonetheless, the extremely efficient removal of Cu, Ag and Hg under environmentally relevant conditions calls for further research, which should focus on the immobilization of the ILs.

Oxidative stress response and proteomic analysis reveal the mechanisms of toxicity of imidazolium-based ionic liquids against Arabidopsis thaliana

Ionic liquids (ILs) are extensively used in various fields, posing a potential threat in the ecosystem because of their high stability, excellent solubility, and biological toxicity. In this study, the toxicity mechanism of three ILs, 1-octyl-3-methylimidazolium chloride ([C₈MIM]Cl), 1-decyl-3-methylimidazolium chloride ([C₁₀MIM]Cl), and 1-dodecyl-3-methylimidazolium chloride ([C₁₂MIM]Cl) on Arabidopsis thaliana were revealed. Reactive oxygen species (ROS) level increased with higher concentration and longer carbon chain length of ILs, which led to the increase of malondialdehyde (MDA) content and antioxidase activity, including superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (GPX) and peroxidase (POD) activities. SOD, CAT, and GPX activities decreased in high ILs concentration due to the excessive ROS. Differentially expressed protein was analyzed based on Gene ontology (GO) and KEGG pathways analysis. 70, 45, 84 up-regulated proteins, and 72, 104, 79 down-regulated proteins were identified in [C₈MIM]Cl, [C₁₀MIM]Cl, and [C₁₂MIM]Cl treatment, respectively (fold change ≥ 1.5 with ≥95% confidence). Cellular aldehyde metabolic process, mitochondrial and mitochondrial respiratory chains, glutathione transferase and oxidoreductase activity were enriched as up-regulated proteins as the defense mechanism of A. thaliana to resist external stresses. Chloroplast, photosynthetic membrane and thylakoid, structural constituent of ribosome, and transmembrane transport were enriched as the down-regulated protein. Compared with the control, 8 and 14 KEGG pathways were identified forup-regulated and down-regulated proteins, respectively, in three IL treatments. Metabolic pathways, carbon metabolism, biosynthesis of amino acids, porphyrin and chlorophyll metabolism were significantly down-regulated. The GO terms annotation demonstrated the oxidative stress response and effects on photosynthesis of A. thaliana in ILs treatment from biological process, cellular component, and molecular function categories.

Alkylimidazolium Ionic Liquids as Antifungal Alternatives: Antibiofilm Activity Against Candida albicans and Underlying Mechanism of Action

Candida albicans is an opportunistic pathogen causes fungal infections that range from common skin infections to persistent infections through biofilm formation on tissues, implants and life threatening systemic infections. New antifungal agents or therapeutic methods are desired due to high incidence of infections and emergence of drug-resistant strains. The present study aimed to evaluate (i) the antifungal and antibiofilm activity of 1-alklyl-3-methyl imidazolium ionic liquids ([CnMIM]+[X]-, n = 4, 12 and 16) against Candida albicans ATCC 10231 and two clinical C. albicans strains and (ii) the mechanism of action of promising antifungal ionic liquid on C. albicans. Two of the tested compounds were identified as more effective in preventing growth and biofilm formation. These ionic liquid compounds with -dodecyl and -hexadecyl alkyl groups effectively prevented biofilm formation by fluconazole resistant C. albicans 10231 and two other clinical C. albicans strains. Although both the compounds caused viability loss in mature C. albicans biofilms, an ionic liquid with -hexadecyl group ([C16MIM]+[Cl]-) was more effective in dispersing mature biofilms. This promising ionic liquid compound ([C16MIM]+[Cl]-) was chosen for determining the underlying mode of action on C. albicans cells. Light microscopy showed that ionic liquid treatment led to a significant reduction in cell volume and length. Increased cell membrane permeability in the ionic liquid treated C. albicans cells was evident in propidium iodide staining. Leakage of intracellular material was evident in terms of increased absorbance of supernatant and release of potassium and calcium ions into extracellular medium. A decrease in ergosterol content was evident when C. albicans cells were cultured in the presence of antifungal ionic liquid. 2',7'-Dichlorodihydrofluorescein acetate assay revealed reactive oxygen species generation and accumulation in C. albicans cells upon treatment with antifungal ionic liquid. The effect of antifungal ionic liquid on mitochondria was evident by decreased membrane potential (measured by Rhodamine 123 assay) and loss of metabolic activity (measured by MTT assay). This study demonstrated that imidazolium ionic liquid compound exert antifungal and antibiofilm activity by affecting various cellular processes. Thus, imidazolium ionic liquids represent a promising antifungal treatment strategy in lieu of resistance development to common antifungal drugs.

Transcriptomic analysis of the phytotoxic effects of 1-allyl-3-methylimidazolium chloride on the growth and plant hormone metabolic pathways of maize (Zea mays L.) seedlings

In this study, we investigated the phytotoxicity of an imidazolium-based ionic liquid, 1-allyl-3-methylimidazolium chloride ([Amim]Cl), against maize seedlings. It was found that in response to an increase in [Amim]Cl treatment concentrations, there were significant decreases in growth parameters (fresh weights and lengths) and the photosynthetic pigment contents of maize plants, whereas in contrast, the malondialdehyde content increased. In order to determine the molecular basis of [Amim]Cl-induced plant growth inhibition, an RNA-Seq analysis to examine the gene expression profiles of selected central biological pathways was performed. And a total of 4024 genes that were differentially expressed between control and 400 mg/L [Amim]Cl-treated plants were accordingly identified. Pathway enrichment analysis for the differentially expressed genes revealed that 12 of 15 genes in the porphyrin and chlorophyll metabolic pathways were down-regulated in response to [Amim]Cl treatment. Moreover, all six genes encoding key chlorophyll synthetic enzymes were down-regulated by [Amim]Cl. With regards to plant hormone metabolic pathways, the genes encoding key enzymes involved in ethybilene and abscisic acid (ABA) biosynthesis were up-regulated in response to [Amim]Cl treatment. Genes responsible for gibberellin (GA) inactivation were also stimulated by [Amim]Cl. These observations indicate that [Amim]Cl may promote the biosynthesis of senescence-related hormones (ethylene and ABA) as well as inactivation of growth-promoting hormones (GAs). It might be concluded that the observed [Amim]Cl-induced inhibition of maize seedling growth could be associated with changes in the gene expression profiles of these metabolic pathways.

Ionic Liquid-Like Pharmaceutical Ingredients and Applications of Ionic Liquids in Medicinal Chemistry: Development, Status and Prospects

Background:

As a new kind of green media and bioactive compounds with special structure, Ionic Liquids (ILs) are attracting much attention and applied widely in many fields. However, their roles and potential have not been fully recognized by many researchers of medicinal chemistry. Because of obvious differences from other traditional drugs and reagents, their uses and performance together with advantages and disadvantages need to be explored and reviewed in detail.

Methods:

For a systematic and explicit description of the relationship between ILs and medicinal chemistry, all of the contents were elucidated and summarized in a series of independent parts. In each part, it started from the research background or a conceptual framework and then specific examples were introduced to illustrate the theme. Finally, the important conclusions were drawn and its future was outlooked after the discussion about related key problems appearing in each mentioned research. Meanwhile, methodologies such as empirical analysis, comparison and induction were applied in different sections to exposit our subject.

Results:

The whole review was composed of five parts, and 148 papers were cited in total. Related basic information of ionic liquids was provided on the basis of representative references, including their concepts and important characters. Then 82 papers outlined ionic liquid-like active pharmaceutical ingredients, which unfolded with their major biological activities (antimicrobial activity, antibiofilm activity, antitumor activity, anticholinesterase activity and so on). Applications of ionic liquids in the synthesis of drugs and pharmaceutical intermediates were elaborated in 92 papers to illustrate the important roles of ILs and their extraordinary properties in this field. Moreover, new technologies (such as immobilization of IL, microwave reaction, solventfree synthesis, microreactor, etc) were introduced for further innovation. Finally, 26 papers were included to expound the status of the IL-assisted derivatization of various natural lead compounds.

Conclusion:

This review placed emphasis on chemical structures of ILs and their structureactivity relationships in a specific manner, leading to meaningful and valuable related information to some related fields and thus promotes further development and application of various ILs for medicinal chemistry. The deep exploration for key scientific problems is the driving force to propel their theoretical breakthrough and industrial production.

Synthesis of new water-soluble ionic liquids and their antibacterial profile against gram-positive and gram-negative bacteria

A series of imidazolium bromide salts (NIM-Br 1a, 1b and 1c) bearing different lengths of alkyl chains were synthesized and theirin vitro antibacterial activities were determined by measuring the minimum inhibitory concentration (MIC) values for Staphylococcus aureus, Escherichia coli, Pseudomonas aeruginosa and Enterococcus faecalis. In addition, these imidazolium derivatives were also evaluated against biofilm produced by these bacterial strains. All compounds were found to be effective against Gram-positive and Gram-negative bacteria, and also more effective on the S. aureus biofilm production than the others.

Effects of 1-butyl-3-methylimidazolium chloride on the photosynthetic system and metabolism of maize (Zea mays L.) seedlings

Ionic liquids (ILs) are widely used in various chemical processes. However, a growing number of studies have found that ILs are potentially toxic to different types of living organisms, including crops. The present study analysed the effects of 1-butyl-3-methylimidazolium chloride ([C₄mim]Cl) on the photosynthetic system and metabolism of maize seedlings. Results showed that [C₄mim]Cl could significantly reduce maize leaf chlorophyll level and cause extensive leaf bleaching. The activity of photosystem II (PSII) was significantly inhibited when seedlings exposed to higher concentration of [C₄mim]Cl. The maximum quantum yield of PSII and the potential efficiency of PSII were reduced by 63% and 88% under 800 mg/L [C₄mim]Cl treatment in comparison with the control treatment. The RNA sequencing analysis performed to examine gene expression profiles of maize leaves under [C₄mim]Cl treatment revealed 639 differentially expressed genes (DEGs), 115 of which were categorized into different metabolic pathways. Among these DEGs, the seven genes involved in the photosynthetic Calvin cycle were down-regulated by [C₄mim]Cl exposure. For carbohydrates and amino acids metabolism, the genes for starch synthesis were down-regulated, while the genes for amino acids and protein degradation were up-regulated. The changes observed in these major metabolic pathways might be an important reason for [C₄mim]Cl toxicity.

Novel Imidazole and Methoxybenzylamine Growth Inhibitors Affecting Salmonella Cell Envelope Integrity and its Persistence in Chickens

The control of Salmonella from farm to fork is challenging due to the emergence of antimicrobial-resistant isolates and the limited effects of current control methods. Advanced chemical technologies have made accessible a wide range of uncharacterized small molecules (SMs) with encouraging chemical properties for antimicrobial treatment. Of the 4,182 SMs screened in vitro, four cidal SMs were effective at 10 µM and higher against several serotypes, antibiotic-resistant, and biofilm embedded Salmonella enterica subsp. enterica serotype Typhimurium by altering cell membrane integrity. The four SMs displayed synergistic effects with ciprofloxacin, meropenem and cefeprime against Salmonella. Further, the SMs were not pernicious to most eukaryotic cells at 200 μM and cleared internalized Salmonella in infected Caco-2, HD11, and THP-1 cells at 6.25 µM and higher. The SMs also increased the longevity of Salmonella-infected Galleria mellonella larvae and reduced the population of internalized Salmonella Typhimurium. Two of the SMs (SM4 and SM5) also reduced S. Typhimurium load in infected chicken ceca as well as its systemic translocation into other tissues, with minimal impact on the cecal microbiota. This study demonstrated that SMs are a viable source of potential antimicrobials applicable in food animal production against Salmonella.

Virucidal or Not Virucidal? That Is the Question-Predictability of Ionic Liquid's Virucidal Potential in Biological Test Systems

For three decades now, ionic liquids (ILs), organic salts comprising only ions, have emerged as a new class of pharmaceuticals. Although recognition of the antimicrobial effects of ILs is growing rapidly, there is almost nothing known about their possible virucidal activities. This probably reflects the paucity of understanding virus inactivation. In this study, we performed a systematic analysis to determine the effect of specific structural motifs of ILs on three different biological test systems (viruses, bacteria and enzymes). Overall, the effects of 27 different ILs on two non-enveloped and one enveloped virus (P100, MS2 and Phi6), two Gram negative and one Gram positive bacteria (E. coli, P. syringae and L. monocytogenes) and one enzyme (Taq DNA polymerase) were investigated. Results show that while some ILs were virucidal, no clear structure activity relationships (SARs) could be identified for the non-enveloped viruses P100 and MS2. However, for the first time, a correlation has been demonstrated between the effects of ILs on enveloped viruses, bacteria and enzyme inhibition. These identified SARs serve as a sound starting point for further studies.