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Cellulose is a widespread macromolecule in terrestrial environments and a major architectural component of microbial biofilm. Therefore, cellulose might be considered a biosignature that indicates the presence of microbial life. We present, for the first time, characteristics of bacterial cellulose after long-term spaceflight and exposure to simuled Mars-like stressors. The pristine cellulose-based pellicle membranes from a kombucha microbial community (KMC) were exposed outside the International Space Station, and after their return to Earth, the samples were reactivated and cultured for 2.5 years to discern whether the KMC could be restored. Analyses of cellulose polymer integrity and mechanical properties of cellulose-based pellicle films, as well as the cellulose biosynthesis-related genes' structure and expression, were performed. We observed that (i) the cellulose polymer integrity was not significantly changed under Mars-like conditions; (ii) de novo cellulose production was 1.5 times decreased in exposed KMC samples; (iii) the dry cellulose yield from the reisolated Komagataeibacter oboediens was 1.7 times lower than by wild type; (iv) there was no significant change in mechanical properties of the de novo synthesized cellulose-based pellicles produced by the exposed KMCs and K. oboediens; and (v) the gene, encoding biosynthesis of cellulose (bcsA) of the K. oboediens, was downregulated, and no topological change or mutation was observed in any of the bcs operon genes, indicating that the decreased cellulose production by the space-exposed samples was probably due to epigenetic regulation. Our results suggest that the cellulose-based pellicle could be a good material with which to protect microbial communities during space journeys, and the cellulose produced by KMC members could be suitable in the fabrication of consumer goods for extraterrestrial locations.

Background: Currently, a study on the relationship between candidiasis and cancer has been conducted. Until recent years, the opportunistic fungus C. albicans is mainly associated with cancer processes and is able to stimulate carcinogenesis and metastasis. Methods: A number of ionic liquids as potential anticancer and anti-Candida agents have been investigated based on modern theoretical and experimental data about the relationship between oncopathology and candida infection. Results: The analysis of the received experimental results demonstrates that ionic liquid with alkyl chain length of 6 carbon atoms (C6) has not shown anti-Candida activity. The indicators of its cytotoxicity ІС50 (28,617μМ) and MTC (9,050 μМ) against HEP-2 tumor cell line were also very low. Compounds with alkyl chain length C12 have shown high potential of anti-Candida activity and anticancer properties. Conclusion: Based on the obtained results, сompound 4 (C12C1IM-Cl) is proposed for further study as a potential double-acting agent with high anticancer and anti-Candida activities. N-myristoyltransferase is presented and used for docking as a potential molecular target responsible for the dual anti-Сandidа and anticancer activities of studied ionic liquids.

A series of long-chain imidazolium-based ionic liquids (ILs) 1-dodecyl-3-methylimidazolium chloride (1), 1,3-bis(octyloxycarbonylmethyl)imidazolium chloride (2) and 1-dodecyloxycarbonylmethyl-3-methyloxycarbonylmethylimidazolium chloride (3), were synthesized and evaluated as antimicrobials against a wide range of bacteria and fungi. Toxicological risks of selected compounds were assessed using the biomodels of various organizational and functional levels. All compounds demonstrated significant antibacterial and antifungal activity. The toxicity results indicate that ILs containing an ester functional group in the alkyl side chain exhibited much lower toxicity to D. magna and acetylcholinesterase inhibition than ILs with long alkyl chain without polar substituents, while toxicity toward Danio rerio was on a par. The HSA-binding properties of ILs have been investigated by FT-IR spectroscopy technique and the evidences have suggested that the test compounds could induce the protein unfolding and changes in the secondary structure of HSA. The docking studies were carried out to provide structural insights of the ILs–HSA-binding interactions. The docked compounds exhibit a high binding affinity to HSA and the hydrogen bonding, hydrophobic and electrostatic interactions played a major role in the process. ILs 2 and 3 may be perspective for further investigation as potential low-toxic biocides with high antimicrobial activity against reference and clinical multidrug-resistant strains.

New antimicrobial polymer composite based on commercial polyurethane (PU) Laripur®LPR9020 and polymeric biocide polyhexamethylene guanidine hydrochloride (PHMG-Cl) has been prepared by solvent casting method. Modified PU films containing from 1 to 4 wt% of PHMG-Cl were characterized in terms of mechanical, thermal and surface properties, biocide release behavior, as well as antibacterial activity against Gram-negative (Escherichia coli) and Gram-positive (Bacillus subtilis) bacterial strains. The results of mechanical testing indicate that the introduction of PHMG-Cl did not cause noticeable changes in the tensile strength of PU films, but improved their elasticity by at least 20–30%. The surface of PU/PHMG-Cl films was found to possess significantly higher hydrophobicity than neat polymer that is manifested in sharply increased water contact angle value from 72° for neat PU to 95° for PU/PHMG-Cl (2%). According to thermogravimetric analysis data, PU/PHMG-Cl composites are thermally stable to at least 300 °C which indicate their availability for melt processing by common methods. The results of differential scanning calorimetry showed reduction of both glass transition and melting temperatures of PU by more than 7 °C when contained only 1% of PHMG-Cl. Gradual release of polymeric biocide from modified PU films into water has been detected spectrophotometrically. The total biocide release ratio was found to be in the range from 29% to 48% after 50 hours immersion, depending on its content in polymer composite. PU/PHMG-Cl films showed much lower leaching rate into physiological saline solution compared to pure water (from 10% to 21% after 50 hours), which may be caused by poor solubility of polymeric biocide in sodium chloride solutions. The study of antibacterial activity of modified PU films using both disc agar diffusion and contact methods indicate high efficacy against tested microorganisms when contained 3% of polymeric biocide. So, this approach, based on the modification of PU resin with polymeric biocide PHMG-Cl, has been discussed in terms of potential medical applications when biocide release system or contact active material are necessary.

Four water insoluble room-temperature protic ionic liquids (PILs) based on the N-alkylimidazolium cation with the alkyl chain length from 1 to 4 and bis(trifluoromethylsulfonyl)imide anion were synthesized and their chemical structure was confirmed by the 1H NMR and 19F NMR analysis. PILs were revealed to be thermally stable up to 360 and 400 &deg, C. At the same time, the proton conductivity of PILs was found to be dependent mostly on the temperature and, to a less extent, on the type of the cation, i.e., the increase of the conductivity from ~3 &times, 10&minus, 4 S/cm at 25 &deg, C to 2 &times, 2 S/cm at 150 &deg, C was observed. The water vapour sorption capacity of PILs was evaluated as a function of relative humidity and the influence of the alkyl chain length on the phase behaviour in the PIL-water system was discussed. The composite polyimide/PILs membranes were prepared by the PIL immobilization in the porous polymer (Matrimid&reg, 5218) film. The composite membranes showed a high level of proton conductivity (~10&minus, 3 S/cm) at elevated temperatures (up to 160 &deg, C). The obtained results reveal that the elaborated composite polyimide/PIL membranes are promising candidates for the application as proton exchange membrane at middle and high temperatures.

International audience; Filamentous fungi are present everywhere in our environment and can grow on almost any substance in presence of moisture. Protecting the indoor environment against microbial growth remains a complex issue especially in sanitary applications or where protection against moulds is critical. Silicone samples containing 2% or 5% (w/w) of the cationic biocides polyhexamethylene guanidine dodecylbenzenesulfonate (PHMG-DBS), 1-octyl-3-me-thylimidazolium tetrafluoroborate (OMIM-BF 4) or 1-dodecyl-3-methylimidazolium tetrafluoroborate (DMIM-BF 4) were tested against a series of fungal species implicated in indoor fungal contamination. Our investigations were conducted according to the international standard ISO 16869 i.e. with a carbon-poor Nutrient-Salt-Agar (NSA) culture medium, and also with a carbon-rich Peptone-Dextrose-Agar (PDA) culture medium composed of pancreatic peptone, glucose and agar-agar as the spore suspension agar overlay. The experimental protocol using the PDA medium proved to be the most efficient procedure for discriminating, in a week only, the control analysis and those using modified silicones. Our results demonstrate that silicones containing 5% of polymeric biocide PHMG-DBS present higher antifungal activity on the filamentous fungi than longchain imidazolium ionic liquids-containing silicones. The possible mechanisms of antifungal action of cationic biocides are discussed. The efficacy of PHMG-DBS demonstrates that such modified-silicones can prevent microbial growth and silicone deterioration by microorganisms in areas with high humidity levels such as kitchens and bathrooms as well as hospitals and microbiology laboratories.

The use of graphene for ‘conducting phase + glass’ thick films that are screen-printed onto an alumina ceramic substrate and then heat-treated in a vacuum furnace has been studied. Quantitative microanalysis of carbon and glass elements has been carried out and the microstructure and electrical properties of the films have been examined. The film surface layer shows an increased carbon content, the current–voltage curve is linear, indicating that Ohm’s law is obeyed, and resistivity decreases with increasing temperature. The temperature resistance coefficient is negative. It has been concluded that graphene can be used as a conducting phase in thick films.

New protic ionic liquid N-butylguanidinium tetrafluoroborate (BG-BF4) has been synthesized by single-step method. The ionic liquid is thermally stable to at least 300 °C and has ionic conductivity value of 8⋅10−3 S/cm at room temperature increasing to 0.18 S/cm at 180 °C. To develop a new proton conducting membrane, the nano-fibrillar matrix of bacterial cellulose (BC) has been impregnated with BG-BF4. The composite BC/BG-BF4 membrane containing 80 wt% of ionic liquid was found to have tensile strength of 35 MPa and ionic conductivity of 4.5⋅10−4 S/cm at 180 °C. The high saturation of BC with protic ionic liquid to 95 wt% allowed obtain composite membrane with reduced tensile strength of 6 MPa but excellent ionic conductivity of 5.2⋅10−2 S/cm at 180 °C. The deposition of polyaniline (PANI, emeraldine base) into BC matrix by oxidative polymerization of aniline on the surface of cellulose nanofibrils was found to improve the ionic conductivity of BC/BG-BF4 system significantly, reaching the value of 4⋅10−3 S/cm at 180 °C for cellulose film containing 80 wt% of ionic liquid. According to results of dynamical mechanical analysis (DMA), both BC/BG-BF4 and BC/PANI/BG-BF4 composites keep excellent storage modulus values at 180 °C (1000 MPa and 835 MPa, respectively). Due to the excellent holding capacity of BC matrix to ionic liquid, as well as good thermal and mechanical properties of BC/BG-BF4 composite it can be promising material for the fabrication of proton conducting membranes for fuel cells operating at elevated temperatures in water free conditions.

The interaction between human serum albumin (HSA) and synthesized imidazolium and pyridinium based ionic liquids (ILs), as good potential microbial growth inhibitors, was investigated by spectroscopic techniques combined with molecular docking analysis. All compounds were significant active against the tested bacterial and fungal strains. FT-IR spectroscopy indicated that the interaction of HSA with ILs generates considerable changes in protein secondary structure. The results of the molecular docking study showed that the studied ILs are able to firmly bind in the subdomain IIA of HSA with almost equal binding affinity (about −6.23 kcal/mol). Investigated HSA–ILs complex binds through hydrogen bonding or/and cation-π interactions. This study provides a better understanding of the binding of imidazolium and pyridinium based ILs to HSA and opens the way for their further biological and pharmaceutical investigations as candidates with antimicrobial properties.

A new polymeric biocide polyhexamethylene guanidine (PHMG) molybdate has been synthesized. The obtained cationic polymer has limited water solubility of 0.015 g/100 mL and is insoluble in paint solvents. The results of acute toxicity studies indicate moderate toxicity of PHMG molybdate, which has a median lethal dose at 48 h of 0.7 mg/L for Daphnia magna and at 96 h of 17 mg/L for Danio rerio (zebrafish) freshwater model organisms. Commercial ship paint was then modified by the addition of a low concentration of polymeric biocide 5% (w/w). The painted steel panels were kept in Dnipro River water for the evaluation of the dynamics of fouling biomass. After 129-d exposure, Bryozoa dominated in biofouling of tested substrates, forming 86% (649 g/m2 ) of the total biomass on control panel surfaces. However, considerably lower Bryozoa fouling biomass (15 g/m2 ) was detected for coatings containing PHMG molybdate. Dreissenidae mollusks were found to form 88% (2182 g/m2 ) of the fouling biomass on the control substrates after 228 d of exposure, whereas coatings containing PHMG molybdate showed a much lower biomass value of 23.6 g/m2 . The leaching rate of PHMG molybdate in water was found to be similar to rates for conventional booster biocides ranging from 5.7 μg/cm2 /d at the initial stage to 2.2 μg/cm2 /d at steady state. Environ Toxicol Chem 2017;36:2543-2551. © 2017 SETAC.

New hydrophobic protic ionic liquid, 2-butylaminoimidazolinium bis(trifluoromethylsulfonyl)imide (BAIM-TFSI), has been synthesized. The ionic liquid showed good thermal stability to at least 350 °C. The conductivity of BAIM-TFSI determined by electrochemical impedance method was found to be 5.6 × 10−2 S/cm at 140 °C. Homogeneous composite films based on commercial polyimide (PI) Matrimid and BAIM-TFSI containing 30–60 wt% of ionic liquid were prepared by casting from methylene chloride solutions. Thermogravimetric analysis data indicated an excellent thermal stability of PI/BAIM-TFSI composites and thermal degradation points in the temperature range 377 °C–397 °C. The addition of ionic liquid up to 50 wt% in PI films does not lead to any significant deterioration of the tensile strength of the polymer. The dynamic mechanical analysis results indicated both an increase of storage modulus E′ of PI/BAIM-TFSI composites at room temperature and a significant E′ decrease with temperature compared with the neat polymer. The cross-linking of the PI with polyetheramine Jeffamine D-400 allowed to prepare PI/Jeffamine/BAIM-TFSI (50%) membrane with E′ value of 300 MPa at 130 °C. The ionic conductivity of this cross-linked composite membrane reached the level of 10−2 S/cm at 130 °C, suggesting, therefore, its potential use in medium-temperature fuel cells operating in water-free conditions.

Quantitative structure-activity relationships (QSAR) of imidazolium ionic liquids (ILs) as inhibitors of C. albicans collection strains (IOA-109, KCTC 1940, ATCC 10231) have been studied. Predictive QSAR models were built using different descriptor sets for a set of 88 ionic liquids with known minimum inhibitory concentrations (MIC) against C. albicans. We applied the state-of-the-art QSAR methodologies such as WEKA Random Forest (RF) as a binary classifier, Associative Neural Networks (ASNN) and k-Nearest Neighbors (k-NN) to build continuum non-linear regression models. The obtained models were validated using a 5-fold cross-validation approach and resulted in the prediction accuracies of 80% ± 5.0 for the classification models and q2 = 0.73-0.87 for the non-linear regression models. Biological testing of newly synthesized 1,3-dialkylimidazolium ionic liquids with predicted activity was performed by disco-diffusion method against C. albicans ATCC 10231 M885 strain and clinical isolates C. albicans, C. krusei and C. glabrata strains. The high percentage of coincidence between the QSAR predictions and the experimental results confirmed the high predictive power of the developed QSAR models within the applicability domain of new imidazolium ionic liquids.

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Online Chemical Modeling Environment (OCHEM) was used for QSAR analysis of a set of ionic liquids (ILs) tested against multi-drug resistant (MDR) clinical isolate Acinetobacter baumannii and Staphylococcus aureus strains. The predictive accuracy of regression models has coefficient of determination q2 = 0.66 &minus, 0.79 with cross-validation and independent test sets. The models were used to screen a virtual chemical library of ILs, which was designed with targeted activity against MDR Acinetobacter baumannii and Staphylococcus aureus strains. Seven most promising ILs were selected, synthesized, and tested. Three ILs showed high activity against both these MDR clinical isolates.

International audience; A strong catalytic effect of 1.0 wt% ionic liquids (ILs) on kinetic parameters of dicyanate ester of bisphenol E (DCBE) polycyclotrimerization was evidenced, and structure-property relationships of resulting densely cross-linked cyanate ester resins (CERs) were investigated. Three different ILs with contrasted reactivity were employed as a catalysts: an aprotic IL, i.e. 1-octyl-3-methyl imidazolium tetrafluoroborate ([OMIm][BF4]), a protic IL, i.e. 2-(hydroxyethylamino) imidazolinium chloride ([HEAIm][Cl]), and a protic polymeric IL, i.e. poly(hexamethylene guanidine) toluene sulfonate ([PHMG][TS]). Both [HEAIm][Cl] and [PHMG][TS] were reactive towards DCBE monomer, whereas [OMIm][BF4] was chemically inert, as confirmed by Fourier Transform Infrared (FTIR) spectroscopy. Noticeably, the conversion (αc) of cyanate groups in the presence of ILs dramatically increased, and a significant dependence of αc values on IL chemical structure was found. The corresponding mechanisms of DCBE polycyclotrimerization in the presence of different ILs were proposed. All the CER/IL networks exhibited a high thermal stability inherent to neat CER, as shown by TGA, whereas unexpected significant changes of the viscoelastic characteristics for CER/IL networks compared to pure CER analogue were observed using DMTA.

Several model plants are known to respond to bacterial quorum sensing molecules with altered root growth and gene expression patterns and induced resistance to plant pathogens. These compounds may represent novel elicitors that could be applied as seed primers to enhance cereal crop resistance to pathogens and abiotic stress and to improve yields. We investigated whether the acyl-homoserine lactone N-hexanoyl-L-homoserine lactone (C6-HSL) impacted winter wheat (Triticum aestivum L.) seed germination, plant development and productivity, using two Ukrainian varieties, Volodarka and Yatran 60, in both in vitro experiments and field trials. In vitro germination experiments indicated that C6-HSL seed priming had a small but significant positive impact on germination levels (1.2x increase, p < 0.0001), coleoptile and radicle development (1.4x increase, p < 0.0001). Field trials over two growing seasons (2015-16 and 2016-17) also demonstrated significant improvements in biomass at the tillering stage (1.4x increase, p < 0.0001), and crop structure and productivity at maturity including grain yield (1.4 – 1.5x increase, p < 0.0007) and quality (1.3x increase in good grain, p < 0.0001). In some cases variety effects were observed (p ≤ 0.05) suggesting that the effect of C6-HSL seed priming might depend on plant genetics, and some benefits of priming were also evident in F1 plants grown from seeds collected the previous season (p ≤ 0.05). These field-scale findings suggest that bacterial acyl-homoserine lactones such as C6-HSL could be used to improve cereal crop growth and yield and reduce reliance on fungicides and fertilisers to combat pathogens and stress.

Ester-functionalized pyridinium ionic liquids (ILs), 1-decyloxycarbonylmethylpyridinium chloride (PyrСOOC10-Cl), and 1-dodecyloxycarbonylmethylpyridinium chloride (PyrСOOC12-Cl) have been synthesized and studied for their environmental toxicity. Simple long-chain pyridinium ILs, 1-dodecylpyridinium chloride (PyrC12-Cl), and commercial disinfectant cetylpyridinium chloride (CPC) were used as reference compounds. Both ester-functionalized ILs and CPC showed significantly reduced antibacterial activity compared to PyrC12-Cl. However, ester-functionalized ILs were found to have excellent antifungal activity towards Candida albicans fungus strains, similar to PyrC12-Cl and much higher than for CPC. The molecular docking of ILs in the active site of the known antifungal target N-myristoyltransferase (Nmt) C. albicans has been conducted. The obtained results indicate the possibility of ILs binding into the Nmt pocket. The high stability of the complexes, especially for PyrCOOC10-Cl, is ensured by hydrogen bonding, electrostatic anion-pi interactions, as well as hydrophobic pi-alkyl and alkyl interactions that was confirmed by calculated binding energy values. The acute toxicity studies of ester-functionalized ILs on D. rerio (zebrafish) hydrobiont have shown their dramatically reduced ecotoxicity compared to PyrC12-Cl and CPC. Thus, LD50 values of 15.2 mg/L and 16.8 mg/L were obtained for PyrCOOC10-Cl and PyrCOOC12-Cl, respectively, whereas CPC had LD50 value of 0.018 mg/L. The primary biodegradation test CEC L-33-A93 of ILs indicated an improved biodegradability of ester-functionalized compounds compared to simple long-chain ILs. Based on the obtained results, PyrCOOC10-Cl may be considered as very promising cationic biocide due to the combination of soft antimicrobial activity and reduced ecotoxicity, as well as improved biodegradability.

Novel thermosetting systems based on cyanate ester resins (CERs) have been created through the polycyclotrimerization reaction of dicyanate ester of bisphenol E (DCBE) in the presence of different amounts of 1-heptyl pyridinium tetrafluoroborate [HPyr][BF4] Ionic Liquid (IL). A significant accelerating effect on the curing kinetics of DCBE was found by FTIR analysis. The reaction mechanism for the [HPyr][BF4]-catalyzed polycyclotrimerization of DCBE was newly proposed via the formation of a [CN]δ+–[HPyr]δ− complex as a key intermediate. Structure–properties relationships for the thermostable CER/IL networks were investigated by using DSC, DMTA, dielectric spectroscopy, tensile testing, quasi-dc measurements (I-V characteristics), and TGA. All the nanocomposites showed excellent thermal stability up to 300 °C, indicating the formation of a densely crosslinked network even at high IL content (40 wt%), and they could be used at high temperatures above their Tg without significant thermal degradation. Nanoscale phase separation led to the creation of ionic channels within the CER matrix to ensure photosensitivity properties.

International audience

The polycyclotrimerization reaction of dicyanate ester of bisphenol E (DCBE) in the presence of varying amounts (from 0.5 to 5 wt%) of 1-octyl-3-methylimidazolium tetrafluoroborate ((OMIm)(BF4)) ionic liquid has been investigated using differential scanning calorimetry (DSC) and Fourier transform infrared spectroscopy (FTIR) techniques, after a curing stage at 150 °C for 6 h. It is noteworthy that an amount of (OMIm)(BF4) as low as 0.5 wt% accelerates dramatically the ther- mal curing process leading to the formation of a polycyanurate network. The conversion of DCBE increased with increasing (OMIm)(BF4) content in the temperature range studied. A reaction mechanism associated with the ionic liquid-catalyzed DCBE polycyclotrimerization is newly proposed via the involvement of a (CN) δ+ -(OMIm) δ- complex as a key intermediate.

Water immiscible ionic liquid 1-dodecyl-3-methylimidazolium tetrafluoroborate (DMIM-BF 4 ) and its inclusion complex with β-cyclodextrin (β-CD) in molar ratio 1:1 have been synthesized. The formation of DMIM-BF 4 /β-CD complex was confirmed by FT-IR analysis, 1 H NMR analysis, and differential scanning calorimetry data. Our results indicate that the aliphatic tail of DMIM-BF 4 is included into β-CD inner cavity whereas imidazolium ring is located outside the torus. Moreover, the weak interaction between polar components of ionic liquid and hydrophilic outer surface of β-CD has also been detected. The standard agar disk diffusion method was performed to evaluate antimicrobial efficiency of the obtained compounds against Staphylococcus aureus (ATCC-25923), Escherichia coli (ATCC-25922) and Pseudomonas aeruginosa (ATCC-27853), Candida albicans (M 885 ATCC 10231) and its clinical isolate test-cultures. It has been found that both DMIM-BF 4 and DMIM-BF 4 /β-CD complex possess high antimicrobial activity as revealed by similar zone inhibition values against all tested microorganisms. The acute toxicity studies on Danio rerio (zebrafish) model organism showed that the pure ionic liquid DMIM-BF 4 is slightly toxic compound having LD 50 value of 7 mg/L, whereas DMIM-BF 4 /β-CD complex has considerably reduced toxicity (LD 50 = 100 mg/L) and therefore have potentially wider application areas.

The imidazolium-based ionic liquids (ILs) (1-n-alkyl-3-methylimidazolium tetrafluoroborate, where n = 4, 6–8, 12) were synthesized and characterized in terms of their spectral characteristics, thermal stability, and water, ethanol and cyclohexane vapour sorption behaviour. It was found that the highest hydrophilic character had IL with the shortest alkyl chain on the cation. At the same time, the IL thermal stability was decreased with the increase of the cation alkyl chain length. D'Arcy and Watt and NRTL sorption models allowed to well describe the vapour sorption experimental data. The supported ionic liquid membranes (SILMs) were prepared by impregnation of the porous poly(vinylidene fluoride) (PVDF) membrane with the synthesized ILs. The sorption capacity of PVDF was found to increase after its swelling in IL. An experimental evaluation of the SILMs permeability was carried out for water, ethanol and cyclohexane. The effect of operation parameters such as temperature and concentration of the permeant was studied. It was observed that the presence of the IL strongly influenced the permeability performance of the membrane by reducing the pore sizes and changing the hydrophobic/hydrophilic balance. It is found from the permeation kinetics curves that the SILMs have high potential for separation of organic solvent/water mixtures.

Аbstract This paper describes Quantitative Structure-Activity Relationships (QSAR) studies, molecular docking and in vitro antibacterial activity of several potent imidazolium-based ionic liquids (ILs) against S. aureus ATCC 25923 and its clinical isolate. Small set of 131 ILs was collected from the literature and uploaded in the OCHEM database. QSAR methodologies used Associative Neural Networks and Random Forests (WEKA-RF) methods. The predictive ability of the models was tested through cross-validation, giving cross-validated coefficients q2 = 0.82–0.87 for regression models and overall prediction accuracies of 80–82.1% for classification models. The proposed QSAR models are freely available online on OCHEM server at https://ochem.eu/article/107364 and can be used for estimation of antibacterial activity of new imidazolium-based ILs. A series of synthesized 1,3-dialkylimidazolium ILs with predicted activity were evaluated in vitro. The high activity of 7 ILs against S. aureus strain and its clinical isolate was measured and thereafter analyzed by the molecular docking to prokaryotic homologue of a eukaryotic tubulin FtsZ.

Novel nanoporous film materials of thermostable cyanate ester resins (CERs) were generated by polycyclotrimerization of dicyanate ester of bisphenol E in the presence of varying amounts (from 20 to 40 wt%) of an ionic liquid (IL), i.e., 1-heptylpyridinium tetrafluoroborate, followed by its quantitative extraction after complete CER network formation. The completion of CER formation and IL extraction was assessed using gel fraction content determination, FTIR, 1H NMR, and energy-dispersive X-ray spectroscopy (EDX). SEM and DSC-based thermoporometry analyses demonstrated the formation of nanoporous structures after IL removal from CER networks, thus showing the effective role of IL as a porogen. Pore sizes varied from ~20 to ~180 nm with an average pore diameter of around 45–60 nm depending on the initial IL content. The thermal stability of nanoporous CER-based films was investigated by thermogravimetric analysis.

We have tested silicones containing 2% or 5% of the cationic biocides polyhexamethylene guanidine dodecylbenzenesulfonate (PHMG-DBS), 1-octyl-3-methylimidazolium tetrafluoroborate (OMIM-BF4) or 1-dodecyl-3-methylimidazolium tetrafluoroborate (DMIM-BF4) against the major relevant bacterial and yeast species in health care-associated infections (HCAI). Study conducted according to the international standard ISO 22196 revealed that silicones containing 2% or 5% DMIM-BF4 or 5% PHMG-DBS presented the highest antimicrobial activity, leading to a logarithmic growth reduction of 3.03 to 6.46 and 3.65 to 4.85 depending on the bacterial or fungal species. Heat-pretreated silicones containing 2% DMIM-BF4 kept a high activity, with at least a 3-log reduction in bacterial growth, except against P. aeruginosa where there was only a 1.1-log reduction. After 33days, the release ratio of cationic biocide from silicone films containing 5% of DMIM-BF4 was found to be 5.6% in pure water and 1.9% in physiological saline solution, respectively. No leaching of PHMG-DBS polymeric biocide was detected under the same conditions. These results demonstrate unambiguously that silicones containing 2% DMIM-BF4 or 5% PHMG-DBS present high antimicrobial activity, as well as high leaching resistance and therefore may be good candidates for the development of safer medical devices.

Antimicrobial polyamide 11 (PA-11) films containing low-cost, thermally stable and water resistant polymeric biocide polyhexamethylene guanidine dodecylbenzenesulfonate (PHMG-DBS) have been obtained by compression moulding. The structure of the modified PA-11 films containing from 3 to 10 wt% of PHMG-DBS was characterized using Raman and FTIR spectroscopy and atomic force microscopy (AFM). The surface properties were evaluated both by contact angle and contactless inductive method. The introduction of PHMG-DBS into PA-11 films was found to increase positive surface charge density to 5.5·10−11 C/cm2 for 10 wt% of PHMG-DBS. Antibacterial activity of PA-11/PHMG-DBS films against both Gram-positive (Escherichia coli) and Gram-negative (Bacillus subtilis) bacteria was demonstrated for films containing from 5 to 7 wt% of polymeric biocide. According to thermal investigations data, PA-11/PHMG-DBS composite has excellent thermal stability to at least 390 °C both in air and in argon atmosphere which indicates on its availability for the melt processing by common methods. It has also been found that polymeric biocide is highly resistant to leaching from PA-11 film.

Predictive QSAR models for the inhibitors of B. subtilis and Ps. aeruginosa among imidazolium-based ionic liquids were developed using literary data. The regression QSAR models were created through Artificial Neural Network and k-nearest neighbor procedures. The classification QSAR models were constructed using WEKA-RF (random forest) method. The predictive ability of the models was tested by fivefold cross-validation; giving q(2) = 0.77-0.92 for regression models and accuracy 83-88% for classification models. Twenty synthesized samples of 1,3-dialkylimidazolium ionic liquids with predictive value of activity level of antimicrobial potential were evaluated. For all asymmetric 1,3-dialkylimidazolium ionic liquids, only compounds containing at least one radical with alkyl chain length of 12 carbon atoms showed high antibacterial activity. However, the activity of symmetric 1,3-dialkylimidazolium salts was found to have opposite relationship with the length of aliphatic radical being maximum for compounds based on 1,3-dioctylimidazolium cation. The obtained experimental results suggested that the application of classification QSAR models is more accurate for the prediction of activity of new imidazolium-based ILs as potential antibacterials.

The water sorption behavior for various RTILs ([C4C1im][BF4], [C4C1im][PF6], [C6C1im][PF6], [C4im][DBP], [C4im][BEHP] and [Et3HN][CF3SO3]) was studied over the whole range of water activity using a continuous gravimetric method. Analysis of the water sorption isotherms using the non-random two-liquid model (NRTL) and the combination of a dual-mode sorption (Henry-clustering) allowed a better understanding of the RTIL-water interactions. It is noticed that the sorption of water by RTILs is mainly controlled by the anion's nature. Anions interact with water molecules by hydrogen bonds that promotes the formation of a hydrogen bond network between the water molecules. The water uptake by RTILs increases in the following order (up to 0.8 in the water activity a): [C6C1im][PF6] ≤ [C4C1im][PF6] 0.8), water molecules are aggregated only in water-miscible RTILs (case of [C4im][DBP] and [Et3HN][CF3SO3]) because of their stronger anion basicity. To complete the sorption study, the molecular state of water dissolved in RTILs was studied by the infrared spectroscopy. The water molecules dissolved in water-immiscible RTIL such as [C4C1im][PF6] are not self-associated independently of the water content and, thus, can be defined as “free” water molecules interacting via H-bonding with the anions in the symmetric complex: anion⋯HOH⋯anion. On the contrary, the water molecules sorbed in water-miscible RTILs such as [C4im][DBP] or [Et3HN][CF3SO3] are strongly associated by H-bonds and also with the anions even at low water activity, and are easily aggregated when the water content reaches the critical concentration at high activity.