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New water-immiscible cationic biocide 1-dodecylpyridinium dodecylbenzenesulfonate (PyrC12-DBS) has been synthesized and tested as potential antifouling agent for commercial alkyd paint PP-115 (Ukraine). The modified PP-115/PyrC12-DBS coatings containing 8% and 16% (w/w) of PyrC12-DBS were prepared by dissolution directly of the cationic biocide into the PP-115 paint. Once the stainless steel bars were painted, the surface wettability of the coating was found to be significantly increased when modified with cationic biocide. The results of scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDX) studies indicate high homogeneity of the modified coatings. Infrared analysis revealed hydrogen bonding between ester groups of alkyd resin and pyridinium cations of PyrC12-DBS. The plasticizing effect of the cationic biocide on the alkyd binder has also been revealed by differential scanning calorimetry analysis. According to spectrophotometric analysis data, PyrC12-DBS has excellent resistance to leaching from protective coatings into water. Antibiofilm efficiency of PyrC12-DBS was evaluated by assessing the capability of two biofilm-forming model strains, namely Staphylococcus aureusATCC 25923 and Pseudomonas aeruginosaPA01, to form attached biofilms on the surface coated with modified alkyd paint. A significant decrease in biofilm metabolic activity, as well as in cell biomass, was determined for PP-115/PyrC12-DBS (16%) coatings. The antifouling activity was evaluated by exposure to experimental substrates in freshwater (Dnipro River) for 143 days. The surface of PP-115/PyrC12-DBS (16%) coatings showed an almost 13-fold reduction of total biomass formed by Dreissenidae mussels compared with control substrates. Overall, the obtained data indicate that the contact-active protective coatings based on water-insoluble polymer matrix and water-insoluble cationic biocide may effectively resist biofouling at relatively high biocide content.

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Background: Escherichia coli especially its multiresistant strains as the common foodborne pathogens cause bloodstream infections, nosocomial pneumonia, infections of the skin and soft tissues. Therefore, the search for new effective biologically active compounds has been rapidly increasing in recent few decades. In this paper, we describe Quantitative Structure-Activity Relationships (QSAR) studies, molecular docking and in vitro antibacterial activity evaluation of a series of imidazolium-based Ionic Liquids (ILs) against E. coli spp. Methods: M2D fragment-based, classification and regression QSAR models were created using machine learning methods and types of descriptors via the OCHEM server. Biological testing of a series of synthesized imidazolium ILs with predicted activity was performed by the disc diffusion method. The most typical structures of symmetric and asymmetric ILs with high anti-E. coli activity (1e, 1h) were docked into the active site of Enoyl-Acyl Carrier Protein Reductase (ENR) in E. coli. Results: Symmetric imidazolium ILs with C8 alkyl chain length demonstrated the highest antibacterial activity in comparison to the high antibacterial potential of asymmetric ILs with C12 alkyl chain length against drug-sensitive and drug-resistant E. coli strains including hemolytic E. coli. It should be noted that symmetric ILs with C6 or C9 alkyl chain length have a slightly lower activity against certain E. coli strains. The key role in the binding of compounds (1e, 1h) in the E. coli ENR active site is associated with the NAD molecule and the amino acid residue Tyr146. Conclusion: The highly active symmetric and asymmetric imidazolium ILs can be considered as promising drug-candidates effective against E. coli spp. pathogens including multidrug-resistant strains.

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.

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 × 10-2S/cm at 140 °C. Homogeneous composite films based on commercial polyimide Matrimid® (PI) and BAIM-TFSI containing from 30 to 60 wt.% of ionic liquid were prepared by casting from methylene chloride solutions. Thermogravimetric analysis data (TGA) indicated an excellent thermal stability of PI/BAIM-TFSI composites and thermal degradation points in the temperature range 377-397 °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 dynamical mechanical analysis (DMA) 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 to 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 ºC. The ionic conductivity of this cross-linked composite membrane reached the level of 10-2S/cm at 130 ºC suggesting therefore its potential use in medium temperature fuel cells operating in water free conditions.