Self-assembly and antimicrobial activity of long-chain amide-functionalized ionic liquids in aqueous solution

Interaction and antibacterial activity of ciprofloxacin with choline based ionic liquid and CTAB: A comparative spectroscopic study

In this study, the complexation of potential chemo-therapeutic antibacterial drug, ciprofloxacin (CIP) with varying concentrations of surface active compounds (SACs) i.e., (N-(2-hydroxyethyl)-N,N-dimethyl-1-dodecanaminium bromide (12Cho.Br) and cetyltrimethylammonium bromide (CTAB) has been studied. Multispectroscopic techniques were exploited to carry out the study. The higher binding constant (Kb) value for CIP-CTAB than CIP-12Cho.Br obtained from fluorescence data revealed stronger binding of CTAB than 12Cho.Br, owing to the stronger hydrophobic-hydrophobic interaction betweeen CIP and CTAB compared to CIP and 12Cho.Br. The time resolve fluorescence decay shows changes in average lifetime (τavg) with the increasing concentration of 12Cho.Br and CTAB. The changes in τavg suggests that complex formation is taking place between CIP and 12Cho.Br / CTAB. Further, the formation of micelles by 12Cho.Br / CTAB and the effect of alkyl chain length was studied by dynamic light scattering (DLS) and zeta potential to confirm the drug complexation with 12Cho.Br and CTAB. The antibacterial activity has been performed for CIP and 12Cho.Br and CTAB. It was observed that in presence of lower concentrations of 12Cho.Br/ CTAB, the activity of the drug increased. The activity was also found cationic alkyl chain length dependent. Moreover, in-vitro cytotoxicity of CIP and its combinations with 12Cho.Br and CTAB was performed using MTT assay on HEK293 (Human embryonic kidney cells).

Development of Cholinium-Based API Ionic Liquids with Enhanced Drug Solubility: Biological Evaluation and Interfacial Properties

We report an efficient sustainable two-step anion exchange synthetic procedure for the preparation of choline API ionic liquids (Cho-API-ILs) that contain active pharmaceutical ingredients (APIs) as anions combined with choline-based cations. We have evaluated the in vitro cytotoxicity for the synthesized compounds using three different cells lines, namely, HEK293 (normal kidney cell line), SW480, and HCT 116 (colon carcinoma cells). The solubility of APIs and Cho-API-ILs was evaluated in water/buffer solutions and was found higher for Cho-API-ILs. Further, we have investigated the antimicrobial potential of the pure APIs, ILs, and Cho-API-ILs against clinically relevant microorganisms, and the results demonstrated the promise of Cho-API-ILs as potent antimicrobial agents to treat bacterial infections. Moreover, the aggregation and adsorption properties of the Cho-API-ILs were observed by using a surface tension technique. The aggregation behavior of these Cho-API-ILs was further supported by conductivity and pyrene probe fluorescence. The thermodynamics of aggregation for Cho-API-ILs has been assessed from the temperature dependence of surface tension. The micellar size and their stability have been studied by dynamic light scattering, transmission electron microscopy, and zeta potential. Therefore, the duality in the nature of Cho-API-ILs has been explored with the upgradation of their physical, chemical, and biopharmaceutical properties, which enhance the opportunities for advances in pharmaceutical sciences.

Efficacy of Novel Quaternary Ammonium and Phosphonium Salts Differing in Cation Type and Alkyl Chain Length against Antibiotic-Resistant Staphylococcus aureus

Antibacterial resistance poses a critical public health threat, challenging the prevention and treatment of bacterial infections. The search for innovative antibacterial agents has spurred significant interest in quaternary heteronium salts (QHSs), such as quaternary ammonium and phosphonium compounds as potential candidates. In this study, a library of 49 structurally related QHSs was synthesized, varying the cation type and alkyl chain length. Their antibacterial activities against Staphylococcus aureus, including antibiotic-resistant strains, were evaluated by determining minimum inhibitory/bactericidal concentrations (MIC/MBC) ≤ 64 µg/mL. Structure-activity relationship analyses highlighted alkyl-triphenylphosphonium and alkyl-methylimidazolium salts as the most effective against S. aureus CECT 976. The length of the alkyl side chain significantly influenced the antibacterial activity, with optimal chain lengths observed between C10 and C14. Dose-response relationships were assessed for selected QHSs, showing dose-dependent antibacterial activity following a non-linear pattern. Survival curves indicated effective eradication of S. aureus CECT 976 by QHSs at low concentrations, particularly compounds 1e, 3e, and 5e. Moreover, in vitro human cellular data indicated that compounds 2e, 4e, and 5e showed favourable safety profiles at concentrations ≤ 2 µg/mL. These findings highlight the potential of these QHSs as effective agents against susceptible and resistant bacterial strains, providing valuable insights for the rational design of bioactive QHSs.

Sustainable ionic liquids-based molecular platforms for designing acetylcholinesterase reactivators

We report a green chemistry approach for preparation of oxime-functionalized ILs as AChE reactivators: amide/ester linked IL, l-alanine, and l-phenylalanine derived salts bearing pyridinium aldoxime moiety. The reactivation capacities of the novel oximes were evaluated towards AChE inhibited by typical toxic organophosphates, sarin (GB), VX, and paraoxon (PON). The studied compounds are mostly non-toxic up to the highest concentrations screened (2 mM) towards Gram-negative and Gram-positive bacteria cell lines and both filamentous fungi and yeasts in the in vitro screening experiments as well as towards the eukaryotic cell (CHO-K1 cell line). Introduction of the oxime moiety in initially biodegradable structure decreases its ability to biodegradation. The compound 3d was shown to reveal remarkable activity against the AChE inhibited by VX, exceeding conventional reactivators 2-PAM and obidoxime. The regularities on antidotal activity, cell viability, plasma stability, biodegradability as well as molecular docking study of the newly synthesized oximes will be used for further improvement of their structures.

Cholinium-Based Ionic Liquids as Promising Antimicrobial Agents in Pharmaceutical Applications: Surface Activity, Antibacterial Activity and Ecotoxicological Profile

Cholinium-based ionic liquids are compounds increasingly studied in pharmaceutics and biomedicine to enhance bioavailability in drug delivery systems and as bioactive ingredients in pharmaceutical formulations. However, their potential as antimicrobial agents has scarcely been investigated. Herein, we explored the antimicrobial activity of a series of surface-active cholinium-based ionic liquids (Chol-ILs). For this purpose, Chol-ILs with alkyl chains of 10-16 carbon atoms were synthesized and their self-assembly in aqueous medium was investigated. Subsequently, their antimicrobial activity against a panel of clinically relevant bacteria and their ability to eradicate MRSA and P. aeruginosa PAO1 biofilms was evaluated. Finally, we analyzed the ecotoxicological profile of Chol-ILs in terms of susceptibility to aerobic biodegradation and acute aquatic toxicity against D. magna and V. fisheri. Our results reveal that cholinium-based ILs with alkyl chain lengths ≥12 C show a broad spectrum of antibacterial activity. Their antimicrobial efficacy depends on their hydrophobicity, with the C₁₄-C₁₆ homologs being the most effective compounds. These ILs exhibit antimicrobial activity similar to that of imidazolium ILs and quaternary ammonium antiseptics. Moreover, the longer alkyl chain Chol-ILs are able to eradicate established biofilms at concentrations as low as 16-32 µg/mL. The biodegradation rate of cholinium-based ILs decreases with alkyl chain elongation. Our results reinforce the suitability of Chol-ILs as promising multifunctional compounds for application in pharmaceutical and biomedical formulation.

Synthesis, Self-Aggregation, Surface Characteristics, Electrochemical Property, Micelle Size, and Antimicrobial Activity of a Halogen-Free Picoline-Based Surface-Active Ionic Liquid

We present a new approach toward the design of a halogen-free picoline-based surface-active ionic liquid (SAIL) (1-octyl-4-methyl pyridinium dodecyl sulfate) [C₈γPic]DS consisting of long dodecyl sulfate (DS) as an anion. The surface properties, micellization behavior, and antimicrobial activity in an aqueous solution were investigated using tensiometry, conductometry, and ultraviolet (UV) spectroscopy. Incorporating the DS group in SAIL leads to lower critical micellar concentration (CMC) and enhanced adsorption at the air/water interface of the functionalized ionic liquid compared to the C₈-alkyl chain-substituted pyridine ionic liquids. The antimicrobial activity was evaluated against a representative Gram-negative and Gram-positive bacteria panel. Antibacterial activities increased with the alkyl chain length, C₈ being the homologous most effective antimicrobial agent. The micelle size of [C₈γPic]DS was determined by the dynamic light-scattering (DLS) study. Cyclic voltammetry (CV) measurements have been employed to evaluate the interaction between the SAIL micelle and working electrode, diffusion coefficient, and micelle size of the SAIL solution. The diffusion coefficient explored the correlation of surface properties and the antimicrobial activity of [C₈γPic]DS. This halogen-free SAIL is the future of wetting agents and emulsion studies in agriculture due to its small micelle size and surface characteristics.

Ionic Liquids: Emerging Antimicrobial Agents

Antimicrobial resistance has become a serious threat to global health. New antimicrobials are thus urgently needed. Ionic liquids (ILs), salts consisting of organic cations and anions with melting points less than 100°C, have been recently found to be promising in antimicrobial field as they may disrupt the bacterial wall and membrane and consequently lead to cell leakage and death. Different types of antimicrobial ILs are introduced in the review, including cationic, polymeric, and anionic ILs. Being the main type of the antimicrobial ILs, the review focuses on the structure and the antimicrobial mechanisms of cationic ILs. The quantitative structure-activity relationship (QSAR) models of the cationic ILs are also included. Increase in alkyl chain length and lipophilicity is beneficial to increase the antimicrobial effects of cationic ILs. Polymeric ILs are homopolymers of monomer ILs or copolymers of ILs and other monomers. They have great potential in the field of antibiotics as they provide stronger antimicrobial effects than the sum of the monomer ILs. Anionic ILs are composed of existing anionic antibiotics and organic cations, being capable to enhance the solubility and bioavailability of the original form. Nonetheless, the medical application of antimicrobial ILs is limited by the toxicity. The structural optimization aided by QSAR model and combination with existing antibiotics may provide a solution to this problem and expand the application range of ILs in antimicrobial field.

Sustainable Synthesis of Ionic Liquid-Functionalized Zinc Oxide Nanosheets (IL@ZnO): Evaluation of Antibacterial Potential Activity for Biomedical Applications

Zinc oxide (ZnO)-derived materials exhibit unique antibacterial, antifungal, and photochemical activities and are widely used in antibacterial formulations. In this work, ZnO nanosheets were prepared by green and cost-effective synthesis via a hydrothermal method, and the prepared ZnO nanosheets were further functionalized with an eco-friendly ionic liquid (IL). Thus, a sustainable approach was established to synthesize ZnO nanosheets. The functionalization of ZnO with the synthesized IL was fully characterized by advanced spectroscopic and microscopic techniques. The prepared ionic liquid-functionalized ZnO (IL@ZnO) showed self-organized layered-sheet arrangements caused by the intercalation of the IL onto the surface of ZnO nanosheets as revealed by scanning electron microscopy (SEM). The design of the IL comprised a carboxylic acid moiety for functionalization onto the surface of ZnO, whereas the hydrophobicity was tuned through the incorporation of a long alkyl chain. The developed IL@ZnO material was also tested against both Gram-positive and Gram-negative pathogenic bacteria for potential antibacterial activity by colony-forming unit (CFU) and minimum inhibitory concentration tests. The results revealed that the IL@ZnO exhibits significant antibacterial activity against tested strains. In particular, potent activity was observed against the Gram-positive skin-specific Staphylococcus aureus bacteria strain. The mechanism of bactericidal activity against bacteria was also explored along with the cytotoxicity toward mammalian cells, which reveals that the IL@ZnO is nontoxic in nature. To utilize the developed material owing to its bactericidal activity for practical applications, the IL@ZnO was fabricated onto the surface of cotton fabric, and its surface morphology was examined by SEM; the activity of IL@ZnO-treated cotton fabric was evaluated by the zone of inhibition assay. Additionally, the IL@ZnO-treated cotton fabric exhibited remarkable stability along with significant hydrophobicity and breathability and thus can be utilized as a biomaterial for biomedical applications, especially in medical masks, for reducing the risk of transmission of infectious diseases.

Mixed Oxime-Functionalized IL/16-s-16 Gemini Surfactants System: Physicochemical Study and Structural Transitions in the Presence of Promethazine as a Potential Chiral Pollutant

The increasing concern about chiral pharmaceutical pollutants is connected to environmental contamination causing both chronic and acute harmful effects on living organisms. The design and application of sustainable surfactants in the remediation of polluted sites require knowledge of partitioning between surfactants and potential pollutants. The interfacial and thermodynamic properties of two gemini surfactants, namely, alkanediyi-α,ω-bis(dimethylhexadecyl ammonium bromide) (16-s-16, where s = 10, 12), were studied in the presence of the inherently biodegradable oxime-functionalized ionic liquid (IL) 4-((hydroxyimino)methyl)-1-(2-(octylamino)-2-oxoethyl)pyridin-1-ium bromide (4-PyC8) in an aqueous solution using surface tension, conductivity, fluorescence, FTIR and 1H NMR spectroscopic techniques. The conductivity, surface tension and fluorescence measurements indicated that the presence of the IL 4-PyC8 resulted in decreasing CMC and facilitated the aggregation process. The various thermodynamic parameters, interfacial properties, aggregation number and Stern–Volmer constant were also evaluated. The IL 4-PyC8-gemini interactions were studied using DLS, FTIR and NMR spectroscopic techniques. The hydrodynamic diameter of the gemini aggregates in the presence of promethazine (PMZ) as a potential chiral pollutant and the IL 4-PyC8 underwent a transition when the drug was added, from large aggregates (270 nm) to small micelles, which supported the gemini:IL 4-PyC8:promethazine interaction. The structural transitions in the presence of promethazine may be used for designing systems that are responsive to changes in size and shape of the aggregates as an analytical signal for selective detection and binding pollutants.

Mixed Oxime-Functionalized IL/16-s-16 Gemini Surfactants System: Physicochemical Study and Structural Transitions in the Presence of Promethazine as a Potential Chiral Pollutant

The increasing concern about chiral pharmaceutical pollutants is connected to environmental contamination causing both chronic and acute harmful effects on living organisms. The design and application of sustainable surfactants in the remediation of polluted sites require knowledge of partitioning between surfactants and potential pollutants. The interfacial and thermodynamic properties of two gemini surfactants, namely, alkanediyi-α,ω-bis(dimethylhexadecyl ammonium bromide) (16-s-16, where s = 10, 12), were studied in the presence of the inherently biodegradable oxime-functionalized ionic liquid (IL) 4-((hydroxyimino)methyl)-1-(2-(octylamino)-2-oxoethyl)pyridin-1-ium bromide (4-PyC8) in an aqueous solution using surface tension, conductivity, fluorescence, FTIR and 1H NMR spectroscopic techniques. The conductivity, surface tension and fluorescence measurements indicated that the presence of the IL 4-PyC8 resulted in decreasing CMC and facilitated the aggregation process. The various thermodynamic parameters, interfacial properties, aggregation number and Stern–Volmer constant were also evaluated. The IL 4-PyC8-gemini interactions were studied using DLS, FTIR and NMR spectroscopic techniques. The hydrodynamic diameter of the gemini aggregates in the presence of promethazine (PMZ) as a potential chiral pollutant and the IL 4-PyC8 underwent a transition when the drug was added, from large aggregates (270 nm) to small micelles, which supported the gemini:IL 4-PyC8:promethazine interaction. The structural transitions in the presence of promethazine may be used for designing systems that are responsive to changes in size and shape of the aggregates as an analytical signal for selective detection and binding pollutants.

Phosphonium-based ionic liquids as antifungal agents for conservation of heritage sandstone

With a view to preventing fungal deterioration of historical stone artworks, we report the use of phosphonium-based ionic liquids (ILs) as potent antifungal agents against dematiaceous fungi commonly found on heritage stones. Three ILs: tributyldodecylphosphonium polyoxometalate [P44412][POM], tributyltetradecylphosphonium polyoxometalate [P44414][POM], and trihexyltetradecylphosphonium polyoxometalate [P66614][POM] were prepared and their thermal stabilities and in vitro antifungal activities were evaluated. From the ramped temperature thermogravimetric analysis and antifungal experiments it can be clearly observed that the alkyl chain length of the tetraalkylphosponium cation has a significant influence on the thermal and antifungal properties. The thermal stability and antifungal activity decreased as the number of carbon atoms of the alkyl substituents increased and, thus, followed the order [P44412][POM] > [P44414][POM] > [P66614][POM]. In addition, inoculation of four fungal species on IL-coated sandstone surfaces showed significant inhibition of fungal growth, endowing the materials with potential applications in heritage sandstone conservation.

Influence of the alkyl chain length on the physicochemical properties and microbial biocompatibility of phosphonium based fatty acid ionic liquids

Ionic liquids (ILs) have remarkable properties and applications in many areas of science. Phosphonium ILs have become important because of their unique chemical and thermal stabilities. The present work is focused on the synthesis, characterisation, physicochemical properties, and microbial toxicity assessment of phosphonium ILs bearing seven different fatty acid anions. The structures of the synthesised ILs were confirmed by 1H and 13C nuclear magnetic resonance (NMR) and FTIR spectroscopy. Physicochemical properties such as density and viscosity of pure ILs were measured at temperatures ranging from 298.15 to 313.15 K. The experimental density decreased, whereas the viscosity increased with an increasing number of carbon atoms in the anion. The derived properties were also found to be anion dependent. The thermal decomposition temperature was investigated by TGA. Subsequently, the toxicity profile of the ILs was determined for selected Gram positive and Gram negative bacteria and some species of fungi in terms of minimum inhibitory concentrations (MIC). The results show that the antimicrobial activities of the ILs are strongly related to the structures of the ILs, where an increase in toxicity was observed with increasing alkyl group chain length of the fatty acid anion.

Surfing the Third Wave of Ionic Liquids: A Brief Review on the Role of Surface-Active Ionic Liquids in Drug Development and Delivery

The relevance of ionic liquids (ILs) is now well established in many fields, as their unique properties make them appealing as 1) greener alternatives to organic solvents (first-generation ILs), 2) tunable task-specific materials (second-generation ILs), and 3) multifunctional players in life and pharmaceutical sciences (third-generation ILs). This third wave of ILs encompasses a wide range of compounds, from bioactive molecules with single or even dual therapeutic action, to potential ingredient molecules for drug formulation and transport systems. In this context, the focus of this review is the emergent role of surface-active ionic liquids (SAILs) in drug development and delivery.

Profound implication of histological alterations, haematological responses and biocidal assessment of cationic amphiphiles unified with their molecular architecture

The interfacial properties depicting the micellization behaviour of the cationic amphiphiles (surfactants) belonging to the class of quaternary ammonium salts varying in degree of hydrophobicity were evaluated using tensiometry, conductivity and fluorescence spectrophotometric methods at 303.15 K. The impact of the amphiphilic nature of these amphiphiles as a function of their concentration is accounted against the selective microbial strains using the well-diffusion approach. Also, its influence on the histological (shrinkage/curling of lamellae, necrosis, haemorrhage, hyperplasia of villi in gills and intestine) alterations and haematological (blood parameters) changes in fingerling of Cirrhinus mrigala (C. mrigala) offers an insight into the stern damages reported as aquatic toxicity. The lesions exhibited moderate to severe alterations that are further correlated with the semi-quantitative mean alteration value (MAV). The in vitro and in vivo findings are explained significantly in terms of amphiphilic hydrophobicity which followed the order: C₁₆TAB > C₁₂TAB. All the observed outcomes are rationalized by the structural assessment of the selected amphiphiles as specified by the computational simulation approach using density functional theory (DFT) with B3LYP method and 3-21G basis source set. This work also portrays the biodegradability of these cationic amphiphiles and their fate on the environment. Graphical abstract Molecular architecture of cationic amphiphiles integrated with their in vitro and in vivo rejoinders.

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.

Multi-spectroscopic monitoring of molecular interactions between an amino acid-functionalized ionic liquid and potential anti-Alzheimer's drugs

Inhibiting the formation of amyloid fibrils is a crucial step in the prevention of the human neurological disorder, Alzheimer's disease (AD). Ionic liquid (IL) mediated interactions are an expedient approach that exhibits inhibition effects on amyloid fibrils. In view of the beneficial role of ILs, in this work we have explored complexation of anti-Alzheimer's drugs (i.e., tacrine and PC-37) and an amino acid-functionalized IL [AIL (4-PyC8)]. Maintaining standard physiological conditions, the binding mechanism, thermo-dynamical properties and binding parameters were studied by employing UV-vis, fluorescence, FTIR, ¹H NMR, COSY and NOESY spectroscopy. The present investigation uncovers the fact that the interaction of anti-Alzheimer's drugs with 4-PyC8 is mediated through H-bonding and van der Waals forces. The Benesi–Hildebrand relation was used to evaluate the binding affinity and PC-37 showed the highest binding when complexed with 4-PyC8. FTIR spectra showed absorption bands at 3527.98 cm⁻¹ and 3527.09 cm⁻¹ for the PC-37 + 4-PyC8 system which is quite promising compared to tacrine. ¹H-NMR experiments recorded deshielding for tacrine at relatively higher concentrations than PC-37. COSY investigations suggest that anti-Alzheimer's drugs after complexation with 4-PyC8 show a 1 : 1 ratio. The cross-peaks of the NOESY spectra involve correlations between anti-Alzheimer's drugs and AIL protons, indicating complexation between them. The observed results indicate that these complexes are expected to have a possible therapeutic role in reducing/inhibiting amyloid fibrils when incorporated into drug formulations.

Ionic liquids mediated interactions are an expedient approach that exhibit inhibition effect on amyloid fibrils which is beneficial for the treatment of Alzheimer's disease.

Concentration- and Temperature-Responsive Reversible Transition in Amide-Functionalized Surface-Active Ionic Liquids: Micelles to Vesicles to Organogel

A ubiquitous example of DNA and proteins inspires the scientific community to design synthetic systems that can construct various self-assembled complex nano-objects for high-end physiological functions. To gain insight into judiciously designed artificial amphiphilic structures that through self-assembling form various morphological architectures within a single system, herein, we have studied self-aggregation of amide-functionalized surface-active ionic liquids (AFSAILs) with different head groups in the DMSO/water mixed system. The AFSAIL forms stimuli-responsive reversible micelle and vesicle configurations that coexist with three-dimensional (3D) network structures, the organogel in the DMSO/water mixed system. The self-assembly driving forces, self-organization patterns, network morphologies, and mechanical properties of these network structures have been investigated. With the proven biodegradability and biocompatibility, one can envisage these AFSAILs as the molecules with a new dimension of versatility.

Study on the Surface Properties and Aggregation Behavior of Quaternary Ammonium Surfactants with Amide Bonds

A number of techniques, including conductivity, surface tension, dynamic light scattering, transmission electron microscopy, and ¹H nuclear magnetic resonance (¹H NMR), Fourier transform infrared (FT-IR), and ¹H-¹H 2D nuclear Overhauser effect spectroscopy (¹H-¹H 2D NOESY), have been used to investigate the effect of amide bonds on the interfacial and assembly properties of a cationic surfactant, N-anilinoformylmethyl-N-cetyl-N,N-dimethyl ammonium chloride (AMC-C ₁₆ ), in aqueous solutions. The adsorption of AMC-C ₁₆ has been found to be much better than that of the conventional cationic surfactant, benzyl cetyldimethylammonium chloride (BAC-16) at the air/water interface and in solution. The surface tension measurements show the presence of two critical aggregation concentrations (CAC₁ and CAC₂) for AMC-C ₁₆ . The presence of a strong intermolecular hydrogen bond of AMC-C ₁₆ was confirmed by ¹H NMR and FT-TR. The molecular interactions of AMC-C ₁₆ were detected by ¹H-¹H 2D NOESY. The results show that the rigid group (phenyl) of AMC-C ₁₆ was partially overlapped with its alkyl chain in aqueous solution, and the possible aggregation behavior for AMC-C ₁₆ was proposed. The effects of an inorganic salt (NaCl) and an organic salt (C₆H₅COONa) to the aggregates of AMC-C ₁₆ have been discussed.

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.

Multi-spectroscopic monitoring of molecular interactions between an amino acid-functionalized ionic liquid and potential anti-Alzheimer's drugs

Ionic liquids mediated interactions are an expedient approach that exhibit inhibition effect on amyloid fibrils which is beneficial for the treatment of Alzheimer's disease.

Validating interfacial behaviour of surface-active ionic liquids (SAILs) with computational study integrated with biocidal and cytotoxic assessment

Surface-active ionic liquids (SAILs) belonging to the series of N-alkylmethylimidazolium halides [C₈mimX] (X = Br, Cl, and BF₄) and [C_nmimBr] (n = 10, 12, 14, and 16) were employed to understand the influence of hydrophobicity of alkyl chain length and the chaotropicity of counter-ions of SAILs on the micellization, antimicrobial action and cytotoxicity properties. The micellization phenomenon of SAILs in an aqueous environment was examined employing tensiometry and steady-state fluorescence spectrophotometry. The corresponding interfacial parameters viz., critical micelle concentration (CMC), effectiveness (γ_CMC), surface pressure (П_CMC), maximum surface excess concentration (Г_max), and the minimum area engaged per molecule (A_min) at the air-water interface were evaluated at 303.15 K. These experimental findings were monitored and geometrically optimized theoretically using Gaussian software to highlight the recent advances in this field of theoretical calculations for putative structure. The simulation descriptors correlated the micellization behavior as a function of hydrophobicity which may contribute to obtaining awareness on their ecological behavior and fate. In addition, the biological screening of all the examined SAILs was undertaken with a combined experimental and theoretical (optimized) method against bacteria and fungus. Results revealed that SAILs with the alkyl chain-length greater than C₈- act as a fair antimicrobial agent against the selected microbial strain which is attributed to the enhanced degree of SAILs hydrophobicity. The cytotoxicity of these imidazolium-based SAILs was also assessed on the cervical human cell line (HeLa) using the MTT cell viability assay and the data thus obtained were subjected to statistical analysis.

N-alkylimidazolium Salts Functionalized with p-Coumaric and Cinnamic Acid: A Study of Their Antimicrobial and Antibiofilm Effects

The bacterial resistance to antibiotics has compromised the therapies used for bacterial infections. Nowadays, many strategies are being carried out to address this problem. Among them, the use of natural compounds like cinnamic and p-coumaric acids stands out. Nevertheless, their utilization is limited because of their unfavorable physicochemical properties. Due to the lack of new therapeutic alternatives for bacterial infections, novel strategies have emerged, such as the use of ionic liquids; given that they can show a broad spectrum of antibacterial activity, this is why we herein report the antibacterial and antibiofilm activity of a series of N-alkylimidazolium salts functionalized with p-coumaric and cinnamic acids. The results from this study showed better antibacterial activity against Gram-positive bacteria, with a predominance of the salts derived from coumaric acid and a correlation with the chain length. Additionally, a lower efficacy was observed in the inhibition of biofilm formation, highlighting the antibiofilm activity against Staphylococcus aureus, which decreased the production of the biofilm by 52% over the control. In conclusion, we suggest that the salts derived from p-coumaric acid are good alternatives as antibacterial compounds. Meanwhile, the salt derived from cinnamic acid could be a good alternative as an antibiofilm compound.

Reduced ecotoxicity and improved biodegradability of cationic biocides based on ester-functionalized pyridinium ionic liquids

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.

Imidazolium and benzimidazolium-containing compounds: from simple toxic salts to highly bioactive drugs

The toxicity of simple imidazolium and benzimidazolium salts started to be more and more investigated in the last few years and was taken in consideration in the context of microorganisms, plants and more evolved organisms' exposure. However, the toxicity of these salts can be exploited in the development of different biological applications by incorporating them in the structure of compounds that specifically target microorganisms and cancer cells. We highlight in this minireview the way researchers became aware of the inherent problem of the stability and bioaccumulation of imidazolium and benzimidazolium salts and how they found inspiration to exploit their toxicity by incorporating them into new highly potent drugs.