Self-assembly and antimicrobial activity of cationic gemini surfactants containing triazole moieties

1,2,3-Triazole-based gemini bis-quaternary ammonium surfactants with varying hydrophobic chain length and ethylene or butylene spacers were synthesized and characterized. Their surface and aggregation properties were analyzed using tensiometry and conductimetry. The gemini surfactants showed significantly lower CMC values compared to their single-tail counterparts and conventional gemini surfactants described in the literature. The micellization and surface adsorption processes in water can be tailored according to the hydrophobic chain and the spacer length and were substantially improved by the presence of the heterocycle. These surfactants are active against various Gram-positive and Gram-negative bacterial stains, as well as fungi. The gemini surfactant with tetradecyl chain and ethylene spacer (Bis 14-2-14) exhibited the highest activity against all investigated microbial strains.

New bis- and tetrakis-1,2,3-triazole derivatives: Synthesis, DNA cleavage, molecular docking, antimicrobial, antioxidant activity and acid dissociation constants

In this study, a series of bis- and tetrakis-1,2,3-triazole derivatives were synthesized using copper-catalyzed azide-alkyne cycloaddition (CuAAC) click chemistry in 73-95% yield. The bis- and tetrakis-1,2,3-triazoles exhibited significant DNA cleavage activity while the tetrakis-1,2,3-triazole analog 6g completely degraded the plasmid DNA. Molecular docking simulations suggest that compound 6g acts as minor groove binder of DNA by binding through several noncovalent interactions with base pairs. All bis- and tetrakis-1,2,3-triazole derivatives were screened for antibacterial activity against E. coli, B. cereus, S. aureus, P. aeruginosa, E. hirae, L. pneumophila subsp. pneumophila strains and antifungal activity against microfungus C. albicans and C. tropicalis strains. Compound 4d exhibited the best antibacterial activity among bis-1,2,3-triazoles against E. coli and E. hirae, while 6c exhibited the best antibacterial activity among tetrakis-1,2,3-triazoles against E. hirae. Furthermore, the best antifungal activity against C. albicans and C. tropicalis was reported for the compound 5, while 6d displayed the best antifungal activity against C. tropicalis and C. albicans. Reasonable iron chelating activities and DPPH radical scavenging abilities were found for some of the compounds. Finally, the acid dissociation constants (pK_a) of the bis-1,2,3-triazoles were also determined with the help of HYPERQUAD program using the data obtained from potentiometric titrations. The reported data here concludes that the bis- and tetrakis-1,2,3-triazoles are important cores that should be considered for further development of especially new anticancer agents acting through the DNA cleavage activity.

Biological and Physico-Chemical Characteristics of Arginine-Rich Peptide Gemini Surfactants with Lysine and Cystine Spacers

Ultrashort cationic lipopeptides (USCLs) and gemini cationic surfactants are classes of potent antimicrobials. Our recent study has shown that the branching and shortening of the fatty acids chains with the simultaneous addition of a hydrophobic N-terminal amino acid in USCLs result in compounds with enhanced selectivity. Here, this approach was introduced into arginine-rich gemini cationic surfactants. l-cystine diamide and l-lysine amide linkers were used as spacers. Antimicrobial activity against planktonic and biofilm cultures of ESKAPE (Enterococcus faecium, Staphylococcus aureus, Klebsiella pneumoniae, Acinetobacter baumannii, Pseudomonas aeruginosa, and Enterobacter spp.) strains and Candida sp. as well as hemolytic and cytotoxic activities were examined. Moreover, antimicrobial activity in the presence of human serum and the ability to form micelles were evaluated. Membrane permeabilization study, serum stability assay, and molecular dynamics were performed. Generally, critical aggregation concentration was linearly correlated with hydrophobicity. Gemini surfactants were more active than the parent USCLs, and they turned out to be selective antimicrobial agents with relatively low hemolytic and cytotoxic activities. Geminis with the l-cystine diamide spacer seem to be less cytotoxic than their l-lysine amide counterparts, but they exhibited lower antibiofilm and antimicrobial activities in serum. In some cases, geminis with branched fatty acid chains and N-terminal hydrophobic amino acid resides exhibited enhanced selectivity to pathogens over human cells.

Improving heavy oil recovery, part (I): synthesis and surface activity evaluation of some novel organometallic surfactants based on salen-M complexes

This study focuses on preparing a new family of organometallic surfactants based on five ion complexes, namely Co²⁺, Ni²⁺, Cu²⁺, Fe³⁺, and Mn²⁺. The first step is the preparation of 5-chloromethyl salicylaldehyde (Salen, S). The second step is the formation of sodium alkoxide of Pluronic F-127 (AP). The third step is the formation of the modified AP–Salen (new ligand). This ligand was reacted with the metal chlorides as mentioned earlier to obtain the organometallic surfactants (OMS) named AP–Salen–M complexes. FT-IR, ¹H-NMR, SEM, and EDX justified the chemical structure of the as-prepared materials. The surface tension of these surfactants was measured for surfactant solutions at different concentrations to determine the CMC and calculate their surface–active properties. The interfacial tension at CMC was measured against heavy crude oil to predict the availability and use these surfactants in the enhanced oil recovery (EOR) process. From the results, this class of surfactants exhibited good surface–active properties and high efficiency on the interface adsorption; besides, they reduced the interfacial tension in the order between 10⁻¹ and 10⁻² mN m⁻¹, which gives a good indication to use these surfactants in EOR application for the heavy crude oil.

This study focuses on preparing a new family of organometallic surfactants based on five ion complexes, namely Co²⁺, Ni²⁺, Cu²⁺, Fe³⁺, and Mn²⁺.

Synthesis and Aggregation Behavior of Jellyfish-Shaped Triazine Hexamer Quaternary Ammonium Chloride Surfactant

A novel jellyfish-shaped triazine hexamer quaternary ammonium chloride surfactant (TH₁₂QC) was synthesized, which consisted of one triazine spacer group and six long flexible hydrophobic chains. The molecular structure and aggregation behavior of TH₁₂QC was investigated by nuclear magnetic resonance (NMR), surface tension, electrical conductivity, dynamic light scattering (DLS), transmission electron microscope (TEM), etc. The results show that the jellyfish-shaped TH₁₂QC has better surface activity and lower surface tension than traditional ionic and Gemini surfactants in aqueous solution. There are two inflection points in the curve of conductivity versus concentration of the TH₁₂QC aqueous solution, which correspond to the critical aggregation concentration (CAC) and the critical micelle concentration (CMC) respectively. The existence of CAC indicates that there is a pre-aggregation process before TH₁₂QC forms micelles. The results of DLS and TEM show that network pre-aggregation, spherical aggregation and dense spherical aggregation were observed in different concentration of TH₁₂QC aqueous solution, and the electrostatic equilibrium of the system subtly depends on the concentration of the solution. In addition, intramolecular and intermolecular hydrogen bonding is also an important factor. This study provides a method for studying the aggregation behavior and morphology of oligomeric surfactants with rigid spacer groups.

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.

Effects of temperature and polyols on the ciprofloxacin hydrochloride-mediated micellization of sodium dodecyl sulfate

Herein, a conductivity method was engaged to explore the effects of a fluoroquinolone drug, namely ciprofloxacin hydrochloride (CFH)/CFH + polyols (organic compounds with multiple hydroxyl groups (glucose and fructose)), on the aggregation phenomenon of sodium dodecyl sulfate (SDS) at different temperatures (298.15–318.15 K) while maintaining a gap of 5 K. In this study, the critical micelle concentration (cmc) of the SDS/SDS + CFH mixture in water and polyols media was determined from plots of the specific conductivity versus the concentration of SDS to gain knowledge of the effects of CFH/CFH + polyols on the micelle formation behavior of SDS. The cmc value of the surfactant decreases in the presence of CFH in an aqueous medium; thus, CFH favors the micellization of SDS. The cmc values of SDS and the SDS + CFH mixture were enhanced in polyols media. The cmc values of SDS/SDS + CFH show a U-shaped behavior with temperature. The counterion dissociation (α) of the pure surfactant is higher in the presence of the drug and is further enhanced through an increase in the CFH concentration in water/polyols media. Different thermodynamic parameters, such as the Gibbs free energy of micellization , standard enthalpy , entropy , different transfer energies and enthalpy–entropy compensation parameters of micellization were determined and illustrated in detail to compare these parameters between the pure SDS and SDS + CFH mixture in polyols media. The negative values of for the SDS/SDS + CFH mixture in all cases indicate spontaneous micelle formation. The and values indicate the presence of both hydrophobic and electrostatic interactions amongst the studied components.

A conductivity method was used to see effects of a ciprofloxacin hydrochloride (CFH)/CFH + polyols (organic compounds with multiple hydroxyl groups (glucose and fructose)) on aggregation phenomenon of sodium dodecyl sulfate (SDS) at 298.15–318.15 K.

Biophysical investigation of promethazine hydrochloride binding with micelles of biocompatible gemini surfactants: Combination of spectroscopic and electrochemical analysis

Knowledge of binding parameters for drug and surfactant complexations is crucially vital in order to design effective drug carrier systems with requisite features. To this end, this work was designed to demonstrate the biophysical characterization of the interaction of a phenothiazine drug promethazine hydrochloride (PMT) with relatively lower cytotoxic and easily degradable biomimetic micellar self-assemblies of oxy-diester functionalized gemini surfactants (C_m-E2O-C_m, m = 12, 14 and 16), possessing different hydrophobic character. The binding propensity of C_m-E2O-C_m increases upon increasing the hydrophobic tail length as manifested through both intrinsic fluorescence and absorption spectral profiles of PMT ̶ C_m-E2O-C_m, showing 1:1 stoichiometry. K_sv values also follow the trend of increasing hydrophobic character (i.e., C₁₂-E2O-C₁₂ < C₁₄-E2O-C₁₄ < C₁₆-E2O-C₁₆). Moreover, the determined thermodynamic parameters, particularly the positive values of ΔH_b^o and ΔS_b^o, reveal that the involved complexations are dominated by the hydrophobic interactions. In addition, micropolarity assay was done to deduce the microenvironmental changes upon PMT ̶ C_m-E2O-C_m complexations. Beside this, comparative appraisal of all the three systems helps to underpin a reasonable knowledge of the effect of structural variation of surfactants on their binding ability with drug which, in turn, may also open new avenues for the designing of potential tunable drug carrier systems.

Conformational and solution dynamics of hemoglobin (Hb) in presence of a cleavable gemini surfactant: Insights from spectroscopy, atomic force microscopy, molecular docking and density functional theory

Herein, we have explored the conformational alterations of hemoglobin (Hb) in presence of a cleavable gemini surfactant (C16-C4O2-C16). The concerned surfactant was found to induce significant structural perturbations in Hb. UV-vis spectroscopy, steady-state/time-resolved fluorescence, and other utilized techniques have authenticated the complexation of Hb with the gemini surfactant. CD has demonstrated the alterations in secondary structural elements (α-helicity, β-sheet, β-turn, and random coil) of Hb upon C16-C4O2-C16 addition. Atomic force microscopy (AFM) has revealed the existence of unique star-shaped gemini surfactant microstructures aligned to Hb in a necklace pattern. The ¹H NMR peak broadening and lower delta values hint at the binding of the concerned gemini surfactant to Hb. Molecular docking and DFT calculations have further substantiated the Hb-gemini complex formation and the involvement of electrostatic/hydrophobic forces therein. In future, these results might pave-the-way to construct self-assembled, sustainable, and green surfactant-protein mixtures for their end-use in industrial, engineering, biomedical, drug delivery, gene transfection, and other relevant excipient formulations.

The adsorption and aggregation properties of dendritic cationic tetrameric surfactants

A series of dendritic cationic tetrameric surfactants (4C_ntetraQ, n = 12, 14, 16) were synthesized with raw materials that are commercially available.

Advances in the synthesis, molecular architectures and potential applications of gemini surfactants

Gemini surfactants have been the subject of intensive scrutiny by virtue of their unique combination of physical and chemical properties and being used in ordinary household objects to multifarious industrial processes. In this review, we summarize the recent developments of gemini surfactants, highlighting the classification of gemini surfactants based on the variation in headgroup polarity, flexibility/rigidity of spacer, hydrophobic alkyl chain and counterion along with potential applications of gemini surfactants, depicting the truly remarkable journey of gemini surfactants that has just come of age. We have focused on those objectives which will act as suitable candidates to take the field forward. The preceding information will permit us to estimate the effect of structural variation on the aggregation behavior of gemini surfactants for nanoscience and biological applications like antimicrobial, anti-fungal agent, better gene and drug delivery agent with low cytotoxicity and biodegradability, which makes them more advantageous for a number of technological processes and hence reduces the impact of these gemini surfactants on the environment.

Benzimidazole derivative fluorescent probe for cascade recognition of phosphate and iron ions in aqueous medium and its logic gate behavior

A fluorescent probe based on benzimidazole was synthesized, and its cascade recognition of PO₄³⁻ and Fe³⁺ ions was investigated using spectroscopic techniques.

Sustainable oleic and stearic acid based biodegradable surfactants

Renewable ester functionalized fatty acid based imidazolium surfactant.

Unraveling the interaction of hemoglobin with a biocompatible and cleavable oxy-diester-functionalized gemini surfactant

Surfactant-protein mixtures have attracted considerable research interest in recent years at the interface of chemical biology and medicinal chemistry. Herein, the interaction between a green gemini surfactant (C₁₆-E2O-C₁₆) and a redox protein hemoglobin was examined through a series of in vitro experimental techniques with an attempt to provide a comprehensive knowledge of the surfactant-protein binding interactions. Quantitative appraisal of the fluorescence/CV data showed that the binding of C₁₆-E2O-C₁₆ to Hb leads to the formation of thermodynamically favorable non-covalent adduct with 1:1 stoichiometry. UV-vis spectra demonstrated that the effect of C₁₆-E2O-C₁₆ on Hb is highly concentration dependent. Far-UV and near-UV CD spectra together elucidated the formation of molten globule state of Hb upon C₁₆-E2O-C₁₆ addition. Temperature dependent CD explicated the effect of C₁₆-E2O-C₁₆ on the thermal stability of Hb. Furthermore, the structural investigation of Hb via pyrene/synchronous/three-dimensional fluorescence and FT-IR spectroscopy provided the complementary information related to its microenvironmental and conformational changes. Computational studies delineated that C₁₆-E2O-C₁₆ binds in the vicinity of β-37 Trp at the α₁β₂ interface of Hb. Overall, this study is expected to clarify the binding mechanism between Hb/other congeners and surfactant at the molecular level that are known to have immense potential in biomedical and industrial areas.

The equilibrium and dynamic surface tension of polymeric surfactants based on epoxidized soybean oil grafted hydroxyethyl cellulose

Analysis of the equilibrium and dynamic surface tension of epoxidized soybean oil grafted hydroxyethyl cellulose (H-ESO-HEC) surfactants with different molecular weights were carried out at pH values that ranged from 8 to 13.

Bio-physicochemical analysis of ethylene oxide-linked diester-functionalized green cationic gemini surfactants

A novel series of oxy-diester-functionalized gemini surfactants (Cm-E2O-Cm) were synthesized and a comprehensive analysis of their biophysicochemical properties was carried out.

Synthesis, physiochemical property and antibacterial activity of gemini quaternary ammonium salts with a rigid spacer

Aggregate morphologies of GQASs change from vesicles and micelles to network aggregates and then to globular vesicles with increase of concentration.