Pyridinium Gemini Surfactants Research Articles

Impacts of pyridinium gemini surfactants on corrosion inhibition of carbon steel

Pyridinium gemini surfactants (PGS-n) are an important class of amphiphiles with antibacterial properties and hence, are usually preferred in industrial and medicinal applications. In this work, three PGS-n with different alkyl chain lengths having two amide spacers, 3,3′-(Malonylbis(azanediyl))bis(1-dodecylpyridin-1-ium) dibromide (PGS-12), 3,3′-(Malonylbis(azanediyl))bis(1-tetradecylpyridin-1-ium) dibromide (PGS-14), and 3,3′-(Malonylbis(azanediyl))bis(1-octadecylpyridin-1-ium) dibromide (PGS-18), were synthesized, characterized and tested as corrosion inhibitor on carbon steel in HCl for the first time. The corrosion inhibition efficiency was examined by weight loss measurement, electrochemical impedance spectroscopy (EIS), and potentiodynamic measurements at 30 °C. Furthermore, micellization parameters such as critical micelle concentration (cmc), degree of counter ion dissociation, and Gibb's energy of micellization of these PGS-n were determined. The inhibition efficiency of the studied PGS-n was found to be maximum near their cmc values and found to follow the order: PGS-18 > PGS-14 > PGS-12. The PGS-n with the longest alkyl chain could achieve a maximum inhibition efficiency of 99.2 %. The adsorption of PGS-n on the surface of carbon steel was found to follow the Langmuir adsorption isotherm. The results obtained from EIS measurements agreed well with those of polarization and weight loss studies. Field emission scanning electron microscopic analysis revealed that the corrosion of the carbon steel surface is not severe, especially in the presence of PGS -18. Density functional theory was employed to calculate various quantum chemical parameters of the PGS-n. The results suggest PGS-n as an effective inhibitor for corrosion inhibition of carbon steel.

Gene-Delivery Ability of New Hydrogenated and Partially Fluorinated Gemini bispyridinium Surfactants with Six Methylene Spacers.

The pandemic emergency determined by the spreading worldwide of the SARS-CoV-2 virus has focused the scientific and economic efforts of the pharmaceutical industry and governments on the possibility to fight the virus by genetic immunization. The genetic material must be delivered inside the cells by means of vectors. Due to the risk of adverse or immunogenic reaction or replication connected with the more efficient viral vectors, non-viral vectors are in many cases considered as a preferred strategy for gene delivery into eukaryotic cells. This paper is devoted to the evaluation of the gene delivery ability of new synthesized gemini bis-pyridinium surfactants with six methylene spacers, both hydrogenated and fluorinated, in comparison with compounds with spacers of different lengths, previously studied. Results from MTT proliferation assay, electrophoresis mobility shift assay (EMSA), transient transfection assay tests and atomic force microscopy (AFM) imaging confirm that pyridinium gemini surfactants could be a valuable tool for gene delivery purposes, but their performance is highly dependent on the spacer length and strictly related to their structure in solution. All the fluorinated compounds are unable to transfect RD-4 cells, if used alone, but they are all able to deliver a plasmid carrying an enhanced green fluorescent protein (EGFP) expression cassette, when co-formulated with 1,2-dioleyl-sn-glycero-3-phosphoethanolamine (DOPE) in a 1:2 ratio. The fluorinated compounds with spacers formed by six (FGP6) and eight carbon atoms (FGP8) give rise to a very interesting gene delivery activity, greater to that of the commercial reagent, when formulated with DOPE. The hydrogenated compound GP16_6 is unable to sufficiently compact the DNA, as shown by AFM images.

Synthesis and characterisation of carboxy amide-bonded pyridinium Gemini surfactants: influence of the nature of the spacer group and counterions on the aggregation behaviour

Abstract A series of novel dimeric pyridinium surfactants has been synthesised and the effects of a semi-flexible p-xylyl spacer and flexible, polyethylene glycol spacers have been studied. The nature of the spacer determines solubility and aggregation behaviour in two- and three-dimensional systems. Some of these insoluble compounds form two-dimensional, rigid-condensed structures at the air–water interface, while others form liquid-analogue monolayers. Whereas the latter compounds become soluble after exchange of the counterions, the former remain insoluble. The aggregation behaviour of Langmuir layers was, inter alia, investigated by Brewster angle microscopy. The micellisation behaviour of diluted aqueous solutions of soluble surfactants was primarily investigated by conductometric measurements and thermodynamic parameters of aggregation have been deduced with respect to the spacer length.

Synthesis, micellization behaviour and cytotoxic properties of imidazolium-based gemini surfactants

A three-member series of imidazolium-based gemini surfactants, 1, 1′- (propane-1,3-diyl-2-ol) bis(3-alkyl-1H-imidazol-3-ium)bromide, [CnIm-3OH-ImCn]Br2, of variable hydrocarbon chain length and a hydroxyl group-containing spacer, was synthesized. Their structures were characterized by FT-IR, 1H NMR, 13C NMR and mass spectral techniques. The critical micelle concentration (cmc) of aqueous solutions of these surfactants was determined by conductivity and surface tension measurements. Owing to the lower cmc values of these imidazolium-based gemini surfactants they exhibit superior micellization behaviour than the ammonium as well as pyridinium gemini surfactants. The counterion binding constant and thermodynamic parameters were evaluated from conductivity data. The cytotoxic properties of these newly synthesized gemini surfactants were determined by their hemolytic assay (HC50 analysis). These surfactants were found to be less cytotoxic making them potentially applicable in industrial and biomedical fields, where safety and efficiency are closely related.

Enhanced corrosion inhibition of carbon steel by pyridyl gemini surfactants with different alkyl chains

Three pyridyl gemini surfactants varying in alkyl chain length (DBP: decamethylene bis-pyridinium dibromide; OBP: octamethylene bis-pyridinium dibromide; HBP: hexamethylene bis-pyridinium dibromide.) were applied as corrosion inhibitors for the first time. The inhibition performance of three inhibitors on P110 steel corrosion in HCl solution were studied using gravimetric measurement, electrochemical analysis, scanning electron microscopy (SEM), and quantum chemical calculation. Adsorption of inhibitors onto the steel surface was described well by Langmuir isotherm. All of three compounds were mixed-type inhibitors. The inhibition efficiency of the three inhibitors was in the order: DBP > OBP > HBP, especially as high as efficiency of 91.76% in case of DBP. Increment of the non-polar chain length within the inhibitor contributed to the improvement of corrosion inhibition, which may be due to the stronger hydrophobicity with longer alkyl chain. Results in this study reveal the potential application of non-polar pyridinium gemini surfactants as excellent inhibitors, providing new ideas for synthesizing novel corrosion inhibitor.

Synthesis, surface properties and antimicrobial performance of novel gemini pyridinium surfactants

A series of novel gemini pyridinium surfactants with different alkyl chains were synthesized and characterized. The surface properties and aggregation behavior of the gemini surfactants in solution were studied. The gemini pyridinium salts exhibit higher surface activity than quaternary ammonium salts and can form vesicles above critical micellization concentration (CMC). The antimicrobial performance of these surfactants against E. coli was investigated and compared with those of quaternary ammonium salts. Alkyl chain length has a significant effect on the antimicrobial activity of the gemini surfactants, and the surfactant with decyl group showed more effective antimicrobial activity than quaternary ammonium salts. The high cationic charge density on the polar head group and the strong adsorption tendency confer relatively high antimicrobial of the gemini surfactants.

Effects of Chirality on the Aggregation Properties of Amide-Bonded Pyridinium Gemini Surfactants.

In a series of experiments, we synthesized and characterized a new type of cationic gemini surfactant, the chiral and the achiral forms, which were compared regarding their surface-active properties. These surfactants show interesting aggregation processes, which are affected by the interplay of different structural characteristics. By substituting the counterions, we found a way to control the solubility of these compounds in order to investigate the behavior of solutions as well as insoluble monolayers. The comparison of the chiral with the meso compound instead of the racemic mixture is a major advantage for the analysis of the effects of chirality because racemates can be understood as a mixed surfactant system with one additional degree of Gibbs freedom. Furthermore, we investigated the viscoelastic behavior of concentrated aqueous surfactant solutions which formed elongated wormlike micelles. A strong effect of the stereochemistry on the aggregation properties of Langmuir layers as well as elongated micelles was found.

Organo-vermiculites modified by heating and gemini pyridinium surfactants: Preparation, characterization and sulfamethoxazole adsorption

Organo-vermiculites (organo-Vts) with different preheating temperatures and gemini pyridinium surfactants (1,1’-didodecyl-4,4’-trimethylene bispyridinium bromide (BPy-12-3-12) and 1,1’-didodecyl-4,4’ bispyridinium bromide (BPy-12-0-12)) were prepared and used as antibiotics adsorbents for the first time. The resultant adsorbents were characterized by Fourier Transform Infrared spectroscopy (FT-IR), X-ray diffraction (XRD), scanning electron microscope (SEM) and Zeta potential. Batch experiments were conducted to research adsorption of sulfamethoxazole (SMX) on organo-Vts. Vermiculite with BPy-12-3-12 showed higher removal efficiency (95%) than that of BPy-12-0-12-Vt (43%), and preheating at 100 °C further facilitated the efficiency up to 98%. Adsorption process was observed to be pH dependent and fast (95% were removed in 10 min), which followed a pseudo-second-order model as well as Freundlich isotherm. In addition, there is an interesting phenomenon that endothermic process occurred on BPy-12-3-12-Vt and BPy-12-3-12-Vt100, but exothermic one on other organo-Vts. In view of the practical significance, low concentration SMX in real-life waters were removed by organo-Vt, and the result showed an excellent and fast adsorption performance of this kind of adsorbent, even in low dosage of BPy-12-3-12 (0.4 CEC). Therefore, organo-Vts will challenge the current existing adsorbents as promising candidates.

Ester-Based Pyridinium Gemini Surfactants as Novel Inhibitors for Mild Steel Corrosion in 1 M HCl Solution

AbstractThe corrosion inhibition ability of ester based pyridinium Gemini surfactants (GS) with different hydrophobic character (14-Py and 16-Py) towards mild steel (MS) in 1 M HCl solution was investigated at various concentrations and temperatures (303–333 K). Potentiodynamic polarization, electrochemical impedance spectroscopy, weight loss, surface analysis (SEM/EDAX and AFM) and FT-IR were combined to investigate the corrosion inhibition behaviour of the surfactants. 14-Py and 16-Py were found to be efficient, mixed type inhibitors. The inhibition efficiencies increased with increasing concentration, hydrophobicity and solution temperature. The existence of a protective film of the adsorbed inhibitors on the MS surface was confirmed by SEM/EDX/AFM.

Detailed study of interactions between eosin yellow and gemini pyridinium surfactants

Interactions of dianionic dye, eosin yellow with gemini pyridinium surfactants have been investigated using conductivity, UV-visible, fluorescence, cyclic voltammetry, differential pulse voltammetry, potentiometry and dynamic light scattering.

Enhanced removal of bisphenol A from aqueous solution by organo-montmorillonites modified with novel Gemini pyridinium surfactants containing long alkyl chain

To utilize the π–π interaction and the hydrophobic affinity of modifiers with long alkyl chain in the interlayer of montmorillonites for effective removal of bisphenol A (BPA) from aqueous solution, organo-montmorillonites modified with novel Gemini pyridinium surfactants containing both the aromatic ring and long alkyl chain, 1,1′-didodecyl-4,4′-trimethylene bispyridinium bromide (BPy-12-3-12) and 1,1′-dihexadecyl-4,4′-trimethylene bispyridinium bromide (BPy-16-3-16) were designed and prepared in this study. The raw montmorillonite and organo-montmorillonites (BPy-12-3-12-Mt and BPy-16-3-16-Mt) were specified with X-ray diffraction (XRD), Fourier transform infrared (FTIR) spectroscopy, scanning electron microscopy (SEM), thermogravimetric analysis (TGA). The main effect factors which played a significant role in removal of BPA from aqueous solution, such as the amount of modifier, alkyl chain length, contact time and solution pH were investigated in detail. The experimental results indicated that the maximum adsorption capacities of BPA obtained from Langmuir isotherms were 222.2mg/g for BPy-12-3-12-Mt and 208.3mg/g for BPy-16-3-16-Mt at pH 6, suggesting that organoclays with shorter alkyl chain presented higher affinity for BPA. This may be due to the combined contribution of π–π interaction and hydrophobic interaction, especially π–π interaction played a dominated role in BPA adsorption. Additionally, the experimental data were best fitted with the Langmuir isotherm model. The obtained kinetics data for BPA adsorption onto the organoclays were described well by the pseudo-second-order model. Thermodynamic parameters demonstrated that the adsorption process of BPA was spontaneous and exothermic in nature.

Synthesis, Physicochemical Characterization, and Interaction with DNA of Long‐Alkyl‐Chain Gemini Pyridinium Surfactants

Pyridinium gemini surfactants with hexadecyl chains linked to nitrogen atoms and a tuned aliphatic spacer that bridges the two pyridinium polar heads in 2,2'-positions have been synthesized and characterized. A multitechnique approach allowed us to study the aggregation behavior, using conductivity, surface tension, and fluorescence. Graphs of the specific conductivity (κ) versus the surfactant molar concentration (C), and graphs of the molar conductivity (Λ) versus C0.5 suggest pre-aggregation phenomena of these amphiphiles at very low concentration. The trends of Amin as a function of the spacer length confirm the hypothesis of a conformational change of the molecule with four methylene groups as spacer owing to stacking interactions between the two pyridinium rings mediated by the counterion. Moreover, the trends of Amin and counterion binding (β) suggest that the spacer must be longer than eight carbon atoms to fold efficiently toward the micellar core. The opportunity to tune the surfactant structure and aggregation properties make those surfactants-particularly the long-chain ones for which the DNA complexing ability was shown by means of atomic force microscopy (AFM) imaging-desirable candidates for gene-delivery experiments.

Modulation of pyridinium cationic lipid-DNA complex properties by pyridinium gemini surfactants and its impact on lipoplex transfection properties.

The study presents the effects of blending a cationic gemini surfactant into cationic lipid bilayers and its impact on the plasmid DNA compaction and delivery process. Using nanoDSC, dynamic light scattering, zeta potential, and electrophoretic mobility measurements, together with transfection (2D- and 3D-) and viability assays, we identified the main physicochemical parameters of the lipid bilayers, liposomes, and lipoplexes that are affected by the gemini surfactant addition. We also correlated the cationic bilayer composition with the dynamics of the DNA compaction process and with transfection efficiency, cytotoxicity, and the internalization mechanism of the resultant nucleic acid complexes. We found that the blending of gemini surfactant into the cationic bilayers fluidized the supramolecular assemblies, reduced the amount of positive charge required to fully compact the plasmid DNA and, in certain cases, changed the internalization mechanism of the lipoplexes. The transfection efficiency of select ternary lipoplexes derived from cationic gemini surfactants and lipids was several times superior to the transfection efficiency of corresponding binary lipoplexes, also surpassing standard transfection systems. The overall impact of gemini surfactants into the formation and dynamic of cationic bilayers was found to depend heavily on the presence of colipids, their nature, and amount present in lipoplexes. The study confirmed the possibility of combining the specific properties of pyridinium gemini surfactants and cationic lipids synergistically to obtain efficient synthetic transfection systems with negligible cytotoxicity useful for therapeutic gene delivery.

Self-assembly, DNA binding and cytotoxicity trends of ether functionalized gemini pyridinium amphiphiles

Six new ether functionalized gemini pyridinium amphiphiles have been synthesized having dodecyl, tetradecyl alkyl chain lengths and three different spacers (i.e. –(CH2)n–, where n is 4, 5 and 6) and investigated for their self-assembling behavior by state of the art techniques such as tensiometry, conductivity and spectrofluorometry. These new pyridinium gemini surfactants exhibit lower cmc values as compared to other gemini surfactants reported in literature. These amphiphiles form stable complexes with DNA as established by agarose gel electrophoresis and ethidium bromide exclusion experiments. MTT (3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide) assay was carried out in vitro on C6 glioma cell line for cytotoxicity assessment of new pyridinium geminis. The dynamic light scattering (DLS) and transmission electron microscopy (TEM) have been used to measure the micellar size of gemini surfactants. Further, thermal stability of these amphiphiles has been evaluated by thermogravimetric analysis (TGA). The dependence of self-assembly behavior and other properties on spacer as well as alkyl chain length has been established.

Interfacial engineering of pyridinium gemini surfactants for the generation of synthetic transfection systems

Pyridinium gemini surfactants possess a soft charge, a high charge/mass ratio and a high molecular flexibility – all key parameters that recommend their use in synthetic gene delivery systems with in vitro and in vivo efficiency. In present study we generated a DNA delivery system through interfacial engineering of pyridinium gemini surfactants at the level of linker, hydrophobic chains and counterions. The self-assembling of the pyridinium amphiphiles and the physicochemical properties of the resultant supra-molecular assemblies were studied in bulk and in solution through a combination of techniques that included DSC, X-ray diffraction, polarized microscopy, CMC, dynamic light scattering and zeta potential measurements. We assessed the impact of different structural elements and formulation parameters of these pyridinium amphiphiles on their DNA compaction properties, transfection efficiency, cytotoxicity, in a complete structure–activity relationship study. This interfacial engineering process generated transfection systems with reduced cytotoxicity and high transfection efficiency in media containing elevated levels of serum that mimic the in vivo conditions.

Synthesis of Ester Based Cationic Pyridinium Gemini Surfactants and Appraisal of Their Surface Active Properties

AbstractNew pyridinium gemini surfactants have been synthesized by esterification of halogenated carboxylic acids with long chain fatty alcohols furnishing respective esters (dodecyl‐2‐chloroacetate, tetradecyl‐2‐chloroacetate, hexadecyl‐2‐chloroacetate, dodecyl‐2‐bromoacetate, tetradecyl‐2‐bromoacetate and hexadecyl‐2‐bromoacetate) followed by their subsequent treatment with 4,4′‐trimethylene dipyridine resulting in the formation of title Gemini surfactants: 4,4′‐(propane‐1,3‐diyl)bis1‐{2‐(dodecyloxy)‐2‐oxoethyl}; 4,4′‐(propane‐1,3‐diyl)bis{1‐(2‐(tetradecyloxy)‐2‐oxoethyl}; 4,4′‐(propane‐1,3‐diyl)bis{1‐(2‐(hexadecyloxy)‐2‐oxoethyl} dipyridinium chlorides; 4,4′‐(propane‐1,3‐diyl)bis{1‐(2‐(dodecyloxy)‐2‐oxoethyl}; 4,4′‐(propane‐1,3‐diyl)bis{1‐(2‐(tetradecyloxy)‐2‐oxoethyl} and 4,4′‐(propane‐1,3‐diyl)bis{1‐(2‐(hexadecyloxy)‐2‐oxoethyl} dipyridinium bromides. Their identifications are based on IR, 1H‐NMR, 13C‐NMR, DEPT, COSY and Mass spectral studies. Their surface active properties were also evaluated on the basis of surface tension and conductivity measurements.

Physicochemical studies of pyridinium gemini surfactants with promethazine hydrochloride in aqueous solution

The mixed micellization and interfacial behavior of pyridinium gemini surfactants, 1,1'-(1,1'-(ethane-1,2-diylbis-(sulfanediyl))bis(alkane-2,1-diyl))dipyridinium bromide, i.e., [12-(S-2-S)-12], [14-(S-2-S)-14], [16-(S-2-S)-16] with a phenothiazine tranquilizer drug, promethazine hydrochloride (PMT), has been investigated by conductivity, surface tension and steady state fluorescence measurements. Different spectroscopic techniques like fluorescence, UV-visible and NMR were also employed to understand the nature of interactions between the pyridinium gemini surfactants and PMT. The various micellar, interfacial and associated thermodynamic parameters for different mole fractions of PMT-pyridinium gemini surfactant mixtures have been evaluated. Synergism was observed in the mixed micelle as well as the monolayer formed by these mixtures. The fluorescence quenching experiment indicates that the interactions between PMT and surfactants are hydrophobic in nature. The UV-visible measurements reveal the distinct formation of a drug-surfactant complex. The detailed mechanism for the type of interactions was further studied by NMR titrations which show cation-π interactions between PMT and pyridinium gemini surfactant molecules.

Novel Gemini Pyridinium Surfactants: Synthesis and Study of Their Surface Activity, DNA Binding, and Cytotoxicity

New pyridinium gemini amphiphiles having ethane-1,2-dithiol spacer have been synthesized by regioselective electrophilic cobromination of alpha-olefins. Ethane-1,2-dithiol (1) and N-bromosuccinimide (6) on reaction with alpha-olefins (dodecene (2), tetradecene (3), hexadecene (4), and octadecene (5)) gave the respective 1,2-bis(2-bromoalkylthio)ethane (7-10). The bromoalkylthio ethers when reacted with pyridine (11) gave the respective gemini bispyridinium bromide (12-15). The surface properties of new geminis were evaluated by surface tension and conductivity measurements. These gemini surfactants have also been found to be having low cytotoxicity by MTT (3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide) assay on C6 glioma cells. The DNA binding capabilities of these amphiphiles have been determined below as well as above critical micelle concentration. The preliminary studies by agarose gel electrophoresis indicated chain length dependent DNA binding abilities which has further been proved by ethidium bromide exclusion experiments and transmission electron microscopy (TEM).

Synthesis and Characterization of Highly Fluorinated Gemini Pyridinium Surfactants

AbstractA series of fluorinated gemini pyridinium amphiphiles have been prepared, purified and fully characterized. The synthesis was performed using alkyl trifluoromethanesulfonates as the quaternizing agents, provided very good yields and overcame problems arising with other less powerful alkylating agents. The use of different characterization techniques, such as conductivity and surface tension measurements, shed light on the aggregation process. The title products showed interesting, unusual properties, which could be interpreted in view of a peculiar aggregating behaviour. This family of compounds is very interesting for their possible transfection activity and application in gene therapy. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009)

Synthesis and Properties of a Novel Class of Gemini Pyridinium Surfactants

A novel class of gemini pyridinium surfactants with a four-methylene spacer group was synthesized, and their surface-active properties and interactions with polyacrylamide (PAM) were evaluated by surface tension, fluorescence, and viscosity measurements. A comparison between the gemini pyridinium surfactants and their corresponding monomers was also made. The cmc's of gemini pyridinium surfactants are much lower than those of the corresponding monomeric surfactants. The C20 value is about one order of magnitude lower than that of corresponding monomers, and the longer the hydrophobic chains of the surfactants, the lower the cmc value. Surface tension measurements of the surfactant-PAM mixed systems show that the critical aggregation concentration (cac) value is much lower than the cmc value of the surfactant system alone. Viscosity measurements of the surfactant-PAM mixed systems show that the relative viscosity of the surfactant-PAM system decreased with increasing concentration of surfactant. Additionally, fluorescence measurements of the surfactant-PAM mixed system suggest the formation of surfactant-polymer aggregates, and the gemini pyridinium surfactant with longer hydrophobic chains have a stronger interaction with PAM, owing to the stronger hydrophobic interaction.