Surface-Active Ionic Liquids and Surface-Active Quaternary Ammonium Salts from Synthesis, Characterization to Antimicrobial Properties

The present work provides new evidence of the ongoing potential of surface-active ionic liquids (SAILs) and surface-active quaternary ammonium salts (surface-active QASs). To achieve this, a series of compounds were synthesized with a yield of ≥85%, and their thermal analyses were studied. Additionally, antimicrobial activity against both human pathogenic and soil microorganisms was investigated. Subsequently, their surface properties were explored with the aim of utilizing SAILs and surface-active QASs as alternatives to commercial amphiphilic compounds. Finally, we analyzed the wettability of the leaves' surface of plants occurring in agricultural fields at different temperatures (from 5 to 25 °C) and the model plant membrane of leaves. Our results show that the synthesized compounds exhibit higher activity than their commercial analogues such as, i.e., didecyldimethylammonium chloride (DDAC) and dodecyltrimethylammonium bromide (C12TAB), for which the CMC values are 2 mM and 15 mM. The effectiveness of the antimicrobial properties of synthesized compounds relies on their hydrophobic nature accompanied by a cut-off effect. Moreover, the best wettability of the leaves' surface was observed at 25 °C. Our research has yielded valuable insights into the potential effectiveness of SAILs and surface-active QASs as versatile compounds, offering a promising alternative to established antimicrobials and crop protection agents, all the while preserving substantial surface activity.

Synergism and properties of binary mixtures based on an arginine dodecyl ester surfactant

The properties of binary mixtures of new cationic amino acid surfactant arginine dihydrochloride dodecyl ester (ADDE) with alkyl poly glycosides (APGs) were studied systematically by evaluating surface tension, conductivity, dynamic...

Aspartic-Acid-Based Ampholytic Amphiphiles: Synthesis, Characterization, and pH-Dependent Properties at Air/Water and Oil/Water Interfaces

A facile and two-step strategy was employed to synthesize a series of novel aspartic-acid-based ampholytic amphiphiles from sustainable and commercially viable substances as starting materials. The molecular structures of the synthetic compounds were well-identified by mass spectrometry and ¹H/¹³C nuclear magnetic resonance analysis, and the physicochemical, pH-dependent foaming, and emulsifying properties were evaluated by the use of multiple techniques, such as Fourier transform infrared spectroscopy, differential scanning calorimetry, Langmuir-Blodgett study, and fluorescence microscopy imaging. As a result of the co-existence of amino and carboxyl groups in the synthetic compounds, the compounds presented varying charges (cationic, ampholytic, and anionic) depending upon the pH of the medium compared to the dissociation constants (p K_a). Compounds with cationic (pH 1.0) and anionic (pH 9.0) forms had significantly higher γ_0.1 and critical micelle concentration values than those with ampholytic forms (pH 7.0). sn-1-Lauroyl- sn-3-aspartic acid (compound 3) at neutral and alkaline conditions displayed comparable foaming properties, including foaming, calcium-tolerant, and temperature-resistant abilities, with commercial sulfonate sodium dodecyl sulfate (SDS), and thus might be a promising alternative to SDS, applied in personal care products and detergent formula. sn-1-Palmtoyl- sn-3-aspartic acid (compound 5a) with an ampholytic structure was proven as the most excellent stabilizer for the preparation of oil-in-water emulsions compared to palmityl aspartic acid (compound 5b), commercial food ingredient diacetyltartaric acid esters of mono- and diglycerides, and glyceride monopalmitate at aqueous phase pH 7.0. Thus, it has promising use as a pH-dependent emulsifying agent in various fields.

Benzalkonium Salts of Amino Acids – Physicochemical Properties and Anti-Microbial Activity

New salts combining a benzalkonium cation and chiral amino acid anions were synthesized and characterized. The identification was performed by NMR spectroscopy. Properties such as temperature of phase transformation, specific rotation, thermal stability and surface activity and antimicrobial activity were determined and compared with that of benzalkonium chloride. Benzalkonium amino acids salts can be used as conditioners in cosmetics. It has been shown they have weak impact on symbiotic microorganisms which occupy a wide range of skin, and this confirms that they do not disturb the biological balance of human skin.

Synthesis, Surface and Biological Activities of Cationic Surfactants Based on Glycine Moiety

Two series of cationic surfactants based on glycine molecule as sulfonate salt of N,N-diethyl glycine fatty esters having a hydrocarbon chain length of C12,C16 and C18 followed by quaternerization with ethyl iodide were synthesized. Their chemical structures were confirmed using IR,1H-NMR, and mass spectroscopy. The surface activity of these amphiphiles has been determined by measurement of their surface tension. Parameters like surface tension (γ), critical micelle concentration (cmc), effectiveness (Πcmc), efficiency (pC20), maximum surface excess (Γmax), minimum surface area (Amin) and Gibbs free energy of the micellization (ΔGmic) and adsorption (ΔGads) have been determined from the measurements obtained by surface tension method. All these surfactants showed much lower CMC values compared to the similar hydrophobic chain length surfactant. All synthesized compounds have been evaluated for their biological activity against bacteria and fungi.

Amino acid–based surfactants: New antimicrobial agents

The rapid increase of drug resistant bacteria makes necessary the development of new antimicrobial agents. Synthetic amino acid-based surfactants constitute a promising alternative to conventional antimicrobial compounds given that they can be prepared from renewable raw materials. In this review, we discuss the structural features that promote antimicrobial activity of amino acid-based surfactants. Monocatenary, dicatenary and gemini surfactants that contain different amino acids on the polar head and show activity against bacteria are revised. The synthesis and basic physico-chemical properties have also been included.

Self-Assembly, Supramolecular Organization, and Phase Behavior of L-Alanine Alkyl Esters (n = 9-18) and Characterization of Equimolar L-Alanine Lauryl Ester/Lauryl Sulfate Catanionic Complex

A homologous series of l-alanine alkyl ester hydrochlorides (AEs) bearing 9-18 C atoms in the alkyl chain have been synthesized and characterized with respect to self-assembly, supramolecular structure, and phase transitions. The CMCs of AEs bearing 11-18 C atoms were found to range between 0.1 and 10 mM. Differential scanning calorimetric (DSC) studies showed that the transition temperatures (Tt), enthalpies (ΔHt) and entropies (ΔSt) of AEs in the dry state exhibit odd-even alternation, with the odd-chain-length compounds having higher Tt values, but the even-chain-length homologues showing higher values of ΔHt and ΔSt. In DSC measurements on hydrated samples, carried out at pH 5.0 and pH 10.0 (where they exist in cationic and neutral forms, respectively), compounds with 13-18 C atoms in the alkyl chain showed sharp gel-to-liquid crystalline phase transitions, and odd-even alternation was not seen in the thermodynamic parameters. The molecular structure, packing properties, and intermolecular interactions of AEs with 9 and 10 C atoms in the alkyl chain were determined by single crystal X-ray diffraction, which showed that the alkyl chains are packed in a tilted interdigitated bilayer format. d-Spacings obtained from powder X-ray diffraction studies exhibited a linear dependence on the alkyl chain length, suggesting that the other AEs also adopt an interdigitated bilayer structure. Turbidimetric, fluorescence spectroscopic, and isothermal titration calorimetric (ITC) studies established that in aqueous dispersions l-alanine lauryl ester hydrochloride (ALE·HCl) and sodium dodecyl sulfate (SDS) form an equimolar complex. Transmission electron microscopic and DSC studies indicate that the complex exists as unilamellar liposomes, which exhibit a sharp phase transition at ∼39 °C. The aggregates were disrupted at high pH, suggesting that the catanionic complex would be useful to develop a base-labile drug delivery system. ITC studies indicated that ALE·HCl forms a strong complex with DNA, suggesting that the AEs may find use in DNA therapeutics as well.

Gemini surfactants from natural amino acids

In this review, we report the most important contributions in the structure, synthesis, physicochemical (surface adsorption, aggregation and phase behaviour) and biological properties (toxicity, antimicrobial activity and biodegradation) of Gemini natural amino acid-based surfactants, and some potential applications, with an emphasis on the use of these surfactants as non-viral delivery system agents. Gemini surfactants derived from basic (Arg, Lys), neutral (Ser, Ala, Sar), acid (Asp) and sulphur containing amino acids (Cys) as polar head groups, and Geminis with amino acids/peptides in the spacer chain are reviewed.

Dynamic properties of cationic diacyl-glycerol-arginine-based surfactant/phospholipid mixtures at the air/water interface

In this Article, we study the binary surface interactions of 1,2-dimyristoyl-rac-glycero-3-O-(N(alpha)-acetyl-L-arginine) hydrochloride (1414RAc) with 1,2-dipalmitoyl-sn-glycero-3-phosphatidylcholine (DPPC) on 0.1 M sodium chloride solutions. 1414RAc is a novel monocationic surfactant that has potential applications as an antimicrobial agent, is biodegradable, and shows a toxicity activity smaller than that of other commercial cationic surfactants. DPPC phospholipid was used as a model membrane component. The dynamic surface tension of 1414RAc/DPPC aqueous dispersions injected into the saline subphase was followed by tensiometry. The layer formation for the mixtures is always accelerated with respect to DPPC, and surprisingly, the surface tension reduction is faster and reaches lower surface tension values at surfactant concentration below its critical micellar concentration (cmc). Interfacial dilational rheology properties of mixed films spread on the air/water interface were determined by the dynamic oscillation method using a Langmuir trough. The effect of surfactant mole fraction on the rheological parameters of 1414RAc/DPPC mixed monolayers was studied at a relative amplitude of area deformation of 5% and a frequency of 50 mHz. The monolayer viscoelasticity shows a nonideal mixing behavior with predominance of the surfactant properties. This nonideal behavior has been attributed to the prevalence of electrostatic interactions.

Lysine-bisglycidol conjugates as novel lysine cationic surfactants

The synthesis of a novel class of lysine-based cationic amphiphilic derivatives of the type N(epsilon),N(epsilon)'-bis(n-acyloxypropyl)-l-lysine methyl ester salts combining several hydroxyl functions and aliphatic chains of 12 or 14 carbon atoms is described. The compounds have one, two, three, and four alkyl chains. Aggregation in water was studied by four different methods: surface tension, conductivity, chloride ion activity, and nuclear magnetic resonance ((1)H NMR). The critical aggregation concentration value of the new surfactants depends on both the number of alkyl chains and the alkyl chain length. The formation of vesicles at low concentrations was confirmed by H(1) NMR and optical microscopy. Antimicrobial activity was determined on the basis of the minimum inhibitory concentration (MIC) values. These novel lysine-based surfactants showed moderate antimicrobial activity which may be an important advantage for many biomedical applications.

Chemoenzymatic synthesis and antimicrobial and haemolytic activities of amphiphilic bis(phenylacetylarginine) derivatives

Novel bis(N(alpha)-phenylacetyl-L-arginine)-alpha,omega-alkanediamide dihydrochloride (bis(PhAcArg)) derivatives with antimicrobial activity were designed and synthesised by a chemoenzymatic strategy. The new structures consist of two N(alpha)-phenylacetyl-L-arginine moieties connected by an alkanediamine spacer chain of 6, 8, 10, 12, and 14 methylene units through amide bonds. The key step in the chemoenzymatic strategy is the double aminolysis of the N(alpha)-phenylacetyl-L-arginine methyl ester by the corresponding alpha,omega-alkanediamine catalyzed by papain in ethanolic media. The compounds synthesised were tested as antimicrobials against 15 bacterial and 8 fungal species. The antimicrobial activity and selectivity depend strongly on the spacer chain length. The bis(PhAcArg) derivative with the spacer chain of 12 methylene groups gave the lowest MIC values against Gram-positive bacteria, whereas that with 14 methylene units was the best against Gram-negative bacteria. Interestingly, these novel compounds showed enhanced antibacterial activity relative to the lead compound, bis(N(alpha)-caproyl-L-arginine)-1,3-propanediamide dihydrochloride (C(3)(CA)(2)), and moderate antifungal activity. Moreover, tests of haemolytic activity toward human erythrocytes revealed that haemolysis increases with spacer chain length. Importantly, the compounds were classified as not irritating to eyes, with the exception of the compound with the spacer chain of 14 methylene groups, which was a slight eye irritant.

The biological properties of lysine-derived surfactants

We examine the effects of aquatic toxicity on Daphnia magna, the antimicrobial activity of new anionic lysine-derivative surfactants, and the influence of different-sized counterions associated with the surfactants. Surfactants with Tris and Lithium had less of a toxic effect on Daphnia, while all surfactants proved highly active against yeasts and the gram-negative bacteria Bordetella bronchiseptica. Counterion size was found to have no effect on aquatic toxicity or antimicrobial activity.

A synthetic alternative to natural lecithins with antimicrobial properties

Two soft biocompatible cationic surfactants from the amino acid arginine, 1,2-dilauroyl-3-acetylarginyl-rac-glycerol (1212RAc) and 1,2-dimirystoyl-3-acetylarginyl-rac-glycerol (1414RAc), were prepared. Their physicochemical properties show that they can be classified as multifunctional surfactants with self-aggregation behaviour comparable to that of short-chain lecithins. The two surfactants can simultaneously stabilise water-in-oil (W/O) droplets and oil-in-water (O/W) droplets, forming multiple emulsions. They have antimicrobial activity similar to that of conventional cationic surfactants and are as harmless as amphoteric betaines. These surfactants constitute an interesting alternative to the diglycerides and lecithins in formulations that require antimicrobial properties.

Assessment of primary eye and skin irritants by in vitro cytotoxicity and phototoxicity models: an in vitro approach of new arginine-based surfactant-induced irritation

Extensive efforts have been made, recently, to find surfactants with lower irritation potential than those presently commercially available, for use in pharmaceutical and cosmetic preparations. Cytotoxic and phototoxic effects of a novel family of dicationic arginine-diglyceride surfactant compounds, 1,2-diacyl,3-O-(l-arginyl)-rac-glycerol with alkyl chain lengths in the range from 8 to 14 carbon atoms, were compared to three commercial surfactants. The end-points used to assess toxicity were the red blood cell lysis assay and uptake of the vital dye neutral red 24h after dosing (NRU), respectively. Two immortalized cell lines, murine fibroblast cell line, 3T3, and one human keratinocyte cell line, HaCaT, were used as in vitro models to predict the potential phototoxicity which could result in irritation, determined by resazurin reduction to resorufin and neutral red uptake (NRU). All tested surfactants had cytotoxicity effects as demonstrated by and decrease of NR uptake, which showed a clear concentration-response relationship. Concentrations resulting in 50% inhibition of NR uptake (IC(50)) range from 1 microM(-1) (hexadecyl trimethyl ammonium bromide) to 565 microM(-1) (12,12-l-arginine). Erythrocyte haemolysis also showed a clear concentration-response relationship, the 50% of haemolysis ranged from 37 microM(-1) (10,10-l-arginine) to 151 microM(-1) (sodium lauryl sulphate). Phototoxicity was performed with 12,12-l-acetyl-arginine, the most stable chemical structure. The validated 3T3 NRU photoxicity assay was used and revealed a phototoxic potential.