Complex rhamnolipid mixture characterization and its influence on DPPC bilayer organization

Rhamnolipids (RL) are one of the most important classes of biosurfactants produced by microorganisms using a wide range of carbon sources, from a simple carbon source like glucose to complex wastes such as the used cooking oils used in this work. The objective of this work was to learn about the rhamnolipid-phospholipid dipalmitoyl phosphatidyl choline (DPPC) molecular interactions through the behaviour observed in the neat products and four RL/DPPC mixtures. Size and z-potential were used to characterize the size and the charge of the vesicles, and small angle X-ray scattering (SAXS) was used to measure the vesicle bilayer characteristics, and the release of carboxyfluorescein to study the bilayer disrupting effect promoted by rhamnolipids. The results show that rhamnolipids are disposed in ordered bilayers with long repeating distances, which are stabilized by the charging of the bilayer and also by a strong fluidity of the bilayers. The ability of rhamnolipids to increase the fluidity of DPPC bilayers may be related with the strong haemolytic power of these molecules.We thank Jaume Caelles from the SAXS-WAXS service at IQAC for the X-Ray measurements. Financial support from MINECO CTQ2010-14897 and 24 MAT2012-38047-CO2-02 is gratefully acknowledged. Also financial support from Generalitat de Catalunya 2009SGR1331 is gratefully acknowledged.Peer reviewe

Aggregation Behavior, Antibacterial Activity and Biocompatibility of Catanionic Assemblies Based on Amino Acid-Derived Surfactants

Abstract: The surface activity, aggregates morphology, size and charge characteristics of binary catanionic mixtures containing a cationic amino acid-derived surfactant N(π), N(τ)-bis(methyl)- L-Histidine tetradecyl amide (DMHNHC14) and an anionic surfactant (the lysine-based surfactant Nα-lauroyl-Nεacetyl lysine (C12C3L) or sodium myristate) were investigated for the first time. The cationic surfactant has an acid proton which shows a strong pKa shift irrespective of aggregation. The resulting catanionic mixtures exhibited high surface activity and low critical aggregation concentration as compared with the pure constituents. Catanionic vesicles based on DMHNHC14/sodium myristate showed a monodisperse population of medium-size aggregates and good storage stability. According to Small-Angle X-Ray Scattering (SAXS), the characteristics of the bilayers did not depend strongly on the system composition for the positively charged vesicles. Negatively charged vesicles (cationic surfactant:myristate ratio below 1:2) had similar bilayer composition but tended to aggregate. The DMHNHC14-rich vesicles exhibited good antibacterial activity against Gram-positive bacteria and their bactericidal effectivity declined with the decrease of the cationic surfactant content in the mixtures. The hemolytic activity and cytotoxicity of these catanionic formulations against non-tumoral (3T3, HaCaT) and tumoral (HeLa, A431) cell lines also improved by increasing the ratio of cationic surfactant in the mixture. These results indicate that the biological activity of these systems is mainly governed by the cationic charge density, which can be modulated by changing the cationic/anionic surfactant ratio in the mixtures. Remarkably, the incorporation of cholesterol in those catanionic vesicles reduces their cytotoxicity and increases the safety of future biomedical applications of these systems. Keywords: amino acid-based surfactants; catanionic vesicles; SAXS; self-assembly; antibacterial activity; cytotoxicit

Physicochemical characterization and antimicrobial properties of rhamnolipids produced by Pseudomonas aeruginosa 47T2 NCBIM 40044

7 pages, 2 figures, 3 tables.-- PMID: 12474254 [PubMed].-- Available online Dec 3, 2002.Pseudomonas aeruginosa 47T2, grown in submerged culture with waste frying oil as a carbon source, produced a mixture of rhamnolipids with surface activity. Up to 11 rhamnolipid homologs (Rha-Rha-C8-C10; Rha-C10-C8/Rha-C8-C10;Rha-Rha-C8-C12:1; Rha-Rha-C10-C10; Rha-Rha-C10-C12:1; Rha-C10-C10; Rha-Rha-C10-C12/Rha-Rha-C12-C10; Rha-C10-C12:1/Rha-C12:1-C10; Rha-Rha-C12:1-C12; Rha-Rha-C10-C14:1; Rha-C10-C12/Rha-C12-C10) were isolated from cultures of P. aeruginosa 47T2 from waste frying oil and identified by HPLC-MS analysis. This article deals with the production, isolation, and chemical characterization of the rhamnolipid mixture RL47T2. The physicochemical and biological properties of RL47T2 as a new product were also studied. Its surface tension decreased to 32.8 mN/m; and the interfacial tension against kerosene to 1 mN/m. The critical micellar concentration for RL47T2 was 108.8 mg/mL. The product showed excellent antimicrobial properties. Antimicrobial activity was evaluated according to the minimum inhibitory concentration (MIC), the lowest concentration of an antimicrobial agent that inhibits development of visible microbial growth. Low MIC values were found for bacteria Serratia marcescens (4 g/mL), Enterobacter aerogenes (8 g/mL), Klebsiella pneumoniae (0.5 g/mL), Staphylococcus aureus and Staphylococcus epidermidis (32 g/mL), Bacillus subtilis (16 g/mL), and phytopathogenic fungal species: Chaetonium globosum (64 g/mL), Penicillium funiculosum (16 g/mL), Gliocadium virens (32 g/mL) and Fusarium solani (75 g/mL).Finnancial support by the CIRIT and CICYT; Grant Number: 199956R 00024, PPQ-2000-0105-P4-03, REN 2001-3224.Peer reviewe

Mixed monolayer of DPPC and lysine-based cationic surfactants: An investigation into the antimicrobial activity

In this paper, we report studies which aim to elucidate the mechanisms involved in the antimicrobial activity of three cationic lysine-based surfactants: LLM, LALM, and C6 (LL)2. To this end, a simple membrane model (i.e., 1,2-dipalmitoyl-sn-phosphatidylcholine, DPPC) was used to explore the monolayer properties at the air/liquid interface. Compression π-A isotherms of mixtures of DPPC/lysine surfactants at different pH showed an expansion of the DPPC monolayer, suggesting cationic lysine surfactant/DPPC interactions, which strongly depend on surfactant structure and hydrophobic interactions. Antimicrobial activity of the three surfactants has also been assessed with transmission electron microscopy, observing the effects on Staphylococcus aureus and Escherichia coli. The three surfactants caused various kinds of damage to the bacteria tested, such as structural alterations, leakage of internal material, and cell destruction.Authors have been supported by the CICYT Spanish Research Agency under the projects CTQ2009-14151-C02-01 and CTQ2010-14897 and by AGAUR Research Agency of the Generalitat de Catalunya under the project 2009 SRG 246Peer reviewe

Green Catanionic Gemini Surfactant-Lichenysin Mixture: Improved Surface, Antimicrobial, and Physiological Properties

Catanionic surfactant mixtures form a wide variety of organized assemblies and aggregates with improved physicochemical and biological properties. The green catanionic mixture (NN omega)-N-alpha-Bis(N(alpha)caproylarginine) alpha,omega-propyldiamide (C-3(CA)(2)):Lichenysin (molar ratio 8:2) showed antimicrobial synergies against Yersinia enterocolitica, Bacillus subtilis, Escherichia coli O157:H7, and Candida albicans. Flow cytometry and viability studies indicated that this catanionic mixture increases the probability of Y. enterocolitica (38.2%) and B. subtilis (17.1%) cells entering a viable but nonculturable state. Zeta potential showed that one of the cationic charges of C-3(CA)(2) is neutralized by Lichenysin. An isotherm study demonstrated the formation of a stable aggregate between the two surfactants. The catanionic aggregate was able to interact with bacterial phospholipids. The lowest hemolysis (22.1 mu M) was obtained with the catanionic mixture, although an irritant potential (0.70) was characterized. According to the therapeutic index, the C-3(CA)(2):Lichenysin mixture was the formulation least toxic to eukatyotic cells. Partial neutralization of C-3(CA)(2) by Lichenysin modified the mode of action that enhances the transition of bacterial cells into a viable but nonculturable state (VBNC) and improved the cell selectivity. KEYWORDS:antimicrobial activity catanionic mixtures biosurfactant Lichenysin gemini surfactants flow cytometry VBNC Langmuir balanc

Biocompatible Catanionic Vesicles from Arginine-Based Surfactants: A New Strategy to Tune the Antimicrobial Activity and Cytotoxicity of Vesicular Systems

Their stability and low cost make catanionic vesicles suitable for application as drug delivery systems. In this work we prepared catanionic vesicles using biocompatible surfactants: two cationic arginine-based surfactants (the monocatenary Nα-lauroyl-arginine methyl ester LAM and the gemini Nα,Nϖ-bis(Nα-lauroylarginine) α, ϖ-propylendiamide C3(CA)2) and three anionic amphiphiles (the single chain sodium dodecanoate, sodium myristate, and the double chain 8-SH). The critical aggregation concentration, colloidal stability, size, and charge density of these systems were comprehensively studied for the first time. These catanionic vesicles, which form spontaneously after mixing two aqueous solutions of oppositely charged surfactants, exhibited a monodisperse population of medium-size aggregates and good stability. The antimicrobial and hemolytic activity of the vesicles can be modulated by changing the cationic/anionic surfactant ratio. Vesicles with a positive charge efficiently killed Gram-negative and Gram-positive bacteria as well as yeasts; the antibacterial activity declined with the decrease of the cationic charge density. The catanionic systems also effectively eradicated MRSA (Methicillin-resistant Staphylococcus Aureus) and Pseudomonas aeruginosa biofilms. Interestingly, the incorporation of cholesterol in the catanionic mixtures improved the stability of these colloidal systems and considerably reduced their cytotoxicity without affecting their antimicrobial activity. Additionally, these catanionic vesicles showed good DNA affinity. Their antimicrobial efficiency and low hemolytic activity render these catanionic vesicles very promising candidates for biomedical application

Interfacial chiral selection by bulk species

A chiral selection process in a self-assembled soft monolayer of an achiral amphiphile as a consequence of its interaction with chiral species dissolved in the aqueous subphase, is reported. The extent of the chiral selection is statistically measured in terms of the enantiomorphic excess of self-assembled submillimeter domains endowed with well-defined orientational chirality that is unambiguously resolved using optical microscopy. Our results show that the emergence of chirality is mediated by electrostatic interactions and significantly enhanced by hydrophobic effects. This chiral chemical effect can be suppressed and even reversed by opposing a macroscopic physical influence, such as vortical stirring. This result gives evidence for the crucial role of hydrodynamic effects in supramolecular aggregation

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

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

Lichenysin-geminal amino acid-based surfactants: Synergistic action of an unconventional antimicrobial mixture

Recently it has been demonstrated that catanionic mixtures of oppositely charged surfactants have improved physicochemical-biological properties compared to the individual components. Isotherms of mixtures of an anionic biosurfactant (lichenysin) and a cationic aminoacid surfactant (C-3(LA)(2)) indicate a strong interaction suggesting the formation of a new 'pseudo-surfactant'. The antimicrobial properties of the mixture lichenysin and C-3(LA)(2) M80:20, indicate a synergistic effect of the components. The mechanism of action on the bacterial envelope was assessed by flow cytometry and Transmission Electron Microscopy. (C) 2016 Elsevier B.V. All rights reserved. Keywords: Antimicrobial properties; Arginine; Escherichia coli; Flow cytometry; Gemini surfactants; Lichenysin; Listeria nonocytogenes; Potassium leakage; Transmission electron microscopy