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.

Self assembly of pH-sensitive cationic lysine based surfactants.

Three cationic surfactants of the type N(ε)-acyl lysine methyl ester hydrochloride have been studied with respect to solution behavior and adsorption on the air/water interface, as well as the thermolyotropic behavior. The self-assembly of these surfactants, which have the cationic charge on amine protonated groups, was assessed by different physicochemical methods. Depending on the pH value, these surfactants can dissociate in aqueous solutions, losing the cationic charge.

pH-Sensitive surfactants from lysine: assessment of their cytotoxicity and environmental behavior.

The toxicity and environmental behavior of new pH-sensitive surfactants from lysine are presented. Three different chemical structures are studied: surfactants with one amino acid and one alkyl chain, surfactants with two amino acids on the polar head and one alkyl chain, and gemini surfactants. The pH sensitivity of these compounds can be tuned by modifying their chemical structures.

Physicochemical and toxicological properties of novel amino acid-based amphiphiles and their spontaneously formed catanionic vesicles.

The design of efficient liposomal systems for drug delivery is of considerable biomedical interest. In this context, vesicles prepared from cationic/anionic surfactants may offer several advantages, mainly due to their spontaneity in formation and long-term stability. There is also an impending need to produce less toxic, more biocompatible amphiphiles, while maintaining the desirable aggregation properties.

Comparative evaluation of cytotoxicity and phototoxicity of mono and diacylglycerol amino acid-based surfactants.

Extensive efforts have been made, recently, to find surfactants with lower irritancy potential than those presently commercially employed in pharmaceutical and cosmetic preparations. Cytotoxic and phototoxic effects of novel mono and diacylglycerol amino acid-based surfactants (glutamic acid, or arginine) were evaluated. All tested surfactants showed a clear concentration-response relationship to two immortalized cell lines, murine fibroblast cell line, 3T3, and one human keratinocyte cell line, HaCaT, demonstrated by and decrease of NR uptake.

Interactions between gemini surfactants and polymers: thermodynamic studies.

Aqueous mixtures containing a homopolymer, poly(vinylpyrrolidone) (PVP), or a hydrophobically modified graft copolymer, HM-pullulan, (PULAU9, where 9 stands for the nominal substitution degree), and different Gemini surfactants have been investigated at 25.0 degrees C. A wide variety of experimental conditions were addressed by changing the amount of polymer and of surfactant.

Antibacterial activity, structure and CMC relationships of alkanediyl alpha,omega-bis(dimethylammonium bromide) surfactants.

Some alpha,omega-alkanediyl bis-dimethylammonium bromide compounds (gemini surfactants) referred as "m-s-m" have been synthesized, purified and characterized by usual spectroscopic methods. These compounds have been screened for antibacterial activity against Escherichia coli, Pseudomonas aeruginosa and Staphylococcus aureus. Their activity was compared.

Spontaneous formation of vesicles and dispersed cubic and hexagonal particles in amino acid-based catanionic surfactant systems.

Mixed catanionic surfactant systems based on amino acids were investigated with respect to the formation of liquid crystal dispersions and the stability of the dispersions. The surfactants used were arginine-N-lauroyl amide dihydrochloride (ALA) and N(alpha)-lauroyl-arginine-methyl ester hydrochloride (LAM), which are arginine-based cationic surfactants; sodium hydrogenated tallow glutamate (HS), a glutamic-based anionic surfactant; and the anionic surfactants sodium octyl sulfate (SOS) and sodium cetyl sulfate (SCS). It is demonstrated that in certain ranges of composition there is a spontaneous formation of vesicular, cubic, and hexagonal structures.

Langmuir monolayers of the zwitterionic surfactant hexadecyl 1-N-L-tryptophan glycerol ether.

We report the formation of Langmuir monolayers of pure zwitterionic hexadecyl 1-N-L-tryptophan glycerol ether (C(16)-TGE) surfactant and mixed monolayers of cationic-zwitterionic surfactant obtained modifying the pH of the subphase. The pressure-area and surface potential-area isotherms and fluorescence microscopy measurements have been used to characterize the surface phase transitions in the monolayers. These transitions appeared at larger areas as the pH decreased from 6.

Assessment of the potential irritation and photoirritation of novel amino acid-based surfactants by in vitro methods as alternative to the animal tests.

The ultraviolet-A radiation damage effects on skin and eyes will be increased by phototoxic compounds which could be present in pharmaceutical or cosmetic formulations. Great efforts have been made in the last years to find surfactants to replace those with phototoxic potential in commercial use. Series of different in vitro models for phototoxicity, included to validated neutral red uptake (NRU) 3T3 phototoxicity assay are useful screening tools.

Biological properties of arginine-based gemini cationic surfactants.

Biological properties of novel gemini (double-chain/double-head) cationic surfactants, Nalpha,Nomega-bis(Nalpha-acylarginine)alpha,omega-alkylendiamides, so-called bis(Args), are reported. The effect of both the alkyl (10 and 12 carbon atoms) and the spacer chain (from 2-10 methylene groups) of bis(Args) on their antimicrobial activity, acute toxicity on Daphnia magna and Photobacterium phosphoreum, and aerobic biodegradability is studied. These surfactants constitute a novel class of chemicals of low toxicity with excellent surface properties and considerable antimicrobial activity.