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.
[Show abstract][Hide abstract] ABSTRACT: New dimeric surfactants [16-s-16, s: (CH2)4; CH2–COO–(CH2)2–OCO–CH2; CH2–COO–ISO–OCO–CH2 (ISO = d-isorbide) and CH2–CONH–(CH2)2–NHCO–CH2] were synthesized and characterized (I–IV, respectively). The micellization behavior of dimeric surfactants with various spacers was studied by conductance/steady-state fluorescence quenching (SSFQ) measurement and compared with the conventional surfactant (cetyltrimethylammoniumbromide, CTAB). The critical micelle concentration (CMC) values of several surfactants were found to be nearly the same by both techniques. Conductance measurements were used exclusively to obtain CMC and degree of dissociation (α) values at various temperatures, while SSFQ measurements were used to obtain a few CMC values (for comparison) and an aggregation number (N
agg). A decrease in CMC and N
agg values and an increase in α were observed for dimeric surfactants when compared with CTAB. CMC decreases and then increases with a continuous increase in temperature (U-shaped behavior). The temperature of minimum CMC, T
m, was distinctly different for CTAB and the dimeric surfactants. T
m values were dependent on the nature of the spacer. The temperature dependence of CMC and α value was used to calculate the thermodynamic parameters of micelle formation for two classes of surfactant (conventional and dimeric). Enthalpy-entropy compensation plots exhibited fair linearity except for IV. Compensation lines for spacers containing ester groups are parallel to one another. Micro-polarity and apparent dielectric constant (ε
a) data suggest that the micellar environment felt by pyrene is similar to that of an alkanol with a 3–4 carbon chain.
Journal of Surfactants and Detergents 09/2013; 16(5). DOI:10.1007/s11743-013-1467-z · 1.69 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Surfactants are chemical products consumed in large quantities every day on a worldwide scale. The development of less irritant, less toxic, consumer-friendly surfactants is, therefore, of general interest. Amino-acid-based surfactants constitute a novel class of surfactants produced from renewable raw materials and can be seen as an alternative to conventional surfactants. With the aim of testing their applicability in formulations for pharmaceutical, food, and cosmetic industries we have carried out exhaustive studies to elucidate their properties as surfactants. We considered amino acid-based surfactants with one single chain, cystine or arginine gemini surfactants, lysine derivatives, and surfactants with glycerolipid-like structure.
[Show abstract][Hide abstract] ABSTRACT: In this paper, we report on a catanionic vesicles-based strategy to reduce the cytotoxicity of the diacyl glycerol arginine-based synthetic surfactants 1,2-dimyristoyl-rac-glycero-3-O-(N(α)-acetyl-L-arginine) hydrochloride (1414RAc) and 1,2-dilauroyl-rac-glycero-3-O-(N(α)-acetyl-L-arginine) hydrochloride (1212RAc). The behavior of these surfactants was studied either as pure components or after their formulation as pseudo-tetra-chain catanionic mixtures with phosphatidylglycerol (PG) and as cationic mixtures with 1,2-dipalmitoyl-sn-glycero-3-phosphatidylcholine (DPPC) used as control. The antimicrobial activity of the negatively charged formulations against Acinetobacter baumannii was maintained with respect to the surfactant alone, while a significant improvement of the antimicrobial activity against Staphylococcus aureus was observed, together with a strong decrease of hemolytic activity. The influence of the net charge of the catanionic vesicles on membrane selectivity was studied using model membranes. The dynamics of surface tension changes induced by the addition of 1414RAc/PG aqueous dispersions into phospholipid monolayers composed of zwitterionic DPPC as model system for mammalian membranes and of negatively charged PG mimicking cytoplasmic membrane of gram-positive bacteria was followed by tensiometry. Our results constitute a proof of principle that tuning formulation can reduce the cytotoxicity of many surfactants, opening their possible biological applications.
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