Possible effects of counterions on biological activities of anionic surfactants

The aggressiveness in terms of apogenic and necrotic activities of lysine-derived anionic surfactants towards a mammalian cell line (U937) were studied. We used N(alpha)N(epsilon)-dioctanoyl lysine as the model surfactant with lysine, tris, Na(+) or Li(+) as counterions. The aggressiveness of the different surfactants was assessed as the concentrations leading to apoptosis or necrosis after the cells were incubated in the presence of surfactants and then cultivated in their absence. Used in the same conditions, acetates associated with the same cations, had no effects on the cells. Our results show that the aggressiveness of the surfactants depended on the nature of the counterions: it was high when surfactants were associated with small counterions, and low with large counterions.Peer reviewe

Erythrocyte hemolysis and shape changes induced by new lysine-derivate surfactants

The effects of new synthetic lysine-derived anionic surfactants on human and rat erythrocytes were studied. The surfactants were salts of Nalpha,Nepsilon-dioctanoyl lysine with different counterions: lysine (77KK), tris (trishydroxymethyl amminomethane) (77KT), sodium (77KS), and lithium (77KL). 77KK and 77KT showed a biphasic hemolytic behavior in the erythrocytes. The surfactants 77KS and 77KL showed concentration-dependent hemolysis with a CH50 of about 3.4 and 2.6 mmol/l, respectively. 77KK and 77KT induced protection against hypotonic hemolysis in rat erythrocytes at the concentration which showed the least hemolytic activity under isotonic conditions. With human erythrocytes, 77KT did not show biphasic behavior in isotonic medium, but under hypotonic conditions biphasic behavior was present. Changes in shape of the erythrocyte, from discocytic to stomatocytic were observed after incubation with the anionic surfactants studied. Such shape changes occurred progressively over time, with total alteration in shape occuring after about 20 min of incubation.Peer reviewe

Interactions of surfactants with living cells. Induction of apoptosis by detergents containing a β-lactam moiety

The toxicity of new surfactants containing a beta-lactam ring has been established by studying their interaction with a hybridoma cell line. An hour of contact is sufficient to generate an apoptotic signal after two days of culture. Under the experimental conditions chosen for the experiments, surfactants have been divided into three categories: i) biocompatible and non-apogenic; ii) surfactants triggering an apoptotic signal without inducing cell necrosis; iii) surfactants triggering an apoptotic signal at low concentrations and destroying the cells by necrosis at higher concentrations. The necrosis inducing surfactants also had haemolytic properties. These properties were related to the values of the hydrophilic-lipophilic balance of the molecules.This work was generously supported by CNRS and CSIC “Cooperation project n° 1940”.Peer reviewe

Tensiobioactifs trimodulaires non ioniques comportant un cycle β-lactame et un sucre

A synthetic methodology for surfactant molecules containing a beta-lac tame ring and a glycosamine has been developed. From 3-hydroxy-2-hydro xymethyl-2-methyl-propionic acid we prepared a hydrophobic 1,3-diol mo dule A by selective amidation using a fatty amine. One of the primary alcohol functions of this product A is selectively activated in the fo rm of the ATDP sit B. The cyclization of B into the beta-lactame C is then effected by reaction in a basic medium (K2CO3). These derivatives C: constitute an interesting bimodular surfactant. By esterification of C with succinic anhydride we obtained products D. The carboxy[ic fu nction introduced by the succinyl group was activated by BOP and coupl ed to the glucosamine giving the trimodular biotensides E. These deriv atives display air-water interface activity as shown by the surface te nsion; the values of which have been lowered to 32 mN/m. The Critical Micellar Concentration (CMC) is of the order of 10(-4) mol dm(-3), com parable in magnitude to what has been observed for surfactants with su gar-type polar heads. Binary phase diagrams with water for these produ cts C, as a function of temperature and concentration, show the behavi or of hydrophilic surfactants with a large direct micellar phase L-1. Products E show little toxicity in cell culture, however they induce a poptosis at concentrations larger than 3x10(-4) g/L. They also show an tibiotic properties with respect to gram(+) or gram(-) bacterial strai ns with Minimal Inhibition Concentrations (MIG) on the order of 32 mu g/mL in the cases where they appear to be the most efficient. These va lues remain, however, below those of commercial monobactames.Peer reviewe

The role of counterions in the membrane-disruptive properties of pH-sensitive lysine-based surfactants

Surfactants are among the most versatile and widely used excipients in pharmaceuticals. This versatility, together with their pH-responsive membrane-disruptive activity and low toxicity, could also enable their potential application in drug delivery systems. Five anionic lysine-based surfactants which differ in the nature of their counterion were studied. Their capacity to disrupt the cell membrane was examined under a range of pH values, concentrations and incubation times, using a standard hemolysis assay as a model for endosomal membranes. The surfactants showed pH-sensitive hemolytic activity and improved kinetics at the endosomal pH range. Low concentrations resulted in negligible hemolysis at physiological pH and high membrane lytic activity at pH 5.4, which is in the range characteristic of late endosomes. With increasing concentration, the surfactants showed an enhanced capacity to lyse cell membranes, and also caused significant membrane disruption at physiological pH. This observation indicates that, at high concentrations, surfactant behavior is independent of pH. The mechanism of surfactant-mediated membrane destabilization was addressed, and scanning electron microscopy studies were also performed to evaluate the effects of the compounds on erythrocyte morphology as a function of pH. The in vitro cytotoxicity of the surfactants was assessed by MTT and NRU assays with the 3T3 cell line. The influence of different types of counterion on hemolytic activity and the potential applications of these surfactants in drug delivery are discussed. The possibility of using pH-sensitive surfactants for endosome disruption could hold great promise for intracellular drug delivery systems in future therapeutic applications

Comparative sensitivity of tumor and non-tumor cell lines as a reliable approach for in vitro cytotoxicity screening of lysine-based surfactants with potential pharmaceutical applications

Surfactants are used as additives in topical pharmaceuticals and drug delivery systems. The biocompatibility of amino acid-based surfactants makes them highly suitable for use in these fields, but tests are needed to evaluate their potential toxicity. Here we addressed the sensitivity of tumor (HeLa, MCF-7) and non-tumor (3T3, 3T6, HaCaT, NCTC 2544) cell lines to the toxic effects of lysine-based surfactants by means of two in vitro endpoints (MTT and NRU). This comparative assay may serve as a reliable approach for predictive toxicity screening of chemicals prior to pharmaceutical applications. After 24-h of cell exposure to surfactants, differing toxic responses were observed. NCTC 2544 and 3T6 cell lines were the most sensitive, while both tumor cells and 3T3 fibroblasts were more resistant to the cytotoxic effects of surfactants. IC(50)-values revealed that cytotoxicity was detected earlier by MTT assay than by NRU assay, regardless of the compound or cell line. The overall results showed that surfactants with organic counterions were less cytotoxic than those with inorganic counterions. Our findings highlight the relevance of the correct choice and combination of cell lines and bioassays in toxicity studies for a safe and reliable screen of chemicals with potential interest in pharmaceutical industry.This research was supported by Project CTQ2009-14151-C02-02 from Ministerio de Ciencia e Innovación (Spain). Daniele Rubert Nogueira holds doctoral grant from MAEC-AECID (Spain).Peer reviewe