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Sant Jordi Desvalls, Spain
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Colomer A.,IQAC | Pinazo A.,IQAC | Garcia M.T.,IQAC | Mitjans M.,University of Barcelona | And 4 more authors.
Langmuir | Year: 2012

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. Cytotoxicity has been evaluated using erythrocytes and fibroblast cells. The toxic effects against these cells depend on the hydrophobicity of the molecules as well as their cationic charge density. The effect of hydrophobicity and cationic charge density on toxicity is different for each type of cells. For erythrocytes, the toxicity increases as hydrophobicity and charge density increases. Nevertheless, for fibroblasts cationic charge density affects cytotoxicity in the opposite way: the higher charge density, the lower the toxicity. The effect of the pH on hemolysis has been evaluated in detail. The aquatic toxicity was established using Daphnia magna. All surfactants yielded EC 50 values considerably higher than that reported for cationic surfactants based on quaternary ammonium groups. Finally, their biodegradability was evaluated using the CO 2 headspace test (ISO 14593). These lysine derivatives showed high levels of biodegradation under aerobic conditions and can be classified as "readily biodegradable compounds". © 2012 American Chemical Society.


Nogueira D.R.,University of Barcelona | Mitjans M.,University of Barcelona | Busquets M.A.,University of Barcelona | Perez L.,IQAC | Vinardell M.P.,University of Barcelona
Langmuir | Year: 2012

Amino acid-based surfactants constitute an important class of natural surface-active biomolecules with an unpredictable number of industrial applications. To gain a better mechanistic understanding of surfactant-induced membrane destabilization, we assessed the phospholipid bilayer-perturbing properties of new cationic lysine-based surfactants. We used erythrocytes as biomembrane models to study the hemolytic activity of surfactants and their effects on cells' osmotic resistance and morphology, as well as on membrane fluidity and membrane protein profile with varying pH. The antihemolytic capacity of amphiphiles correlated negatively with the length of the alkyl chain. Anisotropy measurements showed that the pH-sensitive surfactants, with the positive charge on the α-amino group of lysine, significantly increased membrane fluidity at acidic conditions. SDS-PAGE analysis revealed that surfactants induced significant degradation of membrane proteins in hypo-osmotic medium and at pH 5.4. By scanning electron microscopy examinations, we corroborated the interaction of surfactants with lipid bilayer. We found that varying the surfactant chemical structure is a way to modulate the positioning of the molecule inside bilayer and, thus, the overall effect on the membrane. Our work showed that pH-sensitive lysine-based surfactants significantly disturb the lipid bilayer of biomembranes especially at acidic conditions, which suggests that these compounds are promising as a new class of multifunctional bioactive excipients for active intracellular drug delivery. © 2012 American Chemical Society.


Rubio J.,Jaume I University | Alfonso I.,IQAC | Burguete M.I.,Jaume I University | Luis S.V.,Jaume I University
Chemical Communications | Year: 2012

The formation of soluble nano-spheres or stable hydrogels through the self-assembling of a simple gemini amphiphilic pseudopeptide can be controlled by the tuning of the hydrophilic/hydrophobic interactions in aqueous medium. © 2012 The Royal Society of Chemistry.


Colomer A.,IQAC | Pinazo A.,IQAC | Manresa M.A.,University of Barcelona | Vinardell M.P.,University of Barcelona | And 3 more authors.
Journal of Medicinal Chemistry | Year: 2011

Three different sets of cationic surfactants from lysine have been synthesized. The first group consists of three monocatenary surfactants with one lysine as the cationic polar head with one cationic charge. The second consists of three monocatenary surfactants with two amino acids as cationic polar head with two positive charges. Finally, four gemini surfactants were synthesized in which the spacer chain and the number and type of cationic charges have been regulated. The micellization process, antimicrobial activity, and hemolytic activity were evaluated. The critical micelle concentration was dependent only on the hydrophobic character of the molecules. Nevertheless, the antimicrobial and hemolytic activities were related to the structure of the compounds as well as the type of cationic charges. The most active surfactants against the bacteria were those with a cationic charge on the trimethylated amino group, whereas all of these surfactants showed low hemolytic character. © 2011 American Chemical Society.


Morros J.,IQAC | Levecke B.,BENEO Bio Based Chemicals | Infante M.R.,IQAC
Carbohydrate Polymers | Year: 2011

Medium and long chain esters of inulin have been prepared by reaction of alkenyl succinic anhydrides (ASA) such as 2-octen-1-ylsuccinic anhydride (OSA), and 2-dodecen-1-ylsuccinic anhydride (DDSA) in aqueous media and aqueous surfactant media, respectively. The design of the chemical process was based on the study of the influence of several reaction parameters on reaction efficiency (estimated by 1H NMR analysis of the pure end product) and reaction time. Inulin concentration, pH range, temperature, and the addition of a cationic surfactant such as dodecyltrimethylammonium bromide (DTAB) to the reaction media were evaluated for both OSA and DDSA anhydrides. Inulin slurry aqueous systems were found the best reaction media to carry out the esterification with OSA. In case of DDSA, the addition of a cationic surfactant such as DTAB was required to convert 65% of anhydride. Inulin precipitation was prevented at pH range 8.5-9.0 by the addition of DTAB. The reaction time for the synthesis of dodecenyl succinic esters of inulin, estimated as the total time required to consume all DDSA, was reduced dramatically from 24 h (without DTAB) to less than 1 h in presence of cationic surfactant. The use of micellar basic catalysis resulted in a useful way to obtain long chain alkenyl succinic esters of inulin. © 2011 Elsevier Ltd. All rights reserved.


Martins-Costa M.T.C.,University of Lorraine | Anglada J.M.,IQAC | Francisco J.S.,Purdue University | Ruiz-Lopez M.F.,University of Lorraine
Journal of the American Chemical Society | Year: 2012

Knowledge of the role of water droplets and aerosols in atmospheric chemistry is crucial to significantly improve our understanding of global warming and air quality. Chemistry at the air/water interface, in particular, is still poorly understood. There is a great need to understand how clouds and aerosols process chemistry of organics prevalent in the atmosphere. We report in this study the first computer simulation of a volatile organic compound (formaldehyde) at the air/water interface with explicit description of its ground and excited states electronic properties. We use an elaborated technique that combines molecular dynamics simulations together with a quantum/classical description of the formaldehyde-water system. We show that in spite of a large affinity for water, formaldehyde exhibits a preference for the air/water interface with respect to the bulk, roughly by 1.5 kcal/mol. Another important finding in our simulations is that frontier orbitals HOMO and LUMO undergo substantial stabilization at the interface due to surface water reorientation, which induces a local positive electrostatic potential. Such a potential is significantly larger than the one estimated in bulk water suggesting that the reactivity of formaldehyde could change with respect to both gas phase and bulk water. The conclusions presented in this work are expected to help/guide future experiments studying the chemical reactivity of volatile organic compounds at the air/water interface. © 2012 American Chemical Society.


Nogueira D.R.,University of Barcelona | Tavano L.,IQAC | Tavano L.,University of Calabria | Mitjans M.,University of Barcelona | And 3 more authors.
Biomaterials | Year: 2013

Nanoparticles with pH-sensitive behavior may enhance the success of chemotherapy in many cancers by efficient intracellular drug delivery. Here, we investigated the effect of a bioactive surfactant with pH-sensitive properties on the antitumor activity and intracellular behavior of methotrexate-loaded chitosan nanoparticles (MTX-CS-NPs). NPs were prepared using a modified ionotropic complexation process, in which was included the surfactant derived from Nα,Nε-dioctanoyl lysine with an inorganic lithium counterion. The pH-sensitive behavior of NPs allowed accelerated release of MTX in an acidic medium, as well as membrane-lytic pH-dependent activity, which facilitated the cytosolic delivery of endocytosed materials. Moreover, our results clearly proved that MTX-CS-NPs were more active against the tumor HeLa and MCF-7 cell lines than the free drug. The feasibilty of using NPs to target acidic tumor extracellular pH was also shown, as cytotoxicity against cancer cells was greater in a mildly acidic environment. Finally, the combined physicochemical and pH-sensitive properties of NPs generally allowed the entrapped drug to induce greater cell cycle arrest and apoptotic effects. Therefore, our overall results suggest that pH-sensitive MTX-CS-NPs could be potentially useful as a carrier system for tumor and intracellular drug delivery in cancer therapy. © 2013 Elsevier Ltd.


Nogueira D.R.,University of Barcelona | Mitjans M.,University of Barcelona | Moran M.C.,University of Barcelona | Perez L.,IQAC | Vinardell M.P.,University of Barcelona
Amino Acids | Year: 2012

Many strategies for treating diseases require the delivery of drugs into the cell cytoplasm following internalization within endosomal vesicles. Thus, compounds triggered by low pH to disrupt membranes and release endosomal contents into the cytosol are of particular interest. Here, we report novel cationic lysine-based surfactants (hydrochloride salts of Nε and Nα-acyl lysine methyl ester) that differ in the position of the positive charge and the length of the alkyl chain. Amino acid-based surfactants could be promising novel biomaterials in drug delivery systems, given their biocompatible properties and low cytotoxic potential. We examined their ability to disrupt the cell membrane in a range of pH values, concentrations and incubation times, using a standard hemolysis assay as a model of endosomal membranes. Furthermore, we addressed the mechanism of surfactant-mediated membrane destabilization, including the effects of each surfactant on erythrocyte morphology as a function of pH. We found that only surfactants with the positive charge on the a-amino group of lysine showed pH-sensitive hemolytic activity and improved kinetics within the endosomal pH range, indicating that the positive charge position is critical for pH-responsive behavior. Moreover, our results showed that an increase in the alkyl chain length from 14 to 16 carbon atoms was associated with a lower ability to disrupt cell membranes. Knowledge on modulating surfactant-lipid bilayer interactions may help us to develop more efficient biocompatible amino acid-based drug delivery devices. © 2011 Springer-Verlag.


Nogueira D.R.,University of Barcelona | Mitjans M.,University of Barcelona | Infante M.R.,IQAC | Vinardell M.P.,University of Barcelona
Acta Biomaterialia | Year: 2011

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. © 2011 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.


News Article | April 28, 2016
Site: phys.org

A new study led by ICTA-UAB (Universitat Autònoma de Barcelona) researcher Víctor Sarto and colleagues from the Institute of Advanced Chemistry of Catalonia (CSIC-IQAC) has described for the first time in two centuries of knowledge a case of evolutionary convergence in the order of butterflies (Lepidoptera), certainly representing an evolutionary breakthrough to what has been known about their sexual communication. The research has discovered important behavior and physiological changes in the mating process of the moth Paysandisia archon (Castniidae). This neotropical moth that reached Europe in 2001 from Argentina (also inhabiting Uruguay and Brasil) breaks the known sexual rules by behaving like a diurnal butterfly.

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