Eduardo Marques - Academia.edu (original) (raw)

Papers by Eduardo Marques

Mixed polymer-surfactant systems have been intensively investigated in the last two decades, with... more Mixed polymer-surfactant systems have been intensively investigated in the last two decades, with the main focus on surfactant micelles as the surfactant aggregate in interaction. The main types of phase behavior, driving forces and structural/rheological effects at stake are now fairly well understood. Polymer-vesicle systems, on the other hand, have received comparatively less attention from a physico-chemical perspective. In this review, our main goal has been to bridge this gap, taking a broad approach to cover a field that is in clear expansion, in view of its multiple implications for colloid and biological sciences and in applied areas. We start by a general background on amphiphile self-assembly and phase separation phenomena in mixed polymer-surfactant solutions. We then address vesicle formation, properties and stability not only in classic lipids, but also in various other surfactant systems, among which catanionic vesicles are highlighted. Traditionally, lipid and surfactant vesicles have been studied separately, with little cross-information and comparison, giving duplication of physico-chemical interpretations. This situation has changed in more recent times. We then proceed to cover more in-depth the work done on different aspects of the associative behavior between vesicles (of different composition and type of stability) and different types of polymers, including polysaccharides, proteins and DNA. Thus, phase behavior features, effects of vesicle structure and stability, and the forces/mechanisms of vesicle-macromolecule interaction are addressed. Such association may generate gels with interesting rheological properties and high potential for applications. Finally, special focus is also given to DNA, a high charge polymer, and its interactions with surfactants, and vesicles, in particular, in the context of gene transfection studies.

Journal of Physical Chemistry B, Aug 1, 1998

Catanionic mixtures are aqueous mixtures of oppositely charged surfactants which display novel ph... more Catanionic mixtures are aqueous mixtures of oppositely charged surfactants which display novel phase behavior and interfacial properties in comparison with those of the individual surfactants. One phase behavior property is the ability of these systems to spontaneously form stable vesicles at high dilution. The phase behavior of the mixture sodium dodecyl sulfate (SDS)didodecyldimethylammonium bromide (DDAB) in water has been studied in detail, and two regions of isotropic vesicular phases (anionic-rich and cationic-rich) were identified. Cryo-transmission electron microscopy allowed direct visualization of relatively small and polydisperse unilamellar vesicles on the SDS-rich side. Monitoring of the microstructure evolution from mixed micelles to vesicles as the surfactant mixing ratio is varied toward equimolarity was also obtained. Further information was provided by water self-diffusion measurements by pulsed field gradient spin-echo NMR. Water molecules can be in fast or slow exchange between the inside and outside of the vesicle with respect to the experimental time scale, depending on membrane permeability and vesicle size. For the SDSrich vesicles, a slow-diffusing component of very low molar fraction observed for the echo decays was traced down to very large vesicles in solution. Light microscopy confirmed the presence of vesicles of several microns in diameter. Thus, polydispersity seems to be an inherent feature of the system.

Membranes

Mixtures of cationic and anionic surfactants often originate bilayer structures, such as vesicles... more Mixtures of cationic and anionic surfactants often originate bilayer structures, such as vesicles and lamellar liquid crystals, that can be explored as model membranes for fundamental studies or as drug and gene nanocarriers. Here, we investigated the aggregation properties of two catanionic mixtures containing biomimetic surfactants derived from serine. The mixtures are designated as 12Ser/8-8Ser and 14Ser/10-10Ser, where mSer is a cationic, single-chained surfactant and n-nSer is an anionic, double-chained one (m and n being the C atoms in the alkyl chains). Our goal was to investigate the effects of total chain length and chain length asymmetry of the catanionic pair on the formation of catanionic vesicles, the vesicle properties and the vesicle/micelle transitions. Ocular observations, surface tension measurements, video-enhanced light microscopy, cryogenic scanning electron microscopy, dynamic and electrophoretic light scattering were used to monitor the self-assembly process a...

U.Porto Journal of Engineering, 2020

In the last years, sustainable practices have been developed to minimize the negative effects of ... more In the last years, sustainable practices have been developed to minimize the negative effects of production and excessive consumption on the environment. The textile and clothing industry is one of the most polluting industries globally and needs to rethink its strategies. The fast-fashion caused an increase in production, and the environmental weight associated with the textile industry also increased. The problems range from the enormous expenditure of water resources to the carbon and greenhouse gas emissions to reaching the consumer. This review focuses on the eco-friendly approaches taken by the industry towards supportable apparel manufacturing, from the choice of raw materials to the last step in the textile industry.

Chemistry – A European Journal, 2020

Drug delivery vectors based on amphiphiles have important features such as versatile physicochemi... more Drug delivery vectors based on amphiphiles have important features such as versatile physicochemical properties and stimuli-responsiveness. Amino acid-based surfactants are especially promising amphiphiles due to their enhanced biocompatibility compared to conventional surfactants. They can self-organize into micelles, vesicles and complex hierarchical structures, such as fibers, twisted and coiled ribbons, and tubules. In this work, we investigated the self-assembly and drug loading properties of a family of novel anionic double-tailed lysine-derived surfactants, with variable degree of tail length mismatch, designated as m Lys10 and 10Lys n , where m and n are the carbon atoms in the tails. These surfactants form tubular aggregates with assorted morphologies in water that undergo gelation due to dense entanglement, as evidenced by light and electron microscopy. Lysozyme (LZM), an enzyme with antimicrobial properties, was selected as model protein for loading. After the characterization of the interfacial properties and phase behavior of the amphiphiles, the LZM-loading ability of the tubules was investigated, under varying experimental conditions, to assess the efficiency of the aggregates as pH- and temperature-sensitive nanocarriers. Further, the toxicological profile of the surfactants per se and surfactant/LZM hydrogels was obtained, using human skin fibroblasts (BJ-5ta cell line). Overall, the results show that the tubule-based hydrogels exhibit very interesting properties for the transport and controlled release of molecules of therapeutic interest.

International Journal of Molecular Sciences, 2020

Ionic liquids derived from classical antimalarials are emerging as a new approach towards the cos... more Ionic liquids derived from classical antimalarials are emerging as a new approach towards the cost-effective rescuing of those drugs. Herein, we disclose novel surface-active ionic liquids derived from chloroquine and natural fatty acids whose antimalarial activity in vitro was found to be superior to that of the parent drug. The most potent ionic liquid was the laurate salt of chloroquine, which presented IC50 values of 4 and 110 nM against a chloroquine-sensitive and a chloroquine-resistant strain of Plasmodium falciparum, respectively, corresponding to an 11- and 6-fold increase in potency as compared to the reference chloroquine bisphosphate salt against the same strains. This unprecedented report opens new perspectives in both the fields of malaria chemotherapy and of surface-active ionic liquids derived from active pharmaceutical ingredients.

Journal of Colloid and Interface Science, 2021

comparison with a commercially available standard indicating that these gemini:MO systems are pro... more comparison with a commercially available standard indicating that these gemini:MO systems are promising candidates as lipofection vectors for RNA interference (RNAi)-based therapies.

The Journal of Physical Chemistry C, 2018

Debundling and dispersing single-walled carbon nanotubes (SWNTs) is essential for applications, b... more Debundling and dispersing single-walled carbon nanotubes (SWNTs) is essential for applications, but the process is not well understood. In this work, aqueous SWNT dispersions were produced by sonicating pristine SWNT powder in the presence of an amphiphilic triblock copolymer (Pluronic F127) as dispersant. Upon centrifugation, one obtains a supernatant with suspended individual tubes and thin bundles and a precipitate with large bundles (and impurities). In the supernatant, that constitutes the final dispersion, we determined the dispersed SWNT concentration by thermogravimetric analysis (TGA) and UV−vis spectroscopy, and the dispersant concentration by 1 H NMR. The fraction of dispersant adsorbed at the SWNT surface was obtained by 1 H diffusion NMR. Sigmoidal dispersion curves recording the concentration of dispersed SWNTs as a function of supernatant dispersant concentration were obtained at different SWNT loadings and sonication times. As SWNT bundles are debundled into smaller and smaller ones, the essential role of the dispersant is to sufficiently quickly cover the freshly exposed surfaces created by shear forces induced during sonication. Primarily kinetic reasons are behind the need for dispersant concentrations required to reach a substantial SWNT concentration. Centrifugation sets the size threshold below which SWNT particles are retained in the dispersion and consequently determines the SWNT concentration as a function of sonication time.

Soft Matter, 2019

Stimuli-sensitive self-assembled nanostructures are relevant for efficient drug delivery and nano... more Stimuli-sensitive self-assembled nanostructures are relevant for efficient drug delivery and nanomaterial templating.

Nanoscale, 2018

Novel serine amino acid-based catanionic vesicles with tunable surface charge and high cell uptak... more Novel serine amino acid-based catanionic vesicles with tunable surface charge and high cell uptake for doxorubicin drug delivery.

Journal of colloid and interface science, May 1, 2017

Mechanical agitation is commonly used to fragment and disperse insoluble materials in liquids. Ho... more Mechanical agitation is commonly used to fragment and disperse insoluble materials in liquids. However, here we show that when pristine single-walled carbon nanotubes pre-dispersed in water are subject to vortex-shaking for very short periods (typically 10-60s, power density ∼0.002WmL(-1)), re-aggregation counterintuitively occurs. The initial dispersions are produced using surfactants as dispersants and powerful tip sonication (∼1WmL(-1)) followed by centrifugation. Detailed imaging by light and electron microscopies shows that the vortex-induced aggregates consist of loose networks (1-10(2)μm in size) of intertwined tubes and thin bundles. The average aggregate size increases with vortexing time in an apparently logarithmic manner and depends on the dispersant used, initial concentration of nanotubes and size distribution of bundles. The aggregation is, nonetheless, reversible: if the vortex-shaken dispersions are mildly bath-sonicated (∼0.03WmL(-1)), the flocs break down and re-d...

Soft Matter, 2014

Cationic serine-based gemini surfactants have strong potential as compaction agents of nucleic ac... more Cationic serine-based gemini surfactants have strong potential as compaction agents of nucleic acids for efficient non-viral gene delivery.

Thermochimica Acta, 2002

Dilute solutions of catanionic vesicles formed by the mixed single-chained (sodium dodecylsulphat... more Dilute solutions of catanionic vesicles formed by the mixed single-chained (sodium dodecylsulphate, SDS) and doublechained (didodecyldimethylammonium bromide, DDAB) surfactants have been investigated by differential scanning calorimetry. It is for the first time reported a gel-to-liquid crystal phase transition temperature, T m , in this type of mixed vesicles. The SDS-rich vesicles (at X SDS = 0.71) show a concentration-dependent T m in the range 9-16 • C. Addition of salt is seen to have an effect on T m similar to that observed with increasing surfactant concentration, both inducing a decrease in T m. These results differ from those obtained for neat DDAB vesicles. The observed effects in the two types of vesicles are rationalised in terms of headgroup electrostatic interactions which may have influence on the chain packing and phase transition temperature.

The Journal of Physical Chemistry B

Vesicles composed of an anionic and a cationic surfactant, with a net negative charge, associate ... more Vesicles composed of an anionic and a cationic surfactant, with a net negative charge, associate strongly with a hydrophobically modified polycation (LM200) and with an unmodified polycation with higher charge density (JR400), forming viscoelastic gel-like structures. Calorimetric results show that in these gels, LM200 induces a rise of the chain melting temperature (T m) of the vesicles, whereas JR400 has the opposite effect. For both polymer-vesicle systems, the shear viscosity exhibits an inflection point at T m , and for the LM200 system the measured relaxation times are significantly higher below T m. The neat vesicles and the polycationbound vesicles have a polygonal-like faceted shape when the surfactant chains in the bilayer are crystallized, as probed by cryo-transmission electron microscopy. Above T m , the neat and the LM200-bound vesicles regain a spheroidal shape, whereas those in the JR400 system remain with a deformed faceted shape even above T m. These shape changes are interpreted in terms of different mechanisms for the polymer-vesicle interaction, which seem to be highly dependent on polymer architecture, namely charge density and hydrophobic modification. A crystallization-segregation mechanism is proposed for the LM200-vesicle system, while, for the JR400-vesicle one, charge polarization-lateral segregation effects induced by the polycation in the catanionic bilayer are envisaged.

Synthetic Communications, 2008

Double-chained surfactants with potential biocompatibility have been prepared in high yields by l... more Double-chained surfactants with potential biocompatibility have been prepared in high yields by lysine acylation with four natural saturated fatty acids (C 6 to C 12) and with cis-undec-5-enoic acid. The surfactants were found to assemble into nanotubules in aqueous medium and, when mixed with a commercial cationic surfactant, to spontaneously form liposomes.

Pure and Applied Chemistry, 1993

Macromolecules, 1999

Structural and phase behavior effects resulting from the addition of a polyelectrolyte to a solut... more Structural and phase behavior effects resulting from the addition of a polyelectrolyte to a solution of oppositely charged vesicles are investigated in this work. Two cationic polyelectrolytes derived from hydroxyethylcellulose were used: JR400, a homopolymer, and Quatrisoft LM200, a polymer modified with alkyl side chains. The vesicles are composed of mixed anionic surfactant (sodium dodecyl sulfate) and cationic surfactant (didodecyldimethylammonium bromide), bearing 29 mol % of the cationic amphiphile. The phase behavior for the two mixed polymer-surfactant systems was investigated for polymer concentrations between 0.001 and 3 wt%. Three main regions were found in the two-phase maps, upon polymer addition: (i) a bluish solution phase; (ii) a wide region of phase separation, containing a precipitate and a solution; and (iii) a polymer-rich gel region, forming upon charge reversal of the system. Cryo-TEM imaging of the solution phase shows the formation of faceted vesicles and disklike aggregates, upon addition of JR400. For the LM200 system, besides the formation of faceted vesicles, clusters of vesicles and other bilayer structures are imaged. In the polymer-rich phase of JR400, membrane fragments, disklike aggregates, and vesicles are also found. These bilayer aggregates are likely to be involved with the polymer in highly connected networks, giving rise to the observed bluish gels. Electrostatic interactions, reinforced by hydrophobic interactions in the case of LM200, are the main driving force for the structural transitions observed.

Langmuir, 2000

The phase behavior of several binary sodium bile saltwater systems is investigated over the entir... more The phase behavior of several binary sodium bile saltwater systems is investigated over the entire concentration range, with emphasis on concentrated regions beyond the isotropic solution phase. The studied bile acid salts comprise the free salt sodium deoxycholate (SDC), the taurine conjugates sodium taurocholate (STC), sodium taurodeoxycholate (STDC), and sodium taurochenodeoxycholate (STCDC) and the glycine conjugate sodium glycodeoxycholate (SGDC). A combination of classical techniques is used, including phase diagram determination, polarizing microscopy, 2 H NMR, and small-angle X-ray scattering (SAXS). The aggregation behavior in the isotropic micellar solutions of STC and STDC is also investigated by pulsed-field gradient NMR self-diffusion. The optical textures and the data from SAXS and 2 H NMR clearly point to the formation of hexagonal liquid crystals, possibly of the reverse type, beyond the micellar solution for all the bile salts. Several unusual kinetic effects, such as very slow equilibration times and the formation of transient spherulitic crystals in biphasic regions, are observed. The phase diagrams and structural data are qualitatively discussed in terms of the molecular structure and solubility of the different salts. The formation of lyotropic liquid crystals by bile salts, which has remained unknown for decades, is clearly demonstrated in this work.

Langmuir, 2008

The use of amino acids for the synthesis of novel surfactants with vesicle-forming properties pot... more The use of amino acids for the synthesis of novel surfactants with vesicle-forming properties potentially enhances the biocompatibility levels needed for a viable alternative to conventional lipid vesicles. In this work, the formation and characterization of catanionic vesicles by newly synthesized lysine-and serine-derived surfactants have been investigated by means of phase behavior mapping and PFG-NMR diffusometry and cryo-TEM methods. The lysinederived surfactants are double-chained anionic molecules bearing a pseudogemini configuration, whereas the serinederived amphiphile is cationic and single-chained. Vesicles form in the cationic-rich side for narrow mixing ratios of the two amphiphiles. Two pairs of systems were studied: one symmetric with equal chain lengths, 2C 12 /C 12 , and the other highly asymmetric with 2C 8 /C 16 chains, where the serine-based surfactant has the longest chain. Different mechanisms of the vesicle-to-micelle transition were found, depending on symmetry: the 2C 12 /C 12 system entails limited micellar growth and intermediate phase separation, whereas the 2C 8 /C 16 system shows a continuous transition involving large wormlike micelles. The results are interpreted on the basis of currently available models for the micelle-vesicle transitions and the stabilization of catanionic vesicles (energy of curvature vs mixing entropy).