Publications by authors named "Natalia Hassan"

24 Publications

  • Page 1 of 1

Microfluidics-assisted conjugation of chitosan-coated polymeric nanoparticles with antibodies: Significance in drug release, uptake, and cytotoxicity in breast cancer cells.

J Colloid Interface Sci 2021 Jun 13;591:440-450. Epub 2021 Feb 13.

Laboratorio de Inmunología, Departamento de Fisiología, Centro Universitario de Ciencias de la Salud (CUCS), Universidad de Guadalajara, Guadalajara 44340, Mexico. Electronic address:

Nanoparticle-based drug delivery systems, in combination with high-affinity disease-specific targeting ligands, provide a sophisticated landscape in cancer theranostics. Due to their high diversity and specificity to target cells, antibodies are extensively used to provide bioactivity to a plethora of nanoparticulate systems. However, controlled and reproducible assembly of nanoparticles (NPs) with these targeting ligands remains a challenge. In this context, determinants such as ligand density and orientation, play a significant role in antibody bioactivity; nevertheless, these factors are complicated to control in traditional bulk labeling methods. Here, we propose a microfluidic-assisted methodology using a polydimethylsiloxane (PDMS) Y-shaped microreactor for the covalent conjugation of Trastuzumab (TZB), a recombinant antibody targeting HER2 (human epidermal growth factor receptor 2), to doxorubicin-loaded PLGA/Chitosan NPs (PLGA/DOX/Ch NPs) using 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide (EDC) and N-hydroxysulfosuccinimide (sNHS) mediated bioconjugation reactions. Our labeling approach led to smaller and less disperse nanoparticle-antibody conjugates providing differential performance when compared to bulk-labeled NPs in terms of drug release kinetics (fitted and analyzed with DDSolver), cell uptake/labeling, and cytotoxic activity on HER2 + breast cancer cells in vitro. By controlling NP-antibody interactions in a laminar regime, we managed to optimize NP labeling with antibodies resulting in ordered coronas with optimal orientation and density for bioactivity, providing a cheap and reproducible, one-step method for labeling NPs with globular targeting moieties.
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http://dx.doi.org/10.1016/j.jcis.2021.02.031DOI Listing
June 2021

Copper-Modified Polymeric Membranes for Water Treatment: A Comprehensive Review.

Membranes (Basel) 2021 Jan 28;11(2). Epub 2021 Jan 28.

Advanced Mining Technology Center (AMTC), Universidad de Chile, Santiago 8370451, Chile.

In the last decades, the incorporation of copper in polymeric membranes for water treatment has received greater attention, as an innovative potential solution against biofouling formation on membranes, as well as, by its ability to improve other relevant membrane properties. Copper has attractive characteristics: excellent antimicrobial activity, high natural abundance, low cost and the existence of multiple cost-effective synthesis routes for obtaining copper-based materials with tunable characteristics, which favor their incorporation into polymeric membranes. This study presents a comprehensive analysis of the progress made in the area regarding modified membranes for water treatment when incorporating copper. The notable use of copper materials (metallic and oxide nanoparticles, salts, composites, metal-polymer complexes, coordination polymers) for modifying microfiltration (MF), ultrafiltration (UF), nanofiltration (NF), forward osmosis (FO) and reverse osmosis (RO) membranes have been identified. Antibacterial and anti-fouling effect, hydrophilicity increase, improvements of the water flux, the rejection of compounds capacity and structural membrane parameters and the reduction of concentration polarization phenomena are some outstanding properties that improved. Moreover, the study acknowledges different membrane modification approaches to incorporate copper, such as, the incorporation during the membrane synthesis process (immobilization in polymer and phase inversion) or its surface modification using physical (coating, layer by layer assembly and electrospinning) and chemical (grafting, one-pot chelating, co-deposition and mussel-inspired PDA) surface modification techniques. Thus, the advantages and limitations of these modifications and their methods with insights towards a possible industrial applicability are presented. Furthermore, when copper was incorporated into membrane matrices, the study identified relevant detrimental consequences with potential to be solved, such as formation of defects, pore block, and nanoparticles agglomeration during their fabrication. Among others, the low modification stability, the uncontrolled copper ion releasing or leaching of incorporated copper material are also identified concerns. Thus, this article offers modification strategies that allow an effective copper incorporation on these polymeric membranes and solve these hinders. The article finishes with some claims about scaling up the implementation process, including long-term performance under real conditions, feasibility of production at large scale, and assessment of environmental impact.
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http://dx.doi.org/10.3390/membranes11020093DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7911616PMC
January 2021

Biodegradable photoresponsive nanoparticles for chemo-, photothermal- and photodynamic therapy of ovarian cancer.

Mater Sci Eng C Mater Biol Appl 2020 Nov 17;116:111196. Epub 2020 Jun 17.

Laboratorio de Inmunología, Departamento de Fisiología, Centro Universitario de Ciencias de la Salud (CUCS), Universidad de Guadalajara, Guadalajara 44340, Mexico. Electronic address:

Ovarian cancer (OC) is the deadliest gynecological cancer. Standard treatment of OC is based on cytoreductive surgery followed by chemotherapy with platinum drugs and taxanes; however, innate and acquired drug-resistance is frequently observed followed by a relapse after treatment, thus, more efficient therapeutic approaches are required. Combination therapies involving phototherapies and chemotherapy (the so-called chemophototherapy) may have enhanced efficacy against cancer, by attacking cancer cells through different mechanisms, including DNA-damage and thermally driven cell membrane and cytoskeleton damage. We have designed and synthesized poly(lactic-co-glycolic) nanoparticles (PLGA NPs) containing the chemo-drug carboplatin (CP), and the near infrared (NIR) photosensitizer indocyanine green (ICG). We have evaluated the drug release profile, the photodynamic ROS generation and photothermal capacities of the NPs. Also, the antitumoral efficiency of the NPs was evaluated using the SKOV-3 cell line as an in vitro OC model, observing an enhanced cytotoxic effect when irradiating cells with an 800 nm laser. Evidence here shown supports the potential application of the biodegradable photoresponsive NPs in the clinical stage due to the biocompatibility of the materials used, the spatiotemporal control of the therapy and, also, the less likely development of resistance against the combinatorial therapy.
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http://dx.doi.org/10.1016/j.msec.2020.111196DOI Listing
November 2020

Noble microfluidic system for bioceramic nanoparticles engineering.

Mater Sci Eng C Mater Biol Appl 2019 Sep 13;102:221-227. Epub 2019 Apr 13.

Soft Matter and Molecular Biophysics Group, Department of Applied Physics, University of Santiago de Compostela, 15782 Santiago de Compostela, Spain. Electronic address:

Bioceramic nanoparticles have many potential applications within the biomedical device industry. However, these applications demand a precise control of their sizes, shapes and morphology which play a main role in most properties. In this work, we report a new route for the synthesis of hydroxyapatite nanoparticles using a microfluidic device. The process is carried out by continuous laminar flow through the device. The obtained nanoparticles have showed same properties (composition, length, orientation, roughness) than those produced by conventional methods, however, our device can afford to fine tune the structure via simple engineering, i.e., produce nanoparticles of different size only by varying the flow velocity. In addition to the efficiency and novelty of this system, the optimization of personnel costs makes it very profitable economically.
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http://dx.doi.org/10.1016/j.msec.2019.04.037DOI Listing
September 2019

Easy, Quick, and Reproducible Sonochemical Synthesis of CuO Nanoparticles.

Materials (Basel) 2019 Mar 8;12(5). Epub 2019 Mar 8.

Programa Institucional de Fomento a la I+D+i, Universidad Tecnológica Metropolitana. Ignacio Valdivieso 2409, San Joaquín, Santiago 8940577, Chile.

Copper oxide nanoparticles (CuO NPs) were synthesized in air by reducing copper (II) sulfate pentahydrate salt (CuSO₄·5H₂O) in the presence of sodium borohydride. The reaction was stabilized with Hexadecyltrimethylammonium bromide (CTAB) in a basic medium and using ultrasound waves. Different molar ratios of CTAB:Cu and NaBH₄:Cu were explored, to optimize the synthesis conditions, and to study the stability, size, and Zeta potential of the colloidal suspension. Optimum conditions to generate spherical, stable, and monodispersed nanoparticles with hydrodynamic diameters of 36 ± 1.3 nm were obtained, using 16 mM CTAB and 2 M NaBH₄ (molar ratios Cu:CTAB:NaBH₄ of 1:6:10). X-ray diffraction (XRD) was implemented, and a monoclinic CuO crystal system was formed. This demonstrated a monoclinic crystal system corresponding to CuO. The diffraction peaks were identified and confirmed according to their selected area electron diffraction (SAED) patterns.
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http://dx.doi.org/10.3390/ma12050804DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6427414PMC
March 2019

Gold nanorods/siRNA complex administration for knockdown of PARP-1: a potential treatment for perinatal asphyxia.

Int J Nanomedicine 2018 25;13:6839-6854. Epub 2018 Oct 25.

Department of Pharmacological and Toxicology Chemistry, Facultad de Ciencias Químicas y Farmacéuticas, Universidad de Chile, Santiago, Chile,

Background: Perinatal asphyxia interferes with neonatal development, resulting in long-term deficits associated with systemic and neurological diseases. Despite the important role of poly (ADP-ribose) polymerase 1 (PARP-1) in the regulation of gene expression and DNA repair, overactivation of PARP-1 in asphyxia-exposed animals worsens the ATP-dependent energetic crisis. Inhibition of PARP-1 offers a therapeutic strategy for diminishing the effects of perinatal asphyxia.

Methods: We designed a nanosystem that incorporates a specific siRNA for PARP-1 knockdown. The siRNA was complexed with gold nanorods (AuNR) conjugated to the peptide CLPFFD for brain targeting.

Results: The siRNA was efficiently delivered into PC12 cells, resulting in gene silencing. The complex was administered intraperitoneally in vivo to asphyxia-exposed rat pups, and the ability of the AuNR-CLPFFD/siRNA complex to reach the brain was demonstrated.

Conclusion: The combination of a nanosystem for delivery and a specific siRNA for gene silencing resulted in effective inhibition of PARP-1 in vivo.
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http://dx.doi.org/10.2147/IJN.S175076DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6207385PMC
December 2018

Biopolymers: Relation of Structure to Function in Medicinal Chemistry.

Curr Top Med Chem 2018 ;18(14):1169-1170

Department of Applied Physics University of Santiago de Compostela Acorina, Spain.

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http://dx.doi.org/10.2174/156802661814180917104432DOI Listing
November 2018

Role of Biomacromolecules in Biomedical Engineering.

Curr Top Med Chem 2018 ;18(14):1171-1187

Programa Institucional de Fomento, Universidad Tecnologica Metropolitana. Ignacio Valdivieso 2409, San Joaquin, Santiago, Chile.

Biomacromolecules structures and their interaction between different systems have been extensively studied in the last years. Nevertheless, in the medicinal context, it has not been studied deeply. For this reason, the interest to investigate the behavior of different biomacromolecules such us proteins, organelles, phospholipids, etc. with soft materials has opened new research lines. Computational and experimental methodologies have tried to answer different questions that have been difficult to solve, due to the complexity of the phenomenon, as an example, competition between biomacromolecules and soft materials for a specific organ. In this review, we would like to demonstrate how soft materials influence the biomacromolecules structures and how to change their response, biodistribution and also biocompatibility for future applications.
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http://dx.doi.org/10.2174/1568026618666180816155917DOI Listing
November 2018

Peptide multifunctionalized gold nanorods decrease toxicity of β-amyloid peptide in a Caenorhabditis elegans model of Alzheimer's disease.

Nanomedicine 2017 Oct 30;13(7):2341-2350. Epub 2017 Jun 30.

Departamento de Química Farmacológica y Toxicológica, Facultad de Ciencias Químicas y Farmacéuticas, Universidad de Chile, Santiago; Advanced Center for Chronic Diseases (ACCDiS), Sergio Livingstone 1007, Independencia, Santiago, Chile. Electronic address:

The properties of nanometric materials make nanotechnology a promising platform for tackling problems of contemporary medicine. In this work, gold nanorods were synthetized and stabilized with polyethylene glycols and modified with two kinds of peptides. The D1 peptide that recognizes toxic aggregates of Aβ, a peptide involved in Alzheimer's disease (AD); and the Angiopep 2 that can be used to deliver nanorods to the mammalian central nervous system. The nanoconjugates were characterized using absorption spectrophotometry, dynamic light scattering, and transmission electron microscopy, among other techniques. We determined that the nanoconjugate does not affect neuronal viability; it penetrates the cells, and decreases aggregation of Aβ peptide in vitro. We also showed that when we apply our nanosystem to a Caenorhabditis elegans AD model, the toxicity of aggregated Aβ peptide is decreased. This work may contribute to the development of therapies for AD based on metallic nanoparticles.
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http://dx.doi.org/10.1016/j.nano.2017.06.013DOI Listing
October 2017

Gastric Cancer: Nanoparticles as Tools to Improve Treatment Efficacy.

Curr Pharm Des 2016 ;22(39):5988-5997

Facultad de Ciencias Químicas y Farmacéuticas, Universidad de Chile. Santos Dumont 964, Independencia, Santiago, Chile.

In recent years, advances in nanotechnology have raised the specter of developing effective agents for the treatment of high-impact diseases, like gastric cancer, which remains one of the major causes of cancer deaths worldwide. This article reviews advances in the treatment of this pathology using several types of nanoparticles. First, we start with an overview of gastric cancer, its prevention, detection and the available treatments. Then, we discuss nanotechnology-based novel strategies using polymeric nanosystems, nanovesicular systems and inorganic nanoparticles. All of these systems are being evaluated in the perspective of improving the targeting of anticancer drugs and reducing their negative side effects.
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http://dx.doi.org/10.2174/1381612822666160712165409DOI Listing
December 2017

Complex Behavior of Aqueous α-Cyclodextrin Solutions. Interfacial Morphologies Resulting from Bulk Aggregation.

Langmuir 2016 07 23;32(26):6682-90. Epub 2016 Jun 23.

Laboratorio de Biofisicoquímica, Departamento de Fisicoquímica, Facultad de Química, Universidad Nacional Autónoma de México , México D. F. 04510, Mexico.

The spontaneous aggregation of α-cyclodextrin (α-CD) molecules in the bulk aqueous solution and the interactions of the resulting aggregates at the liquid/air interface have been studied at 283 K using a battery of techniques: transmission electron microscopy, dynamic light scattering, dynamic surface tensiometry, Brewster angle microscopy, neutron reflectometry, and ellipsometry. We show that α-CD molecules spontaneously form aggregates in the bulk that grow in size with time. These aggregates adsorb to the liquid/air interface with their size in the bulk determining the adsorption rate. The material that reaches the interface coalesces laterally to form two-dimensional domains on the micrometer scale with a layer thickness on the nanometer scale. These processes are affected by the ages of both the bulk and the interface. The interfacial layer formed is not in fast dynamic equilibrium with the subphase as the resulting morphology is locked in a kinetically trapped state. These results reveal a surprising complexity of the parallel physical processes taking place in the bulk and at the interface of what might have seemed initially like a simple system.
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http://dx.doi.org/10.1021/acs.langmuir.6b01646DOI Listing
July 2016

Gold nanoparticles for photothermally controlled drug release.

Nanomedicine (Lond) 2014 Sep;9(13):2023-39

Departamento de Química Farmacológica y Toxicológica, Facultad de Ciencias Químicas y Farmacéuticas, Universidad de Chile. Santos Dumont 964, Independencia, Santiago, Chile.

In this article, we describe how nanoparticles work in photothermally triggered drug delivery, starting with a description of the plasmon resonance and the photothermal effect, and how this is used to release a drug. Then, we describe the four major functionalization strategies and each of their different applications. Finally, we discuss the biodistribution and toxicity of these systems and the necessary requirements for the use of gold nanoparticles for spatially and temporally controlling drug release through the photothermal effect.
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http://dx.doi.org/10.2217/nnm.14.126DOI Listing
September 2014

Flow chemistry to control the synthesis of nano and microparticles for biomedical applications.

Curr Top Med Chem 2014 Mar;14(5):676-89

UPMC Université Paris 6: Pierre et Marie Curie (UPMC), Laboratoire de Physico-Chimie des Electrolytes Colloïdes et Sciences Analytiques (PECSA), 4 place Jussieu, 75005, Paris-France.

In this article we review the flow chemistry methodologies for the controlled synthesis of different kind of nano and microparticles for biomedical applications. Injection mechanism has emerged as new alternative for the synthesis of nanoparticles due to this strategy allows achieving superior levels of control of self-assemblies, leading to higher-ordered structures and rapid chemical reactions. Self-assembly events are strongly dependent on factors such as the local concentration of reagents, the mixing rates, and the shear forces, which can be finely tuned, as an example, in a microfluidic device. Injection methods have also proved to be optimal to elaborate microsystems comprising polymer solutions. Concretely, extrusion based methods can provide controlled fluid transport, rapid chemical reactions, and cost-saving advantages over conventional reactors. We provide an update of synthesis of nano and microparticles such as core/shell, Janus, nanocrystals, liposomes, and biopolymeric microgels through flow chemistry, its potential bioapplications and future challenges in this field are discussed.
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http://dx.doi.org/10.2174/1568026614666140118213915DOI Listing
March 2014

Enhancing CaP biomimetic growth on TiO2 cuboids nanoparticles via highly reactive facets.

Langmuir 2013 Feb 6;29(7):2350-8. Epub 2013 Feb 6.

Department of Applied Physics, University of Santiago de Compostela, Santiago de Compostela, Spain.

Pure decahedral anatase TiO(2) particles with high content of reactive {001} facets were obtained from titanium(IV) tetrachloride (TiCl(4)) using a microemulsions droplet system at specific conditions as chemical microreactor. The product was systematically characterized by X-ray diffraction, field-emission scanning and transmission electron microscopy (FE-SEM, TEM), N(2) adsorption-desorption isotherms, FT-IR and UV-vis spectroscopy, and photoluminescence studies. The obtained cuboids around 90 nm in size have a uniform and dense surface morphology with a BET specific surface area of 11.91 m(2) g(-1) and a band gap energy (3.18 eV) slightly inferior to the anatase dominated by the less-reactive {101} surface (3.20 eV). The presence of reactive facets on titania anatase favors the biomimetic growth of amorphous tricalcium phosphate after the first day of immersion in simulated human plasma. The results presented here can facilitate and improve the integration of anchored implants and enhance the biological responses to the soft tissues.
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http://dx.doi.org/10.1021/la305080xDOI Listing
February 2013

Continuous multistep microfluidic assisted assembly of fluorescent, plasmonic, and magnetic nanostructures.

Angew Chem Int Ed Engl 2013 Feb 14;52(7):1994-7. Epub 2013 Jan 14.

UPMC Université Paris 6, Laboratoire de Physicochimie des Electrolytes Colloïdes et Sciences Analytiques, UMR 7195, équipe Colloïdes Inorganiques, Université Paris 6 (UPMC) Bat F(74), case 51, 4 place Jussieu, 75252 Paris Cedex 05, France.

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http://dx.doi.org/10.1002/anie.201208324DOI Listing
February 2013

Assembling magneto-plasmonic microcapsules using a microfluidic device.

Chem Commun (Camb) 2013 Jan 27;49(4):412-4. Epub 2012 Nov 27.

UPMC Univ. Paris 6, Laboratoire de Physicochemie des Electrolytes Colloïdes et Sciences Analytiques (PECSA), UMR 7195, équipe Colloïdes Inorganiques Université Paris 6 (UPMC) Bat F(74), case 51, 4 place Jussieu, F-75252 Paris Cedex 05, France.

Magneto-plasmonic microcapsules were prepared by the assembly of gold and γ-Fe(2)O(3) magnetic nanoparticles at the oil-water interface of microdroplets generated in a microfluidic device.
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http://dx.doi.org/10.1039/c2cc37666kDOI Listing
January 2013

Hydrogenated/fluorinated catanionic surfactants as potential templates for nanostructure design.

Langmuir 2011 Aug 20;27(16):9719-28. Epub 2011 Jul 20.

Soft Matter and Molecular Biophysics Group, Department of Applied Physics, University of Santiago de Compostela, Campus Vida s/n, 15782, Santiago de Compostela, Spain.

The structure and physicochemical properties of the nanoparticles spontaneously formed within aqueous mixtures of the hydrogenated/fluorinated catanionic surfactant cetyltrimetylammonium perfluorooctanoate in the absence of counterions as a function of its concentration are investigated by a combined experimental/computational study at room temperature. Apparent molar volumes, isentropic apparent molar compressibilities, and dynamic light scattering measurements together with transmission and cryo-scanning electron as well as confocal laser microscopy images, and computational molecular dynamics simulations indicate that a variety of structures of different sizes coexist in solution with vesicles of ∼160 nm diameter. Interestingly, the obtained nanostructures were observed to self-assemble from a random distribution of monomers in a time scale easily accessible by atomistic classical molecular dynamics simulations, allowing to provide a comprehensive structural and dynamic characterization of the surfactant molecules at atomic level within the different aggregates. Overall, it is demonstrated that the use of mixed fluorinated hydrogenated surfactant systems represents an easy strategy for the design of specific nanoscale structures. The detailed structural analysis provided in the present work is expected to be useful as a reference to guide the design of new nanoparticles based on different hydrogenated/fluorinated catanionic surfactants.
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http://dx.doi.org/10.1021/la2019346DOI Listing
August 2011

Investigating the effect of an arterial hypertension drug on the structural properties of plasma protein.

Colloids Surf B Biointerfaces 2011 Oct 16;87(2):489-97. Epub 2011 Jun 16.

Department of Applied Physics University of Santiago de Compostela, Santiago de Compostela, Spain.

Propanolol is a betablocker drug used in the treatment of arterial hypertension related diseases. In order to achieve an optimal performance of this drug it is important to consider the possible interactions of propanolol with plasma proteins. In this work, we have used several experimental techniques to characterise the effect of addition of the betablocker propanolol on the properties of bovine plasma fibrinogen (FB). Differential scanning calorimeter (DSC), circular dichroism (CD), dynamic light scattering (DLS), surface tension techniques and atomic force microscopy (AFM) measurements have been combined to carry out a detailed physicochemical and surface characterization of the mixed system. As a result, DSC measurements show that propranolol can play two opposite roles, either acting as a structure stabilizer at low molar concentrations or as a structure destabilizer at higher concentrations, in different domains of fibrinogen. CD measurements have revealed that the effect of propanolol on the secondary structure of fibrinogen depends on the temperature and the drug concentration and the DLS analysis showed evidence for protein aggregation. Interestingly, surface tension measurements provided further evidence of the conformational change induced by propanolol on the secondary structure of FB by importantly increasing the surface tension of the system. Finally, AFM imaging of the fibrinogen system provided direct visualization of the protein structure in the presence of propanolol. Combination of these techniques has produced complementary information on the behavior of the mixed system, providing new insights into the structural properties of proteins with potential medical interest.
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http://dx.doi.org/10.1016/j.colsurfb.2011.06.015DOI Listing
October 2011

Fibrinogen stability under surfactant interaction.

J Colloid Interface Sci 2011 Oct 15;362(1):118-26. Epub 2011 Jun 15.

Soft Matter and Molecular Biophysics Group, Department of Applied Physics, University of Santiago de Compostela, Campus Vida s/n, 15782 Santiago de Compostela, Spain.

Differential scanning calorimetry (DSC), circular dichroism (CD), difference spectroscopy (UV-vis), Raman spectroscopy, and small-angle X-ray scattering (SAXS) measurements have been performed in the present work to provide a quantitatively comprehensive physicochemical description of the complexation between bovine fibrinogen and the sodium perfluorooctanoate, sodium octanoate, and sodium dodecanoate in glycine buffer (pH 8.5). It has been found that sodium octanoate and dodecanoate act as fibrinogen destabilizer. Meanwhile, sodium perfluorooctanoate acts as a structure stabilizer at low molar concentration and as a destabilizer at high molar concentration. Fibrinogen's secondary structure is affected by all three studied surfactants (decrease in α-helix and an increase in β-sheet content) to a different extent. DSC and UV-vis revealed the existence of intermediate states in the thermal unfolding process of fibrinogen. In addition, SAXS data analysis showed that pure fibrinogen adopts a paired-dimer structure in solution. Such a structure is unaltered by sodium octanoate and perfluoroctanoate. However, interaction of sodium dodecanoate with the fibrinogen affects the protein conformation leading to a complex formation. Taken together, all results evidence that both surfactant hydrophobicity and tail length mediate the fibrinogen stability upon interaction.
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http://dx.doi.org/10.1016/j.jcis.2011.06.010DOI Listing
October 2011

Mimicking natural fibrous structures of opals by means of a microemulsion-mediated hydrothermal method.

Langmuir 2011 Jul 14;27(14):8905-12. Epub 2011 Jun 14.

INQUISUR-CONICET, Department of Chemistry, Universidad Nacional del Sur, Bahía Blanca, Argentina.

Silica-based nanomaterials are of great interest because of their potential applications in constructing electronic and optoelectronic nanodevices. Especially significant are those that combine the properties of photonic crystal with a fibrous semiconductor structure. Here we report the use of microemulsion droplet systems as a simple and controllable route for the synthesis of 3D opals materials with an unusual fibrous microstructure similar to those that exist in nature. By this method, we demonstrate the creation of very long fibrils of 30-50 nm diameter and more than 20 μm length showing simultaneous short and long wavelength light emissions and band gap values (5.50 and 4.41 eV) comparable to those obtained for silicon-based metal oxide semiconductors.
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http://dx.doi.org/10.1021/la201555fDOI Listing
July 2011

Surface characterization and AFM imaging of mixed fibrinogen-surfactant films.

J Phys Chem B 2011 May 14;115(19):6304-11. Epub 2011 Apr 14.

Soft Matter and Molecular Biophysics Group, Department of Applied Physics University of Santiago de Compostela, Campus Sur s/n, 15782, Santiago de Compostela, Spain.

This study describes the adsorption behavior of mixed protein/surfactant systems at the air-water interface: specifically fibrinogen and the fluorinated and hydrogenated surfactants (C(8)FONa, C(8)HONa, and C(12)HONa). Surface tension techniques and atomic force microscopy (AFM) have been combined to investigate the adsorption behavior of these mixed systems. Interfacial rheology showed that fibrinogen has a low dilatational modulus at the air-water interface when compared to other proteins, suggesting the formation of a weak surface network. Fluorinated and hydrogenated surfactants severely decreased the dilatational modulus of the adsorbed fibrinogen film at the air-water interface. These measurements suggest the progressive displacement of fibrinogen from the air-water interface by both types of surfactants. However, in the case of fibrinogen/fluorinated surfactant systems, surface tension and dilatational rheology measurements suggest the formation of complexes with improved surface activity. AFM imaging of fibrinogen in the presence and absence of surfactants provided new information on the structure of mixed surface films, and revealed new features of the interaction of fibrinogen with hydrogenated and fluorinated surfactants. These studies suggest complexes formed between fibrinogen and fluorinated surfactants which are more surface active than fibrinogen, while the absence of interaction between fibrinogen and hydrogenated surfactants (C(8)HONa and C(12)HONa) results in compaction of the surface layer.
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http://dx.doi.org/10.1021/jp200835jDOI Listing
May 2011

Rheological properties of ovalbumin hydrogels as affected by surfactants addition.

Int J Biol Macromol 2011 Apr 22;48(3):495-500. Epub 2011 Jan 22.

Soft Matter and Molecular Biophysics Group, Department of Applied Physics, University of Santiago de Compostela, E-15782, Spain.

The gel properties of ovalbumin mixtures with three different surfactants (sodium perfluorooctanoate, sodium octanoate and sodium dodecanoate) have been studied by rheological techniques. The gel elasticities were determined as a function of surfactant concentration and surfactant type. The fractal dimension of the formed structures was evaluated from plots of storage modulus against surfactant concentration. The role of electrostatic, hydrophobic and disulfide SS interactions in these systems has been demonstrated to be the predominant. The viscosity of these structures tends to increase with surfactant concentration, except for the fluorinated one. Unfolded ovalbumin molecules tend to form fibrillar structures that tend to increase with surfactant concentration, except for the fluorinated one. This fact has been related to the particular nature of this molecule.
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http://dx.doi.org/10.1016/j.ijbiomac.2011.01.015DOI Listing
April 2011

Mechanisms of fibrinogen-acebutolol interactions: Insights from DSC, CD and LS.

Colloids Surf B Biointerfaces 2011 Feb 15;82(2):581-7. Epub 2010 Oct 15.

Soft Matter and Molecular Biophysics Group, Department of Applied Physics University of Santiago de Compostela, Campus Vida s/n, 15782, Santiago de Compostela, Spain.

The complex formed due to the interaction of the amphiphilic betablocker acebutolol with fibrinogen in a buffer solution (50mN glycine, pH of 8.5) has been investigated using a multipronged physicochemical approach. Differential scanning calorimetry measurements of the complexes have shown no reversibility of thermal denaturation as indicated by the three observed peaks and the opposite role that acebutolol plays in the folding different domains of the fibrinogen molecule and the stability of such domains. While circular dichroism measurements have revealed that interaction of acebutolol with fibrinogen affects the protein secondary structure to a different extent depending on the temperature and drug concentration, dynamic light scattering analysis showed evidence for protein aggregation mainly to tetramers and dimers.
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http://dx.doi.org/10.1016/j.colsurfb.2010.10.020DOI Listing
February 2011

On the self-assembly of a highly selective benzothiazole-based TIM inhibitor in aqueous solution.

Langmuir 2010 Nov 15;26(22):16681-9. Epub 2010 Oct 15.

Soft Matter and Molecular Biophysics Group, Department of Applied Physics, University of Santiago de Compostela, Campus Vida s/n, 15782, Santiago de Compostela, Spain.

Benzothiazole is a common scaffold on which many bioactive structures, including protein inhibitors and biosensors, are based. The potential self-aggregation of such molecules to form nanoparticles is relevant for a number of practical applications. 3-(2-Benzothiazolylthio)-propanesulfonic acid (BTS) has been reported as a powerful and selective inhibitor of triosephosphate isomerase from Trypanosoma cruzi, the parasite that causes the Chagas' disease. Electrical conductivity, sound velocity, density, and nuclear magnetic resonance experiments as a function of temperature and of NaCl concentration have been performed in the present work to provide a comprehensive physicochemical description of this compound in aqueous solution. Molecular dynamics simulations of the same system were also performed to characterize the structure and dynamic behavior of the corresponding aggregates at several concentrations of BTS.
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http://dx.doi.org/10.1021/la102916xDOI Listing
November 2010