ORCID Profile
0000-0001-6372-723X
Current Organisations
University of South Australia
,
University of Granada
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Publisher: Elsevier BV
Date: 11-2013
DOI: 10.1016/J.COLSURFB.2013.05.029
Abstract: In this work, we provide an accurate characterization of non-ionic triblock copolymer Pluronic PE9400 at the air-water and limonene-water interfaces, comprising a systematic analysis of surface tension isotherms, dynamic curves, dilatational rheology and desorption profiles. The surface pressure isotherms display two different slopes of the Π-c plot suggesting the existence of two adsorption regimes for PE9400 at both interfaces. Application of a theoretical model, which assumes the coexistence of different adsorbed states characterized by their molar areas, allows quantification of the conformational changes occurring at the adsorbed layer, indentifying differences between the conformations adopted at the air-water and the limonene-water interface. The presence of two maxima in the dilatational modulus vs. interfacial pressure importantly corroborates this conformational change from a 2D flat conformation to 3D brush one. Moreover, the dilatational response provides mechanical diferences between the interfacial layers formed at the two interfaces analyzed. Dynamic surface pressure data were transformed into a dimensionless form and fitted to another model which considers the influence of the reorganization process on the adsorption dynamics. Finally, the desorption profiles reveal that Pluronic PE9400 is irreversibly adsorbed at both interfaces regardless of the interfacial conformation and nature of the interface. The systematic characterization presented in this work provides important new findings on the interfacial properties of pluronics which can be applied in the rational development of new products, such as biocompatible limonene-based emulsions and/or microemulsions.
Publisher: Elsevier BV
Date: 04-2021
Publisher: Royal Society of Chemistry (RSC)
Date: 2014
DOI: 10.1039/C3SM52428K
Abstract: Complexation of DNA with lipids is currently being developed as an alternative to classical vectors based on viruses. Most of the research to date focuses on cationic lipids owing to their spontaneous complexation with DNA. Nonetheless, recent investigations have revealed that cationic lipids induce a large number of adverse effects on DNA delivery. Precisely, the lower cytotoxicity of anionic lipids accounts for their use as a promising alternative. However, the complexation of DNA with anionic lipids (mediated by cations) is still in early stages and is not yet well understood. In order to explore the molecular mechanisms underlying the complexation of anionic lipids and DNA we proposed a combined methodology based on the surface pressure-area isotherms, Gibbs elasticity and Atomic Force Microscopy (AFM). These techniques allow elucidation of the role of the surface pressure in the complexation and visualization of the interfacial aggregates for the first time. We demonstrate that the DNA complexes with negatively charged model monolayers (DPPC/DPPS 4 : 1) only in the presence of Ca(2+), but is expelled at very high surface pressures. Also, according to the Gibbs elasticity plot, the complexation of lipids and DNA implies a whole fluidisation of the monolayer and a completely different phase transition map in the presence of DNA and Ca(2+). AFM imaging allows identification for the first time of specific morphologies associated with different packing densities. At low surface coverage, a branched net like structure is observed whereas at high surface pressure fibers formed of interfacial aggregates appear. In summary, Ca(2+) mediates the interaction between DNA and negatively charged lipids and also the conformation of the ternary system depends on the surface pressure. Such observations are important new generic features of the interaction between DNA and anionic lipids.
Publisher: Elsevier BV
Date: 09-2022
DOI: 10.1016/J.COLSURFB.2022.112636
Abstract: Studying interactions between potential anticancer drugs and cell membrane models is of great interest to explore the capability of novel drugs in the development of anticancer treatments. Lipid membrane models are useful to understand cellular interactions and to discern drug mechanism action. Here, the interactions of curcumin, as a bioactive natural compound with anti-cancer properties, with both healthy and cancerous or tumor cell membrane models, based on Langmuir monolayers, have been studied. The healthy-cell membrane model is composed of cholesterol 67%, and saturated lipid dipalmitoylphosphatidylcholine 33%. The cancerous-cell-membrane-model is composed of a lower proportion of cholesterol, 25%, and unsaturated lipid sphingomyelin 75%. To compare their interaction with curcumin we report the compression isotherms registered for both lipid membrane models and curcumin in different proportions, their compression moduli and the thermodynamic interaction parameters. From this analysis, we evidence a destabilizing interaction between curcumin and the cancerous cell membrane model in comparison with the healthy one. This interaction is further visualized by micro-Brewster Angle and Atomic Force Microscopies. Our experiments show that the drug enhances cohesion in the healthy membrane model whereas it fluidifies the cancerous cell membrane model causing thermodynamic destabilization. These are useful results to improve the selectivity of the drug avoiding adverse side effects of most current anticancer therapies.
Publisher: American Chemical Society (ACS)
Date: 14-04-2011
DOI: 10.1021/JP200835J
Abstract: 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.
Publisher: American Chemical Society (ACS)
Date: 07-03-2008
DOI: 10.1021/JP7112686
Abstract: This research work aims to investigate the behavior of a mixed system composed of a commercial protein (whole casein) and a low molecular weight surfactant (Tween 20) in order to understand its foam stability on the basis of fundamental surface quantities such as surface and disjoining pressure. These experiments prove to be extremely useful in the understanding of the processes determining foam stability. The complex behavior of whole casein/Tween 20 mixtures is directly deduced from the surface pressure isotherms. Concretely, the isotherm of the mixed system is displaced to smaller surfactant concentrations as compared to the pure surfactant system. This feature is quantified by a critical aggregation concentration and suggests formation of protein/surfactant complexes within the surface layer. The disjoining pressure isotherms of the pure and mixed systems provide key information regarding the structure and composition of the mixed whole casein/Tween 20 surface layers. Furthermore, they provide a direct correlation with the foam stability in terms of the thickness of the final foam film the thinner the film, the less stable the foam. The experimental results are further discussed in terms of literature studies of similar systems, and a final rather accurate description of the system arises. This work investigates the importance of the nature of the protein in the stability of the foams of protein/surfactant mixtures and highlights the fundamental role of the surface properties in the understanding of such a major phenomenon in colloid science and technology.
Publisher: American Chemical Society (ACS)
Date: 21-09-2010
DOI: 10.1021/LA102294U
Abstract: Understanding the effects of digestion conditions on the structure of interfacial protein networks is important in order to rationally design food emulsions which can moderate lipid digestion. This study compares the effect of gastric conditions (pH, temperature, and ionic strength) on β-lactoglobulin films at different fluid interfaces: air-water, tetradecane-water, and olive oil-water. The experiments have been designed to simulate the passage into the stomach media. Hence, preformed interfacial protein (β-lactoglobulin) networks have been exposed to gastric conditions in order to establish generic aspects of the digestion process. The results show that the presence of an oil phase affects both the unfolding of the protein at the interface on adsorption and the subsequent interprotein associations responsible for network formation at the interface. Furthermore, the effects of the physiological conditions characteristic of the stomach also altered differently the preformed protein layer at different fluid interfaces. Initially, the effects of temperature, acid pH, and ionic strength on the dilatational modulus of β-lactoglobulin adsorbed layers at tetradecane-water and olive oil-water interfaces were studied in isolation. The presence of salt was found to have a major effect on the dilatational response at the oil-water interface in contrast to the observations at the air-water interface: it enhanced intermolecular association, hence increasing the packing at the interface causing it to become more elastic. Exposure to acid pH (2.5) also increased the elasticity of the interface, possibly due to the fact that strong electrostatic interactions acting at the interface compensated for the reduced level of intermolecular association. However, the increase in dilatational modulus at the oil-water interface was less noticeable upon exposure to combined changes in acid pH and ionic strength, as would occur in the stomach. This is consistent with previously reported observations at the air-water interface. The quantitative differences in the response of the protein networks to gastric media at different fluid interfaces are discussed in terms of the conformation of β-lactoglobulin within the networks formed at each interface based on detailed theoretical modeling of adsorption data.
Publisher: Elsevier BV
Date: 10-2023
Publisher: Elsevier BV
Date: 06-2019
DOI: 10.1016/J.COLSURFB.2019.02.058
Abstract: Anionic lipids are increasingly being used in lipoplexes for synthetic gene vectors as an alternative to cationic lipids. This is primarily due to their lower toxicity, which makes them biocompatible and adaptable to be tissue specific. However, anionic lipoplexes require the presence of multivalent cations to promote the electrostatic attraction between DNA and anionic lipid mono- and bilayers. In this work we provide for the first time experimental results of the adsorption of linear DNA onto anionic/zwitterionic lipid monolayers without any addition of cations. This is demonstrated experimentally by means of Langmuir monolayers of DOPE/DOPG (1:1) lipids spread on a water subphase that contains calf thymus DNA. The adsorption of DNA onto anionic/zwitterionic lipid monolayers is discussed in terms of the surface pressure-molecular area isotherms recorded in the absence and in the presence of different electrolytes. Measurements of the surface potential provide additional evidence of the different interaction of DNA anionic/zwitterionic lipid monolayers depending on the presence and nature of electrolyte. These experimental results are further analysed in terms of the overall dipole moment normal to the monolayers providing new insight into the behaviour of anionic lipoplexes and the role of zwitterionic lipids.
Publisher: Elsevier BV
Date: 07-2022
DOI: 10.1016/J.FOODCHEM.2022.132330
Abstract: Liquid lipid nanocapsules are oil droplets surrounded by a protective shell, which enable high load and allow controlled delivery of lipophilic compounds. However, their use in food formulations requires analysing their digestibility and interaction with mucin. Here, serum albumins and hyaluronic acid shelled olive oil nanocapsules are analysed to discern differences between human and bovine variants, the latter usually used as model system. Interfacial interaction of albumins and hyaluronic acid reveals that human albumin presents limited conformational changes upon adsorption, which increase by complexation with the polysaccharide present at the interface. The latter also promotes hydrophobic interactions with mucin, especially at pH 3 and protects albumin interfacial layer under in vitro gastric digestion. The interfacial unfolding induced in human albumin by hyaluronic acid facilitates in vitro lipolysis while its limited conformational changes provide the largest protection against in vitro lipolysis.
Publisher: MDPI AG
Date: 30-10-2020
DOI: 10.3390/PHARMACEUTICS12111039
Abstract: The use of foams to deliver bioactive agents and drugs is increasing in pharmaceutics. One ex le is the use of foam as a delivery system for polidocanol (POL) in sclerotherapy, with the addition of bioactive compounds to improve the delivery system being a current subject of study. This work shows the influence of two bioactive additives on the structure and stability of POL foam: hyaluronic acid (HA) and Pluronic-F68 (F68). HA is a natural non-surface-active biopolymer present in the extracellular matrix while F68 is a surface-active poloxamer that is biocompatible with plasma-derived fluids. Both additives increase the bulk viscosity of the s le, improving foam stability. However, HA doubled and F68 quadruplicated the foam half lifetime of POL. HA reduced the size and polydispersity of the bubble size distribution and increased the surface elasticity with respect to POL. Both facts have a positive impact in terms of foam stability. F68 also altered bubble structure and increased surface elasticity, again contributing to the enhancement of foam stability. The surface characterization of these systems is important, as in foam sclerotherapy it is crucial to assure the presence of POL at the surface of the bubbles in order to deliver the sclerosant agent in the target vein.
Publisher: Elsevier BV
Date: 07-2021
Publisher: Royal Society of Chemistry (RSC)
Date: 2012
DOI: 10.1039/C2SM07317J
Publisher: Elsevier BV
Date: 04-2018
DOI: 10.1016/J.FOODCHEM.2017.10.149
Abstract: AS-48 is a bacteriocin with potential application as food biopreservative. In order to optimize its use for oral consumption, we assess the impact of gastrointestinal digestion, both in bulk and adsorbed at the air-water interface. Analysis of AS-48 digestion fragments in bulk by SDS-PAGE, RP-HPLC, and MALDI-TOF proves that the previous pepsin exposition promotes digestion by trypsin/chymotrypsin by exposing new cleavage sites. Regarding adsorbed AS-48, the in vitro digestion profile shows that the conformational change undergone by AS-48 upon adsorption affects its digestibility. Gastrointestinal enzymes cleave only susceptible residues, which are oriented into the aqueous phase, while hydrophobic susceptible residues remain undigested. Evaluation of the elasticity of the adsorbed layer confirms also the presence of undigested AS-48. These results are important towards the use of AS-48 in food formulations assuring that some intact AS-48 resists digestion guarantees its antibacterial activity throughout the gastrointestinal tract.
Publisher: Royal Society of Chemistry (RSC)
Date: 2017
DOI: 10.1039/C6SM01375A
Abstract: Poly( N -vinylcaprolactam) (PVCL) is a new temperature-responsive type of polymer microgel with improved biocompatibility as compared to more commonly used poly( N -isopropylacrylamide) (PNIPAM).
Publisher: MDPI AG
Date: 05-05-2016
DOI: 10.3390/MA9050340
Publisher: Springer Science and Business Media LLC
Date: 08-03-2009
DOI: 10.1140/EPJE/I2008-10426-0
Abstract: Understanding and manipulating the interfacial mechanisms that control human digestion of food emulsions is a crucial step towards improved control of dietary intake. This article reports initial studies on the effects of the physiological conditions within the stomach on the properties of the film formed by the milk protein (β-lactoglobulin) at the air-water interface. Atomic force microscopy (AFM), surface tension and surface rheology techniques were used to visualize and examine the effect of gastric conditions on the network structure. The effects of changes in temperature, pH and ionic strength on a preformed interfacial structure were characterized in order to simulate the actual digestion process. Changes in ionic strength had little effect on the surface properties. In isolation, acidification reduced both the dilatational and the surface shear modulus, mainly due to strong repulsive electrostatic interactions within the surface layer and raising the temperature to body temperature accelerated the rearrangements within the surface layer, resulting in a decrease of the dilatational response and an increase of surface pressure. Together pH and temperature display an unexpected synergism, independent of the ionic strength. Thus, exposure of a pre-formed interfacial β-lactoglobulin film to simulated gastric conditions reduced the surface dilatational modulus and surface shear moduli. This is attributed to a weakening of the surface network in which the surface rearrangements of the protein prior to exposure to gastric conditions might play a crucial role.
Publisher: Elsevier BV
Date: 04-2020
Publisher: Royal Society of Chemistry (RSC)
Date: 2010
DOI: 10.1039/C0SM00300J
Publisher: MyJove Corporation
Date: 18-11-2022
DOI: 10.3791/64158
Publisher: Elsevier BV
Date: 02-2019
Publisher: American Chemical Society (ACS)
Date: 07-07-2010
DOI: 10.1021/LA101632V
Abstract: Force-distance data obtained from an atomic force microscope have been used to follow the in situ displacement of beta-lactoglobulin from tetradecane droplets by Tween 20 (polyoxyethylenesorbitan monolaurate). Interpretation of the force-distance curves has shown that the slope of the region, traditionally termed the constant compliance region, is a useful indicator of droplet deformation within a given experiment. The magnitude of this slope can be used to monitor how the deformability of the droplet changes upon addition of surfactant. It has been found that, immediately after initial addition of surfactant, there is an increase in magnitude of this slope, indicating a stiffening of the droplet, attributed to a stiffening of the protein network formed at the surface of the droplet. Subsequent additions of Tween 20 reduce the magnitude of the slope until an equilibrium value is reached, where the interface becomes surfactant-dominated. These observations suggest that it is possible to monitor in situ the displacement of protein from in idual oil droplets. The data have been interpreted in terms of the "orogenic" model of displacement, which is based on studies made on model interfaces. These data have been compared to those obtained using the more traditional techniques of dilatational rheology, surface loading, and surface potential measurements for analogous beta-lactoglobulin-stabilized droplets or emulsions.
Publisher: Elsevier BV
Date: 08-2021
Publisher: MDPI AG
Date: 17-03-2022
DOI: 10.3390/GELS8030184
Abstract: Micro- and nanogels are being increasingly used to encapsulate bioactive compounds. Their soft structure allows large loading capacity while their stimuli responsiveness makes them extremely versatile. In this work, the complexation of DNA with thermoresponsive microgels is presented. To this end, PEGylated charged microgels based on poly-N-isopropylacrylamide have been synthesized, allowing one to explore the electrostatics of the complexation. Cationic microgels complexate spontaneously by electrostatic attraction to oppositely charged DNA as demonstrated by electrophoretic mobility of the complexes. Then, Langmuir monolayers reveal an increased interaction of DNA with swollen microgels (20 °C). Anionic microgels require the presence of multivalent cations (Ca2+) to promote the complexation, overcoming the electrostatic repulsion with negatively charged DNA. Then again, Langmuir monolayers evidence their complexation at the surface. However, the presence of Ca2+ seems to induce profound changes in the interaction and surface conformation of anionic microgels. These alterations are further explored by measuring adsorbed films with the pendant drop technique. Conformational changes induced by Ca2+ on the structure of the microgel can ultimately affect the complexation with DNA and should be considered in the design. The combination of microstructural and surface properties for microgels offers a new perspective into complexation of DNA with soft particles with biomedical applications.
Publisher: American Chemical Society (ACS)
Date: 09-2003
DOI: 10.1021/LA034242Z
Publisher: American Chemical Society (ACS)
Date: 05-06-2008
DOI: 10.1021/LA800551U
Abstract: The competitive displacement of a model protein (beta-lactoglobulin) by bile salts from air-water and oil-water interfaces is investigated in vitro under model duodenal digestion conditions. The aim is to understand this process so that interfaces can be designed to control lipid digestion thus improving the nutritional impact of foods. Duodenal digestion has been simulated using a simplified biological system and the protein displacement process monitored by interfacial measurements and atomic force microscopy (AFM). First, the properties of beta-lactoglobulin adsorbed layers at the air-water and the olive oil-water interfaces were analyzed by interfacial tension techniques under physiological conditions (pH 7, 0.15 M NaCl, 10 mM CaCl2, 37 degrees C). The protein film had a lower dilatational modulus (hence formed a weaker network) at the olive oil-water interface compared to the air-water interface. Addition of bile salt (BS) severely decreased the dilatational modulus of the adsorbed beta-lactoglobulin film at both the air-water and olive oil-water interfaces. The data suggest that the bile salts penetrate into, weaken, and break up the interfacial beta-lactoglobulin networks. AFM images of the displacement of spread beta-lactoglobulin at the air-water and the olive oil-water interfaces suggest that displacement occurs via an orogenic mechanism and that the bile salts can almost completely displace the intact protein network under duodenal conditions. Although the bile salts are ionic, the ionic strength is sufficiently high to screen the charge allowing surfactant domain nucleation and growth to occur resulting in displacement. The morphology of the protein networks during displacement is different from those found when conventional surfactants were used, suggesting that the molecular structure of the surfactant is important for the displacement process. The studies also suggest that the nature of the oil phase is important in controlling protein unfolding and interaction at the interface. This in turn affects the strength of the protein network and the ability to resist displacement by surfactants.
Publisher: Elsevier BV
Date: 04-2005
Publisher: Elsevier BV
Date: 04-2014
DOI: 10.1016/J.CIS.2013.11.005
Abstract: Currently self-assembled DNA delivery systems composed of DNA multivalent cations and anionic lipids are considered to be promising tools for gene therapy. These systems become an alternative to traditional cationic lipid-DNA complexes because of their low cytotoxicity lipids. However, currently these nonviral gene delivery methods exhibit low transfection efficiencies. This feature is in large part due to the poorly understood DNA complexation mechanisms at the molecular level. It is well-known that the adsorption of DNA onto like charged lipid surfaces requires the presence of multivalent cations that act as bridges between DNA and anionic lipids. Unfortunately, the molecular mechanisms behind such adsorption phenomenon still remain unclear. Accordingly a historical background of experimental evidence related to adsorption and complexation of DNA onto anionic lipid surfaces mediated by different multivalent cations is firstly reviewed. Next, recent experiments aimed to characterise the interfacial adsorption of DNA onto a model anionic phospholipid monolayer mediated by Ca(2+) (including AFM images) are discussed. Afterwards, modelling studies of DNA adsorption onto charged surfaces are summarised before presenting preliminary results obtained from both CG and all-atomic MD computer simulations. Our results allow us to establish the optimal conditions for cation-mediated adsorption of DNA onto negatively charged surfaces. Moreover, atomistic simulations provide an excellent framework to understand the interaction between DNA and anionic lipids in the presence of alent cations. Accordingly,our simulation results in conjunction go beyond the macroscopic picture in which DNA is stuck to anionic membranes by using multivalent cations that form glue layers between them. Structural aspects of the DNA adsorption and molecular binding between the different charged groups from DNA and lipids in the presence of alent cations are reported in the last part of the study. Although this research work is far from biomedical applications, we truly believe that scientific advances in this line will assist, at least in part, in the rational design and development of optimal carrier systems for genes and applicable to other drugs.
Publisher: Royal Society of Chemistry (RSC)
Date: 2014
DOI: 10.1039/C4SM01667J
Abstract: Modifying the protein conformation appears to improve the digestibility of proteins in the battle against allergies.
Publisher: Elsevier BV
Date: 12-2019
DOI: 10.1016/J.CIS.2019.102045
Abstract: Because of their unusual chemical structure, bile salts (BS) play a fundamental role in intestinal lipid digestion and transport. BS have a planar arrangement of hydrophobic and hydrophilic moieties, which enables the BS molecules to form peculiar self-assembled structures in aqueous solutions. This molecular arrangement also has an influence on specific interactions of BS with lipid molecules and other compounds of ingested food and digestive media. Those comprise the complex scenario in which lipolysis occurs. In this review, we discuss the BS synthesis, composition, bulk interactions and mode of action during lipid digestion and transport. We look specifically into surfactant-related functions of BS that affect lipolysis, such as interactions with dietary fibre and emulsifiers, the interfacial activity in facilitating lipase and colipase anchoring to the lipid substrate interface, and finally the role of BS in the intestinal transport of lipids. Unravelling the roles of BS in the processing of lipids in the gastrointestinal tract requires a detailed analysis of their interactions with different compounds. We provide an update on the most recent findings concerning two areas of BS involvement: lipolysis and intestinal transport. We first explore the interactions of BS with various dietary fibres and food emulsifiers in bulk and at interfaces, as these appear to be key aspects for understanding interactions with digestive media. Next, we explore the interactions of BS with components of the intestinal digestion environment, and the role of BS in displacing material from the oil-water interface and facilitating adsorption of lipase. We look into the process of desorption, solubilisation of lipolysis, products and formation of mixed micelles. Finally, the BS-driven interactions of colloidal particles with the small intestinal mucus layer are considered, providing new findings for the overall assessment of the role of BS in lipid digestion and intestinal transport. This review offers a unique compilation of well-established and most recent studies dealing with the interactions of BS with food emulsifiers, nanoparticles and dietary fibre, as well as with the luminal compounds of the gut, such as lipase-colipase, triglycerides and intestinal mucus. The combined analysis of these complex interactions may provide crucial information on the pattern and extent of lipid digestion. Such knowledge is important for controlling the uptake of dietary lipids or lipophilic pharmaceuticals in the gastrointestinal tract through the engineering of novel food structures or colloidal drug-delivery systems.
Publisher: Elsevier BV
Date: 09-2016
DOI: 10.1016/J.COLSURFB.2016.06.014
Abstract: Human serum albumin (HSA) has been shown to be an ideal protein for nanoparticle preparation. These are usually prepared by using cross linker agents such as glutaraldehyde (GAD). Liquid lipid nanocapsules (LLN) constitute a new generation of nanoparticles more biocompatible and versatile for oral delivery of lipophylic drugs. The first barrier that an orally administered formulation must cross is the gastrointestinal tract. Hence, it is crucial to address the impact of gastrointestinal digestion on these structures in order to achieve an optimal formulation. This study evaluates the effect of gastric digestion on HSA emulsions structured with GAD as a model substrate for the preparation of LLN. This is done by SDS-PAGE, emulsion microstructure, and interfacial tension techniques. Our results demonstrate that the cross- linking procedure with GAD strongly inhibits pepsin digestion by formation of inter- and/or intramolecular covalent bonds between substrate amino acids. Emulsification of HSA also protects from gastric digestion probably by the orientation of the HSA molecule, which exposes the majority of pepsin cleaving sites preferably to the hydrophobic part of the oil-water interface. In this emulsified HSA, cross-linking with GAD at the interface promotes structural modifications on the HSA interfacial layer, restricting the access of pepsin to cleavage sites. We identify interfacial aspects underlying enzymatic hydrolysis of the protein. Assuring that HSA-GAD structures resist passage through the gastric compartment is crucial is important towards the rational design of oral delivery systems and the first step to get the complete digestion profile.
Publisher: Elsevier BV
Date: 08-2010
Publisher: The Royal Society
Date: 09-2020
Abstract: The vesicular microstructure is a very distinctive arrangement of calcite, consisting of hollow cavities (vesicles) of erse sizes and shapes, usually elongated in the direction of shell thickening. It is uniquely found among living bivalves in a single oyster family, Gryphaeidae. The vesicles are distributed in lenses interleaved with compact foliated layers. We have studied the morphology and distribution of vesicles within the lenses using optical and electron microscopy, and micro-computed tomography. At a small scale, vesicles do not follow a classical von Neumann–Mullins route typical of ideal foams. At a larger scale, the initiation and evolution of a vesicular layer statistically proceed like a foam, with vesicles becoming more numerous, larger and more even in size. In summary, the vesicular material follows a foam-like coarsening to reduce the number of energetically costly interfaces. However, a steady state is never reached because the animal permanently introduces energy in the system by creating new vesicles. The fabrication of the vesicular material is mediated by the production of an emulsion between the extrapallial fluid and the precursor PILP of the calcitic walls within the thin extrapallial space. For this mechanism to proceed, the mantle cells must perform highly sophisticated behaviours of contact recognition and secretion. Accordingly, the vesicular material is under mixed physical–biological control.
Publisher: Elsevier BV
Date: 10-2011
DOI: 10.1016/J.COLSURFB.2011.06.015
Abstract: 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.
Publisher: Elsevier BV
Date: 12-2023
Publisher: Elsevier BV
Date: 02-2021
Publisher: Walter de Gruyter GmbH
Date: 03-2010
Publisher: Royal Society of Chemistry (RSC)
Date: 2013
DOI: 10.1039/C2SM26843D
Publisher: Elsevier BV
Date: 05-2005
Publisher: Elsevier BV
Date: 08-2014
DOI: 10.1016/J.COLSURFB.2014.05.014
Abstract: Bile salts (BS) are bio-surfactants which constitute a vital component in the process of fat digestion. Despite the importance of the interfacial properties in their biological role, these have been scarcely studied in the literature. In this work, we present the adsorption-desorption profiles of two BS (NaTC and NaGDC) including dilatational rheology. Findings from this study reveal very different surface properties of NaTC and NaGDC which originate from different complexation properties relevant to the digestion process. Dynamic adsorption curves show higher adsorption rates for NaTC and suggest the existence of various conformational regimes in contrast to NaGDC which presents only one conformational regime. This is corroborated by analysis of the adsorption isotherms and more in detail by the rheological behaviour. Accordingly, the dilatational response at 1Hz displays two maxima of the dilatational modulus for NaTC as a function of bulk concentration, in contrast to NaGDC which displays only one maximum. The desorption profiles reveal that NaTC adopts an irreversibly adsorbed form at high surface coverage whereas NaGDC fully desorbs from the surface within the whole range of concentrations used. Analysis of the adsorption-desorption profiles provides new insight into the surface properties of BS, suggesting a surface complexation of NaTC. This knowledge can be useful since through interfacial engineering we might control the extent of lipolysis providing the basis for the rational design of food products with tailored digestibility.
Publisher: Elsevier BV
Date: 2022
Publisher: Elsevier BV
Date: 07-2022
Publisher: Wiley
Date: 25-03-2016
DOI: 10.1002/JEMT.22654
Abstract: The Atomic Force Microscopy (AFM) technique appears as a central tool for the characterization of DNA adsorption onto lipid interfaces. Regardless of the huge number of surveys devoted to this issue, there are still fascinating phenomena in this field that have not been explored in detail by AFM. For instance, adsorption of DNA onto like-charged lipid surfaces mediated by cations is still not fully understood even though it is gaining popularity nowadays in gene therapy and nanotechnology. Studies related to the complexation of DNA with anionic lipids as a non-viral gene delivery vehicle as well as the formation of self-assembled nanoscale DNA constructs (DNA origami) are two of the most attractive systems. Unfortunately, molecular mechanisms underlying the adsorption of DNA onto anionic lipid interfaces remain unclear so far. In view of that, AFM becomes an appropriate technique to provide valuable information to understand the adsorption of DNA to anionic lipid surfaces. As a second part of this review we provide an illustrative ex le of application of the AFM technique to probe the DNA adsorption onto a model lipid monolayer negatively charged. Microsc. Res. Tech. 80:11-17, 2017. © 2016 Wiley Periodicals, Inc.
Publisher: Elsevier BV
Date: 2018
DOI: 10.1016/J.COLSURFB.2017.11.027
Abstract: The behaviour of proteins (β-lactoglobulin (βlg) and soy protein isolate (SPI)) and a surface active polysaccharide (hydroxypropylmethylcellulose, HPMC) o/w interfacial films under simulated gastrointestinal conditions using the interfacial tensiometer Octopus were compared and related to the performance of the emulsions (using the same emulsifiers) under in vitro digestion. The evolution of interfacial tension (γ) was used to investigate the effect of gastrointestinal fluids on o/w interfacial films. Clear differences were observed among these emulsifiers. During the gastric phase, HPMC showed the lowest change in γ values as compared to protein films. The most important changes occurred during the intestinal stage where it was observed an important decrease of γ associated with the rapid penetration of BS, followed by a lower rate of decrease attributable to the accumulation of FFA at the interface. In the last stage, the subphase was exchanged by buffer alone, to remove the reversibly adsorbed digestion products. SPI formed the most resistant interface to the remotion of digestion products, followed by HPMC and finally by βlg. The results agree with the degree of lipolysis reported for the emulsions stabilized by these emulsifiers, which suggest that lipid digestion could be modulated by the ability of emulsifiers to prevent the BS activity (to adsorb at the O/W interface or remove the inhibitory digestion products from the interface). Thus, emulsifiers-BS interactions appears as a key factor in controlling the lipolysis.
Publisher: Elsevier BV
Date: 2019
DOI: 10.1016/J.COLSURFB.2018.09.072
Abstract: The use of polymer-based surfactants in the double-emulsion (water/oil/water, W/O/W) solvent-evaporation technique is becoming a widespread strategy for preparing biocompatible and biodegradable polymeric nanoparticles (NPs) loaded with biomolecules of interest in biomedicine, or biotechnology. This approach enhances the stability of the NPs, reduces their size and recognition by the mononuclear phagocytic system, and protects the encapsulated biomolecule against losing biological activity. Different protocols to add the surfactant during the synthesis lead to different NP colloidal properties and biological activity. We develop an in vitro model to mimic the first step of the W/O/W NP synthesis method, which enables us to analyze the surfactant-biomolecule interaction at the O/W interface. We compare the interfacial properties when the surfactant is added from the aqueous or the organic phase, and the effect of pH of the biomolecule solution. We work with a widely used biocompatible surfactant (Pluronic F68), and lysozyme, reported as a protein model. The surfactant, when added from the water phase, displaces the protein from the interface, hence protecting the biomolecule. This could explain the improved colloidal stability of NPs, and the higher biological activity of the lysozyme released from nanoparticles found with the counterpart preparation.
Publisher: Elsevier BV
Date: 06-2011
DOI: 10.1016/J.CIS.2010.12.002
Abstract: Bile salts (BS) are bio-surfactants present in the gastrointestinal tract (GIT) that play a crucial role in the digestion and absorption of nutrients. The importance of BS for controlled release and transport of lipid soluble nutrients and drugs has recently stimulated scientific interest in these physiological compounds. BS are so-called facial hiphiles showing a molecular structure that is very distinct from classical surfactants. This peculiar molecular structure facilitates the formation of dynamic aggregates able to solubilise and transport lipid soluble compounds. The detergent nature of BS has been studied in the literature, mostly concentrating on the self-assembly behaviour of BS in solution but also in relation to protein denaturation and its effect on improving proteolysis. In contrast, the affinity of BS for hydrophobic phases has received less attention and studies dealing directly with the interfacial behaviour of BS are very limited in the literature. This is despite the fact that the interfacial activity of BS plays a vital role in fat digestion since it is closely involved with lypolisis. BS adsorb onto fat droplets and can remove other materials such as proteins, emulsifiers and lipolysis products from the lipid surface. The unusual surface behaviour of BS is directly related to their intriguing molecular structure and further knowledge could provide an improved understanding of lipid digestion. This review aims to combine the new insights gained into the surface properties of BS and their role in digestion. A better understanding of surface activity of BS would allow manipulation of physico-chemical and interfacial properties to modulate lipid digestion, improve bioavailability of lipid soluble nutrients and reduce absorption of saturated fats, cholesterol and trans fats.
Publisher: MDPI AG
Date: 27-07-2019
Abstract: The condensing effect and the ability of cholesterol (CHOL) to induce ordering in lipid films is a question of relevance in biological membranes such as the milk fat globule membrane (MFGM) in which the amount of CHOL influences the phase separation and mechanical resistance to rupture of coexisting phases relevant to emulsified food systems. Here, we study the effect of different salts (NaCl, CaCl2, MgCl2, LaCl3) on monolayers made of a model mixture of lipids (DPPC:DPPS 4:1) and CHOL. To this end, we apply Langmuir Film Balance to report a combined analysis of surface pressure-area (π-A) and surface potential-area (ΔV–A) isotherms along with Micro-Brewster Angle Microscopy (Micro-BAM) images of the monolayers in the presence of the different electrolytes. We show that the condensation of lipid by CHOL depends strongly on the nature of the ions by altering the shape and features of the π-A isotherms. ΔV–A isotherms provide further detail on the ion specific interactions with CHOL. Our results show that the condensation of lipids in the presence of CHOL depends on the combined action of ions and CHOL, which can alter the physical state of the monolayer.
Publisher: Wiley
Date: 18-02-2013
Publisher: MDPI AG
Date: 11-04-2023
Abstract: Bile Salts (BS) adsorb onto emulsified oil droplets to promote lipolysis and then desorb, solubilizing lipolytic products, a process which plays a crucial role in lipid digestion. Hence, investigating the mechanism of adsorption and desorption of BS onto the oil–water interface is of major importance to understand and control BS functionality. This can have implications in the rational design of products with tailored digestibility. This study shows the adsorption and desorption curves of BS at air–water and oil–water interfaces obtained by pendant drop tensiometry. Three BS have been chosen with different conjugation and hydroxyl groups: Sodium Taurocholate (NaTC), Glycodeoxycholate (NaGDC) and Sodium Glycochenodeoxycholate (NaGCDC). Experimental results show important differences between the type of BS and the nature of the interface (air/oil–water). At the air–water interface, Glycine conjugates (NaGDC and NaGCDC) are more surface active than Taurine (NaTC), and they also display lower surface tension of saturated films. The position of hydroxyl groups in Glycine conjugates, possibly favors a more vertical orientation of BS at the surface and an improved lateral packing. These differences diminish at the oil–water interface owing to hydrophobic interactions of BS with the oil, preventing intermolecular associations. Desorption studies reveal the presence of irreversibly adsorbed layers at the oil–water interface in all cases, while at the air–water interface, the reversibility of adsorption depends strongly on the type of BS. Finally, dilatational rheology shows that the dilatational response of BS is again influenced by hydrophobic interactions of BS with the oil thus, adsorbed films of different BS at the oil–water interface are very similar, while larger differences arise between BS adsorbed at the air–water interface. Results presented here highlight new features of the characteristics of adsorption layers of BS on the oil–water interface, which are more relevant to lipid digestion than characteristics of BS adsorbed at air–water interfaces.
Publisher: American Chemical Society (ACS)
Date: 14-02-2013
DOI: 10.1021/LA3044335
Abstract: Pluronics are being introduced in food research in order to delay lipid digestion, with the length of hydrophilic and hydrophobic chains playing an important role in the rate of such a process. Since bile salts play a crucial role in the lipid digestion process, the aim of this work is to analyze the interactions between Pluronic F127 or F68 and the bile salt NaTDC when the latter is added at physiological concentrations. These interactions are studied at the Pluronic-covered oil-water interface and in the aqueous phase of Pluronic-stabilized emulsions. This work has been carried out with techniques such as differential scanning calorimetry, interfacial tension, dilatational rheology, and scanning electron microscopy. As a result, Pluronic F127 was shown to be more resistant to displacement by bile salt than F68 at the oil-water interface due to the larger steric hindrance and interfacial coverage provided. In addition, Pluronics have the ability to compete for the oil-water interface and interact in the bulk with the bile salt. Concretely, Pluronic F127 seems to interact with more molecules of bile salt in the bulk, thus hindering their adsorption onto the oil-water interface. As a conclusion, Pluronic F127 affects to a larger extent the ability of bile salt to promote the further cascade of lipolysis in the presence of lipase owing to a combination of interfacial and bulk events.
Publisher: Elsevier BV
Date: 08-2015
DOI: 10.1016/J.CIS.2014.08.002
Abstract: The development of the coaxial double capillary 15 years ago opened up the possibility to undertake accurate desorption and penetration studies of interfacial layers in the pendant drop technique. Drop and bubble methods offer several advantages with respect to other interfacial techniques. They allow a more stringent control of the environmental conditions, use smaller amounts of material and provide a much higher interface/volume ratio than in conventional Langmuir Troughs. The coaxial capillary was developed 15 years ago at the University of Granada as an accessory for the pendant drop surface film balance. It allows exchanging the subphase of the drop without disturbing the surface film and preserving the drop volume throughout the subphase exchange. Hence, this methodology enables one to carry out a great variety of interfacial studies well beyond the usual adsorption profiles. Penetration studies, sequential adsorption measurements, desorption kinetics, reversibility of adsorption and testing of enzymatic treatments on interfacial layers are amongst the principal applications. The coaxial capillary has been recently upgraded to a multi-exchange device which has boosted its applicability. It can be now used to address multilayer formation, create soft interfacial nano-composites such as membranes, polyelectrolyte assemblies and simulate in vitro digestion in a single droplet. This review aims to compile the experimental work done, using the pendant drop subphase exchange in the last decade, and how its use has provided new insights into the surface/interfacial properties of many different materials. Special emphasis is placed on recent work regarding simulation of in vitro digestion in order to address issues relating to metabolism degradation profiles. The use of this methodology when dealing with interfacial studies allows setting the foundations of interfacial engineering technology. Based on subphase exchange experiments, we aim to develop models for competitive adsorption of different compounds at the interface and build up layer-by-layer interfacial structures. Future challenges comprise the design of finely adjusted nanoengineering systems, based on multilayer assemblies with tailored functionalities, to match the application demand.
No related grants have been discovered for Julia Maldonado-Valderrama.