13 research outputs found
Lecithin and phytosterols-based mixtures as hybrid structuring agents in different organic phases
In this study the effect of lecithin (L) addition and solvent quality in a well-established oleogel system formed by -sitosterol and -oryzanol (BG) was investigated. Medium chain triglycerides (MCT) and sunflower oil (SFO) were used as triglycerides and hexadecane (HEX) as a model of linear hydrocarbon. Lecithin was proposed due to its natural and versatile properties, showing different functionalities such as emulsifier and co-oleogelator. A study based on hierarchical organization of structured oil was performed applying techniques for bulk, meso and nanoscale. Self-sustained structures could no longer be observed after 40wt% of BG replacement by lecithin. Small-angle X-ray scattering showed that the formed nanostructures (building blocks) were dependent on type of solvent and BG:L ratio in the mixture of oleogelators. Differential scanning calorimetry showed that stability against temperature was improved decreasing the polarity of the oil, and a time-dependent self-assembly of hybrid systems was observed from thermal and rheological measurements. Microscopy images exhibited changes on typical fibril aggregation of BG as lecithin was added, which promoted to a certain extent the suppression of ribbons. Oscillatory shear and uniaxial compression measurements were influenced by BG:L ratio and solvent mainly at higher lecithin amount. The combination of BG and MCT appeared to be the most affected by lecithin incorporation whereas SFO rendered harder oleogels. These results could contribute to understand the role of both lecithin and solvent type influencing the host oleogelator structure. It was hypothesized that intermolecular BG complex formation is hindered by lecithin, besides this phospholipid also might coexist as a different phase, causing structural changes in the gel network. Addressing the role of co-oleogelator it can provide the opportunity to tune soft materials with adjusted properties.Paula Kiyomi Okuro thanks to CNPq (159180/2013-9) and S茫o Paulo Research Foundation (FAPESP) grant #2015/24912-4 and 2016/ 10277-8, for the PhD fellowship; Rosiane Lopes Cunha thanks CNPq (307168/2016-6) for the productivity grant. The authors also thank the Brazilian Synchrotron Light Laboratory (LNLS) for the opportunity to use SAXS1 (proposal number 20160277 and 20170297) beamline and Tsuno Rice Fine Chemicals Co., Ltd. for the donation of gamma oryzanol samples. We thank the access to equipment and assistance provided bytheLaboratory ofProcessEngineering, Department ofFood Engineering, Faculty ofFood Engineering at the University of Campinas co-funded by FAPESP (96/08366-5, 2004/08517-3, 2006/03263-9, 2007/58017-5, 2011/06083-0).info:eu-repo/semantics/publishedVersio
Tuning phytosterols-based oleogels properties by soybean lecithin addition in different organic phases
info:eu-repo/semantics/publishedVersio
Self-organizing structures of phosphatidylcholine in nonaqueous solvents: tailoring gel-like systems
In this paper, we investigated the role played by solvent type and additives (water [W] and citric acid [CA]) on the self-assembly of phosphatidylcholine (PtdCho) into gels. Soybean lecithin (L) served as the PtdCho source used in this study. Lecithin was combined with different oils: hexadecane (HEX), sunflower oil, and medium-chain triacylglycerol to explore its ability to form organogels. Among the solvents, only HEX was able to form a translucent self-sustainable gel with lecithin. It was found that the lower water solubility and viscosity of HEX favored gel formation. Small-angle X-ray scattering revealed different structures arisen from lecithin organization depending on the organic medium type. In addition, the gel properties of the L-HEX binary system were also tailored through inclusion of the primers W or CA. Oscillatory rheological behavior of organogels was effectively described by a single relaxation-time Maxwell model, with good fitting at low and intermediate frequencies and with deviations at higher frequencies, indicating the presence of reverse wormlike micelles. Organogels were thermoreversible and, upon CA addition, a substantial increase in zero-shear viscosity was observed. Incorporation of W led to a similar microstructure to that obtained only with L, whereas CA promoted a different ordering of PtdCho assemblies. Formation and properties of PtdCho-based organogels were dictated by using different oil types or by changing the polarity of the medium with the incorporation of primers. A better understanding of phospholipid-based nonlamellar mesophases in organic solvent offers the prospect of adapting the gel properties to the desired application and functionality.Paula Kiyomi Okuro thanks to grant#2015/24912-4; 2016/10277-8 and 2018/20308-3, S~ao PauloResearch Foundation (FAPESP) and CNPq (159180/2013-9);Rosiane Lopes Cunha thanks CNPq (307168/2016-6) for the productivitygrant. Authors want to thank Dr. Ashok R. Patel for his scientific inputsand Dra. Ana Paula Badan Ribeiro for the fatty acid composition analysis.The authors thank the Brazilian Synchrotron Light Laboratory (LNLS) forthe opportunity to use SAXS 1 (Proposal: 19015) beamline. We thank theaccess to equipment and assistance provided by the Laboratory of ProcessEngineering, Department of Food Engineering, Faculty of Food Engineer-ing at the University of Campinas co-funded by FAPESP (96/08366-5,2004/08517-3, 2006/03263-9, 2007/58017-5, 2011/06083-0). This studywas alsofinanced in part by the Coordena莽~ao de Aperfei莽oamento dePessoal de N铆vel Superior鈥擝rasil (CAPES)鈥擣inance Code 001.info:eu-repo/semantics/publishedVersio
Periodic bilayer organization in the complexes of Beta-2 Glycoprotein I with anionic lipid membranes
The Link Between Self-Assembly and Molecular Conformation of Amphiphilic Block Copolymers Monolayers at the Air/Water Interface: The Spreading Parameter
Two
amphiphilic block copolymers, namely polystyrene-<i>b</i>-poly颅(methyl-methacrylate) (PS-<i>b</i>-PMMA), at the air/water
interface were studied combining the in situ structural characterization,
by means of X-ray reflectivity (XRR) and grazing incidence small-angle
X-ray scattering (GISAXS), and the ex situ morphological one, by atomic
force microscopy (AFM). We observed that the conformation of the hydrophilic
block spread on the water surface is dramatically influenced by the
morphology of the monolayer. Our results showed that the hydrophilic
PMMA block adopts an expanded conformation when thermodynamically
stable nanodots are formed, whereas a coiled conformation is observed
when the block copolymer formed kinetically frozen nanostrands. This
effect is interpreted in terms of the spreading parameter, which changes
with the relative length ratio between the two blocks. Finally, we
proved that, even for block copolymer monolayer with fixed block length
ratio, it is possible to change the morphology, and in turn the conformation
of the hydrophilic block, by changing the spreading parameter value
Refractive index and thickness determination in Langmuir monolayers of myelin lipids
Langmuir monolayers at the air/water interface are widely used as biomembrane models and for amphiphilic molecules studies in general. Under controlled intermolecular organization (lateral molecular area), surface pressure, surface potential, reflectivity (R) and other magnitudes can be precisely determined on these planar monomolecular films. However, some physical parameters such as the refractive index of the monolayer (n) still remain elusive. The refractive index is very relevant because (in combination with R) it allows for the determination of the thickness of the film. The uncertainties of n determine important errors that propagate non-linearly into the calculation of monolayers thickness. Here we present an analytical method for the determination of n in monolayers based on refractive index matching. By using a Brewster angle microscopy (BAM) setup and monolayers spread over subphases with variable refractive index (n2), a minimum in R is search as a function of n2. In these conditions, n equals n2. The results shown correspond to monolayers of myelin lipids. The n values remain constant at 1.46 upon compression and equals the obtained value for myelin lipid bilayers in suspension. The values for n and R allow for the determination of thickness. We establish comparisons between these thicknesses for the monolayer and those obtained from two X-ray scattering techniques: 1) GIXOS for monolayers at the air/water interface and 2) SAXS for bilayers in bulk suspension. This allows us to conclude that the thickness that we measure by BAM includes the apolar and polar headgroup regions of the monolayer.Fil: Pusterla, Julio Mart铆n. Consejo Nacional de Investigaciones Cient铆ficas y T茅cnicas. Centro Cient铆fico Tecnol贸gico Conicet - C贸rdoba. Centro de Investigaciones en Qu铆mica Biol贸gica de C贸rdoba. Universidad Nacional de C贸rdoba. Facultad de Ciencias Qu铆micas. Centro de Investigaciones en Qu铆mica Biol贸gica de C贸rdoba; ArgentinaFil: Malfatti-Gasperini, Antonio A.. Centro Nacional de Pesquisa Em Energia E Materiais. Laborat贸rio Nacional de Luz S铆ncrotron; BrasilFil: Puentes-Martinez, Ximena E.. Centro Nacional de Pesquisa Em Energia E Materiais. Laborat贸rio Nacional de Luz S铆ncrotron; BrasilFil: Cavalcanti, Leide P.. Universidade Estadual de Campinas; Brasil. Centro Nacional de Pesquisa Em Energia E Materiais. Laborat贸rio Nacional de Luz S铆ncrotron; BrasilFil: Oliveira, Rafael Gustavo. Consejo Nacional de Investigaciones Cient铆ficas y T茅cnicas. Centro Cient铆fico Tecnol贸gico Conicet - C贸rdoba. Centro de Investigaciones en Qu铆mica Biol贸gica de C贸rdoba. Universidad Nacional de C贸rdoba. Facultad de Ciencias Qu铆micas. Centro de Investigaciones en Qu铆mica Biol贸gica de C贸rdoba; Argentin
Filling nanoporous polymer thin films: an easy route toward the full control of the 3D nanostructure
A novel approach enabling the full control of the 3D nanostructure of polymer thin films is presented. An ordered nanoporous polymer film is obtained using a nanoparticle monolayer as template. The pores are then filled with a second organic component via spin coating which, by modulating the deposition parameters, enables the control of the filling degree with nanometric precision
Filling nanoporous polymer thin films: an easy route toward the full control of the 3D nanostructure
A novel approach enabling the full control of the 3D nanostructure of polymer thin films is presented. An ordered nanoporous polymer film is obtained using a nanoparticlemonolayer as template. The pores are then filled with a second organic component via spin coating which, by modulating the deposition parameters, enables the control of the filling degree with nanometric precision.JRC.I.4-Nanobioscience
Stacks of a Hidden Treasure: on the Self-Assembly of Perovskite Nanoplates in Organic Solvents
In recent years, perovskite nanocrystal superlattices have been reported with collective optical phenomena, offering a promising platform for both fundamental science studies and device engineering. In this same avenue, superlattices of perovskite nanoplates can be easily prepared on different substrates, and they too present ensemble optical response. However, the self-assembly and optical properties of these aggregates in solvents have not been reported to date. Here, we report on the condition for this self-assembly to occur and show a simple strategy to induce the formation of these nanoplates stacks in suspension in different organic solvents. We combined wide- and small-angle X-ray scattering and scanning transmission electron microscopy to evaluate CsPbBr3 and CsPbI3 perovskite nanoplates with different thickness distributions. We observed the formation of these stacks by changing the concentration of nanoplates and the viscosity of the colloidal suspensions, without the need of antisolvent addition. We found that, in hexane, the concentration threshold for the formation of the stacks is rather high and approximately 80 mg/mL. In contrast, in decane, dodecane, and hexadecane, we observe a much easier self-assembly of the nanoplates, presenting a clear correlation between the degree of aggregation and viscosity. We, then, discuss the impact of the self-assembly of perovskite nanoplates on F枚rster resonant energy transfer. Our predictions suggest an energy transfer efficiency higher than 50%, even in a low photoluminescence quantum yield scenario, for both perovskite compositions