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 São 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 Coordenaç~ao de Aperfeiçoamento dePessoal de Nível Superior—Brasil (CAPES)—Finance Code 001.info:eu-repo/semantics/publishedVersio

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(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 Martín. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Centro de Investigaciones en Química Biológica de Córdoba. Universidad Nacional de Córdoba. Facultad de Ciencias Químicas. Centro de Investigaciones en Química Biológica de Córdoba; ArgentinaFil: Malfatti-Gasperini, Antonio A.. Centro Nacional de Pesquisa Em Energia E Materiais. Laboratório Nacional de Luz Síncrotron; BrasilFil: Puentes-Martinez, Ximena E.. Centro Nacional de Pesquisa Em Energia E Materiais. Laboratório Nacional de Luz Síncrotron; BrasilFil: Cavalcanti, Leide P.. Universidade Estadual de Campinas; Brasil. Centro Nacional de Pesquisa Em Energia E Materiais. Laboratório Nacional de Luz Síncrotron; BrasilFil: Oliveira, Rafael Gustavo. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Centro de Investigaciones en Química Biológica de Córdoba. Universidad Nacional de Córdoba. Facultad de Ciencias Químicas. Centro de Investigaciones en Química Biológica de Córdoba; Argentin

High-throughput conventional and stealth cationic liposome synthesis using a chaotic advection-based microfluidic device combined with a centrifugal vacuum concentrator

Microfluidics is an emerging technology that allows efficient mixing of fluids on the nanoliter scale and has recently been employed for the production of lipid-based systems. In this study, we investigated the manufacturing of conventional (EPC/DOTAP/DOPE) and stealth (EPC/DOTAP/DOPE/DSPE-PEG(2000)) cationic liposomes (CLs) in a high-throughput chaotic advection-based microfluidic device (CA-MD) using water and ethanol. We assessed the effects of total flow rate (TFR), flow rate ratio (FRR), and flow configuration on CL formation. We compared the results with properties of CLs produced on a diffusion-based microfluidic device (D-MD). FRR (aqueous/solvent ratio) values were found to have a strong correlation with vesicle formation and values close to 1 led to the production of conventional and stealth CLs with diameter and polydispersity indices close to 200 nm and 0.2, respectively. Both liposomes are unilamellar, and stealth CL production could minimize micelle formation and operate at high flow velocities without altering characteristics of CLs. These findings were supported with dynamic light scattering (DLS), cryo-transmission electron microscopy (Cryo-TEM), and synchrotron small angle X-ray scattering (SAXS) techniques. The high solvent content in liposomes after microfluidic synthesis (FRR = 1) was reduced by employing centrifugal vacuum concentrators (CVC) at low pressure and 43 degrees C as an alternative distillation process for successful ethanol removal without changing the structural properties of these nanoaggregates. Finally, both CLs were able to transfect pDNA into PC-3 cancer cells. The CA-MD coupled to a CVC technique produced conventional and stealth CLs with high productivity, which makes it readily applicable for industrial production382CONSELHO NACIONAL DE DESENVOLVIMENTO CIENTÍFICO E TECNOLÓGICO - CNPQCOORDENAÇÃO DE APERFEIÇOAMENTO DE PESSOAL DE NÍVEL SUPERIOR - CAPESFUNDAÇÃO DE AMPARO À PESQUISA DO ESTADO DE SÃO PAULO - FAPESP310735/2016-5sem informação2015/26701-0; 2015/14468-0The authors thank the financial support from Fundação de Amparo à pesquisa do Estado de São Paulo (São Paulo Research Foundation FAPESP – process number 2015/26701-0) and Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) finance code 001 (Coordination for the Improvement of Higher Education Personnel). The authors kindly thank Professor Sávio Souza Venâncio Vianna and Arthur Lopes Valente for preparing Fig. 1 using ANSYS software. Authors also thank the Microfabrication Laboratory of Brazilian Center for Research in Energy and Materials (CNPEM) for the infrastructure to perform microfabrication as well as the Brazilian National Laboratory of Nanotechnology of CNPEM for the assistance in acquiring Cryo-TEM images of liposomes. The authors also want to thank the Brazilian Synchrotron Light Laboratory for beam times at SAXS1 beamline under research proposal (No. 20170804). Ismail Eş gratefully acknowledges the financial support of the São Paulo Research Foundation (FAPESP) (Grant # 2015/14468-0). Lucimara Gaziola de la Torre thanks Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq – National Council for Scientific and Technological Development) for the productivity grant (310735/2016-5)