scholarly journals Microfluidic Deformability Study of an Innovative Blood Analogue Fluid Based on Giant Unilamellar Vesicles

2018 ◽  
Vol 9 (4) ◽  
pp. 70 ◽  
Author(s):  
Denise Carvalho ◽  
Ana Rodrigues ◽  
Vera Faustino ◽  
Diana Pinho ◽  
Elisabete Castanheira ◽  
...  
Keyword(s):  
Ethical Issues ◽  
Soybean Lecithin ◽  
Flow Behavior ◽  
Extensional Flow ◽  
Point Of View ◽  
Giant Unilamellar Vesicles ◽  
Unilamellar Vesicles ◽  
Lipid Mixture ◽  
Further Development ◽  
Good Agreement

Blood analogues have long been a topic of interest in biofluid mechanics due to the safety and ethical issues involved in the collection and handling of blood samples. Although the current blood analogue fluids can adequately mimic the rheological properties of blood from a macroscopic point of view, at the microscopic level blood analogues need further development and improvement. In this work, an innovative blood analogue containing giant unilamellar vesicles (GUVs) was developed to mimic the flow behavior of red blood cells (RBCs). A natural lipid mixture, soybean lecithin, was used for the GUVs preparation, and three different lipid concentrations were tested (1 × 10−3 M, 2 × 10−3 M and 4 × 10−3 M). GUV solutions were prepared by thin film hydration with a buffer, followed by extrusion. It was found that GUVs present diameters between 5 and 7 µm which are close to the size of human RBCs. Experimental flow studies of three different GUV solutions were performed in a hyperbolic-shaped microchannel in order to measure the GUVs deformability when subjected to a homogeneous extensional flow. The result of the deformation index (DI) of the GUVs was about 0.5, which is in good agreement with the human RBC’s DI. Hence, the GUVs developed in this study are a promising way to mimic the mechanical properties of the RBCs and to further develop particulate blood analogues with flow properties closer to those of real blood.

Fluorescent probe partitioning in giant unilamellar vesicles of ‘lipid raft’ mixtures

2010 ◽  
Vol 430 (3) ◽  
pp. 415-423 ◽  
Author(s):  
Janos Juhasz ◽  
James H. Davis ◽  
Frances J. Sharom
Keyword(s):  
Fluorescent Probe ◽  
Lipid Bilayer ◽  
Fluorescent Probes ◽  
Phase Behaviour ◽  
Model Systems ◽  
Fluorescence Probes ◽  
Lipid Phase ◽  
Giant Unilamellar Vesicles ◽  
Unilamellar Vesicles ◽  
Lipid Mixture

Direct visualization of raft-like lo (liquid-ordered) domains in model systems and cells using microscopic techniques requires fluorescence probes with known partitioning preference for one of the phases present. However, fluorescent probes may display dissimilar partitioning preferences in different lipid sys-tems and can also affect the phase behaviour of the host lipid bilayer. Therefore a detailed understanding of the behaviour of fluorescent probes in defined lipid bilayer systems with known phase behaviour is essential before they can be used for identifying domain phase states. Using giant unilamellar vesicles composed of the ternary lipid mixture DOPC (1,2-dioleoyl-sn-glycero-3-phosphocholine)/DPPC (1,2-dipalmitoyl-sn-glycero-3-phosphocholine)/cholesterol, for which the phase behaviour is known, we examined nine commonly used fluorescent probes using confocal fluorescence microscopy. The partitioning preference of each probe was assigned either on the basis of quantification of the domain area fractions or by using a well-characterized ld (liquid-disordered)-phase marker. Fluorescent probes were examined both individually and using dual or triple labelling approaches. Most of the probes partitioned individually into the ld phase, whereas only NAP (naphtho[2,3-a]pyrene) and NBD-DPPE [1,2-dipalmitoyl-sn-glycero-3-phosphoethanolamine-N-(7-nitro-2-1,3-benzoxadiazol-4-yl] preferred the lo phase. We found that Rh-DPPE (Lissamine™ rhodamine B–1,2-dipalmitoyl-sn-glycero-3-phosphoethanolamine) increased the miscibility transition temperature, Tmix. Interestingly, the partitioning of DiIC18 (1,1′-dioctadecyl-3,3,3′,3′-tetramethylindocarbocyanine perchlorate) was influenced by Bodipy®-PC [2-(4,4-difluoro-5,7-dimethyl-4-bora-3a,4a-diaza-s-indacene-3-pentanoyl)-1-hexa-decanoyl-sn-glycero-3-phosphocholine]. The specific use of each of the fluorescent probes is determined by its photostability, partitioning preference, ability to detect lipid phase separations and induced change in Tmix. We demonstrate the importance of testing a specific fluorescent probe in a given model membrane system, rather than assuming that it labels a particular lipid phase.

Preservation of Documental Heritage of the Republic of Sakha (Yakutia) Peoples

2009 ◽  
pp. 34-39
Author(s):  
Galina F. Leveryeva ◽  
Afanasii R. Batorov
Keyword(s):  
Point Of View ◽  
Information Portal ◽  
Rare Books ◽  
The Republic ◽  
Further Development

Questions of creation and development of information portal “Memory of Yakutia” from the point of view of accumulation and preservation of documental heritage of Yakutia nations are considered. Problems of digitization of manuscripts, rare books, audiovisual documents are highlighted and trends of further development are traced.

scholarly journals Effect of the Membrane Composition of Giant Unilamellar Vesicles on Their Budding Probability: A Trade-Off between Elasticity and Preferred Area Difference

Life ◽  
2021 ◽  
Vol 11 (7) ◽  
pp. 634
Author(s):  
Ylenia Miele ◽  
Gábor Holló ◽  
István Lagzi ◽  
Federico Rossi
Keyword(s):  
Phospholipid Fatty Acid ◽  
Enzymatic Reaction ◽  
Stimuli Responsive ◽  
Membrane Composition ◽  
Giant Unilamellar Vesicles ◽  
Physical Processes ◽  
Unilamellar Vesicles ◽  
Division Process ◽  
The Origin Of Life ◽  
Area Difference

The budding and division of artificial cells engineered from vesicles and droplets have gained much attention in the past few decades due to an increased interest in designing stimuli-responsive synthetic systems. Proper control of the division process is one of the main challenges in the field of synthetic biology and, especially in the context of the origin of life studies, it would be helpful to look for the simplest chemical and physical processes likely at play in prebiotic conditions. Here we show that pH-sensitive giant unilamellar vesicles composed of mixed phospholipid/fatty acid membranes undergo a budding process, internally fuelled by the urea–urease enzymatic reaction, only for a given range of the membrane composition. A gentle interplay between the effects of the membrane composition on the elasticity and the preferred area difference of the bilayer is responsible for the existence of a narrow range of membrane composition yielding a high probability for budding of the vesicles.

The ethics of pandemic preparedness revisited - autonomy, quarantine, transferability and trust

2020 ◽  
Vol 30 (Supplement_5) ◽  
Author(s):  
P Schröder-Bäck ◽  
T Schloemer ◽  
K Martakis ◽  
C Brall
Keyword(s):  
Crisis Management ◽  
Ethical Issues ◽  
Lessons Learned ◽  
Point Of View ◽  
Ethical Challenges ◽  
Pandemic Preparedness ◽  
Ethical Aspects ◽  
Outbreak Management ◽  
Ethics Framework ◽  
Ethical Point

Abstract Background The outbreak of SARS in 2002 lead to a public health ethics discourse. The crisis management of that time was ethically analysed and lessons to be learned discussed. Scholarship and WHO, among others, developed an ethics of pandemic preparedness. The current “corona crisis” also faces us with ethical challenges. This presentation is comparing the two crises from an ethical point of view and a focus on Europe. Methods An ethics framework for pandemic preparedness (Schröder et al. 2006 and Schröder-Bäck 2014) is used to make a synopsis of ethical issues. Ethical aspects of 2002 and 2020 that were discussed in the literature and in the media are compared. For 2020, the focus is on interventions in Italy, Germany, Switzerland, and the Netherlands. Results Topics that emerged from the 2002 crisis were, among others, revolving around aspects of stigmatisation and fair distribution of scarce resources (esp. vaccines, antivirals). Currently, most urgent and ethically challenging aspects relate to social distancing vs. autonomy: Isolation and quarantine are handled differently across Europe and the EU. Questions of transferability of such interventions prevail. Contexts vary vertically over time (2002 vs. 2020) and horizontally (e.g. between Italy and Germany at the same time). Furthermore, trust in authorities, media and health information is a key issue. Conclusions Ethical aspects are key for good pandemic preparedness and management. The context of the crises between 2002 and 2020 has slightly changed, also based on “lessons learned” from 2002. This has implications on ethical issues that are being discussed. New lessons will have to be learned from the 2020 crisis. Key messages Pandemic preparedness and outbreak management entail many ethical tensions that need to be addressed. Currently, questions of trust and transferability are key to the crisis management, further ethical issues could still emerge.

Upward Vertical Two-Phase Flow Through an Annulus—Part II: Modeling Bubble, Slug, and Annular Flow

1992 ◽  
Vol 114 (1) ◽  
pp. 14-30 ◽  
Author(s):  
E. F. Caetano ◽  
O. Shoham ◽  
J. P. Brill
Keyword(s):  
Flow Pattern ◽  
Annular Flow ◽  
Two Phase Flow ◽  
Flow Behavior ◽  
Bubble Flow ◽  
Phase Flow ◽  
Two Phase ◽  
Flow Through ◽  
Physical Phenomena ◽  
Good Agreement

Mechanistic models have been developed for each of the existing two-phase flow patterns in an annulus, namely bubble flow, dispersed bubble flow, slug flow, and annular flow. These models are based on two-phase flow physical phenomena and incorporate annulus characteristics such as casing and tubing diameters and degree of eccentricity. The models also apply the new predictive means for friction factor and Taylor bubble rise velocity presented in Part I. Given a set of flow conditions, the existing flow pattern in the system can be predicted. The developed models are applied next for predicting the flow behavior, including the average volumetric liquid holdup and the average total pressure gradient for the existing flow pattern. In general, good agreement was observed between the experimental data and model predictions.

scholarly journals Comparison of Experimental and Numerical Transient Drop Deformation during Transition through Orifices in High-Pressure Homogenizers

2021 ◽  
Vol 5 (3) ◽  
pp. 32
Author(s):  
Benedikt Mutsch ◽  
Peter Walzel ◽  
Christian J. Kähler
Keyword(s):  
High Pressure ◽  
Visual Analysis ◽  
Imaging Technique ◽  
Extensional Flow ◽  
Droplet Breakup ◽  
Experimental Results ◽  
Drop Deformation ◽  
Droplet Deformation ◽  
Shadow Imaging ◽  
Good Agreement

The droplet deformation in dispersing units of high-pressure homogenizers (HPH) is examined experimentally and numerically. Due to the small size of common homogenizer nozzles, the visual analysis of the transient droplet generation is usually not possible. Therefore, a scaled setup was used. The droplet deformation was determined quantitatively by using a shadow imaging technique. It is shown that the influence of transient stresses on the droplets caused by laminar extensional flow upstream the orifice is highly relevant for the droplet breakup behind the nozzle. Classical approaches based on an equilibrium assumption on the other side are not adequate to explain the observed droplet distributions. Based on the experimental results, a relationship from the literature with numerical simulations adopting different models are used to determine the transient droplet deformation during transition through orifices. It is shown that numerical and experimental results are in fairly good agreement at limited settings. It can be concluded that a scaled apparatus is well suited to estimate the transient droplet formation up to the outlet of the orifice.

Domain Sorting in Giant Unilamellar Vesicles Adsorbed on Glass

Langmuir ◽  
2021 ◽  
Vol 37 (3) ◽  
pp. 1082-1088
Author(s):  
Chiho Kataoka-Hamai ◽  
Kohsaku Kawakami
Keyword(s):  
Giant Unilamellar Vesicles ◽  
Unilamellar Vesicles

scholarly journals Production of giant unilamellar vesicles and encapsulation of lyotropic nematic liquid crystals

Soft Matter ◽  
2021 ◽  
Author(s):  
Peng Bao ◽  
Daniel A. Paterson ◽  
Sally A. Peyman ◽  
J. Cliff Jones ◽  
Jonathan A. T. Sandoe ◽  
...  
Keyword(s):  
Liquid Crystals ◽  
Nematic Liquid Crystals ◽  
Double Emulsion ◽  
Lyotropic Liquid Crystals ◽  
Giant Unilamellar Vesicles ◽  
Unilamellar Vesicles ◽  
Emulsion Droplets ◽  
Double Emulsion Droplets

We describe a modified microfluidic method for making Giant Unilamellar Vesicles (GUVs) via water/octanol-lipid/water double emulsion droplets and encapsulation of nematic lyotropic liquid crystals (LNLCs).

Thermo-Mechanical Modeling and Analysis of Equal Channel Angular Pressing

2005 ◽  
Vol 23 ◽  
pp. 263-266 ◽  
Author(s):  
Qing Xiang Pei ◽  
B.H. Hu ◽  
C. Lu
Keyword(s):  
Equal Channel Angular Pressing ◽  
Temperature Rise ◽  
Flow Behavior ◽  
Material Model ◽  
Workpiece Material ◽  
Element Analysis ◽  
Modeling And Analysis ◽  
Die Geometry ◽  
Angular Pressing ◽  
Good Agreement

Thermo-mechanical finite element analysis was carried out to study the deformation behavior and temperature distribution during equal channel angular pressing (ECAP). The material model used is the Johnson-Cook constitution model that can consider the multiplication effect of strain, strain rate, and temperature on the flow stress. The effects of pressing speed, pressing temperature, workpiece material and die geometry on the temperature rise and flow behavior during ECAP process were investigated. The simulated temperature rise due to deformation heating was compared with published experimental results and a good agreement was obtained. Among the various die geometries studied, the two-turn die with 0° round corner generates the highest and most uniform plastic strain in the workpiece.

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