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  1. Article: Measuring Interfacial Tension of Emulsions in Situ by Microfluidics

    D’Apolito, Rosa / Antonio Perazzo / Giovanna Tomaiuolo / Mariapia D’Antuono / Reinhard Miller / Stefano Guido / Valentina Preziosi

    Langmuir. 2018 Apr. 11, v. 34, no. 17

    2018  

    Abstract: Interfacial tension is a key parameter affecting industrially relevant properties of emulsions, such as morphology and stability. Although several methods are available to measure interfacial tension, they are based on generation of droplets starting ... ...

    Abstract Interfacial tension is a key parameter affecting industrially relevant properties of emulsions, such as morphology and stability. Although several methods are available to measure interfacial tension, they are based on generation of droplets starting from separate emulsion components and cannot directly probe the interfacial tension of an emulsion as such. Here, a novel microfluidic tensiometry device to measure interfacial tension of a water-in-oil emulsion in situ as a function of surfactant concentration is presented. In our approach, interfacial tension is obtained from a quantitative analysis of the deformation of individual emulsion droplets under steady state shear flow in microfluidic channels. The technique is validated by comparing the results with experimental data obtained by the pendant drop method in a broad range of interfacial tension values. A very good agreement is found, and an estimate of the surfactant critical micellar concentration (CMC) is also obtained. The proposed microfluidic setup can be used even at high surfactant concentrations, where the measurement is made more challenging by sample viscoelasticity, thus providing a powerful tool to determine the interfacial tension of complex systems in an extended concentration range. The technique could be also used for in-line monitoring of emulsion processing.
    Keywords deformation ; droplets ; emulsions ; monitoring ; quantitative analysis ; surface tension ; surfactants ; viscoelasticity
    Language English
    Dates of publication 2018-0411
    Size p. 4991-4997.
    Publishing place American Chemical Society
    Document type Article
    ZDB-ID 2005937-1
    ISSN 1520-5827 ; 0743-7463
    ISSN (online) 1520-5827
    ISSN 0743-7463
    DOI 10.1021/acs.langmuir.8b00208
    Database NAL-Catalogue (AGRICOLA)

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  2. Article ; Online: A novel chemotaxis assay in 3-D collagen gels by time-lapse microscopy.

    Angela Vasaturo / Sergio Caserta / Ilaria Russo / Valentina Preziosi / Carolina Ciacci / Stefano Guido

    PLoS ONE, Vol 7, Iss 12, p e

    2012  Volume 52251

    Abstract: The directional cell response to chemical gradients, referred to as chemotaxis, plays an important role in physiological and pathological processes including development, immune response and tumor cell invasion. Despite such implications, chemotaxis ... ...

    Abstract The directional cell response to chemical gradients, referred to as chemotaxis, plays an important role in physiological and pathological processes including development, immune response and tumor cell invasion. Despite such implications, chemotaxis remains a challenging process to study under physiologically-relevant conditions in-vitro, mainly due to difficulties in generating a well characterized and sustained gradient in substrata mimicking the in-vivo environment while allowing dynamic cell imaging. Here, we describe a novel chemotaxis assay in 3D collagen gels, based on a reusable direct-viewing chamber in which a chemoattractant gradient is generated by diffusion through a porous membrane. The diffusion process has been analysed by monitoring the concentration of FITC-labelled dextran through epifluorescence microscopy and by comparing experimental data with theoretical and numerical predictions based on Fick's law. Cell migration towards chemoattractant gradients has been followed by time-lapse microscopy and quantified by cell tracking based on image analysis techniques. The results are expressed in terms of chemotactic index (I) and average cell velocity. The assay has been tested by comparing the migration of human neutrophils in isotropic conditions and in the presence of an Interleukin-8 (IL-8) gradient. In the absence of IL-8 stimulation, 80% of the cells showed a velocity ranging from 0 to 1 µm/min. However, in the presence of an IL-8 gradient, 60% of the cells showed an increase in velocity reaching values between 2 and 7 µm/min. Furthermore, after IL-8 addition, I increased from 0 to 0.25 and 0.25 to 0.5, respectively, for the two donors examined. These data indicate a pronounced directional migration of neutrophils towards the IL-8 gradient in 3D collagen matrix. The chemotaxis assay described here can be adapted to other cell types and may serve as a physiologically relevant method to study the directed locomotion of cells in a 3D environment in response to different chemoattractants.
    Keywords Medicine ; R ; Science ; Q
    Subject code 610
    Language English
    Publishing date 2012-01-01T00:00:00Z
    Publisher Public Library of Science (PLoS)
    Document type Article ; Online
    Database BASE - Bielefeld Academic Search Engine (life sciences selection)

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