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Sticking particles to solid surfaces using Moringa oleifera proteins as a glue
Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Physics.ORCID iD: 0000-0002-5203-8057
Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Physics.
Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Physics.
Namibia University of Science and Technology, Faculty of Health and Applied Sciences, Private Bag 13388, 13 Storch Street, Windhoek, Namibia.
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2018 (English)In: Colloids and Surfaces B: Biointerfaces, ISSN 0927-7765, E-ISSN 1873-4367, Vol. 168, p. 68-75Article in journal (Refereed) In press
Abstract [en]

Experimental studies have been made to test the idea that seed proteins from Moringa oleifera which are novel, natural flocculating agents for many particles could be used to promote adhesion at planar interfaces and hence provide routes to useful nanostructures. The proteins bind irreversibly to silica interfaces. Surfaces that had been exposed to protein solutions and rinsed were then exposed to dispersions of sulfonated polystyrene latex. Atomic force microscopy was used to count particle density and identified that the sticking probability was close to 1. Measurements with a quartz crystal microbalance confirmed the adhesion and indicated that repeated exposures to solutions of Moringa seed protein and particles increased the coverage. Neutron reflectivity and scattering experiments indicate that particles bind as a monolayer. The various results show that the 2S albumin seed protein can be used to fix particles at interfaces and suggest routes for future developments in making active filters or improved interfaces for photonic devices.

Place, publisher, year, edition, pages
2018. Vol. 168, p. 68-75
National Category
Physical Chemistry Condensed Matter Physics
Research subject
Physics with spec. in Atomic, Molecular and Condensed Matter Physics
Identifiers
URN: urn:nbn:se:uu:diva-338407DOI: 10.1016/j.colsurfb.2018.01.004ISI: 000443630200010PubMedID: 29373240OAI: oai:DiVA.org:uu-338407DiVA, id: diva2:1172012
Funder
Swedish Research Council, 348-2011-7241Swedish Research Council, 621-2012-4382Available from: 2018-01-09 Created: 2018-01-09 Last updated: 2018-11-01Bibliographically approved
In thesis
1. Structure formation at solid/liquid interfaces: Understanding self-assembly and environmental challenges
Open this publication in new window or tab >>Structure formation at solid/liquid interfaces: Understanding self-assembly and environmental challenges
2018 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

The work described in the present dissertation has explored the structure of particles and molecules at solid/liquid interfaces, aiming to understand the physics of self-organizing systems and use this knowledge to address some environmental issues. Surface-sensitive neutron scattering techniques, such as reflectometry and grazing incidence small angle scattering, have been used as the primary tool to investigate structures in proximity to an interface. Some of the challenges in the interpretation of neutron scattering data are discussed, and new methods for analyzing the signal have been proposed.

It was shown that charged stabilized colloidal particles can self-assemble and form large areas (20 cm2) of crystalline structures, close to a smooth solid surface extending to depths of several micrometers, while orienting themselves into smaller crystallites in the bulk of the suspension. The adsorption of proteins from the seeds of different species of Moringa trees on alumina, silica and polystyrene surfaces was studied, as a means for using proteins from different sources and with different properties, for the water clarification step in the purification process. The seed proteins also showed to enable locking the structure of colloidal particles at the solid/liquid interface, acting as a molecular glue.

Perfluorinated surfactants (PFASs), widely used in industrial, pharmaceutical and food packing products, have been identified as emerging pollutants, raising a global concern for the environment and wildlife. The present study has shown how PFASs molecules of different fluorocarbon chain length and with different functional groups, create defects in model membranes by partitioning and removing phospholipids from the bilayer, making the bilayer thin and less dense.

The effect of interface roughness was studied on the lamellar structure of a non-ionic surfactant. Concentrated solutions of the surfactant have been shown to form well-ordered and well-aligned structures at a smooth interface, which could be modified further by simply heating the sample. However it was found that even small roughness, of the same order as the bilayer thickness, can distort the structure to a depth of several micrometers from the interface. Heating the sample could improve the alignment but not as much as that formed at a smooth surface.

Place, publisher, year, edition, pages
Uppsala: Acta Universitatis Upsaliensis, 2018. p. 64
Series
Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology, ISSN 1651-6214 ; 1732
Keywords
Solid/liquid interface, neutron scattering, colloidal particles, self-assembly, perfluoroalkyl substance, Moringa seed proteins, adsorption, lamellar disorder, thermal fluctuations.
National Category
Physical Sciences
Identifiers
urn:nbn:se:uu:diva-362075 (URN)978-91-513-0475-5 (ISBN)
Public defence
2018-12-14, Å80127, Ångströmlaboratoriet, Uppsala, 09:15 (English)
Opponent
Supervisors
Available from: 2018-11-19 Created: 2018-10-13 Last updated: 2018-11-30

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Hellsing, Maja S.Rennie, A. R.

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