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Multilayer Based Nanogels and Bio-lubricants
KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface and Corrosion Science.
2014 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Surface chemistry plays an important role in numerous technological innovations, and gives the ability to modify and control surface and interface properties. Layer-by-Layer (LbL) self-assembly is a simple concept that can provide a route to versatile combination of materials as well as fine control of film thickness, hydrophobicity, thermal, optical and electrical properties. This methodology has thus received attention from both academic and industrial experts. A large variety of polymers, proteins and nanoparticles can be utilized in the LbL process. In my PhD-thesis work I made use of the LbL technique to build surface grafted nanogels and bio-lubricant films.

Various surface sensitive techniques have been applied in this PhD thesis work. The three main methods were quartz crystal microbalance with dissipation (QCM-D), total internal reflection Raman (TIR-Raman) spectroscopy, and atomic force microscopy (AFM). In lieu of conventional methods such as reflectometry or ellipsometry, we have combined data obtained from QCM-D and TIR-Raman to gain information on wet and dry LbL films as well as their water content. The relatively new AFM imaging mode known as PeakForce QNM was used to investigate topographical and nano-mechanical properties of LbL films. The colloidal probe technique was implemented with AFM for normal and lateral force measurements.

It is becoming increasingly clear that biopolymers are important for a sustainable society since they are renewable, have useful properties and often are environmentally benign. One main part in this thesis work was to fabricate thin chitosan (CHI) nanogels covalently attached to solid surfaces. This was achieved by first assembling a chitosan/poly(acrylic acid) multilayer using silane chemistry and the LbL method. Next, the chitosan molecules were selectively cross-linked in the film, and finally poly(acrylic acid) was (partly) rinsed out of the nanogel. The final composition and the responsiveness of the nanogel to pH and ionic strength changes were found to depend on the cross-linking density. Statistical analysis, known as target factor analysis, was used to analyze TIR Raman spectra and draw conclusions about e.g. the composition of multilayers during the build-up process, and the kinetics of cross-linking of chitosan.

The other main part in this thesis work also utilized the LbL methodology, but here the main goal was to gain understanding on the unprecedented lubrication of synovial joints. It is in general terms due to a sophisticated hierarchical structure of cartilage combined with synergistic actions of surface-active components present in the synovial fluid, but many aspects of this fascinating biotribological system remain poorly understood. I focused on the lubricating ability of synovial fluid components, and in particular on the association of two components of the synovial fluid, hyaluronan and dipalmitoyl phosphatidyl choline (DPPC), in bulk solution and at interfaces. We found that hyaluronan associated with DPPC vesicles in bulk and adsorbed to supported DPPC bilayers, and that the LbL method could be utilized for forming composite layers of these two components. These composite layers had very favorable lubrication properties, with a low friction coefficient as low as 0.01, and they were also sufficiently stable to shear and load up to the pressure that broke healthy cartilage.

 

 

Place, publisher, year, edition, pages
Stockholm: KTH Royal Institute of Technology, 2014. , xi, 52 p.
Series
TRITA-CHE-Report, ISSN 1654-1081 ; 2014:3
National Category
Natural Sciences
Identifiers
URN: urn:nbn:se:kth:diva-140688ISBN: 978-91-7501-993-2 (print)OAI: oai:DiVA.org:kth-140688DiVA: diva2:692217
Public defence
2014-02-14, F3, Lindstedtsvägen 26, KTH, Stockholm, 10:00 (English)
Opponent
Supervisors
Funder
Swedish Research Council
Note

QC 20140130

Available from: 2014-01-30 Created: 2014-01-30 Last updated: 2014-01-30Bibliographically approved
List of papers
1. Surface grafted chitosan nanogels: Part I: Multilayer build-up
Open this publication in new window or tab >>Surface grafted chitosan nanogels: Part I: Multilayer build-up
(English)Manuscript (preprint) (Other academic)
National Category
Chemical Sciences
Identifiers
urn:nbn:se:kth:diva-140695 (URN)
Note

QS 2014

Available from: 2014-01-30 Created: 2014-01-30 Last updated: 2014-01-30Bibliographically approved
2. Surface grafted chitosan nanogels: Part II: Gel formation and characterization
Open this publication in new window or tab >>Surface grafted chitosan nanogels: Part II: Gel formation and characterization
(English)Manuscript (preprint) (Other academic)
National Category
Chemical Sciences
Identifiers
urn:nbn:se:kth:diva-140696 (URN)
Note

QS 2014

Available from: 2014-01-30 Created: 2014-01-30 Last updated: 2014-01-30Bibliographically approved
3. Surface Forces and Friction between Silica and a Cross-Linked Nanohydrogel Layer of Chitosan
Open this publication in new window or tab >>Surface Forces and Friction between Silica and a Cross-Linked Nanohydrogel Layer of Chitosan
(English)Manuscript (preprint) (Other academic)
National Category
Chemical Sciences
Identifiers
urn:nbn:se:kth:diva-140697 (URN)
Note

QS 2014

Available from: 2014-01-30 Created: 2014-01-30 Last updated: 2014-01-30Bibliographically approved
4. Hyaluronan and phospholipids in boundary lubrication
Open this publication in new window or tab >>Hyaluronan and phospholipids in boundary lubrication
Show others...
2012 (English)In: Soft Matter, ISSN 1744-683X, E-ISSN 1744-6848, Vol. 8, no 40, 10241-10244 p.Article in journal (Refereed) Published
Abstract [en]

Hyaluronan has been found to play an important role in boundary lubrication in joints, but model experiments have shown that free hyaluronan is reluctant to stay between surfaces. We show that hyaluronan, when assisted by a phospholipid bilayer, can act as a boundary lubricant, even at pressures well above those leading to breakdown of cartilage.

Keyword
Boundary lubricants, Boundary lubrications, Hyaluronan, Model experiments, Phospholipid bilayer, Chemistry, Materials science, Phospholipids
National Category
Chemical Sciences
Identifiers
urn:nbn:se:kth:diva-104950 (URN)10.1039/c2sm26615f (DOI)000310829200006 ()2-s2.0-84866994734 (Scopus ID)
Funder
Swedish Foundation for Strategic Research Vinnova
Note

QC 20121119

Available from: 2012-11-19 Created: 2012-11-14 Last updated: 2017-12-07Bibliographically approved
5. Hyaluronan and Phospholipid Association in Biolubrication
Open this publication in new window or tab >>Hyaluronan and Phospholipid Association in Biolubrication
2013 (English)In: Biomacromolecules, ISSN 1525-7797, E-ISSN 1526-4602, Vol. 14, no 12, 4198-4206 p.Article in journal (Refereed) Published
Abstract [en]

It is becoming increasingly clear that the outstanding lubrication of synovial joints is achieved by a sophisticated hierarchical structure of cartilage combined with synergistic actions of surface-active components present in the synovial fluid. In this work we focus on the association of two components of the synovial fluid, hyaluronan and dipalmitoyl phosphatidyl choline (DPPC), in bulk solution and at interfaces. We demonstrate that hyaluronan associates with DPPC vesicles and adsorbs to supported DPPC bilayers. The association structures formed at the interface are sufficiently stable to allow sequential adsorption of DPPC and hyaluronan, whereby promoting the formation of thick composite layers of these two components. The lubricating ability of such composite layers was probed by the AFM colloidal probe technique and found to be very favorable with low friction coefficients and high load bearing capacity. With DPPC as the last adsorbed component, a friction coefficient of 0.01 was found up to pressures significantly above what is encountered in healthy synovial joints. Hyaluronan as the last added component increases the friction coefficient to 0.03 and decreases the load bearing capacity somewhat (but still above what is needed in the synovial joint). Our data demonstrate that self-assembly structures formed by hyaluronan and phospholipids at interfaces are efficient aqueous lubricants, and it seems plausible that such self-assembly structures contribute to the exceptional lubrication of synovial joints.

Keyword
Supported Lipid-Bilayers, Quartz-Crystal Microbalance, Surface-Active Phospholipids, Articular-Cartilage, Boundary Lubrication, Synovial-Fluid, Aqueous-Solutions, Forces Apparatus, Amorphous Layer, Acid
National Category
Biochemistry and Molecular Biology Chemical Sciences
Identifiers
urn:nbn:se:kth:diva-139285 (URN)10.1021/bm400947v (DOI)000328240400006 ()2-s2.0-84890402874 (Scopus ID)
Funder
Swedish Foundation for Strategic Research Vinnova
Note

QC 20140108

Available from: 2014-01-08 Created: 2014-01-08 Last updated: 2017-12-06Bibliographically approved

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