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Relating the Bulk and Interface Structure of Hyaluronan to Physical Properties of Future Biomaterials
Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström.
2013 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

This dissertation describes a structural investigation of hyaluronan (HA) with neutron scattering techniques. HA is a natural biopolymer and one of the major components of the extracellular matrix, synovial fluid, and vitreous humor.  It is used in several biomedical applications like tissue engineering, drug delivery, and treatment of osteoarthritis. Although HA is extensively studied, very little is known about its three-dimensional conformation and how it interacts with ions and other molecules. The study aims to understand the bulk structure of a cross-linked HA hydrogel, as well as the conformational arrangement of HA at solid-liquid interfaces. In addition, the structural changes of HA are investigated by simulation of physiological environments, such as changes in ions, interactions with nanoparticles, and proteins etc. Small-angle neutron scattering and neutron reflectivity are the two main techniques applied to investigate the nanostructure of hyaluronan in its original, hydrated state.

The present study on hydrogels shows that they possess inhomogeneous structures best described with two correlation lengths, one of the order of a few nanometers and the other in the order of few hundred nanometers. These gels are made up of dense polymer-rich clusters linked to each other. The polymer concentration and mixing governs the connectivity between these clusters, which in turn determines the viscoelastic properties of the gels. Surface-tethered HA at a solid-liquid interface is best described with a smooth varying density profile. The shape of this profile depends on the immobilization chemistry, the deposition protocol, and the ionic interactions. HA could be suitably modified to enhance adherence to metal surfaces, as well as incorporation of proteins like growth factors with tunable release properties. This could be exploited for surface coating of implants with bioactive molecules. The knowledge gained from this work would significantly help to develop future biomaterials and surface coatings of implants and biomedical devices.

Place, publisher, year, edition, pages
Uppsala: Acta Universitatis Upsaliensis, 2013. , 66 p.
Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology, ISSN 1651-6214 ; 1043
Keyword [en]
hyaluronan, structure, bulk, interface, small-angle neutron scattering, neutron reflection, hydrogel, grafting, nanoparticles, protein interactions
National Category
Polymer Chemistry Materials Chemistry
URN: urn:nbn:se:uu:diva-198357ISBN: 978-91-554-8669-3 (print)OAI: diva2:616706
Public defence
2013-06-05, Häggsalen, Ångströmlaboratoriet, Lägerhyddsvägen 1, Uppsala, 09:00 (English)
Available from: 2013-05-15 Created: 2013-04-12 Last updated: 2013-08-30Bibliographically approved
List of papers
1. Structure of polymer and particle aggregates in hydrogel composites
Open this publication in new window or tab >>Structure of polymer and particle aggregates in hydrogel composites
2013 (English)In: Journal of Polymer Science Part B: Polymer Physics, ISSN 0887-6266, E-ISSN 1099-0488, Vol. 51, no 6, 421-429 p.Article in journal (Refereed) Published
Abstract [en]

Knowledge of the structure of a biomaterial is usually vital to control its function. This article provides a structural characterization of a hyaluronan scaffold that has demonstrated good biocompatibility and is used to induce bone regeneration. Hyaluronan hydrogels are appealing materials that can function as a matrix to incorporate both organic and inorganic substances to enhance tissue growth. Because of the intrinsic properties of this swollen matrix, one needs a very sensitive technique that can be applied in situ to determine the organization of the polymers in a gel. Small-angle neutron scattering is used to determine the characteristics of the inhomogeneous structure of the hydrogel both with and without added particles. The results are interpreted using models of structure with two length scales that are beyond the traditional picture of homogeneous gels. The observed structure and the dimensions can explain the previously reported rheological properties of gels containing different amount of polymers. Hydroxyapatite nanoparticles added to the gel are frozen in the gel matrix. We are able to determine the distribution and shape of these particles as they aggregate around the polymer chains. We have also concluded, in this case, that the particle structure is concentration independent. Information about the nanostructure for an applicable biomaterial guides the formulation, preparation, and use that should lead to further understanding of its exploitation.

biopolymers, correlation length, hyaluronan, hydrogels, nanocomposites, neutron scattering
National Category
Natural Sciences
urn:nbn:se:uu:diva-197038 (URN)10.1002/polb.23230 (DOI)000315050800005 ()
Available from: 2013-03-19 Created: 2013-03-18 Last updated: 2017-12-06Bibliographically approved
2. Tuning the density profile of surface-grafted hyaluronan and the effect of counter-ions
Open this publication in new window or tab >>Tuning the density profile of surface-grafted hyaluronan and the effect of counter-ions
2013 (English)In: European Physical Journal E, ISSN 1292-8941, Vol. 36, no 7, 70- p.Article in journal (Refereed) Published
Abstract [en]

The present paper investigates the structure and composition of grafted sodium hyaluronanat a solid-liquid interface using neutron reflection. The solvated polymer at the surface could be described with a density profile that decays exponentially towards the bulk solution. The density profileof the polymer varied depending on the deposition protocol. A single-stage deposition resulted in denser polymer layers, while layers created with a two-stage deposition process were more diffuse and had an overall lower density. Despite the diffuse density profile, two-stage deposition leads to a highersurface excess. Addition of calcium ions causes a strong collapse of the sodium hyaluronan chains, increasing the polymer density near the surface. This effect is more pronounced on the sample prepared by two-stage deposition due to the initial less dense profile. This study provides an understanding at a molecular level of how surface functionalization alters the structure and howsurface layers respond to changes in calcium ions in the solvent.

National Category
Polymer Technologies Polymer Chemistry
urn:nbn:se:uu:diva-197814 (URN)10.1140/epje/i2013-13070-7 (DOI)000322872700002 ()
Available from: 2013-04-04 Created: 2013-04-04 Last updated: 2014-02-17Bibliographically approved
3. Adsorption and co-adsorption of human serum albumin and myoglobin with hyaluronan on different substrates
Open this publication in new window or tab >>Adsorption and co-adsorption of human serum albumin and myoglobin with hyaluronan on different substrates
Show others...
(English)Manuscript (preprint) (Other academic)
National Category
Polymer Chemistry Materials Chemistry
urn:nbn:se:uu:diva-197815 (URN)
Available from: 2013-04-12 Created: 2013-04-04 Last updated: 2013-05-06
4. Polymeric Smart Coating Strategy for Titanium Implants
Open this publication in new window or tab >>Polymeric Smart Coating Strategy for Titanium Implants
Show others...
2014 (English)In: Advanced Engineering Materials, ISSN 1438-1656, E-ISSN 1527-2648, Vol. 16, no 11, 1340-1350 p.Article in journal (Refereed) Published
Abstract [en]

Hyaluronan based hydrogel coatings can mimic extracellular matrix components and incorporate growth factors that can be released during a progressive degradation while new tissue regenerates. This paper describes a structural characterization of a hydrogel coating made of modified hyaluronan polymers and how these coatings interact with bone morphogenetic protein-2 (BMP-2). Quartz crystal microbalance and neutron reflectivity measurements were used for in-situ, real-time measurements of the adsorption properties of polymers and proteins on smooth titanium oxide surfaces that mimic implant products in orthopedics. The adsorption of BMP-2 on a bare titanium oxide surface is compared to that on titanium oxide coated with different chemically modified hyaluronan, the most important being hyaluronan with bisphosphonate groups (HA-BP). The subsequent release of the BMP-2 from these hydrogel coatings could be triggered by calcium ions. The amount of adsorbed protein on the surfaces as well as the amount of released protein both depend on the type of hyaluronan coating. We conclude that HA-BP coated titanium oxide surfaces provide an excellent material for growth factor delivery in-vivo.

National Category
Biomaterials Science Polymer Chemistry Polymer Technologies Materials Chemistry
urn:nbn:se:uu:diva-197816 (URN)10.1002/adem.201400009 (DOI)000344790000004 ()
Available from: 2013-04-16 Created: 2013-04-04 Last updated: 2017-12-06Bibliographically approved

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