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Stability of Polypeptide Multilayers As Studied by in Situ Ellipsometry: Effects of Drying and Post-Buildup Changes in Temperature and pH
KTH, Superseded Departments, Chemistry.
KTH, Superseded Departments, Chemistry.
2004 (English)In: Journal of the American Chemical Society, ISSN 0002-7863, E-ISSN 1520-5126, Vol. 126, no 51, 17009-17015 p.Article in journal (Refereed) Published
Abstract [en]

Polyelectrolyte multilayers (PEM) of poly(L-glutamic acid) (PGA) and poly(L-lysine) (PLL) with an initial layer of polyethyleneimine (PEI) were built on silica and titanium surfaces using the layer-by-layer (LbL) technique. The stability of the film during drying/rewetting, temperature cycles, and pH shifts was studied in situ by means of ellipsometry. The film thickness was found to decrease significantly (approximately 70%) upon drying, but the original film thickness was regained upon rewetting, and the buildup could be continued. The thickness in the dry state was found to be extremely sensitive to ambient humidity, needing several hours to equilibrate. Changes in temperature and pH were also found to influence the multilayer thickness, leading to swelling and deswelling of as much as 8% and 10-20% respectively. The film does not necessarily regain its original thickness as the pH is shifted back, but instead shows clear signs of hysteresis.

Place, publisher, year, edition, pages
2004. Vol. 126, no 51, 17009-17015 p.
Keyword [en]
Drying, Ellipsometry, Hysteresis, Multilayers, Organic acids, pH effects, Polyelectrolytes, Silica, Swelling, Thermal effects, Wetting
National Category
Physical Chemistry
Identifiers
URN: urn:nbn:se:kth:diva-8921DOI: 10.1021/ja0464645ISI: 000225910400058Scopus ID: 2-s2.0-11344269733OAI: oai:DiVA.org:kth-8921DiVA: diva2:14407
Note
QC 20100930Available from: 2005-12-08 Created: 2005-12-08 Last updated: 2017-12-14Bibliographically approved
In thesis
1. Multilayer Structures for Biomaterial Applications: Biomacromolecule-based Coatings
Open this publication in new window or tab >>Multilayer Structures for Biomaterial Applications: Biomacromolecule-based Coatings
2005 (English)Doctoral thesis, comprehensive summary (Other scientific)
Abstract [en]

The cellular response to a biomaterial, such as a dental implant, is mainly governed by the surface properties, and can thus be altered by the introduction of a surface coating. In this thesis the buildup of a biomacromolecule-based coating formed by layerby-layer (LbL) deposition of the charged polypeptides poly(L-lysine) (PLL) and poly(L-glutamic acid) (PGA) has been studied. In an attempt to make these coatings bioactive and useful for bone-anchored implants, an amelogenin protein mixture (EMD), has been immobilized in these thin polyelectrolyte multilayer (PEM) films. Multilayers were also built by LbL deposition of the natural biomacromolecules collagen (Col) and hyaluronic acid (HA). Multilayer films of these two extra-cellular biomacromolecules should be of interest for use as a scaffold for tissue engineering.

The buildup of the multilayer films has been followed in situ, using ellipsometry, quartz crystal microbalance with dissipation (QCM-D), and dual polarization interferometry (DPI). The studied PLL/PGA multilayers were found to be highly hydrated, and to exhibit a two-regime buildup behavior, with an initial “slow-growing” regime, and a second “fast-growing” regime with a linear growth in film thickness and more than linear growth in mass. A net diffusion of polypeptides into the film during the buildup led to an increase in density of the films for each layer adsorbed. A change in density was also observed in the Col/HA film, where HA penetrated and diffused into the porous fibrous Col network.

The formed PLL/PGA films were further found to be rather stable during drying, and post-buildup changes in temperature and pH, not losing any mass as long as the temperature was not raised too rapidly. The film thickness responded to changes in the ambient media and collapsed reversibly when dried. A swelling/de-swelling behavior of the film was also observed for changes in the temperature and pH.

The EMD protein adsorbed to silica surfaces as nanospheres, and could by itself form multilayers. The adsorption of EMD onto PLL/PGA multilayer films increased at lower pH (5.0), and EMD could be immobilized in several layers by alternate deposition of EMD and PGA.

Place, publisher, year, edition, pages
Stockholm: KTH, 2005. xvii, 67 p.
Series
Trita-YTK, ISSN 1650-0490 ; 0505
Keyword
multilayer, layer-by-layer deposition, physical chemistry, surface chemistry, adsorption, ellipsometry, QCM-D, DPI, protein adsorption, polypeptides, biomaterials, biosurfaces, amelogenin, solid/liquid interface
National Category
Physical Chemistry
Identifiers
urn:nbn:se:kth:diva-551 (URN)91-7178-216-8 (ISBN)
Public defence
2005-12-16, F3, KTH, Lindstedtsvägen 26, Stockholm, 13:00
Opponent
Supervisors
Note
QC 20101019Available from: 2005-12-08 Created: 2005-12-08 Last updated: 2010-10-19Bibliographically approved

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