Change search
ReferencesLink to record
Permanent link

Direct link
Polymer Dynamics in Layer-by-Layer Assemblies of Chitosan and Heparin
KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface and Corrosion Science.
KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface and Corrosion Science.ORCID iD: 0000-0001-7496-1101
Carnegie Mellon University, Pittsburgh, USA.
2010 (English)In: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 26, no 5, 3242-3251 p.Article in journal (Refereed) Published
Abstract [en]

The layer-by-layer deposition method has been used to build a multilayer thin film with two polysaccharides, chitosan CH (weak polycation) and heparin HEP (strong polyanion), on planar quartz surfaces. The film structure and dynamics in aqueous Solution were studied with fluorescence resonance energy transfer (FRET) and total internal reflection fluorescence (TIRF). Particular emphasis was placed on the effect of deposition conditions, i.e.. pH and salt concentration, on the out-of-plane (vertical) diffusion of fluorescence labeled chitosan in the chitosan/heparin (CH/HEP) film. FRET analysis showed that CH molecules diffused within the film with a diffusion coefficient that was not significantly sensitive to the deposition pH and Solution ionic strength. A pH-sensitive label bound to CH embedded within the CH/HEP Film wits sensitive to the charge of the outermost polymer layer even when buried under 14 alternate layers of CH and HER A consideration of the results obtained with both fluorescence techniques showed that the structure of the CH/HEP thin film wits highly interpenetrated without clear boundaries between each layer. These results are consistent with the hypothesis that the previously observed exponential-like film growth of CH and HEP in terms of, layer thickness and deposited amount versus deposition cycle can be attributed to out-of-plane diffusion of CH molecules in the multilayer.

Place, publisher, year, edition, pages
2010. Vol. 26, no 5, 3242-3251 p.
Keyword [en]
polyelectrolyte multilayer films, internal-reflection fluorescence, exponential-growth, weak polyelectrolyte, molecular-weight, solid-surfaces, buildup, ph, polycations, adsorption
National Category
Chemical Sciences Physical Chemistry
URN: urn:nbn:se:kth:diva-14277DOI: 10.1021/la902968hISI: 000274636900041ScopusID: 2-s2.0-77749255904OAI: diva2:331993
Swedish Research Council

QC 20100729

Available from: 2010-07-29 Created: 2010-07-29 Last updated: 2016-05-18Bibliographically approved
In thesis
1. Adsorption of biopolymers and their layer-by-layer assemblies on hydrophilic surfaces
Open this publication in new window or tab >>Adsorption of biopolymers and their layer-by-layer assemblies on hydrophilic surfaces
2009 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

It is widely known that surfaces play an important role in numerous biological processes and technological applications. Thus, being able to modify surface properties provides an opportunity to control many phenomena occurring at interfaces. One way of controlling surface properties is to adsorb a polymer film onto the surface, for example through layer-by-layer (LbL) deposition of polyelectrolytes. This simple but versatile technique enables various polymers, proteins, colloidal particles etc. to be incorporated into the film, resulting in a multifunctional coating. Due to recent legislations and a consumer demand for more environmentally friendly products, we have chosen to use natural polymers (biopolymers) from renewable resources. The focus of this thesis has been on the adsorption of biopolymers and their layer-by-layer formation at solid-liquid interfaces; these processes have been studied by a wide range of techniques. The main method was the quartz crystal microbalance with dissipation monitoring (QCM-D), which measures the adsorbed mass, including trapped solvent and the viscoelastic properties of an adsorbed film. This technique was often complemented with an optical method, such as ellipsometry or dual polarization interferometry (DPI), which provided information about the “dry” polymer or protein adsorbed mass. From this combination, the solvent content and density of the layers was evaluated. In addition, the surface force apparatus (SFA), X-ray photoelectron spectroscopy (XPS), total internal reflection fluorescence (TIRF), and fluorescence resonance energy transfer (FRET) were utilized, providing further information about the film structure, chemical composition, and polymer inter-layer diffusion. Adsorption studies of the glycoprotein mucin, which has a key role in the mucousal function, showed that despite the net negative charge of mucin, it adsorbed on negatively charged substrates. The adsorbed layer was highly hydrated and the segment density on the substrate was low. We showed the importance of characterizing the mucin used, since differences in purity, such as the presence of albumin, gave rise to different adsorption behaviours in terms of both adsorbed amount and structure. The adsorbed mucin layer was to a large extent desorbed upon exposure to the anionic surfactant sodium dodecyl sulfate (SDS). In order to prevent desorption, we demonstrated that a protective layer of the cationic polysaccharide chitosan could be adsorbed onto the mucin layer and that the mucin-chitosan complexes resisted the desorption normally induced by association with SDS. Moreover, the association between chitosan and SDS was examined at the solid-liquid interface, in the bulk, and at the air-water interface. In all these environments chitosan-SDS complexes were formed and a net charge reversal of the complexes from positive to negative was observed when the concentration of SDS was increased. Furthermore, the LbL deposition method could be used to form a multilayer-like film by alternate adsorption of mucin and chitosan on silica substrates. The LbL technique was also applied to two proteins, lysozyme and β-casein with the aim of building a multilayer film consisting entirely of proteins. These proteins formed complexes at the solid-liquid interface, resulting in a proteinaceous layer, but the build-up was highly irregular with an increase in adsorbed amount per protein deposition cycle that was far less than a monolayer.Continuing with chitosan, known to have antibacterial properties we assembled multilayers with an anti-adhesive biopolymer, heparin, to evaluate the potential of this system as a coating for medical implants. Multilayers were assembled under various solution deposition conditions and the film structure and dynamics were studied in detail. The chitosan-heparin film was highly hydrated, in the range 60-80 wt-% depending on the deposition conditions. The adsorbed amount and thickness of the film increased exponential-like with the number of deposition steps, which was explained by inter-diffusion of chitosan molecules in the film during the build-up. In a novel approach, we used the distant dependent FRET technique to prove the inter-layer diffusion of fluorescent-labelled chitosan molecules within the film. The diffusion coefficient was insignificantly dependent on the deposition pH and ionic strength, and hence on the film structure. With the use of a pH sensitive dye buried under seven chitosan-heparin bilayers, we showed that the dye remained highly sensitive to the charge of the outermost layer. From complementary QCM-D data, we suggested that an increase in the energy dissipation does not necessarily indicate that the layer structure becomes less rigid.

Abstract [sv]

Det är välkänt att ytor spelar en viktig roll i många biologiska processer och tekniska tillämpningar. Att kunna modifiera en ytas egenskaper ger därför en möjlighet att kunna kontrollera många fenomen som sker på ytor. Ett sätt att kontrollera ytegenskaperna är genom att adsorbera en polymerfilm på ytan, till exempel genom att växelvis adsorbera olika polyelektrolyter (LbL-teknik). Denna enkla men mångsidiga teknik möjliggör att många olika material kan införlivas i filmen, vilket resulterar i en multifunktionell beläggning. På grund av dagens lagstiftning och konsumenters ökade efterfrågan på miljövänliga material beslutade vi oss för att använda biologiska polymerer (biopolymerer) i detta projekt. Fokus i den här avhandlingen har varit på adsorption av biopolymerer och deras LbL-formation på gränsytan vätska-fast fas, där adsorptionsförloppet och det adsorberade skiktet bestående av biopolymerer studerats med en mängd olika tekniker. Huvudtekniken var kvartskristallmikrovåg med energidissipations-registrering (QCM-D), som mäter massan inklusive inkorporerat vatten, samt de viskoelastiska egenskaperna hos ett adsorberat skikt. Som komplement till denna teknik användes ofta optiska metoder, till exempel ellipsometri och ”dubbel polarisationsinterferometri (DPI)”, två tekniker som endast mäter massan av de adsorberade biopolymererna. Genom denna kombination av metoder kunde massan av inkorporerat vatten i filmen och filmens densitet bestämmas. Dessutom användes ytkraftsapparaten (SFA), röntgenfotoelektronspektrometri (XPS), och fluorescens-spektroskopiteknikerna TIRF och FRET i några undersökningar för att erhålla information om skiktens struktur, kemiska sammansättning och polymerernas diffusion inom skiktet.Adsorptionsstudier av glycoproteinet mucin, som har en central roll i funktionen av slemhinnan, avslöjade att trots att mucinet har en negativ nettoladdning adsorberade det ändå på negativt laddade substrat. Det adsorberade lagret var väldigt hydratiserat och hade en låg andel mucin i direkt kontakt med ytan. Vi påvisade vikten av att noga undersöka mucinet som användes, eftersom olika renhet, till exempel i form av förekomsten av albumin gav upphov till olika adsorptionsbeteende gällande både adsorberad mängd och struktur. En stor andel av det adsorberade mucinlagret desorberade när det exponerades för den anjoniska tensiden natriumdodecylsulfat, SDS. Vi visade att ett skyddande lager av den katjoniska polysackariden chitosan kunde adsorberas på mucinet och att mucin-chitosan-komplexen inte desorberade när SDS tillsattes. Därtill studerades växelverkan mellan chitosan och SDS på gränsytan vätska-fast fas, i bulken och på luft-vattengränsytan. Komplex av chitosan-SDS bildades i samtliga miljöer och en nettoladdningsomsvängning från positiv till negativ observerades när koncentrationen av SDS ökades.Vidare kunde LbL-tekniken nyttjas för att skapa ett multilagerlikt skikt genom att alternerande adsorbera mucin och chitosan på kiseldioxidsubstrat. Denna teknik användes även med två proteiner, lysozym och β-kasein, med målet att skapa ett multilager bestående av endast proteiner. Dessa proteiner bildade komplex på gränsytan vätska-fast fas i form av ett blandat proteinlager, men uppbyggnaden var väldigt oregelbunden med en ökning i adsorberad mängd per proteindeponeringscykel som var avsevärt mindre än ett monolager.Inom området för biomaterial utgör de antibakteriella och antihäftande egenskaperna hos chitosan respektive heparin en lovande blandning för beläggningar av medicinska implantat. Baserat på detta konstruerade vi multilagerfilmer av chitosan och heparin med olika deponeringslösningar och undersökte dynamiken och filmens struktur i detalj. Chitosan-heparin-filmen var starkt hydratiserad, bestående av cirka 60-80 vikt-% vatten beroende på deponeringsbetingelserna. Den adsorberade mängden och tjockleken på filmen ökade nästan exponentiellt med antal deponeringar, vilket förklarades med chitosanets förmåga att diffundera genom filmen under uppbyggnaden. Med ett nytt angreppssätt använde vi FRET för att bevisa diffusionen av fluorescerande färgmärkt chitosan i filmen under uppbyggnaden. Diffusionskoefficienten var i princip oberoende av pH och jonstyrka under deponeringen och följaktligen av filmens struktur. Genom att använda ett pH-känsligt färgämne begravt under sju biskikt av chitosan-heparin visade vi att färgämnet i hög grad påverkades av laddningen på det yttersta lagret. Från QCM-D-data lade vi fram teorin om att en ökning av energidissipationen för ett lager inte nödvändigtvis indikerar att lagrets struktur har blivit mindre styvt.

Place, publisher, year, edition, pages
Stockholm: KTH, 2009. 69 p.
Trita-CHE-Report, ISSN 1654-1081 ; 2009:49
Layer-by-layer, multilayer, adsorption, biopolymers, Chitosan, Heparin, Mucin, Albumin, Lysozyme, β-casein, SDS, QCM-D, Ellipsometri, DPI, TIRF, FRET, SFA, layer structure, solvent content, vertical diffusion, exponential growth, solid-liquid interface, deposition conditions
National Category
Physical Chemistry
urn:nbn:se:kth:diva-11058 (URN)978-91-7415-419-1 (ISBN)
Public defence
2009-10-09, hörsal F3, KTH, Lindstedtsvägen 26, Stockholm, 13:00 (English)
QC 20100729Available from: 2009-09-21 Created: 2009-09-14 Last updated: 2011-09-20Bibliographically approved

Open Access in DiVA

No full text

Other links

Publisher's full textScopus

Search in DiVA

By author/editor
Lundin, MariaBlomberg, Eva
By organisation
Surface and Corrosion Science
In the same journal
Chemical SciencesPhysical Chemistry

Search outside of DiVA

GoogleGoogle Scholar
The number of downloads is the sum of all downloads of full texts. It may include eg previous versions that are now no longer available

Altmetric score

Total: 43 hits
ReferencesLink to record
Permanent link

Direct link