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The creation of antibacterial fibres through physical adsorption of polyelectrolytes
KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Wood Chemistry and Pulp Technology. (Träkemi)ORCID iD: 0000-0003-1812-7336
2012 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Contact-active antibacterial surfaces with irreversibly attached antibacterial com-pounds are a sustainable alternative to traditional biocides. No chemicals are released into nature and the antibacterial mechanism reduces the risk of the evolution of re-sistant bacteria. However, the preparation of such surfaces is far from sustainable, as organic solvents and harsh reaction conditions commonly are required. An alter-native option is to use polyelectrolyte multilayers (PEM), based on physical ad-sorption, which can be performed in water-based solutions at room temperature. Although contact-active antibacterial PEMs have been reported previously, this is the first study of renewable cellulosic wood fibres.

The build-up of cationic polymer polyvinylamine (PVAm) and anionic polyacrylic acid (PAA) multilayers on model surfaces was studied to optimise adsorption. The amount of adsorbed polyelectrolytes was continuously growing with increasing number of layers, but remained dense and flat as the number of layers increased. The largest adsorption was obtained at a high salt concentration, which shielded the repulsion between the polymers.

Model surfaces were also used to evaluate the influence of the polymer and number of layers on the antibacterial properties. Multilayers on model surfaces showed a low bacteriostatic effect, with up to approximately 40 % inhibition for 3 layers of un-modified PVAm/PAA. In contrast, when the same multilayers were applied on cel-lulosic fibres, bacterial-growth inhibition of > 99.9% was obtained. Hydrophobically modified PVAm did not yield better results, despite being superior in solution. An increase in fibre charge by fibre oxidation led to the largest amount of adsorbed pol-ymer and the best antibacterial properties, an effect that lasted for weeks. Electron microscopy study of bacteria on the fibres showed that the bacteria interacted more on a highly charged surface and that the morphology of the bacterial cell could be affected. The effect was suggested to be due to electrostatic interaction with the pos-itively charged modified fibres. The promising results offer the possibilities of a new generation of antibacterial surfaces based on a renewable resource.

Abstract [sv]

Antibakteriella kontaktaktiva ytor som har ett antibakteriellt ämne permanent fäst på ytan är ett miljövänligt och säkrare alternativ till traditionell biocidanvändning. Inget utsläpp av giftiga ämnen sker från ytorna och detta tillsammans med den anti-bakteriella mekanismen minskar risken för att bakterierna utvecklar resistens. Till-verkningsprocessen i sig har dock hittills varit allt annat än miljövänlig, då den ke-miska modifieringen kräver organiska lösningsmedel och har reaktioner som kräver speciella villkor, t ex höga temperaturer. En alternativ ytmodifiering är att använda sig av fysikalisk adsorption av polyelektrolyter i multiskikt, eftersom detta kan göras i vat-tenlösningar och i rumstemperatur. Det här arbetet är det första som beskriver kon-takt-aktiva multilager på förnyelsebara svedbaserade cellulosafiber.

Som ett första steg gjordes en adsorptionsstudie på modellytor för att optimera ad-sorptionen av katjonisk polyvinylamin (PVAm) och anjonisk polyakrylsyra (PAA). Med ökande antal lager ökade totala mängden adsorberad polymer samtidigt som multilagerna förblev platta och täta. Den högsta adsorptionen skedde vid en hög salt-halt som minimerade den elektrostatiska repulsionen mellan polymerkedjorna.

Modellytor användes även för att studera hur de antibakteriella egenskaperna påver-kades av polymermodifiering och av antal lager. På dessa ytor uppmättes en låg bakte-riostatisk effekt med upp till 40 % inhibering av bakterietillväxten för tre lager av PVAm./PAA När däremot samma multilager fanns på cellulosafiber ökade in-hiberingen till uppemot 99.9 %. Hydrofobmodifiering av PVAm påverkade inte det antibakteriella resultatet när de var i multilager, trots bevisad ökad verkan i lösning. Genom att via oxidering öka fiberladdningen kunde mängden adsorberad polymer yt-terligare öka och resulterade i en förbättrad antibakteriell verkan som höll i sig i flera veckor. Elektronmikroskopi av bakterier på fiber visade en ökad interaktion med hög-laddade ytor och att bakteriernas cellmorfologi kan påverkas av ytorna.Den observerade antibakteriella effekten föreslås vara en följd av elektrostatisk inter-aktion mellan de negativt laddade bakterierna och positivt laddade modifierade fibrena. Resultaten är lovande och banar väg för nya kontakt-aktiva antibakteriella material.

Place, publisher, year, edition, pages
Stockholm: KTH Royal Institute of Technology, 2012. , 58 p.
Series
Trita-CHE-Report, ISSN 1654-1081 ; 2012:11
Keyword [en]
antibacterial, polyelectrolyte multilayers, polyvinylamine, contact-active antibacterial surfaces
National Category
Paper, Pulp and Fiber Technology
Identifiers
URN: urn:nbn:se:kth:diva-90731ISBN: 978-91-7501-274-2 (print)OAI: oai:DiVA.org:kth-90731DiVA: diva2:506212
Public defence
2012-03-16, F3, Lindstedtsvägen 26, KTH, Stockholm, 10:00 (English)
Opponent
Supervisors
Projects
Biointeractive fibres with antibacterial properties
Available from: 2012-02-28 Created: 2012-02-28 Last updated: 2013-02-25Bibliographically approved
List of papers
1. Interactions of Hydrophobically Modified Polyvinylamines: Adsorption Behavior at Charged Surfaces and the Formation of Polyelectrolyte Multilayers with Polyacrylic Acid
Open this publication in new window or tab >>Interactions of Hydrophobically Modified Polyvinylamines: Adsorption Behavior at Charged Surfaces and the Formation of Polyelectrolyte Multilayers with Polyacrylic Acid
2010 (English)In: ACS Applied Materials & Interfaces, ISSN 1944-8244, Vol. 2, no 2, 425-433 p.Article in journal (Refereed) Published
Abstract [en]

The structure and adsorption behaviors of two types of hydrophobically modified polyvinylamines (PVAm) containing substituents of hexyl and octyl chains were compared to a native polyvinylamine sample. The conformation of dissolved polyvinylamines was studied in aqueous salt solutions using dynamic light scattering. Modified PVAm showed hydrodynamic diameters similar to native PVAm, which indicated that all PVAm polymers were present as single molecules in solution. The adsorption of the polyvinylamines, both native and hydrophobically modified, from aqueous solution onto negatively charged silica surfaces was studied in situ by reflectometry and quartz crystal microgravimetry with dissipation. Polyelectrolyte multilayers; (PEM) with up to nine individual layers were formed together with poly(acrylic acid). Obtained PEM structures were rigid and showed high adsorbed amounts combined with low dissipation, with similar results for both the modified and unmodified PVAm. This suggests that electrostatics dominated the PEM formation. At lower salt concentrations, the hydrophobically modified PVAm produced multilayers with low water contents, indicating that secondary interactions induced by the hydrophobic constituents can also have a significant influence on the properties of the formed layers. The surface structure of PEMs with nine individual layers was imaged in dry state using atomic force microscopy in a dynamic mode. Modified PVAm was found to induce a different structure of the PEM at 100 mM, with larger aggregates compared to those of native PVAm. From these results, it is proposed that modified PVAm can induce aggregation within the PEM, whereas PVAm remains as single molecules in solution.

Keyword
polyvinylamine, hydrophobical modification, poly(acrylic acid), polyelectrolyte multilayers, reflectometry, quartz crystal microbalance, amphiphilic polyelectrolytes, weak polyelectrolytes, qcm-d, silica, frequency, cellulose, kinetics, fibers, layers, setup
National Category
Paper, Pulp and Fiber Technology
Identifiers
urn:nbn:se:kth:diva-19236 (URN)10.1021/am9006879 (DOI)000274747200015 ()2-s2.0-79951656241 (Scopus ID)
Note
QC 20110210Available from: 2010-08-05 Created: 2010-08-05 Last updated: 2012-02-28Bibliographically approved
2. Bacterial-growth inhibiting properties of multilayers formed with modified polyvinylamine
Open this publication in new window or tab >>Bacterial-growth inhibiting properties of multilayers formed with modified polyvinylamine
2011 (English)In: Colloids and Surfaces B: Biointerfaces, ISSN 0927-7765, E-ISSN 1873-4367, Vol. 88, no 1, 115-120 p.Article in journal (Refereed) Published
Abstract [en]

New methods are needed to fight antibiotic-resistant bacteria. One alternative that has been proposed is non-leaching, permanently antibacterial surfaces. In this study, we test multilayers formed with antibacterial cationic polyvinylamine (PVAm) and polyacrylic acid (PAA) in a growth-inhibition assay. Both hydrophobically modified and native PVAm were investigated. Multilayers did reduce the bacterial growth, as compared to single layers. However, the sampling time in the assay was critical, as the treated surface area is a capacity-limiting factor. After 2 h incubation, a maximal growth inhibition of more than 99% was achieved with multilayers. In contrast, after 8 h we observed a maximal growth-inhibition of 40%. At longer incubation times, the surface becomes saturated, which explains the observed time-dependent effectiveness. The polymers giving multilayers with the strongest growth-inhibiting properties were native PVAm and PVAm modified with C(8), which also were the polymers with highest charge density. We therefore conclude that this effect is mainly an electrostatically driven process. Viability staining using a fluorescent stain showed a high viability rate of the adhered bacteria. The multilayers are therefore more bacteriostatic than antibacterial.

Keyword
Polyvinylamine, Hydrophobic modification, Polyacrylic acid, Polyelectrolyte multilayers, Antibacterial surfaces
National Category
Chemical Engineering
Identifiers
urn:nbn:se:kth:diva-25252 (URN)10.1016/j.colsurfb.2011.06.023 (DOI)000295344800015 ()2-s2.0-80052083682 (Scopus ID)
Note
QC 20101014 Updated from submitted to published.Available from: 2010-10-14 Created: 2010-10-14 Last updated: 2017-12-12Bibliographically approved
3. Biointeractive antibacterial fibres using polyelectrolyte multilayer modification
Open this publication in new window or tab >>Biointeractive antibacterial fibres using polyelectrolyte multilayer modification
2012 (English)In: Cellulose (London), ISSN 0969-0239, E-ISSN 1572-882X, Vol. 19, no 5, 1731-1741 p.Article in journal (Refereed) Published
Abstract [en]

Contact-active antibacterial surfaces are a novel tool in the antibacterial battle. The preparation of such surfaces usually involves harsh reaction conditions and organic solvents. A more sustainable alternative would involve physical adsorption of water-soluble polyelectrolytes using a renewable substrate. Here, highly charged cationic polyvinylamines (PVAm), with or without hydrophobic modifications, have been adsorbed onto the naturally anionic cellulosic wood-fibres. To increase the amount of PVAm, polyelectrolyte multilayers were prepared using polyacrylic acid as the anionic polyelectrolyte. The modified fibres were characterised for PVAm content, water retention and antibacterial properties. The use of multilayers increased the total polymer content without notably reducing the water swelling. The fibres were shown to have excellent bioactive properties and reduced waterborne Escherichia coli and Bacillus subtilis by more than 99.9 %, which is a generally accepted definition of an antibacterial material. A large reduction in bacterial growth was observed upon addition of nutrients, although minor growth was detected after 24 h. The results further show that one adsorbed polymer layer was sufficient to obtain a contact-active surface, which makes the PVAm multilayer system seemingly unique. No polymer leaching from any of the samples was detected, indicating that the fibres work via a contact-active antibacterial mechanism. The results show the feasibility of constructing a sustainable antibacterial material using a renewable substrate and water-based solutions in the material construction process.

Keyword
Antibacterial, Fibre modification, Contact-active, Polyelectrolyte adsorption, Polyelectrolyte multilayers, Cellulose fibres
National Category
Paper, Pulp and Fiber Technology
Identifiers
urn:nbn:se:kth:diva-90748 (URN)10.1007/s10570-012-9742-0 (DOI)000307768100023 ()2-s2.0-84865423511 (Scopus ID)
Note

QC 20121004. Updated from manuscript to article in journal.

Available from: 2012-02-28 Created: 2012-02-28 Last updated: 2017-12-07Bibliographically approved
4. The Antibacterial Effect of Contact-Active Multilayers: A Mechanistic Approach
Open this publication in new window or tab >>The Antibacterial Effect of Contact-Active Multilayers: A Mechanistic Approach
(English)Manuscript (preprint) (Other academic)
National Category
Paper, Pulp and Fiber Technology
Identifiers
urn:nbn:se:kth:diva-90749 (URN)
Note
QS 2012Available from: 2012-02-28 Created: 2012-02-28 Last updated: 2012-02-28Bibliographically approved
5. Antibacterial Polyelectrolyte Multilayers on Cellulosic Pulp Fibres
Open this publication in new window or tab >>Antibacterial Polyelectrolyte Multilayers on Cellulosic Pulp Fibres
(English)Manuscript (preprint) (Other academic)
National Category
Paper, Pulp and Fiber Technology
Identifiers
urn:nbn:se:kth:diva-90750 (URN)
Note
QS 2012Available from: 2012-02-28 Created: 2012-02-28 Last updated: 2012-02-28Bibliographically approved

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