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Development of New Bacteria-Reducing Surfaces
KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology. (Träkemi)ORCID iD: 0000-0003-1812-7336
2009 (English)Licentiate thesis, comprehensive summary (Other academic)
Abstract [en]

In recent years, antibacterial surfaces have been a subject of increased interest. Especiallyinteresting are non-leaching, contact-active surfaces that physically disrupts the bacterialcell using immobilised cationic polymers. Thus the risks of bacterial resistance and discharge of hazardous biocides is minimised. The assembly of such surfaces is elaborate andusually involves organic solvents. Here, polyelectrolyte multilayers (PEM) are proposed as an effective surface modification method, with an overall goal of producing antibacterial cellulose fibres. The PEM process is based on physical adsorption of oppositely charged polymers in aqueous solutions. Multilayers were formed with the bactericidal polymer polyvinylamine (PVAm) and polyacrylic acid. PVAm compounds with hydrophobic modificationswere applied as well, as they possess increased antibacterial activity in solution.

In this work, the multilayer formation was studied on model surfaces of silicone oxide and glass in order to obtain fundamental knowledge of the polymer system. QCM-D and reflectometry, which detect total mass including bound water and polymer mass only, respectively, were used to analyse the layer formation. Salt-concentrations were varied at 1, 10 or 100 mM NaCl. A stepwise multilayer formation with exponential-like polymer adsorption but with decreasing water content for each layer was seen at all salt concentrations.A higher salt concentration resulted in an increased adsorbed mass. No significant differences in adsorption between the modified and unmodified PVAm could be detected. AFM imaging applied to multilayers having nine layers showed large surface aggregates under high salt conditions for the C6-modified PVAm. Dynamic light scattering showed that the polymer occurred as single molecules in solution; hence it was concluded that theaggregation is surface-associated.

The multilayers were then tested for bacterial growth inhibition. The relative bacterial inhibition was time-dependent, as the surface was saturated with bacteria over time. After two hours, a maximal inhibition of 99 % could be observed for the multilayers. After eight hours, a moderate inhibition of less than 40 % was detected. Using multilayers affected the results positively compared to single layers. After three layers, though, no further reductionwas seen. Viability staining of the surface-adhered bacteria revealed that the adhered bacteria had intact membranes. Therefore, the microbiological properties of the multilayers can at this point be described more as growth-inhibiting by bacterial adhesion effectsthan as biocidal. However, this work has shown the importance of combining surface characterisation and microbial testing to understand the bacteria-surface interaction.

Place, publisher, year, edition, pages
Stockholm: KTH , 2009. , 36 p.
Trita-CHE-Report, ISSN 1654-1081 ; 2009:25
Keyword [en]
antibacterial, polyelectrolyte multilayers, polyvinylamine
National Category
Paper, Pulp and Fiber Technology
URN: urn:nbn:se:kth:diva-10586ISBN: 978-91-7415-340-8OAI: diva2:219982
2009-06-05, STFI-salen, KTH, Drottning Kristinas väg 6, Stockholm, Innventia, 14:00 (Swedish)
Biointeractive fibres
Available from: 2009-06-08 Created: 2009-05-28 Last updated: 2010-10-14Bibliographically 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.

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
urn:nbn:se:kth:diva-19236 (URN)10.1021/am9006879 (DOI)000274747200015 ()2-s2.0-79951656241 (ScopusID)
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.

Polyvinylamine, Hydrophobic modification, Polyacrylic acid, Polyelectrolyte multilayers, Antibacterial surfaces
National Category
Chemical Engineering
urn:nbn:se:kth:diva-25252 (URN)10.1016/j.colsurfb.2011.06.023 (DOI)000295344800015 ()2-s2.0-80052083682 (ScopusID)
QC 20101014 Updated from submitted to published.Available from: 2010-10-14 Created: 2010-10-14 Last updated: 2012-02-28Bibliographically approved

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