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Antimicrobial Polymer Composites for Medical Applications
KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymeric Materials.
2011 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

The current study and discuss the long-term properties of biomedical polymers in vitro and invivo and presents means to design and manufacture antimicrobial composites. Antimicrobialcomposites with reduced tendency for biofilm formation should lead to lower risk for medicaldevice associated infection.The first part analyse in vivo degradation of invasive silicone rubber tracheostomy tubes andpresents degradation mechanism, degradation products and the estimated lifetime of thematerials.. It was found that silicone tubes undergo hydrolysis during the long-term exposurein vivo, which in turn results in decreased stability of the polymer due to surface alterationsand the formation of low molecular weight compounds.The second part of the study presents the manufacturing of composites with single, binary andternary ion-exchanged zeolites as an antimicrobial agent. The ion distribution and release ofthe zeolites and the antimicrobial efficiency of the different systems showed that single silverion-exchanged zeolite was superior to the other samples. Antimicrobial composites wereprepared by mixing the above-mentioned zeolites and pure zeolite (without any ion) withdifferent fractions into polyether (TPU), polyether (PEU) polyurethane and silicone rubber.The antimicrobial efficiency of binary and ternary ion-exchanged samples was similar whichis thought to be due to the ion distribution in the crystal structure.The changes in the mechanical and surface properties of the composites due to the zeolitecontent demonstrated that the increasing zeolite content reduced the mechanical propertieswhile the surface properties did not change significantly. The antimicrobial tests showed thatthe silver-containing composite was the most efficient among all the other samples. Thebinary and ternary ion-exchanged composites expressed similar antimicrobial efficiency as itwas seen previously for the different zeolite systems. Biocompatibility was studied byexposure to artificial body fluids to simulate the degradation of the composites in the humanbody. Significant changes were observed in the morphology, the surface properties and the chemical structure.

Place, publisher, year, edition, pages
Stockholm: KTH Royal Institute of Technology , 2011. , 79 p.
Series
Trita-CHE-Report, ISSN 1654-1081 ; 2011:19
Keyword [en]
medical polymers, antimicrobial, body fluids, degradation
National Category
Polymer Chemistry
Identifiers
URN: urn:nbn:se:kth:diva-33393ISBN: 978-91-7415-899-1OAI: oai:DiVA.org:kth-33393DiVA: diva2:414982
Public defence
2011-05-13, F3, Lindstedtsvägen 23 KTH, Stockholm, 13:00 (English)
Opponent
Supervisors
Note
QC 20110511Available from: 2011-05-11 Created: 2011-05-05 Last updated: 2011-05-11Bibliographically approved
List of papers
1. Degradation of Biomedical Polydimethylsiloxanes During Exposure to In Vivo Biofilm Environment Monitored by FE-SEM, ATR-FTIR, and MALDI-TOF MS
Open this publication in new window or tab >>Degradation of Biomedical Polydimethylsiloxanes During Exposure to In Vivo Biofilm Environment Monitored by FE-SEM, ATR-FTIR, and MALDI-TOF MS
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2010 (English)In: Journal of Applied Polymer Science, ISSN 0021-8995, E-ISSN 1097-4628, Vol. 115, no 2, 802-810 p.Article in journal (Refereed) Published
Abstract [en]

Polymers used for biomedical purposes in medical devices are usually requested to be inert to degradation. This article describes that slow irreversible changes were observed in silicone surfaces exposed to in vivo biofilms even if silicone, in general, is supposed to have excellent long-term properties. Tracheostomy tubes made of silicone rubber were exposed to in vivo biofilm environments in clinical tests for periods of 7, 3, and 6 months. The chemical degradation was monitored by MALDI-TOF MS, ATR-FTI.R, and FE-SEM. In addition, the physical changes were monitored by contact angle and hardness measurements. Cyclic polydimethylsiloxane (PDMS) was detected on the surfaces of new (unaged) silicones. On the surfaces of the in vivo samples new compounds, presumably linear methyl-hydroxyl-terminated PDMS, were detected in addition to cyclic PDMS. These compounds may be formed as a result of the hydrolysis of linear dimethyl terminated PDMS, which is also present in the silicone rubber. ATR-FTIR spectroscopy confirmed that hydrolysis had indeed occurred during the in vivo exposure, since Si-OH groups were detected. Furthermore, significant changes in the topography were detected by FE-SEM, indicating the initiation of degradation. No significant changes in the contact angle of the in vivo used samples were observed, but this information may be shielded by the fact that biofilm may remain on the surface, despite the thorough cleaning before the analysis. It is also possible that the surface hydrophobicity was recovered by the diffusion of linear low-molecular-weight compounds from the bulk.

Keyword
biocompatibility, degradation, MALDI, FTIR, polysiloxanes, silicone-rubber, hydrophobic recovery, ir spectroscopy, identification, elastomers
Identifiers
urn:nbn:se:kth:diva-18955 (URN)10.1002/app.31119 (DOI)000271680700020 ()2-s2.0-73849113712 (ScopusID)
Note
QC 20100525Available from: 2010-08-05 Created: 2010-08-05 Last updated: 2011-07-13Bibliographically approved
2. Antimicrobial properties of Ag+ loaded zeolite polyester polyurethane and silicone rubber and long-term properties after exposure to in-vitro ageing
Open this publication in new window or tab >>Antimicrobial properties of Ag+ loaded zeolite polyester polyurethane and silicone rubber and long-term properties after exposure to in-vitro ageing
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2010 (English)In: Polymer degradation and stability, ISSN 0141-3910, E-ISSN 1873-2321, Vol. 95, no 9, 1456-1465 p.Article in journal (Refereed) Published
Abstract [en]

In biomedical applications, tubes (e.g. catheters etc.) are commonly produced from polyurethane (PU) and silicone rubber which are known to be biocompatible materials. Several studies have shown that tubes, which are connected to the body (invasive) (especially urinary, tracheotomy and central venous catheters) are associated with infections. The present study reports the development of a new method aiming at obtaining antibacterial properties for PU and silicone rubber by mixing respective material with a natural antibacterial agent (Ag+ loaded zeolite) in different weight fractions. The influence of the zeolite content on the antimicrobial properties were analysed by exposure to bacteria (ISO 22196) and mixtures of fungi (ISO 846). The materials were also subject to artificial body fluids (Artificial Lysosomal Fluid (ALF) and Gamble's solution) for periods up to three months and the subsequent changes in the chemical properties after in-vitro exposure were determined by Matrix Assisted Laser Deposition/Ionization Time Of Flight Mass Spectrometry (MALDI-TOF MS) and Attenuated Total Reflection Fourier Transform Infra Red spectroscopy (ATR-FTIR). It was established that the antimicrobial effect of the materials increased with the increase of the zeolite content. The wettability of the materials was found to decrease significantly during the in-vitro exposure, but this could not be correlated to the zeolite content. In the PU samples, the formation of free carbonyl and -OH groups was observed, which corresponds to oxidative degradation. In case of the silicone rubber the ratio of cyclic PDMS to linear PDMS (H, CH3 and dimethyl terminated) decreased, which indicates a change in the concentration of the compounds. The formation and increase of the O-H bond during the exposure was also confirmed by the infrared spectra of the material which corresponds to hydrolysis of the silicone rubber.

Keyword
Degradation, In-vitro, Silver zeolite, Antimicrobial, Polymer, MALDI-TOF MS
National Category
Polymer Chemistry
Identifiers
urn:nbn:se:kth:diva-26717 (URN)10.1016/j.polymdegradstab.2010.06.024 (DOI)000281369500003 ()2-s2.0-77955511183 (ScopusID)
Note
QC 20101126Available from: 2010-11-26 Created: 2010-11-26 Last updated: 2011-05-11Bibliographically approved
3. Modelling the ion distribution in single, binary and ternary ion exchanged Azeolite
Open this publication in new window or tab >>Modelling the ion distribution in single, binary and ternary ion exchanged Azeolite
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2011 (English)In: Microporous and Mesoporous Materials, ISSN 1387-1811Article in journal (Other academic) Published
National Category
Materials Engineering Polymer Chemistry
Identifiers
urn:nbn:se:kth:diva-33589 (URN)
Note
QS 2011Available from: 2011-05-11 Created: 2011-05-11 Last updated: 2011-05-11Bibliographically approved
4. The influence of Ag(+), Zn(2+) and Cu(2+) exchanged zeolite on antimicrobial and long term in vitro stability of medical grade polyether polyurethane
Open this publication in new window or tab >>The influence of Ag(+), Zn(2+) and Cu(2+) exchanged zeolite on antimicrobial and long term in vitro stability of medical grade polyether polyurethane
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2011 (English)In: Express Polymer letters, ISSN 1788-618X, Vol. 5, no 12, 1028-1040 p.Article in journal (Refereed) Published
Abstract [en]

This study aims to investigate the limitations and applicability of different ion exchanged zeolites as antimicrobial additive in thermoplastic polyether type polyurethanes. These composites were designed to improve the health quality of hospitalized patients by expressing both biocompatibility and relevant antimicrobial activity. The zeolites were exchanged with silver, copper and zinc ions and single, binary and ternary ion-exchanged zeolite-polyurethane composites were prepared. The antimicrobial activity and the resistance of the composites against the human environment play vital role in the applicability of the materials as a medical device therefore these properties were investigated. The antimicrobial test were performed on Methicillin-resistant Staphylococcus aureus, Pseudomonas aeruginosa and Candida tropicalis. The tests showed that the efficiency of the silver ions is superior to the other single ionic systems. Besides, the binary and ternary ion-exchanged samples had similar antimicrobial efficiency regardless the type of the ions in the zeolite. The biocompatibility tests were carried out in-vitro in artificial body fluids for a period of 12 weeks. As a result of the in-vitro test, degradation of the composites were observed and the structural changes of the materials were detected and described by Scanning Electron Microscopy, Contact Angle measurements and Attenuated Total Reflection Fourier Transform Infrared Spectroscopy.

Keyword
biocomposites, body fluid, ion-exchanged zeolite, antibacterial, in-vitro test
National Category
Polymer Chemistry
Identifiers
urn:nbn:se:kth:diva-33590 (URN)10.3144/expresspolymlett.2011.101 (DOI)000296092700002 ()2-s2.0-80053918726 (ScopusID)
Funder
Swedish Research Council
Note
QS 2011. Updated from submitted to published. Previous title: The influence of Ag+, Zn2+ and Cu2+ exchanged zeolite on antimicrobial and long term in vitro stability of medical grade polyether polyurethaneAvailable from: 2011-05-11 Created: 2011-05-11 Last updated: 2011-11-17Bibliographically approved
5. Prevention of Biofilm Associated Infections and Degradation of Polymeric Materials Used in Biomedical Applications
Open this publication in new window or tab >>Prevention of Biofilm Associated Infections and Degradation of Polymeric Materials Used in Biomedical Applications
2011 (English)In: Biomedical Engineering, Trends in Materials Science / [ed] Anthony N. Laskovski, InTech , 2011Chapter in book (Refereed)
Place, publisher, year, edition, pages
InTech, 2011
National Category
Polymer Chemistry
Identifiers
urn:nbn:se:kth:diva-33587 (URN)978-953-307-513-6 (ISBN)
Note
QC 20110511Available from: 2011-05-11 Created: 2011-05-11 Last updated: 2011-05-11Bibliographically approved

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