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Degradation of Biomedical Polydimethylsiloxanes During Exposure to In Vivo Biofilm Environment Monitored by FE-SEM, ATR-FTIR, and MALDI-TOF MS
KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.
KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.
KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Materials Process Science.
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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.

Place, publisher, year, edition, pages
2010. Vol. 115, no 2, 802-810 p.
Keyword [en]
biocompatibility, degradation, MALDI, FTIR, polysiloxanes, silicone-rubber, hydrophobic recovery, ir spectroscopy, identification, elastomers
URN: urn:nbn:se:kth:diva-18955DOI: 10.1002/app.31119ISI: 000271680700020ScopusID: 2-s2.0-73849113712OAI: diva2:337002
QC 20100525Available from: 2010-08-05 Created: 2010-08-05 Last updated: 2011-07-13Bibliographically approved
In thesis
1. Antimicrobial Polymer Composites for Medical Applications
Open this publication in new window or tab >>Antimicrobial Polymer Composites for Medical Applications
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.
Trita-CHE-Report, ISSN 1654-1081 ; 2011:19
medical polymers, antimicrobial, body fluids, degradation
National Category
Polymer Chemistry
urn:nbn:se:kth:diva-33393 (URN)978-91-7415-899-1 (ISBN)
Public defence
2011-05-13, F3, Lindstedtsvägen 23 KTH, Stockholm, 13:00 (English)
QC 20110511Available from: 2011-05-11 Created: 2011-05-05 Last updated: 2011-05-11Bibliographically approved

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