Degradation of biomedical polydimethylsiloxanes during exposure to in vivo biofilm environment monitored by FE-SEM, ATR-FTIR, and MALDI-TOF MS

Authors

  • Peter Kaali,

    1. School of Chemical Science and Engineering, Department of Fibre and Polymer Technology, Division of Polymeric Materials, Royal Institute of Technology (KTH), Stockholm SE-100 44, Sweden
    2. Department of Polymer Engineering, University of Miskolc, Miskolc HU-3515, Hungary
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  • Dane Momcilovic,

    1. School of Chemical Science and Engineering, Department of Fibre and Polymer Technology, Division of Polymeric Materials, Royal Institute of Technology (KTH), Stockholm SE-100 44, Sweden
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  • Agneta Markström,

    1. Department of Clinical Sciences, Danderyd Hospital, Karolinska Institutet, National Respiratory Centre, Stockholm SE-18 288, Sweden
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  • Ragnhild Aune,

    1. School of Industrial Engineering and Management, Department of Material Science and Engineering, Division of Materials Process Science Royal Institute of Technology (KTH), Stockholm SE-100 44, Sweden
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  • Gyorgy Czel,

    1. Department of Polymer Engineering, University of Miskolc, Miskolc HU-3515, Hungary
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  • Sigbritt Karlsson

    Corresponding author
    1. School of Chemical Science and Engineering, Department of Fibre and Polymer Technology, Division of Polymeric Materials, Royal Institute of Technology (KTH), Stockholm SE-100 44, Sweden
    • School of Chemical Science and Engineering, Department of Fibre and Polymer Technology, Division of Polymeric Materials, Royal Institute of Technology (KTH), Stockholm SE-100 44, Sweden
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Abstract

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 1, 3, and 6 months. The chemical degradation was monitored by MALDI-TOF MS, ATR-FTIR, 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[BOND]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. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2010

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