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

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 SiAOH 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.

Prevention of Biofilm Associated Infections and Degradation of Polymeric Materials Used in Biomedical Applications

“…During the exposure the formation and increasing concentration of low molecular weight compounds in silicone rubber were observed. These substances were the same hydrolyzed compounds that were detected during the in vivo use of silicone rubber tracheostomy tubes (Kaali et al, 2010a). In addition, polyurethane showed chemical property changes due to the exposure to artificial body fluids and based on the results it was determined that oxidative degradation took place.…”

“…polyurethane) are more likely to hydrolyze or oxidize, while polyether type polymers are more stable, showing minimal degradation during long-term exposure to human body environment. Chain-scissions and/or crosslinking occur in addition to hydrolytic degradation (Kaali et al, 2010a). As previously discussed, the biofilm attachment to the surface of the polymeric materials plays a vital role in the initiation and propagation of the degradation process.…”

“…The chain-ends may adsorb an increasing amount of water which can further catalyze the reaction and lead to the complete breakdown of the material. This is the typical degradation mechanism for polyesters, polyamides and polycarbonates, however, the hydrolytic degradation of the stable poly(dimethylsiloxane) may also occur during in vivo use (Kaali et al, 2010a, Lukasiak et al, 2003. Recent long-term studies have confirmed that silicone tracheostomy tubes undergo hydrolytic degradation during use (Kaali et al, 2010a).…”

“…This is the typical degradation mechanism for polyesters, polyamides and polycarbonates, however, the hydrolytic degradation of the stable poly(dimethylsiloxane) may also occur during in vivo use (Kaali et al, 2010a, Lukasiak et al, 2003. Recent long-term studies have confirmed that silicone tracheostomy tubes undergo hydrolytic degradation during use (Kaali et al, 2010a). Tubes, with an exposure time from one to six months, from several patients were collected and the analysis by Scanning Electron Microscopy (SEM), Fourier Transform Infrared Spectroscopy (FTIR) and Matrix Assisted Laser Desorption/Ionization Time of Flight Mass Spectrometry (MALDI TOF MS) showed degradation of silicone rubber after just 1 months exposure.…”

Monitoring of Wild Pseudomonas Biofilm Strain Conditions Using Statistical Characterization of Scanning Electron Microscopy Images

“…Bacteria removal performance has been compared by DeQueiroz and Day 82 , using different imaging techniques like SEM, TEM, CSLM, and analysed using Fourier transform infrared (FTIR) spectroscopy. Identical analysis has also been used in other applications like material degradation 83 . Comparison of biofilm characterization has been done through combination of SEM, CLSM and light microscopy using gram staining by Kania et al…”