Photosensitisation studies of silicone polymer doped with methylene blue and nanogold for antimicrobial applications
2015
Bovis, M. J. | Noimark, S. | Woodhams, J. H. | Kay, C. W. M. | Weiner, J. | Peveler, W. J. | Correia, A. | Wilson, M. | Allan, E. | Parkin, I. P. | MacRobert, A. J.
Photosensitisation of polymers has important potential clinical applications such as the prevention of catheter-associated urinary tract infections (CAUTIs). Polymers incorporated with methylene blue (MB) and 2 nm gold nanoparticles (AuNPs) are effective in killing bacteria at the surface following low power visible illumination. Studies of medical-grade silicone polymer samples including segments from urinary catheters were carried out to investigate the generation of reactive oxygen species and the involvement of Type 1 and 2 mechanisms. Singlet oxygen was observed using direct phosphorescence detection and hydroxyl radical generation using electron paramagnetic resonance (EPR) spectroscopy; we conclude that both Type 1 and 2 mechanisms can operate with polymeric photosensitisation. Transmission electron microscopy (TEM) directly demonstrated the incorporation of AuNPs at the surface of the silicone. Using silicone doped with MB AuNPs, a ≥3 log₁₀ reduction in the number of viable Staphylococcus epidermidis bacteria was achieved when exposed to low power laser light; prior sterilisation with ethylene oxide (EO) had no influence on efficacy.
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