Photosensitisation studies of silicone polymer doped with methylene blue and nanogold for antimicrobial applications

Abstract

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 log 10 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.

Revisiting Current Photoactive Materials for Antimicrobial Photodynamic Therapy

“…The mechanical properties of the photoactive material (e.g., elasticity) were not affected, confirming the possibility to be incorporated in catheters in order to reduce catheter acquired infections [ 58 , 59 ]. Since then, and following the same approach, this group prepared other photoactive materials based on polymers (polyurethane, silicone) and other materials used in catheters and in hospital touch surfaces (screen protectors for telephones and tablets, covers, keyboards, and hand dryers) embedded with PSs [MB, toluidine blue O (TBO), crystal violet] and AuNP against methicillin-resistant S. aureus (MRSA), S. epidermidis , Saccharomyces cerevisiae , E. coli , Bacteriophage MS2, the fungus-like organism Pythium ultimum , and the filamentous fungus Botrytis cinereal , and the results showed an effective inactivation of all microorganisms [ 60 , 61 , 62 , 63 , 64 , 65 , 66 , 67 , 68 ].…”

Comparative study of singlet oxygen production by photosensitiser dyes encapsulated in silicone: towards rational design of anti-microbial surfaces

“…Current research involves the use of photosensitiser dyes immobilised in polymers as part of an infection-control strategy in healthcare environments. [5][6][7][8][9][10][11][12][13][14][15][16][17][18][19] Cationic dyes such as methylene blue or crystal violet are proven antimicrobial agents against both Gram-positive and Gram-negative bacteria. [8][9][10][11][12][13][14][15][16][17][18][19] Porphyrins and phthalocyanines are also used for photodynamic therapy (PDT) applications, however, although they have been successfully incorporated into polymers, [20][21][22] the procedure is non-trivial as compared to swell-encapsulation.…”

“…Photobactericidal polymers can be synthesised using a simple dipping approach to incorporate photosensitiser dye molecules including methylene blue, toluidine blue O and crystal violet into polymers. 5,[11][12][13][14][15][16][17][18][19] Such dye-incorporated polymers have induced the lethal photosensitisation of both Gram-positive and Gramnegative bacteria, with samples demonstrating strong antimicrobial efficacy under laser irradiation and standard hospital lighting conditions. [5][6][7][8][9][10][11][12][13][14][15][16][17][18][19] Table 1 summarises representative examples of the light-activated antimicrobial activity of these dyes against both Gram-positive and Gram-negative bacteria.…”

Enhancing the Antibacterial Activity of Light-Activated Surfaces Containing Crystal Violet and ZnO Nanoparticles: Investigation of Nanoparticle Size, Capping Ligand, and Dopants

“…7 Type I involves the activated photosensitizer reacting directly with the substrate or molecule to form radicals, and type II involves the formation of singlet oxygen from ground-state molecular oxygen via the triplet state. 9 Common photosensitizers used to destroy cancerous tissues include Rose Bengal, 10,11 methylene blue, 8,12−16 and crystal violet (CV). 17−22 These photosensitizers can be coated onto polymers, and upon light activation, they generate ROS, causing oxidative damage and cell death.…”