Light based anti-infectives: ultraviolet C irradiation, photodynamic therapy, blue light, and beyond.
- Light-based anti-infectives work against biofilms and localized infections.
- Ultraviolet C light will kill all pathogens without killing host mammalian cells.
- Photodynamic inactivation produces reactive oxygen species that kill pathogens.
- Blue light can kill many pathogens due to accumulation of porphyrins.
- Femtosecond infrared laser pulses can selectively kill pathogens.
Owing to the worldwide increase in antibiotic resistance, researchers are investigating alternative anti-infective strategies to which it is supposed microorganisms will be unable to develop resistance.
Prominent among these strategies, is a group of approaches which rely on light to deliver the killing blow.
As is well known, ultraviolet light, particularly UVC (200–280nm), is germicidal, but it has not been much developed as an anti-infective approach until recently, when it was realized that the possible adverse effects to host tissue were relatively minor compared to its high activity in killing pathogens.
Photodynamic therapy is the combination of non-toxic photosensitizing dyes with harmless visible light that together produce abundant destructive reactive oxygen species (ROS).
Certain cationic dyes or photosensitizers have good specificity for binding to microbial cells while sparing host mammalian cells and can be used for treating many localized infections, both superficial and even deep-seated by using fiber optic delivered light.
Many microbial cells are highly sensitive to killing by blue light (400–470 nm) due to accumulation of naturally occurring photosensitizers such as porphyrins and flavins. Near infrared light has also been shown to have antimicrobial effects against certain species.
Clinical applications of these technologies include skin, dental, wound, stomach, nasal, toenail and other infections which are amenable to effective light delivery.
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