Photosensitized inactivation of microorganisms

Abstract

Despite major advances in medicine in the last 100 years, microbiologically-based diseases continue to present enormous global health problems. New approaches that are effective, affordable and widely applicable and that are not susceptible to resistance are urgently needed. The photodynamic approach is known to meet at least some of these criteria and, with the creation and testing of new photosensitisers, may develop to meet all of them. The approach, involving the combination of light and a photosensitising drug, is currently being applied to the treatment of diseases caused by bacteria, yeasts, viruses and parasites, as well as to sterilisation of blood and other products.

A comparative in vitro photoinactivation study of clinical isolates of multidrug-resistant pathogens

“…They possess a slightly negatively charged surface and are also sensitive to cationic PS, although anionic and neutral PSs can also be used to eradicate Gram-positive bacteria. 5,6,19 The susceptibility differences observed between E. coli and S. aureus and pL-ce6 and TBO may be due to their different chemical properties, as indicated by Demidova and Hamblin et al 12 Although both pL-ce6 and TBO are cationic, pL-ce6 possesses a relatively larger molecular weight and the molecule has a greater number of potentially positively charged groups than TBO. The large molecular weight of pL-ce6 may not facilitate its ready penetration into the cell wall of the Gram-positive S. aureus leading to photodestruction.…”

Photodynamic therapy against cyanobacteria

“…A number of ROS can be produced during photo-activation of photosensitive compounds. An example of the principle is illustrated in the following general scheme (Jori and Brown, 2004):…”

“…In the recent years, there has been an effort to use photodynamic therapy for bacterial infection, yeast, and fungi (Bertoloni et al, 1992;Schaffer and Holtz, 1997;Jori and Brown, 2004). An advantage in using these compounds is that they combat bacterial disease without the possible development of resistance, as in the case of using antibiotics (Jori and Brown, 2004).…”

“…An advantage in using these compounds is that they combat bacterial disease without the possible development of resistance, as in the case of using antibiotics (Jori and Brown, 2004). There are a number of compounds that can act as photosensitizers.…”

A simple experiment to show photodynamic inactivation of bacteria on surfaces

“…A new promising approach to treat bacterial infections is called bacterial photodynamic inactivation (PDI, Scheme 1) [3,4]. This is based on the administration of a photosensitizer, which is preferentially accumulated in the microbial cells.…”