Photodynamic inactivation of wound-associated bacteria with new troponyl (pyro)pheophobides

Abstract

In this study, the effect of light activated agent, methyl (pyro)pheophorbide-a, which bears non-aromatic cyclic compound, excited with red light from a LED on the viability of S. aureus, S. epidermidis, and E. coli was investigated. All species were susceptible to killing by photosensitization and photodynamic effect was dependent on both the chemical structure and concentration. However, E. coli was not susceptible to concentrations used to obtain a significant kill with the Gram-positive bacteria upon irradiation. To more closely mimic the conditions of wounds, photodynamic therapy was carried out on S. aureus, which is the most important organism that can cause a range of mild to severe infections in skin and burn wounds, in the presence of human blood plasma and human serum albumin, representing a wound fluid model. Results indicate that microorganisms could be successfully photoinactivated by tropolone methyl (pyro)pheophorbide-a derivatives when suspended in phosphate buffered saline. However, changing the medium into 4.5% and 7% HSA/PBS solutions reduced the effectiveness of lethal photosensitization of bacteria. The same results were obtained with human blood plasma. Also, the mechanism of bacterial cell inactivation by a sensitizer and light was studied with reactive oxygen species scavengers. Further evidence of the involvement of singlet oxygen is provided by the protective effect of the singlet oxygen scavenger, sodium azide.

Production of Reactive Oxygen Species by Photoactive Anthraquinone Compounds and Their Applications in Wastewater Treatment

“…The photoactivated compounds can produce radicals and, in the presence of oxygen, even reactive oxygen species (ROS) such as singlet oxygen, hydroxyl radicals, and superoxide radicals under such photoactivation. These ROS could provide functions such as inactivating microorganisms and decomposing toxic compounds. − Such photoinduced functions are economically and environmentally attractive and can be employed in different applications. , The UV-induced radicals on the compounds could also initiate radical polymerizations, which can be employed in surface modifications of polymers and incorporation of novel functions into the polymers. , For these UV-activated reactions, photosensitizers are the key compounds to induce the desirable reactions. Benzophenone is a common photosensitizer and can photoinitiate graft polymerizations and antibacterial effects on polymers. − Because of their similar structural features, anthraquinone compounds were expected to exhibit similar photoinduced activities.…”

Photodynamic and Antioxidant Activities of Divalent Transition Metal Complexes of Methyl Pheophorbide-a

“…Recently the chlorin derivatives with various functional groups have been synthesized by us 5 and by many other groups, and have been investigated for in vitro study to find out potential PSs.…”

The photoactivated antifungal activity and possible mode of action of sodium pheophorbide a on Diaporthe mahothocarpus causing leaf spot blight in Camellia oleifera

“…For example, a novel photosensitive iridium complex can induce synergistic iron-induced death and apoptosis to inhibit cancer cells ( Yuan et al, 2021 ). Pheophorbide a (PA), which is created by the breakdown of photosynthetic pigment chlorophyll a, is a natural photosensitizer with multiple action sites and significant photoactivated anti-tumor ( Park et al, 2016 ), antibacterial ( Bayarmaa et al, 2009 ), antiviral ( Bouslama et al, 2011 ), and insecticidal ( Singh et al, 2017 ) activities. Hajri et al (1999) found that PA inhibits the growth of cancer cells by inducing apoptosis in human pancreatic cancer cells and animal models (nude mice carrying xenotransplanted tumors).…”