Photodynamic inactivation of methicillin-resistant Staphylococcus aureus and Escherichia coli: A metalloporphyrin comparison

Abstract

Increasing rates of antibiotic resistance coupled with the lack of novel antibiotics threatens proper clinical treatment and jeopardizes their use in prevention. A photodynamic approach appears to be an innovative treatment option, even for multi-drug resistant strains of bacteria. Three components are utilized in photodynamic inactivation: a photosensitizer, light source, and oxygen. Variations in photosensitizers strongly influence microbial binding and bactericidal activity. In this study, four different cationic metalloporphyrins (Cu, Fe, Pd, Zn) were compared to the free-base ligand 5,10,15,20-tetrakis(N-methylpyridinium-4-yl)porphyrin regarding their electronic properties and generation of reactive oxygen species upon subsequent 405nm violet-blue irradiation. Staphylococcus aureus and Escherichia coli were used as representatives of Gram-positive and -negative, respectively, to assess bactericidal effects by the photodynamic process. Bacterial cultures were pre-incubated with porphyrins and exposed to varying doses of 405nm irradiation (0-30J/cm). Metalloporphyrins containing Cu and Fe demonstrated minimal effects on viability. Pronounced bactericidal activity was evident with free-base ligand, Zn, and Pd; though significantly stronger effects were apparent with Pd. Photodynamic killing was directly proportional to reactive oxygen species production post-illumination. These data provide new insight into the influence of metal chelation on photosensitizer activity on bactericidal singlet oxygen production. The strong anti-microbial photodynamic action through the use of a portable light-emitting diode over short time intervals (seconds) provides support for its potential use in self-treatment.

Cationic Porphyrins as Effective Agents in Photodynamic Inactivation of Opportunistic Plumbing Pathogen Legionella pneumophila

“…The impact of positive charges, their number and distribution in a molecule, has been previously investigated, mostly on E. coli and S. aureus [8,12,26,27]. Recently, a tetra-cationic porphyrin similar to TMPyP3 was reported to have higher PDI activity compared to the tri-cationic porphyrin, and was shown to be internalized by E. coli, while the tri-cationic bound to the cellular membrane [25].…”

Oxygen-dependent laser inactivation of murine norovirus using visible light lasers

“…In fact this basic mechanism, by which light interacts with sensitizer molecules, is commonly utilized to inactivate enveloped viruses within plasma and blood products [ 5 , 6 , 8 , 23 , 29 – 31 , 34 , 40 ]. It has also been shown that blue (405 nm) light can inactivate bacteria via its interactions with porphyrins (5 and 6 carbon multi-ring contain alternating single and double bonds) within the membrane of bacteria [ 28 ], and is actively being investigated as a means of disinfection of medical and food surfaces ([ 2 , 17 , 19 , 27 , 39 ]). Complex compounds such as methylene blue, rose bengal (a.k.a.…”

Metalloporphyrin Pd(T4) Exhibits Oncolytic Activity and Cumulative Effects with 5-ALA Photodynamic Treatment against C918 Cells

“…Our previous work established that metalloporphyrin Pd(T4) produces significantly more singlet oxygen than its core porphyrin ring TMPyP or metalloporphyrin Zn(T4) when excited by 405 nm LEDs [27]. When utilized as a photosensitizer and illuminated by 405 nm light, increasing Pd(T4) concentrations exhibited more pronounced oncolytic activity, mimicking patterns of TMPyP [31,39].…”

“…Our study analyzed oncolytic effects of the metalloporphyrin Pd(T4) compared to the current FDA-approved 5-ALA in two-and three-dimensional cell cultures with blue light. Photosensitizer Pd(T4) has demonstrated elevated singlet oxygen production post-illumination compared to its base conjugate TMPyP [27], resulting in photodynamic inactivation of bacteria such as methicillin-resistant Staphylococcus aureus and Escherichia coli [27]. TMPyP4, the base conjugate, has exhibited a strong affinity for G4 quadruplexes [28][29][30], as well as other macromolecules [31,32].…”