title: 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 (Cu2+, Fe2+, Pd2+, Zn2+) 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/cm2). Metalloporphyrins containing Cu2+and Fe2+demonstrated minimal effects on viability. Pronounced bactericidal activity was evident with free-base ligand, Zn2+, and Pd2+; though significantly stronger effects were apparent with Pd2+. 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.
authors: Rockford University, Department of Chemical and Biological Sciences, 5050 E. State St., Rockford, IL 61108, USA; University of Illinois - Chicago at Rockford, College of Medicine, 1601 Parkview Ave., Rockford, IL 61107, USA. Electronic address: tskwor@rockford.edu.
authors: Troy A
authors: TA
authors: Skwor
authors: Rockford University, Department of Chemical and Biological Sciences, 5050 E. State St., Rockford, IL 61108, USA. Electronic address: stephmarie2626@gmail.com.
authors: Stephanie
authors: S
authors: Klemm
authors: Purdue University, School of mechanical engineering, 585 Purdue Mall, West Lafayette, IN 47907, USA. Electronic address: zhang220@purdue.edu.
authors: Hanyu
authors: H
authors: Zhang
authors: Rockford University, Department of Chemical and Biological Sciences, 5050 E. State St., Rockford, IL 61108, USA. Electronic address: bjschardt@me.com.
authors: Brianna
authors: B
authors: Schardt
authors: Rockford University, Department of Chemical and Biological Sciences, 5050 E. State St., Rockford, IL 61108, USA. Electronic address: stephblaszczyk8@gmail.com.
authors: Stephanie
authors: S
authors: Blaszczyk
authors: Rockford University, Department of Chemical and Biological Sciences, 5050 E. State St., Rockford, IL 61108, USA. Electronic address: mbork@rockford.edu.
authors: Matthew A
authors: MA
authors: Bork
mesh_terms: D000900:Anti-Bacterial Agents / Q000494:pharmacology; D004926:Escherichia coli / Q000187:drug effects*; D008665:Metalloporphyrins / Q000494:pharmacology*; D055624:Methicillin-Resistant Staphylococcus aureus / Q000187:drug effects*; D010778:Photochemotherapy; D017319:Photosensitizing Agents / Q000494:pharmacology*
chemical_list: D000900:Anti-Bacterial Agents; D008665:Metalloporphyrins; D017319:Photosensitizing Agents
keywords: E. coli; MRSA; Metalloporphyrin; PDI; Singlet oxygen; TMPyP