title: Effects of divalent cations, EDTA and chitosan on the uptake and photoinactivation of Escherichia coli mediated by cationic and anionic porphyrins.
abstract: The effect of divalent cations, EDTA and chitosan (CS) on the uptake and photoinactivation of Escherichia coli produced by 5,10,15,20-tetrakis(4-N,N,N-trimethylammoniumphenyl)porphyrin (TMAP(4+)), 5,10-di(4-methylphenyl)-15,20-di(4-N,N,N-trimethylammoniumphenyl)porphyrin (MPAP(2+)) and 5,10,15,20-tetra(4-sulphonatophenyl)porphyrin (TPPS(4-)) were examined under different conditions. These porphyrins were rapidly bound to E. coli cells (<2.5min) and the uptake of photosensitizers was not dependent on incubation temperature, reaching values of 0.61, 0.18 and 0.08nmol/10(8) cells for TMAP(4+), MPAP(2+) and TPPS(4-), respectively. The addition of Ca(2+) or Mg(2+) to the cultures enhanced the uptake of MPAP(2+) and TPPS(4-) by cells. In contrast, the amount of TMAP(4+) bound to cells was decreased. The presence of EDTA produced an increase in the uptake of porphyrins by cells, while CS mainly enhanced the amount of TPPS(4-) bound to E. coli. The photoinactivation of E. coli cells mediated by TMAP(4+) was highly effective even at low concentration (1μM) and short irradiation period (5min). However, a reduction in the phototoxicity was found for TMAP(4+) in presence of Ca(2+) and Mg(2+). In contrast, the phototoxic activity mediated by MPAP(2+) and TPPS(4-) was increased. Addition of EDTA did not show effect on the photoinactivation induced by cationic porphyrins, while a small enhance was found for TPPS(4-). Moreover, inactivation of E. coli cells was achieved in the presence CS. This cationic polymer was antimicrobial by itself in the dark. Using a slightly toxic CS concentration, the phototoxic activity induced by TMAP(4+) was diminished. This effect was mainly observed at lower concentration of TMAP(4+) (0.5-1μM). In contrast, an increase in E. coli photoinactivation was obtained for MPAP(2+) and TPPS(4-) in presence of CS. Thus, this natural polymeric destabilizer agent mainly benefited the photoinactivation mediated by TPPS(4-).
authors.affiliation: Departamento de Química, Facultad de Ciencias Exactas, Físico-Químicas y Naturales, Universidad Nacional de Río Cuarto, X5804BYA Río Cuarto, Córdoba, Argentina.
authors.forename: Natalia S
authors.initials: NS
authors.lastname: Gsponer
authors.affiliation: Departamento de Química, Facultad de Ciencias Exactas, Físico-Químicas y Naturales, Universidad Nacional de Río Cuarto, X5804BYA Río Cuarto, Córdoba, Argentina.
authors.forename: Mariana B
authors.initials: MB
authors.lastname: Spesia
authors.affiliation: Departamento de Química, Facultad de Ciencias Exactas, Físico-Químicas y Naturales, Universidad Nacional de Río Cuarto, X5804BYA Río Cuarto, Córdoba, Argentina. Electronic address: edurantini@exa.unrc.edu.ar.
authors.forename: Edgardo N
authors.initials: EN
authors.lastname: Durantini
mesh_terms: D000838:Anions; D017209:Apoptosis / Q000187:drug effects / Q000528:radiation effects; D002118:Calcium / Q000008:administration & dosage; D002413:Cations, Divalent; D002470:Cell Survival / Q000187:drug effects / Q000502:physiology; D048271:Chitosan / Q000008:administration & dosage*; D004492:Edetic Acid / Q000008:administration & dosage; D004926:Escherichia coli / Q000166:cytology / Q000187:drug effects* / Q000378:metabolism*; D008274:Magnesium / Q000008:administration & dosage; D008657:Metabolic Clearance Rate / Q000187:drug effects; D011166:Porphyrins / Q000008:administration & dosage* / Q000493:pharmacokinetics*; D011836:Radiation Tolerance / Q000187:drug effects
chemical_list: D000838:Anions; D002413:Cations, Divalent; D011166:Porphyrins; D048271:Chitosan; D004492:Edetic Acid; D008274:Magnesium; D002118:Calcium
keywords: Chitosan; Escherichia coli; Photodynamic inactivation; Porphyrin; Uptake