title: Effect of polyethylenimine, a cell permeabilizer, on the photosensitized destruction of algae by methylene blue and nuclear fast red.
abstract: The present study reports the effect a cell permeabilizer, polyethylenimine (PEI) has on the photodynamic effect of methylene blue (MB) and nuclear fast red (NFR) in the presence of hydrogen peroxide (H2O2). The photosensitized destruction of the algae Chlorella vulgaris under irradiation with visible light is examined. The photodynamic effect was investigated under aerobic and anaerobic conditions. The presence of a permeabilizer during the photosensitized destruction of C. vulgaris does not enhance the activity of the MB, MB/H2O2 system or the NFR, NFR/H2O2 system under aerobic conditions. However under anaerobic conditions we have determined that when a cell permeabilizer was added to the MB/H202 system, the photosensitized destruction of C. vulgaris proceeded via a combination of Type I and Type II mechanisms. The presence of PEI enforces MB/H2O2 to be active toward the destruction of C. vulgaris whether oxygen is present or absent. Under aerobic and anaerobic conditions the activity of NFR was suppressed in the presence of PEI as a result of electrostatic interactions between the photosensitizer and the cell permeabilizer. The decrease in fluorescence recorded is indicative of destruction of the chlorophyll a pigment.
authors.affiliation: Centre for Research in Energy and the Environment, The Robert Gordon University, Schoolhill, Aberdeen, UK. c.mccullagh@rgu.ac.uk
authors.forename: Cathy
authors.initials: C
authors.lastname: McCullagh
authors.forename: Peter K J
authors.initials: PK
authors.lastname: Robertson
mesh_terms: D002463:Cell Membrane Permeability / Q000187:drug effects; D048408:Chlorella vulgaris / Q000187:drug effects* / Q000502:physiology / Q000528:radiation effects*; D056890:Eukaryota / Q000187:drug effects* / Q000528:radiation effects*; D006861:Hydrogen Peroxide / Q000494:pharmacology; D008751:Methylene Blue / Q000494:pharmacology*; D009499:Neutral Red / Q000494:pharmacology*; D017319:Photosensitizing Agents / Q000494:pharmacology; D011094:Polyethyleneimine / Q000494:pharmacology*
chemical_list: D017319:Photosensitizing Agents; D009499:Neutral Red; D011094:Polyethyleneimine; D006861:Hydrogen Peroxide; D008751:Methylene Blue