title: Reductive dechlorination of 3,3',4,4'-tetrachlorobiphenyl (PCB77) using palladium or palladium/iron nanoparticles and assessment of the reduction in toxic potency in vascular endothelial cells.
abstract: Palladium-based nanoparticles immobilized in polymeric matrices were applied to the reductive dechlorination of 3,3',4,4'-tetrachlorobiphenyl (PCB77) at room temperature. Two different dechlorination platforms were evaluated using (1) Pd nanoparticles within conductive polypyrrole films; or (2) immobilized Fe/Pd nanoparticles within polyvinylidene fluoride microfiltration membranes. For the first approach, the polypyrrole film was electrochemically formed in the presence of perchlorate ions that were incorporated into the film to counter-balance the positive charges of the polypyrrole chain. The film was then incubated in a solution containing tetrachloropalladate ions, which were exchanged with the perchlorate ions within the film. During this exchange, reduction of tetrachloropalladate by polypyrrole occurred, which led to the formation of palladium nanoparticles within the film. For the second approach, the membrane-supported Fe/Pd nanoparticles were prepared in three steps: polymerization of acrylic acid in polyvinylidene fluoride microfiltration membrane pores was followed by ion exchange of Fe(2+), and then chemical reduction of the ferrous ions bound to the carboxylate groups. The membrane-supported iron nanoparticles were then soaked in a solution of tetrachloropalladate resulting in the deposition of Pd on the Fe surface. The nanoparticles prepared by both approaches were employed in the dechlorination of PCB77. The presence of hydrogen was required when the monometallic Pd nanoparticles were employed. The results indicate the removal of chlorine atoms from PCB77, which led to the formation of lower chlorinated intermediates and ultimately biphenyl. Toxicity associated with vascular dysfunction by PCB77 and biphenyl was compared using cultured endothelial cells. The data strongly suggest that the dechlorination system used in this study markedly reduced the proinflammatory activity of PCB77, a persistent organic pollutant.
authors.affiliation: Department of Chemistry, University of Kentucky, Lexington, KY 40506, United States.
authors.forename: Karthik
authors.initials: K
authors.lastname: Venkatachalam
authors.forename: Xabier
authors.initials: X
authors.lastname: Arzuaga
authors.forename: Nitin
authors.initials: N
authors.lastname: Chopra
authors.forename: Vasilis G
authors.initials: VG
authors.lastname: Gavalas
authors.forename: Jian
authors.initials: J
authors.lastname: Xu
authors.forename: Dibakar
authors.initials: D
authors.lastname: Bhattacharyya
authors.forename: Bernhard
authors.initials: B
authors.lastname: Hennig
authors.forename: Leonidas G
authors.initials: LG
authors.lastname: Bachas
mesh_terms: D000818:Animals; D051546:Cyclooxygenase 2 / Q000378:metabolism; D019363:Cytochrome P-450 CYP1A1 / Q000378:metabolism; D004563:Electrochemistry; D042783:Endothelial Cells / Q000187:drug effects*; D004785:Environmental Pollutants / Q000737:chemistry* / Q000633:toxicity*; D008401:Gas Chromatography-Mass Spectrometry; D007202:Indicators and Reagents; D007501:Iron / Q000737:chemistry*; D046529:Microscopy, Electron, Transmission; D032389:Myocytes, Smooth Muscle / Q000187:drug effects*; D053758:Nanoparticles; D010084:Oxidation-Reduction; D010165:Palladium / Q000737:chemistry*; D010316:Particle Size; D011078:Polychlorinated Biphenyls / Q000737:chemistry* / Q000633:toxicity*; D013552:Swine; D019010:Vascular Cell Adhesion Molecule-1 / Q000378:metabolism
chemical_list: D004785:Environmental Pollutants; D007202:Indicators and Reagents; D019010:Vascular Cell Adhesion Molecule-1; D010165:Palladium; D011078:Polychlorinated Biphenyls; D007501:Iron; D019363:Cytochrome P-450 CYP1A1; D051546:Cyclooxygenase 2; C028451:3,4,3',4'-tetrachlorobiphenyl