HR: 16:50h
AN: B44A-03    [Abstracts]
TI: Stability of Commercial Small-Sized Cerium Oxide in the Presence of Biological Material: Dilucidating Relationships between Reactivity and Toxicity of Nanomaterials
AU: * Cervini-Silva, J
EM: jcervini@igg.unam.mx
AF: Instituto de Geografia, Universidad Nacional Autonoma de Mexico, Circuito Exterior, Ciudad Universitaria, Coyoacan, Mexico City, 04510, Mexico
AU: Gilbert, B
EM: BGilbert@lbl.gov
AF: Lawrence Berkeley National Laboratory, Earth Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, CA 94720, United States
AU: Fernandez-Lomelin, P
EM: pilarf@igg.unam.mx
AF: Instituto de Geografia, Universidad Nacional Autonoma de Mexico, Circuito Exterior, Ciudad Universitaria, Coyoacan, Mexico City, 04510, Mexico
AU: Guzman-Mendoza, J
EM:
AF: Instituto de Investigacion en Materiales, Universidad Nacional Autonoma de Mexico, Circuito Exterior, Ciudad Universitaria, Coyoacan, Mexico City, 04510, Mexico
AU: Chavira, E
EM: chavira@servidor.unam.mx
AF: Instituto de Investigacion en Materiales, Universidad Nacional Autonoma de Mexico, Circuito Exterior, Ciudad Universitaria, Coyoacan, Mexico City, 04510, Mexico
AB: Cerium is the most abundant lanthanide and generally the only one to undergo redox reactions at the Earth's surface. Although rarely studied in natural environments, the redox chemistry of cerium may regulate metal toxicity. Unlike Ce(III) or other lanthanide ions, Ce(IV) has shown a remarkably efficacy to hydrolyze DNA. While Ce(IV) has been recognized as an important candidate to occupy peptidases catalytic centers, Ce(III) is virtually inactive for peptide hydrolysis. The selectivity of Ce as Ce(IV) relates to the specific coordination of water molecules and their orientation. Ce(IV) may bind selectivity to biomolecules to instigate conformation changes or cleavage of complexes, which affect metabolic pathways pivotal to growth and survival. For instance, Ce(IV) promotes the selective cleavage of RNA-type substrates, cyclic monophosphates, peptides, or monocleotides such as AMP, leading to mixtures of nucleosides and nucleobases. Association constants for Ce(IV)-DNA complexes are reported to be higher in magnitude for single stranded than double stranded DNA, while cleavage rates for either complexes are comparable. Complexation of Ce(IV) with mitoxantrone results in the intercalation of such complex into DNA, enabling mitoxantrone to bind effectively with DNA, along with concomitant conformational changes in the DNA double helix and inhibition of DNA synthesis. To the authors' knowledge, however, little information is available on the reactivity as it relates to toxicity of Ce-bearing nanoparticles widely used in nanotechnological applications. Here, we study molecular interactions between small-sized CeO2 and biomolecules(e.g., DNA, RNA, proteins) using carbon and cerium spectroscopy. Suspension stability as determined by aggregation kinetics was studied by Dynamic Light Scattering (DSL) and UV. In addition, acidophiles and fungi cultures were analyzed by nephelometry to estimate population density and growth rate values. Results show a progressive increase in the transformation of biomolecules (as % carbon) with decreasing CeO2 particle diameter (13 < d < 84 Å), which substantiates an intimate relation between CeO2 unit cell expansion and reactivity towards organics susceptible to undergo redox transformations. As shown by C and Ce spectroscopy, organic polymers that form because of oxidation are distributed next to the mineral surface and its occurrence is coupled to Ce reduction-oxidation. As evidenced by DSL and UV experiments conducted for the pH 2 to 8 range, the aggregation behavior of nanoCeO2 is susceptible to pH variations imposed because the presence of biological moieties itself over solid concentration.
DE: 0315 Biosphere/atmosphere interactions (0426, 1610)
DE: 0345 Pollution: urban and regional (0305, 0478, 4251)
DE: 0420 Biomolecular and chemical tracers
DE: 0426 Biosphere/atmosphere interactions (0315)
DE: 0428 Carbon cycling (4806)
SC: Biogeosciences [B]
MN: 2007 Joint Assembly