Livermore researchers Mike Malfatti, Heather Palko, Ed Kuhn, and Ken Turteltaub used accelerator mass spectrometry (AMS) measurements to investigate the relationship between administered dose, pharmacokinetics, and long-term biodistribution of carbon-14-labeled silica nanoparticles (SiNPs) in vivo. Because of their unique properties such as monodispersity, large surface area, and high drug-loading efficiency, SiNPs have been developed for a vast array of biomedical uses such as optical imaging, cancer therapy, targeted drug delivery, and controlled drug release for genes and proteins.
However, the increasing use of nanoparticles for a wide variety of commercial, industrial, and biomedical applications has led to safety concerns. Studies have shown that inhalation of microcrystalline silica may be linked with the pulmonary disease silicosis in humans. Chronic inhalation studies in rats have shown an association with pulmonary fibrosis and cancer, and exposure to microscale amorphous silica has been linked to inflammation, granuloma formation, and emphysema. Scientists want to better understand the interactions of SiNPs with biological systems.
The Livermore pharmacokinetics analysis showed that SiNPs were rapidly cleared from the circulatory system (the “central compartment” in pharmacokinetic models) and were distributed to various body tissues, where they persisted over the eight-week study. These results raise questions about the potential for bioaccumulation and associated long-term effects. The team’s findings appeared in the October 17, 2012, edition of Nano Letters.
Contact: Mike Malfatti (925) 422-5732 (malfatti1@llnl.gov).An international collaboration involving Lawrence Livermore has discovered that Earth’s core formed under more oxidizing conditions than was previously predicted. While scientists know that Earth accreted from some mixture of meteoritic material, they have not been able to quantify precisely the processes that led to the separation of various chemical elements to form Earth’s mantle and core. The new research defines how these materials may have been distributed and transported in the early solar system.
The team conducted a series of laser-heated diamond-anvil-cell experiments at high pressures (350,000 to 700,000 atmospheres) and temperatures (2,827 to 4,127°C). Results demonstrated that with increased oxygen, a slight reduction of siderophile elements (such as vanadium and chromium) and moderate depletion of nickel and cobalt would result during core formation, as inferred from geologic measurements. Livermore geophysicist Rick Ryerson says, “A model in which a relatively oxidized Earth is progressively reduced by oxygen transfer to the core-forming metal can reconcile both the need for light elements in the core and the concentration of siderophile elements in the silicate mantle. The model suggests that oxygen is an important constituent in the core.”
Because core formation and accretion are closely linked, constraining the process of core formation allows researchers to place limits on the range of materials that formed our planet and determine whether the composition of those materials changed with time. Other teams members include Julien Siebert and Daniele Antonangeli (former Livermore postdoctoral researchers) from the Université Pierre et Marie Curie, and James Badro (a faculty scholar at Livermore) from the Institut de Physique du Globe de Paris. The research appeared in the January 10, 2013, edition of Science Express.
Contact: Rick Ryerson (925) 422-6170 (ryerson1@llnl.gov).A consortium of scientists including Lawrence Livermore’s Gary Eppich has determined that the Sutter’s Mill Meteorite is the most pristine sample yet collected of the rare Carbonaceous-Mighei (CM) chondrite class of meteorites. CMs contain largely unaltered materials from the dawn of the solar system. The Sutter’s Mill Meteorite had the force of 4 kilotons of TNT on its descent over the towns of Coloma and Lotus in northern California when it hit Earth on April 22, 2012.
Through a series of tests including x-ray and isotopic analyses, the team looked at 1 kilogram—the amount recovered on the ground in the form of 77 meteorites—of the 45,000-kilogram Sutter’s Mill giant. Eppich’s contribution focused on x-ray fluorescence spectrometry, which allowed the team to rapidly and nondestructively determine the major and trace element composition of the meteorite. This technique uses a powerful primary x-ray beam to cause the sample to produce secondary x rays, which are characteristic of the chemical composition of the sample. These data were useful in characterizing the meteorite on the basis of its chemical composition. “We believe we’ve identified the point of origin of these relatively pristine samples of solids formed in the early solar system,” says Eppich.
The team, led by meteor astronomer Peter Jenniskens of the SETI Institute and the NASA Ames Research Center, believes a good candidate source region for CM chondrites is the Eulalia asteroid family, recently proposed as a source of primitive C-class asteroids in orbit that pass Earth. Team members concluded the meteorite was a composite of bits and pieces from different asteroids that collided in space. The research was reported in the December 21, 2012, issue of Science.
Contact: Gary Eppich (925) 422-5731 (eppich1@llnl.gov).