Undergirded by the powerful capabilities, state-of-the-art facilities, and brilliant minds that make up a premier national laboratory, Sandia’s bioscience researchers are on the leading edge of scientific discoveries in biofuels, biodefense, and emerging infectious diseases. Our staff members actively publish key findings in peer-reviewed scientific journals so that the entire global community can learn from our discoveries—joining scientific colleagues worldwide in an effort to try to change the world.
Following are a few examples of thought-provoking journal articles authored by Sandia bioscience researchers in recent years.
Sandia biofuels researchers at the Department of Energy’s Joint BioEnergy Institute (JBEI) in Emeryville, California, are investigating ways to deconstruct lignocellulosic biomass into fermentable sugars for conversion into fuel. One exciting new method, ionic-liquid pretreatment, draws on ionic liquids to break down the plant cell wall, liberating the sugar-rich polysaccharides. Sandia researchers used autofluorescence of the switchgrass cell wall to understand ionic-liquid pretreatment mechanisms, enabling further discoveries regarding the first principles of this technique and how ionic liquids interact with biomass. This research is the first to examine switchgrass and its interactions with ionic liquids to such an extensive degree, as well as the use of advanced imaging to help understand the mechanisms involved. See “Visualization of biomass solubilization and cellulose regeneration during ionic liquid pretreatment of switchgrass,” a 2009 Biotechnology and Bioengineering article (vol. 104, pp 68–75) by Seema Singh, Blake Simmons, and Ken Vogel.
Biotechnology experts at Sandia/California have created a microfluidic approach that enables the continuous purification of microgram levels of proteins. This novel approach uses two innovative features: (1) genetic engineering to attach short peptides to increase the partitioning of a desired protein and (2) a microfluidic device to create a stable polyethylene glycol (PEG)–salt flow for extraction. The extraction process is designed to provide the rapid, automated purification of recombinant proteins that is needed for high-throughput screening applications, such as enzyme engineering for biofuels production. See “Rapid, continuous purification of proteins in a microfluidic device using genetically engineered partition tags,” a 2008 Lab on a Chip article (vol. 8, pp 501–632) by Robert Meagher, Yooli Light, and Anup Singh.
Sandia researchers have created an integrated, portable diagnostic device suitable for detecting biological toxins in bodily fluids. At the heart of the device, which is known as the rapid, automated point-of-care system, is an electrophoretic immunoassay with integrated sample cleanup and preconcentration, enabling the detection of toxins such as ricin, Shiga toxin, and Staphylococcal enterotoxin B with micromolar to picomolar sensitivity. This device can be readily used to detect proteinaceous biomarkers of many other diseases and represents the next generation of diagnostic instruments that are capable of making rapid and quantitative measurements of multiple analytes simultaneously. See “An integrated microfluidic platform for sensitive and rapid detection of biological toxins,” a 2008 Lab on a Chip article (vol. 8, pp 2046–2053) by Robert Meagher, Anson Hatch, Ronald Renzi, and Anup Singh.
Bioengineering experts at Sandia/California have adapted many workhorse biochemical assays—including slab-gel electrophoretic techniques, chromatography, and immunoassays—to microfluidic chips.
For example, our scientists developed a diffusion-based fabrication method for creating chip-sized microfluidic devices that use gradient gels—both linear and nonlinear—to sort proteins by size. Forming gradient gels on-chip offers an easier and cheaper way to separate proteins. In addition, the Sandia method can optimize assays so that they identify targeted protein samples. These on-chip protein separation gels are ideal for high-throughput bioanalytical instrumentation, especially portable, point-of-care diagnostic devices for detecting disease or biotoxin infection. See “Photopolymerized diffusion-defined polyacrylamide gradient gels for on-chip protein sizing,” a 2008 Lab on a Chip “hot article” by Sandians Dan Throckmorton and Anup Singh and coauthors at Yale University and the University of California, Berkeley.
Other Sandia researchers have adapted a wet-etching technique to enable several on-chip cell-handling operations. Specifically, they used an adaptation of single-level isotropic wet etching to radially embed small shallow micropores in larger, deeper microchannels in a fused-silica substrate. By varying the distance between features on the photolithographic mask, the researchers were able to precisely control the overlap between the two etch fronts and create a zero-thickness semielliptical micropore (20 µm wide, 6 µm deep). To illustrate the wide range of cell-handling operations enabled by the micropores, the Sandians investigated and demonstrated three on-chip functionalities: continuous-flow particle concentration, the immobilization of single cells, and picoliter-droplet generation. See “Isotropically etched radial micropore for cell concentration, immobilization, and picodroplet generation,” a 2009 Lab on a Chip article (vol. 9, pp 507–515) by Thomas Perroud, Robert Meagher, Michael Kanouff, Ron Renzi, Meiye Wu, Anup Singh, and Kamlesh Patel.
Directing the orientation of molecular assemblies is a key step toward creating complex hierarchical structures that yield higher order functional materials. Here, we demonstrate the directed orientation of functionalized lipid domains and protein-membrane assemblies, using an electric field. Using relatively weak electric fields (e.g., 1.6 V/cm) we were able to orient domains of lipid assemblies based on net surface charge. That is, negatively charged domains orient towards the positive electrode while positively charged ones orient towards the negative electrode. The orientation is rapid, occurring on the time scale of seconds, and appears to be a general phenomenon regarding membrane composition. Functionality existing within the chemistry of the lipid domain also provides a means to increase the level of complexity of structure and function. We demonstrate this by using metal chelated groups within the domain to capture proteins and show that the orientation behavior is maintained. See "Orientation of Lipid Domains in Giant Vesicles Using an Electric Field," a 2011 Chemical Communications article (vol. 47, pp 7320-7322) by Frank Zendejas, Robert Meagher, Jeanne Stachowiak, Carl Hayden and Darryl Sasaki.
The challenge of assembling biomolecular systems within lipid bilayer boundaries is fundamental to all cells and is thus an essential feature of cell-like synthetic systems. While many methods for forming vesicles exist, very few have provided a monodisperse population of unilamellar vesicles with unrestricted content. Sandia researchers recently demonstrated a method for simultaneously creating and loading giant unilamellar vesicles by using a pulsed microfluidic jet. Akin to blowing a bubble, the microfluidic jet deforms a planar lipid bilayer into a vesicle that is filled with solution from the jet and separates from the planar bilayer. See “Inkjet formation of unilamellar lipid vesicles for cell-like encapsulation,” a 2009 Lab on a Chip article (vol. 9, pp 2003–2009) by Jeanne Stachowiak, David Richmond, Thomas Li, Françoise Brochard-Wyart, and Dan Fletcher.
Sandia bioimaging researchers have applied a novel method for fitting kinetic models to temporally resolved hyperspectral images of fluorescently labeled cells. This new method can be used to mathematically resolve pure-component spatial images, spectra, and reaction profiles. The scientists demonstrated this method on one simulated image and two experimental cell images labeled with fluorescent proteins. The researchers created a kinetic model of the compressed images by using a separable least-squares method. In keeping with the hypothesis that fluorophores are found in various cell environments, several first-order decays were combined to model the photobleaching processes for each observed fluorophore. After testing various kinetic-modeling mechanisms for the photobleaching processes, the most parsimonious and statistically sufficient model was used to prepare spatial maps for each fluorophore. See “Systematic method for the kinetic modeling of temporally resolved hyperspectral microscope images of fluorescently labeled cells,” an Applied Spectroscopy article (vol. 63, pp 261–270) by Patrick Cutler, David Haaland, and Paul Gemperline.