Research Overview

Nature provides us with breathtaking examples of elegant and functional nanosystems. From magnetic bacteria that sense the earth’s magnetic field using nanosized bar magnets, to the nanoparticle- (NP-) mediated transport of inorganic material in wastewater, the world around us is filled with examples of nanomaterials in action. These examples illustrate that the interaction between nanosystems and biosystems can be a strong and important one, a lesson that nanoscientists are now exploring in the design of artificial, chemically prepared nanobiosystems. Our Center’s research seeks to understand and ultimately manipulate this interaction, which we term the wet/dry interface, as it manifests over a wide range of length scales, ranging from biomolecules to the earth’s environment.

CBEN’s research program is oriented toward specific engineered systems that exemplify how nanobiosystems can be used to solve real world problems. One of our engineered systems goals is the development of bioconjugated NPs that can detect and ultimately treat disease. In Theme 2, CBEN researchers under the direction of theme leader Professor West pursue both near-term enabling technologies and longer-term test beds (e.g., animal studies) for using the innovative properties of nanomaterials to solve problems in bioengineering. A second engineered systems goal is the development of more efficient and higher-performance water-treatment systems. This research is carried out in Theme 3 and is directed by Professor Alvarez (Rice University). The programs seek to revolutionize how we treat water and remediate its waste using the latest tools and materials from nanoscale chemistry. Theme 2 and Theme 3 share many crosscutting issues as their technologies approach commercialization; most notably, a major roadblock for each area is an understanding of the environmental and health effects of engineered NPs. CBEN has, since its inception, included such issues in its strategic plan, and now devotes a portion of research in both Theme 2 and Theme 3 to this critical issue. In addition, CBEN was founded on the realization that biological and environmental applications of NPs will require a strong, fundamental understanding of and control over NP behavior in biological systems. Theme 1 addresses these basic questions in chemistry, physics, and biology by studying and developing the science of the wet/dry interface.

While we divide the research into themes for easier management, our engineered systems have multiple interaction points and share numerous enabling technologies. For example, researchers in Theme 1, led by Colvin, provide researchers in Theme 2 and Theme 3 with new varieties of nanomaterials for desired applications. Near-infrared (NIR) emitting quantum dots (QDs), developed under the Theme 1 nanomanufacturing core, are now being used to image cells. Also, we have carefully chosen our portfolio to have overlapping near-term objectives. For example, work on solvating NPs (Theme 1) is complemented by work on NP surface chemistry, aggregation, and contaminant adsorption in the crosscutting environmental impact project (Theme 3). Much of the fundamental chemistry and biology in Theme 1 and Theme 2 has great relevance to topics in Theme 3. Our ongoing studies of the toxicity of C60, for example, have spawned a Theme 3 environmental applications project aimed at leveraging reactive oxygen species (ROS) generation in carbon nanostructures for biofilm reduction. The majority of CBEN projects began as “new start” collaborations in which investigators had no prior collaborative work. The payoff from investing in these new areas is clear now, as CBEN work has resulted in hundreds of published or in-press publications; our indicators of future performance (papers submitted, provisional patents) are equally sizable and are a testament to the productive and high-impact work completed in this Center. Our research highlights for 2007-2008 include:

• CBEN Director Colvin delivered a keynote talk at the Spring 2009 ACS meeting in a special presidential symposium devoted to the future of nanoscience.  This event, sponsored by the Kavli foundation, drew nearly a thousand people.  Her talk on nanotechnology and the environment is available on-line and will be followed by an invited paper in the ACS journal ACS Nano.
• Whitmire and Colvin have developed new families of magneto-optical nanoparticles using both gold and quantum dot nucleation onto metal oxide nanoparticles.  These compact structures both respond to handheld magnets, as well as exhibit extraordinary scattering and emission properties potentially valuable in disease detection that exploits both magnetic imaging as well as optical tomography.
• Colvin and Alvarez examined the effect of quantum dots on microbes.  Their work highlights the importance of weathering phenomena to understanding the nanomaterial-environmental complex; in effect, quantum dot coatings can be removed in the compartments of microbial systems.  After this stage, the cadmium in the interior core becomes bioavailable leading to signatures of conventional cadmium toxicity.  These results parallel prior studies of CBEN researchers evaluating quantum dot toxicity in mammalian cell culture and puts the spotlight on the need to create corrosion resistant coatings for these valuable materials.
• Li and Alvarez have made progress using nanomaterials to reduce viral loads in drinking water.  Viruses often evade conventional disinfection techniques and their presence in drinking water leads to significant suffering and loss of life for people across the globe.  By using nanocomposite silver/titania materials, it is possible to create potent ROS generators that reduce the activity of a model viral bacteriophage.
• West has developed and evaluated the next generation of near-infrared agents for photothermal cancer therapy.  These systems, based not on silica cores but gold sulfide cores, are more compact than conventional gold nanoshells and have more favorable biodistribution properties.
• Tour has applied water dispersed single-walled carbon nanotubes as radical scavengers in model organisms.  These materials are decorated with molecular anti-oxidants that quench and dissipate dangerous free radicals.  Such properties can improve the outcomes of radiation therapies for cancer by protecting patients receiving treatment.
• Drezek has applied the techniques of biological imaging to the problem of tracking particles in environmental systems.  Quantum dot materials could be visualized within a living aquatic organism, Daphnia magna, as they moved through its digestive system.  These materials did cluster in some circumstances but generally did not leave the gut; however, accumulation on the exterior appendages was commonplace.