Environmental Impact of Carbon Nanotubes

image of vials containing carbon nanotubes.
The vials contain similar concentrations of carbon nanotubes in water with different levels of oxidation, displayed as a percentage on the vial’s cap. Credit: Billy Smith/Johns Hopkins

Carbon nanotubes (CNTs) are among the most widely manufactured and commercialized nanomaterials, but what happens to them in the environment? Environmental engineer William Ball and surface chemist Howard Fairbrother at Johns Hopkins recently received funding from INBT to investigate the fate and effects of CNTs in aquatic environments.

“The production and use of CNTs has skyrocketed as their commercial applications, including flat panel displays, biomedical imaging, and targeted drug delivery, grow,“ says Ball. “But research on the health and environmental consequences of these engineered materials has unfortunately lagged behind commercial advancement.“

Concern about the potential impacts of CNTs and other nanoscale materials are being raised by environmental scientists because the roles of the materials’ chemical and physical properties on environmental fate and effect are not fully understood. Such properties are sometimes deliberately altered to enable manipulation or can be incidentally altered by natural environmental processes after the particles are released, says Ball. Thus, scientists do not yet know how these new materials interact with toxic contaminants and how they behave in and move through the natural environment.

Ball and Fairbrother began collaborating on the surface chemistry and environmental fate of black carbon a few years ago. Not long into their work together, the two started discussing CNTs. When INBT announced seed funding to jumpstart new projects at Hopkins focused on health and environmental issues of nanotechnology last fall, Ball and Fairbrother applied and received $25,000 to initiate a study and fund post-doctoral researcher Huyn-Hee Cho.

Their study is focused on the effects that surface oxidation and adsorbed natural organic matter exert on the properties of CNTs in aquatic environments.

“The surface chemistry of a carbon nanotube is particularly important in determining its stability in water,“ says Fairbrother. “As oxygen-containing functional groups (e.g. hydroxyl, carbonyl, and carboxylic) are added to its surface, the carbon nanotube’s stability in aquatic environments increases. We expect the effects of surface oxidation to have profound implications for the fate, transport, and environmental impact of carbon nanotubes.“

The researchers are looking at how CNTs behave in water, to what extent they aggregate, and to what extent they harbor and interact with toxic contaminants. Lab experiments include functionalizing CNTs through surface oxidation and exposing the materials to natural organic matter to test adsorption. The effect of surface oxidation and natural organic matter on the sorption of pollutants is also being studied using new sorption methods for finely dispersed black carbon materials developed by Ball’s research group.

Ball is professor of environmental engineering at Johns Hopkins and faculty member of the following university centers and institutes: Institute for NanoBioTechnology; Center for Contaminant Transport, Fate and Remediation; Center for Hazardous Substances in Urban Environments; Center for Applied and Environmental Fluid Mechanics; and Center for Water and Health.

Fairbrother is associate professor of chemistry and materials science and engineering at Johns Hopkins and faculty member of the Institute for NanoBioTechnology and the Center for Hazardous Substances in Urban Environments.

Nanofiber Scaffolds Grow Neural Stem Cells

Fluorescence microscopic image of rat neural stem cells
Fluorescence microscopic image shows rat neural stem cells (blue with DAPI nuclear staining) cultured on functionalized nanofiber scaffold (green). Credit: G. Christopherson, X.Y. Liu, H.J. Song, and H.Q. Mao/Johns Hopkins

Cells can be controlled in culture, but once they are placed inside the body their environment – and the probability of their survival and growth – changes. Neuroscientist Hongjun Song and materials engineer Hai-Quan Mao at Johns Hopkins are investigating nanofiber scaffolds that can create artificial 3-D local environments for neural stem cells.

Song and Mao have developed nanofibers to which they can attach adult neural stem cells by first binding bioreactive proteins. The nanofiber scaffolds provide an environment for neural stem cells to grow, proliferate, and develop.

“One of the benefits of using nanofibers is the ability to have successful cell self-renewal without requiring a high concentration of growth factors,“ says Song.

The collaborators are exploring new projects together and have recently started to expand their initial work to include embryonic stem cells. Song says stem cell science has much to offer biology. “By studying the mechanisms of stem cell behavior, we can learn how cells do it: what is happening in the body, how an animal can start with one cell type and develop specificity,“ he explains.

“Eventually, stem cells will be very important for treating disease using cell replacement therapy, but more immediately stem cells offer the opportunity to model human disease and find ways to screen for therapeutic drugs to treat the disease.“

Song is assistant professor of neurology and neuroscience, faculty member of the Institute for Cell Engineering and the Institute for NanoBioTechnology at Johns Hopkins, and member of the Johns Hopkins Stem Cell Policy and Ethics Program. Mao is assistant professor of materials science and engineering and faculty member of the Whitaker Biomedical Engineering Institute and the Institute for NanoBioTechnology at Johns Hopkins.

Student Prizes for Cool NanoBio Images

INBT will award one $25 gift certificate each month for a “cool“ nanobio research image, illustration, or graphic submitted by an undergraduate student, graduate student, or post-doctoral fellow.

Images must be the student or post-doc’s original material and it must be relevant to a current nanobiotechnology research project. Each student and post-doc can submit up to three images per month. Images will be judged on visual appeal and depiction of scientific findings. INBT staff will choose one image each month to be featured on the INBT website with credit to the student or post-doc, who will also receive a $25 gift certificate for Barnes & Noble bookstore.

Please submit your image(s) by the 1st of each month to inbt@jhu.edu for consideration. Include a caption for each image and your name, lab group, and contact information.

Spring Symposium

INBT will hold a spring symposium on Friday, April 27, 2007 at the Homewood Campus of Johns Hopkins University. Events will include nanobiotechnology research presentations, a student poster session, and more. Additional details will be announced in coming weeks.

Update (2-22-2007):

More details here. 

INBT Summer Undergraduate Research Fellowships: Applications Due March 9

Beginning summer of 2007, INBT will offer Summer Undergraduate Research Fellowships to qualified undergraduate applicants pursuing research at the interface of engineering, science, and biology.

INBT will fund undergraduate students who develop and use advanced nano-materials and nano-structures and techniques of nano-fabrication to solve important problems in biology, health and the environment, and medicine. Each candidate must have at least one full-time, INBT-affiliated faculty sponsor from one of the following schools: the Krieger School of Arts and Science, the Bloomberg School of Public Health, the Johns Hopkins School of Medicine, or the Whiting School of Engineering.

Students chosen as fellowship recipients will receive $3,500 for 10 weeks of full time research (June 11-August 17, 2007). Recipients will have the option of conducting their research for academic credit.  10 fellowships will be awarded each year.

To apply for a 2007 INBT Summer Undergraduate Research Fellowship, interested undergraduate students should submit a one-page proposal highlighting the engineering/physics and the biological aspects of their research project and a letter of recommendation from his/her faculty sponsor(s).

Application Deadline: March 9, 2007

Please bring or send applications to:

Ashanti Edwards, Educational Program Coordinator
Institute for NanoBioTechnology
214 Maryland Hall
3400 North Charles Street
Baltimore, MD 21218
E-mail: aedwards@jhu.edu

Profile: Terrence Dobrowsky, PhD student

Terrence Dobrowsky has his hands full working in two labs at Johns Hopkins: Denis Wirtz (chemical and biomolecular engineering) and Robert Siliciano (rheumatology and molecular biology and genetics). Dobrowsky moves between the East Baltimore and Homewood campuses in order to investigate binding kinetics for HIV envelope proteins in living cells.

After completing an undergraduate degree in chemical engineering at Notre Dame, Dobrowsky chose to pursue his PhD in chemical and biomolecular engineering at Hopkins to explore research connections between engineering and biology.

“In the past five years, universities around the country have renamed their departments ‘chemical and biological engineering’ but I found that many of them are not really doing bioengineering,“ he says. “I’m glad I chose Hopkins because I feel the experience I’m getting here as a student in the Howard Hughes Medical Institute Graduate Training Program in Nanotechnology for Biology and Medicine will truly prepare me for a career in this interdisciplinary field.“

Dobrowsky says he enjoys working in “two worlds“ with different ways of approaching a problem. “In attempting to affect a system as complicated as HIV infection, it just makes sense to understand the biology involved as well as relevant physical and chemical interactions.“

Dobrowsky acknowledges that work in the lab for 60 hours or so each week can sometimes get tedious, but even then he wouldn’t want to be anywhere else. “When your experiment works, you have a brief moment of enlightenment that inspires you to keep going,“ he says.

Seminar: Designing DNA-Binding Proteins

On Dec. 6, Carl O. Pabo presented a talk on the structure and design of DNA-binding proteins to the Johns Hopkins Department of Biophysics and Biophysical Chemistry.

Pabo, a visiting professor at Harvard University, discovered that several proteins involved in transcription have zinc fingers that allow them to bind to DNA. Pabo began much of his groundbreaking work on protein-DNA interaction while a faculty member at Hopkins from 1982 to 1991.

Pabo discussed his initial crystallographic studies that focused on major DNA-binding proteins. “The discovery of more areas of surface contact was like finding more lottery tickets,“ he said. “We had found more chances to win.“

Pabo said it was clear to him after initial investigations of protein-DNA crystal structures that there is no “simple code“ for recognition. His team pursued geometric analysis and computational modeling of spatial relationships based on the hypothesis that the way a protein approaches DNA may determine the ability for interactions. The group found a wide variety of docking arrangements but discovered the average arrangement had a similar ridge structure.

Pabo then focused on designing new DNA-binding proteins based on observations. His work on engineered zinc fingers, the most abundant and versatile DNA-binding motif in nature, simulated a very complex interaction with diverse applications including targeted DNA cleaving, gene correction, and genome editing.

His current work continues to explore the limits of specificity in zinc finger-DNA interactions for further work in gene editing.

Bacteria Combined with Chemo Helps Fight Cancer

Clostridium novyi bacteria.
Clostridium novyi bacteria. Credit: CDC

A new mouse study at the Johns Hopkins Kimmel Cancer Center demonstrates that combining liposome-encapsulated chemotherapy drugs with bacterial therapy dramatically improves the prospects for cancer eradication. [Read more...]

Biosensor Targets Retina Cells

Layered anatomy of the DNA tethered nanoparticle.
Layered anatomy of the DNA tethered nanoparticle. Credit: Tarl Prow and Gerard A. Lutty / JHU

Researchers affiliated with the Institute for NanoBioTechnology at Johns Hopkins have created a new biosensor that treats damaged cells in the eye’s retina with targeted gene therapy. The approach also may be useful in designing treatments for diseases such as cancer and psoriasis, according to the researchers, since it targets uncontrolled growth of new blood vessels.

Led by cell biologist Gerard Lutty and Research Associate Tarl Prow of the Wilmer Eye Institute at Johns Hopkins, the project includes collaborations with chemists, pathologists, and biomedical engineers.

The biosensor is a DNA promoter sequence tethered to multi-layered magnetic nanoparticles. When activated by oxidative stress, the biosensor allows the cell to regulate its own therapeutic gene expression and quickly respond to damage caused by free radicals. [Read more...]

Assessing Nanotech Risk

Imaging particle distribution in the lungs. John Links / JHU
Imaging particle distribution in the lungs. Credit: John Links / JHU

From drug delivery tools to environmental sensors to “super“ cleaners, the very small products resulting from nanotechnology are demonstrating big potential to improve the quality of life. Researchers at the Institute for NanoBioTechnology (INBT) are involved in both developing new nanotechnologies and analyzing their potential risks.

At the nanoscale, a material’s physical and chemical properties – such as strength, optical absorption, and electrical conductivity – change. These very small materials with different properties are enabling new technologies like nano-sized capsules that can deliver medicine directly to damaged cells in the body. [Read more...]