Nature's Nanoshells
by David Pescovitz
 Printer-friendly
version
William Holtz is a graduate student in the Department of Electrical Engineering and Computer Sciences.
|
Taking inspiration from nature's elegant engineering, UC Berkeley graduate students are working to create novel nanoscale structures modeled after a common marine organism. Using techniques pioneered at the Berkeley Center for Synthetic Biology, the students hope to produce designer materials resembling in form and function the tiny intricate shells of photosynthetic algae called diatoms. Initially, the biomimetic diatoms could be employed as filtration systems or self-contained catalysts for a lab-on-a-chip used for medical testing. Eventually, the structures could enable the fabrication of more powerful computer chips containing circuits patterned in three dimensions or act as substrates for the in vitro growth of human tissue for implantation.
"As an electrical engineer, I come at this work from a microfabrication perspective," says William J. Holtz, a Ph.D. candidate in the Department of Electrical Engineering and Computer Sciences (EECS) who collaborates on the work with Afshan Shaikh, a Ph.D. candidate in the Department of Chemical Engineering, EECS Ph.D. candidate Frank J. Zendejas, and others . "The question we're asking is how can we create very small systems that self-assemble into desired structures?"
Afshan Sheikh is a graduate student in the Department of Chemical Engineering.
|
Holtz and Shaikh are advised by Jay Keasling, professor in the Departments of Chemical Engineering and Bioengineering and director of Berkeley Center for Synthetic Biology. Keasling specializes in genetic techniques to convert bacteria into chemical factories that produce, for example, the precursors of anti-malaria and anti-cancer drugs.
The allure of diatoms is that the shells contain detailed features that are just a few nanometers in size. (A nanometer is one billionth of a meter.) Today, only the most experimental lithography tools are capable of patterning features of comparable scale on silicon, and even then only in two dimensions. Furthermore, those methods aren't suitable for large-scale industrial production.
"Diatoms are living organisms though, so they produce the structures at ambient temperature and pressure at very high rates," says Holtz.
If the researchers can devise a method to mimic the natural generation of the shells, they could potentially make the materials shaped-to-order. For example, a shell with very specific pore sizes would enable some molecules to flow through while keeping others out, acting as a nanoscale filter. Adding other chemicals to the interior surface of the shell could transform it into a miniature test tube containing a built-in catalyst. These kinds of structures would be useful as the basis of, say, an ultrasensitive detector of specific gases or a handheld device for molecular medical diagnostics in the field
" These kinds of devices require a lot of chemistry," Holtz explains. "Diatom-like structures would be very helpful in that."
The synthetic diatoms might also be used as templates for gears smaller than a period, as miniscule lenses, or to bulk manufacture 3D circuits and silicon micromachines that today must be painstakingly fabricated layer by layer. The key is to be able to crank out the synthetic shells in bulk in specific shapes. Holtz, Shaikh, and their colleagues are exploring several possible methods.
Scanning-electron micrograph of another species of diatom.
|
Holtz is attempting to extract diatom proteins responsible for the shell production and plans to use off-the-shelf polymers as the raw materials in the self-assembly process. Tiny amounts of the ingredients mixed in a solution chemistry process could then produce the shell-like structures. But even if the technique is successful, Holtz says, the protein extraction isn't practical for industrial applications.
To that end, Shaikh is attempting to genetically re-engineer bacteria into a microbial factory that cranks out the proteins cheaply and easily. She's working on transferring all of the genes that encode the shell-making protein's metabolic pathway into E.coli. The next step is to get the gene to express itself so the E.coli can actually start producing the protein.
"You could then take those proteins and do the in vitro process to make the shells," Shaikh says.
According to the researchers, the structures are well-suited substrates for the in vitro growth of cells and tissues that could later be implanted into humans to heal injuries. Indeed, someday the synthetic shells may be found inside everything from our bodies to next-generation PCs to handheld medical laboratories.
"Even more intriguing is the possibility of self-repairing systems, in which these low-energy biosynthetic techniques would enable the re-growth of damaged devices in the field," the researchers say.
William J. Holtz's home page
Afshan Shaikh's home page
Jay D. Keasling's home page
Keasling Lab
"Miracles happen: Synthetic biologists tap into ancient herbal pharmacy to cure malaria and AIDS" by David Pescovitz (Forefront, Spring 2005)
Synthetic Biology Department at Lawrence Berkeley National Laboratory
Lab Notes is
published online by the Marketing and Communications Office of the UC Berkeley
College of Engineering. The Lab Notes mission is to illuminate groundbreaking
research underway today at the College of Engineering that will
dramatically change our lives tomorrow.
Media contact: Teresa
Moore, Lab Notes editor, Director of Marketing and Communications
Writer, Researcher: David
Pescovitz
Web Manager: Michele
Foley
Subscribe or send comments to the Engineering Marketing and Communications Office: lab-notes@coe.berkeley.edu.
© 2005 UC Regents.
Updated 12/1/05.
|
