By Tom Henderson
Small Times Senior Writer
CHICAGO — The school semester ended last week at the University of Illinois-Chicago, but that means anything but a vacation for Tejal Desai, an assistant professor in the Department of Bioengineering and director of the school’s cellular microbiology lab.
Friday afternoon she caught a plane to Los Angeles to speak at this week’s bioMEMS symposium at the Clairmount Colleges. On May 17-18, she chairs the BioMEMS 2001 international conference in Sunnyvale, Calif., where close to 1,000 people are expected; including researchers from
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| Implant allows passage of nutrients, prevents |
| passage of larger immunocytes and proteins |
In addition to chairing BioMEMS 2001, Desai will give a presentation on microfabrication techniques for making medical devices on the nanotech scale.
And all summer, Desai’s work continues in earnest on a five-year, $2 million grant for a tissue-engineering project that she hopes will ultimately lead to lab-grown human organs.
In March, the Heart, Lung and Blood Institute of the National Institutes of Health announced the grant for Desai and fellow faculty member Brenda Russell.
Also in March, Desai began the second phase of testing on another project involving micromachined pancreas implants that one day may eliminate the need for insulin injections for diabetics.
The month finished with her presentation, titled “Microfabrication for Tissue Engineering,” at the annual Tissue Engineering Conference in Pittsburgh.
Desai, 28, was named one of the country’s top 100 researchers in Massachusetts Institute of Technology’s Technology Review magazine in 1999 and was one of the first three professors hired at UIC’s fledgling bioengineering department in 1998.
TISSUE ENGINEERING
Desai and her researchers build tiny-scale features on scaffolding that is used to grow organ tissues.
“Organ tissues have very well-defined microstructures — ridges and projections — that keep the cells oriented and attached,” she says. Thanks to micromachined polymers, “we can build cellular structures you could never see in the laboratory before that mimic the structure of the heart,” she says.
Her group did preliminary work for a year and a half before winning the grant. They developed prototype scaffolding several millimeters in size, with nanofeatures between 10-20 microns.
Now, they hope to construct polymer scaffolding four or five centimeters cubed; then grow functioning cells on the framework. They hope to demonstrate feasibility by the end of five years and to be in human testing perhaps at the end of the decade.
A first application for humans would be analogous to the old tire-patch. Heart or liver tissue, for example, could be grown, then grafted into patients’ organs, replacing damaged or non-functioning tissue. Ultimately, entire organs could be grown on scaffolding and transplanted into patients.
“If you can do this, you don’t need to worry about donors,” she says. “This is a new area I’m real excited about. It’s cool, and there’s a lot of potential.”
Desai said she hopes her group can develop and patent processes, then license them to for-profit tissue-engineering companies to bring to market. The grants provide enough funds to demonstrate if the science works, but the far larger amounts of money needed to bring something to market in a heavily regulated environment require for-profit partners with large budgets, she says.
ON THE PANCREAS FRONT
UIC has done short-term, small-animal studies to test the biocompatibility and/or toxicity of implantable pancreatic microcapsules. Each diabetic rat was implanted with six two-by-two-millimeter devices, each packed with up to 100 pancreatic islet cells.
(The cells are called “islet” cells, because they are actually tiny islands of different kinds of cells lumped together, including beta cells, which secrete insulin, and alpha cells, which produce a starch called glucagon.)
Longer-term tests of mice with full-blown diabetes will begin later this summer, using microcapsules that have been modified to give more permeability. Their pancreases will be implanted with pancreatic islet cells of healthy rats.
Some details:
* The capsules have permeable silicon membranes 500 microns thick, coated with polyethylene oxide to improve biocompatibility. Silicon is used because the devices are meant to be long-term, and silicon is much more stable than more biocompatible materials.
* Each capsule will contain up to 100 islet cells, which are each about 100 microns wide.
* The silicon membranes are micro-punctured with holes in the 10- to 20-nanometer range. That allows oxygen and nutrients such as glucose to flow in and insulin to flow out. But the holes are small enough to keep out relatively large antibodies and white blood cells, which would normally attack the islet cells as part of the body’s immune-defense mechanism.
* Eventually, laboratory-altered and -grown insulinoma cells will be used instead. The cells are called “insulinoma” because they are actually tumor cells that produce insulin. They are more useful than islet cells because they have a laboratory lifespan of years versus weeks. Desai said each microcapsule could hold 10,000 to 100,000 insulinoma cells.
If the study, funded for $200,000 by the Whitaker Foundation of Arlington, Va., shows an efficacy with small animals, research will move to large animals. Human studies are at least 10 years away, Desai said.
Desai said she and her researchers need to determine the best pore sizes, how thin the membranes should be, if membranes deteriorate or clog over time, how many healthy cells are needed, and, if huge numbers of cells are required, if it is feasible to implant sufficient microdevices.
A companion project, involving similar technology and the implanting of microcapsules containing neurotransmitters in the brain, has received a two-year, $100,000 grant by the NIH.
That project is in collaboration with John Welsh, a neuroscientist at the University of Oregon. Applications include treating the symptoms of Parkinson’s and Alzheimer’s.
SPACE BECKONS
Desai has applied for a $400,000 grant from NASA and hopes to have an approval by the end of May for a study of tissue growth, using her scaffolding technology, in a simulated gravity-free environment.
“When you’re growing tissue in gravity, things tend to settle toward the bottom. There are advantages to growing things in space,” she says.
She envisions that one day entire organs will be grown in space, then shipped to Earth for transplanting.
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Cover photo: Tejal Desai
To learn more about this research, visit: www.uic.edu/depts/bioe/faculty/tejal_desai