By Tom Henderson
Small Times Senior Writer
COLUMBUS, Ohio, Sept. 25, 2001 – Researchers at the Cleveland Clinic have developed a procedure that could eventually eliminate many of the 500,000 bone grafts in the United States each year.
Bioengineer Shuvo Roy and surgeon George Muschler have discovered that
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| A cell grips the edge of a micropatterned polymer. Researchers hope to use the technique to grow adult stem cells that will turn into bone. |
When the polymer has been molded with tiny bumps 6 microns high and 10 microns wide, cell growth after nine days is about 280 percent better than cell growth in the standard glass petri dishes normally used to grow tissue cultures.
Roy announced the breakthrough at a symposium during the BioMEMS and Biomedical Nanotechnology World 2001 conference, which ends today.
Muschler said that the use of polymer implants could eliminate the long recovery times, scarring, rehabilitation and infection associated with bone grafts.
The polymer polydimethylsiloxane (PDMS) was used in their study because it is flexible, can be processed at room temperature using standard micromachining techniques, is biologically compatible and costs about one-fiftieth as much as silicon.
The PDMS was patterned from molds using a standard micromachining process known as soft lithography. Liquid PDMS was then poured into the molds and pulled out after firming.
Muschler and Roy envision growing adult stem cells on the polymer, then implanting it in the body as a treatment for severe fractures. Placed on bone, the stem cells turn into bone cells.
Once the process of growing tissue on patterned scaffolding is perfected, Roy wants to incorporate MEMS devices into the polymer to further improve bone growth and reduce healing time.
“Eventually I see us building what I call a smart scaffold, where we’re not just building a scaffold but also attaching MEMS-based sensors and actuators,” said Roy.
He said the MEMS devices could have electrodes to provide an electric current, which has been shown to stimulate bone growth, as well microchannels, which could pump controlled doses of the kinds of proteins that have been shown to enhance cell growth.
The MEMS device could also give a wireless signal back to the doctor, providing information on bone density at the site and how the patient was progressing.
The cell growth experiment was performed alongside another collaboration between Muschler, Roy and Roy’s partner in bioengineering at the Cleveland Clinic, Aaron Fleischman.
Roy and Fleischman have designed a sieve with nanoscale pores that is used to help collect the stem cells that are used to grow bone cells.
Muschler first harvests cells from the pelvis bones of patients undergoing other procedures. About one of 20,000 cells gathered is a stem cell, which sits dormant in the body, waiting for an event to activate it. A variety of techniques, including the nanoscale filters, are used to concentrate the stem cells out of the general population of cells.
The stem cells, once concentrated, are put in contact with bone and then turn into bone cells, themselves. First, they divide into two cells, with one cell immediately reverting to a dormant stage. The other cell then begins a rapid cloning process, said Muschler.
Roy said the first stage of the study reported on in Columbus was funded internally by the Cleveland Clinic Foundation. A grant proposal to fund further research, including animal studies, will be made to the National Institutes of Health.
Because PDMS is so well studied and considered biocompatible, Roy said, FDA approvals for human studies and eventual commercialization shouldn’t be too arduous, if animal studies back up the initial results.
“In my heart of hearts, in four or five years, I see this in the marketplace, going into a patient,” said Roy. “That’s not being optimistic, that’s being realistic.”
Muschler said that once the process is perfected and approved for bone growth, the same technology would work for other applications, including growing cartilage, tendons and skin.
“You can use it wherever you need tissue engineering,” said Roy.
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CONTACT THE AUTHOR:
Tom Henderson at [email protected] or call 734-528-6292.