Nano World: Nano for stem-cell research

[Guest guest]

Cutting-edge nanotechnology is beginning to help advance the equally

pioneering field of stem-cell research, with devices that can

precisely control stem cells and provide self-assembling biodegradable

scaffolds and magnetic tracking systems, experts told UPI's Nano World.

" Nanotechnology might show people once and for all that you really

can help regenerate organs with stem-cell biology and help people walk

again, help people after heart attacks, help people after stroke, "

said Kessler, a neurologist at Northwestern University in

ton, Ill.

" My own daughter had a spinal-cord injury, and the thought that I

could contribute to helping my daughter with this is just

overwhelmingly exciting to me, " Kessler added.

Stem cells are the primordial cells of the body; every other cell

type originates from them. Embryonic stem cells have the power to

become any other type of cell, while adult stem cells -- those

collected from adults, children or umbilical cords -- only can become

certain kinds of cells, such as blood or fat. Scientists hope to

create new therapies based on stem-cell implants that repair damaged

or lost organs and tissues.

In their natural environment in the body, stem cells transform

into other cell types based on chemical triggers they receive from

their surroundings.

The exact cues and the placement of those cues for most stem cells

are not known, " and our ability to introduce specific chemicals at

select locations on a cell is extremely limited, " said materials

scientist Nick Melosh at Stanford University in Palo Alto, Calif.

Researchers currently must bathe the entire surface of stem cells

in various chemicals to search for a response, so Melosh and

colleagues are developing a nano lab -- on the scale of billionths of

a meter -- to experiment with individual adult stem cells. Each lab

essentially consists of a capsule on a silicon chip, around which up

to 1,000 nanoreservoirs hold roughly a millionth of a billionth of a

milliliter of liquid, comparable to the size of secretions cells use

to communicate.

" We are in essence building an artificial cell-interface unit

through which we can 'talk' to a stem cell, in much the same way real

cells do, through chemical communication, " Melosh said.

" Nanotechnology is essential for this project. Larger systems just

couldn't provide the number of different reservoirs and chemicals

within a space small enough to select different areas on a cell. "

Future nerve-damage repairs could be accomplished with the aid of

stem cells grown in self-assembling three-dimensional biodegradable

scaffolds of nanofibers developed by Sam Stupp, a materials scientist

working with Kessler at Northwestern.

" When you have nerve fibers try to grow out in the spinal cord,

they need something to grow on, " Kessler said. " This scaffold gives

them physical material to grow across, hang onto. "

The fibers, delivered in liquid form, self-assemble into a

scaffold within seconds of making contact with the electrically

charged ions surrounding cells. An amino acid in the fibers helps

promote the growth of neurites -- branches extending from nerves that

help the cells communicate. The scaffolds then dissolve as cells grow

into place.

Kessler said the preliminary work on repairing spinal-cord damage

in mice and rats with neural-progenitor cells is proceeding well. The

fibers apparently help prevent the cells from developing into scar

tissue around damaged nerves.

" It's important to stress that by no means do we have a treatment

for spinal-cord injury yet in humans, " he cautioned.

Stupp has established Nanotope, a startup company in ton, to

bring a product based on the nanoscaffold concept to human trials.

Kessler said the scaffolds also could help regenerate " many other

organs of the body. "

Kniss, a stem-cell biologist at Ohio State University in

Columbus, and colleagues also are developing nanofibrous scaffolds for

stem cells.

" The non-cell part of a tissue -- the matrix between the cells --

is important (and) can affect cell function, " Kniss explained. " With

nanofiber scaffolds, you mimic the nanometer-scale fibers normally

found in that matrix. This research could help (address) the critical

shortage of transplantable organs. "

His team is creating biodegradable scaffolds to nurture fat stem

cells. During tumor surgery, doctors often extract fat cells from

other parts of the body and transplant them into the tissue from where

the tumor was removed.

" You often have scars from donating portions of the body; instead,

you can have new fat tissue used in reconstituting those defects, "

Kniss said.

Kniss and colleagues are developing non-biodegradable

three-dimensional scaffolds to hold stem cells for pharmaceutical and

biological research.

" You can develop these tissue constructs to test new drugs, " he

said. " Tissues grow in three dimensions and not two, and three

dimensions would be more advantageous for early drug screening. "

In the future, magnetic iron-oxide nanoparticles could help

physicians ensure they are implanting therapeutic stem cells in the

correct location.

" If you inject them in the wrong place, you might inject them into

dead tissue, and they would die right away with no nutrients, "

explained Jeff Bulte, a magnetic-resonance-imaging researcher at The

s Hopkins University School of Medicine in Baltimore.

In animal tests, researchers have had to remove tissue in order to

pinpoint where they implanted stem cells. Using MRI has the potential

to track stem cells non-invasively in living animals, but stem cells

normally do not easily absorb the magnetic particles doctors inject to

enhance MRI scans.

" You need to get a high number of the particles into cells, since

the sensitivity of MRI is not very high, " Bulte said.

In 2001 Bulte and colleagues reported the first success in MRI

tracking of stem cells using magnetic nanoparticles carried into the

cells via branch-like nanostructures called dendrimers. Now, he said,

the process does not even need dendrimers. Instead, it employs

electric pulses that briefly open up pores in stem-cell surfaces,

allowing the magnetic nanoparticles to leak in.

" The beauty of it is that it just takes a second. You just mix the

nanoparticles with the cells and press a button, " he said.

Now Bulte is partnering with two of his Hopkins colleagues

--veterinary radiologist Dara Kraitchman and cardiologist Hare

-- to tag magnetically stem cells implanted in heart-attack patients

in the hopes of gaining insights into repairing heart damage.

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