|
You may never look at a cotton candy machine the same again…
At least that's how assistant professor Leon Bellan felt
after attending a lecture on tissue engineering. He was doing research on
electrospinning and he heard others say that electrospun fibers look like Silly
String or cotton candy. Bellan realized during the lecture that
electrospoinning can make networks somewhat resembling capillaries but at a
much smaller scale, and decided to try it using a cotton candy machine.
The cotton candy machine formed threads that were
approximately one tenth the diameter of a human hair - roughly the same size as
capillaries. And that's where it all started.
The goal
of Bellan's research has been to make fiber networks that can be used as
template to produce the capillary systems required to create full-scale
artificial organs. The template is made out of a network of tiny threads
comparable in size, density, and complexity to the patterns formed by
capillaries. According to an article published February 4 by the Advanced Healthcare Materials
journal, Bellan and his colleagues have succeeded in producing a
three-dimensional artificial capillary system that can keep living cells viable
and functional for more than a week - a dramatic improvement over current
methods.
Most researchers in this area are using hydrogels, a
water-based gel that closely mimics that of the natural extracellular matrix
that surrounds cells in the body. While they are able to support diffusion of
necessary soluble compounds, oxygen, nutrients, and wastes can only diffuse a
limited distance through the gel, so the calls must be close to a source of
nutrients and oxygen and a sink for wastes. Image Credit
This need for a network of
channels that allow fluids to flow has posed a significant challenge to
researchers developing artificial organs. But for Bellan, his cotton-candy
spinning method can produce channels ranging from three to 55 microns. He uses
a material called Poly (N-isopropylacrylamide), or PNIPAM, a polymer that is
not only cell friendly but has the unusual property of being insoluble at
temperatures above 32 degrees Celsius and soluble below that temperature.
The team spins a network of PNIPAM threads using a
modified cotton candy machine. Then they mix up gelatin, water (at 37 degrees),
and human cells with an enzyme that causes the gelatin to irreversibly gel. The
warm mixture is poured over the PNIPAM structure and allowed to gel in an
incubator at 37 degrees. Finally, the gel contaminating cells and fibers are
allowed to cool to room temperature, at which point the embedded fibers
dissolve, leaving behind an intricate network of microscale channels. The
researchers then attach pumps to the network and begin perfusing them with cell
culture media containing necessary chemicals and oxygen.
"Our experiments show that, after seven days, 90 percent
of the cells in a scaffold with perfused microchannels remained alive and
functional compared to only 60 to 70 percent in scaffolds that were not
perfused or did not have microchannels," Bellan reported.
The next step is to fine-tune to technique to match the
characteristics of the small vessel networks in different types of tissues.
To watch the cotton candy in action click HERE.
| 
Re: Spinning Organs
