Collagen often pops up in beauty products and
supermodels' lips. But by mating collagen with a molecular
hitchhiker, materials scientists at Johns Hopkins hope to
create some important medical advances. The researchers
have found a simple new way to modify collagen, paving the
way for better infection-fighting bandages and a treatment
to block the formation of unwanted scar tissue. In
addition, tissue engineers may be able to use modified
collagen in the lab to help control the formation of tiny
new blood vessels that can be used to promote the
integration of tissue implants in patients.
Michael Seungju Yu, an assistant professor in the
Whiting School of
Engineering, described the new collagen modification
process and its potential medical uses in an Aug. 30
presentation in Washington, D.C., at the 230th annual
meeting of the American Chemical Society. His team also
published a paper on the work earlier this year in the
Journal of the American Chemical Society.
The research focuses on the human body's most common
protein. Collagen promotes blood clotting and provides the
spongelike scaffold upon which cells build nerves, bones
and skin. Because it is nontoxic, dissolves naturally over
time and rarely triggers rejection, collagen is commonly
used in cosmetics, drug delivery systems and biocompatible
Yu's goal is to change some of collagen's biochemical
or mechanical properties to give it new medical
applications. Traditionally, scientists have altered
collagen by using intense heat or chemical reactions,
techniques that may damage the protein or limit its safe
use in humans. Yu's method, however, requires only physical
mixing of collagen with even smaller molecules called
collagen mimetic peptides.
"That's the beauty of this," Yu said. "If you want to
attach these molecules to collagen, you don't have to cook
it or use harsh chemicals. You just mix them together in a
In lab experiments, Yu and his colleagues have shown
that this kind of molecular marriage does take place. They
attached fluorescent tags to the peptides and observed the
glow in collagen that had been mixed with the smaller
molecules. Exactly how and why the collagen and the
peptides join is uncertain. But researchers know that
collagen molecules form a distinctive triple helix in which
three long protein strands intertwine like rope. Yu
speculates that because the smaller collagen mimetic
peptides have a propensity to make similar triple-helix
structures, they are naturally attracted to collagen
molecules. He believes the peptides make themselves at home
within gaps formed by loose collagen strands.
This linkup opens the door to new medical treatments,
Yu said, because it is easy to attach bioactive agents to
the peptides. When the peptides bind with collagen, these
attached agents can dramatically change the way collagen
behaves in the body. For example, collagen normally
attracts cells to close up a wound and form scar tissue.
But this property is not always desirable; a clot can be
dangerous inside a blood vessel or at certain injury sites,
where scar tissue can interfere with the formation of new
Modified collagen can follow a different course. In
their recent journal paper, Yu and his colleagues reported
that they had attached a chemical, polyethylene glycol, to
the peptides, causing collagen to repel cells instead of
attracting them. When the researchers added human cells to
a lab dish, the cells migrated toward an untreated collagen
film but avoided the modified collagen sample. This form of
collagen could stop the formation of blood clots and scar
tissue, and scientists may be able to use it to control the
shape and organization of cells and tissue that are grown
in a lab, Yu said.
Still other medical uses are possible. A growth factor
joined to collagen could encourage new cells to multiply.
An antibiotic attached to collagen could help a
collagen-based bandage fight infections over a long period
of time. Modified collagen could also release helpful
medications while serving as a coating for surgical tools
"With this process," Yu said, "we can make the
collagen that's already found in the human body behave in
new ways, including some ways that are not found in nature.
Modified collagen can give us a great new tool for treating
injuries and illnesses."
Yu's collaborators on the Journal of the American
Chemical Society paper were doctoral students Allen Y.
Wang and Xiao Mo and former Biomedical Engineering faculty
member Christopher S. Chen, who is now affiliated with the
University of Pennsylvania. Yu's research is supported by
grants from the National Science Foundation and the
National Institutes of Health.